path: root/keys-expand-keyring.patch

From 96dcf8e91389e509021448ffd798cc68471fcf0f Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:50 +0100
Subject: [PATCH 01/10] KEYS: Skip key state checks when checking for
 possession

Skip key state checks (invalidation, revocation and expiration) when checking
for possession.  Without this, keys that have been marked invalid, revoked
keys and expired keys are not given a possession attribute - which means the
possessor is not granted any possession permits and cannot do anything with
them unless they also have one a user, group or other permit.

This causes failures in the keyutils test suite's revocation and expiration
tests now that commit 96b5c8fea6c0861621051290d705ec2e971963f1 reduced the
initial permissions granted to a key.

The failures are due to accesses to revoked and expired keys being given
EACCES instead of EKEYREVOKED or EKEYEXPIRED.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 security/keys/internal.h         | 1 +
 security/keys/process_keys.c     | 8 +++++---
 security/keys/request_key.c      | 6 ++++--
 security/keys/request_key_auth.c | 2 +-
 4 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/security/keys/internal.h b/security/keys/internal.h
index d4f1468..df971fe 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -124,6 +124,7 @@ extern key_ref_t search_my_process_keyrings(struct key_type *type,
 extern key_ref_t search_process_keyrings(struct key_type *type,
 					 const void *description,
 					 key_match_func_t match,
+					 bool no_state_check,
 					 const struct cred *cred);
 
 extern struct key *find_keyring_by_name(const char *name, bool skip_perm_check);
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 42defae..a3410d6 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -440,6 +440,7 @@ found:
 key_ref_t search_process_keyrings(struct key_type *type,
 				  const void *description,
 				  key_match_func_t match,
+				  bool no_state_check,
 				  const struct cred *cred)
 {
 	struct request_key_auth *rka;
@@ -448,7 +449,7 @@ key_ref_t search_process_keyrings(struct key_type *type,
 	might_sleep();
 
 	key_ref = search_my_process_keyrings(type, description, match,
-					     false, cred);
+					     no_state_check, cred);
 	if (!IS_ERR(key_ref))
 		goto found;
 	err = key_ref;
@@ -468,7 +469,8 @@ key_ref_t search_process_keyrings(struct key_type *type,
 			rka = cred->request_key_auth->payload.data;
 
 			key_ref = search_process_keyrings(type, description,
-							  match, rka->cred);
+							  match, no_state_check,
+							  rka->cred);
 
 			up_read(&cred->request_key_auth->sem);
 
@@ -675,7 +677,7 @@ try_again:
 		/* check to see if we possess the key */
 		skey_ref = search_process_keyrings(key->type, key,
 						   lookup_user_key_possessed,
-						   cred);
+						   true, cred);
 
 		if (!IS_ERR(skey_ref)) {
 			key_put(key);
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index c411f9b..172115b 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -390,7 +390,8 @@ static int construct_alloc_key(struct key_type *type,
 	 * waited for locks */
 	mutex_lock(&key_construction_mutex);
 
-	key_ref = search_process_keyrings(type, description, type->match, cred);
+	key_ref = search_process_keyrings(type, description, type->match,
+					  false, cred);
 	if (!IS_ERR(key_ref))
 		goto key_already_present;
 
@@ -539,7 +540,8 @@ struct key *request_key_and_link(struct key_type *type,
 	       dest_keyring, flags);
 
 	/* search all the process keyrings for a key */
-	key_ref = search_process_keyrings(type, description, type->match, cred);
+	key_ref = search_process_keyrings(type, description, type->match,
+					  false, cred);
 
 	if (!IS_ERR(key_ref)) {
 		key = key_ref_to_ptr(key_ref);
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 85730d5..92077de 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -247,7 +247,7 @@ struct key *key_get_instantiation_authkey(key_serial_t target_id)
 		&key_type_request_key_auth,
 		(void *) (unsigned long) target_id,
 		key_get_instantiation_authkey_match,
-		cred);
+		false, cred);
 
 	if (IS_ERR(authkey_ref)) {
 		authkey = ERR_CAST(authkey_ref);
-- 
1.8.3.1


From 9b1294158dd1fbca78541b5d55c057e46b1a9ca2 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:51 +0100
Subject: [PATCH 02/10] KEYS: Use bool in make_key_ref() and is_key_possessed()

Make make_key_ref() take a bool possession parameter and make
is_key_possessed() return a bool.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 Documentation/security/keys.txt | 7 +++----
 include/linux/key.h             | 4 ++--
 security/keys/keyring.c         | 5 +++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 7b4145d..9ede670 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -865,15 +865,14 @@ encountered:
      calling processes has a searchable link to the key from one of its
      keyrings. There are three functions for dealing with these:
 
-	key_ref_t make_key_ref(const struct key *key,
-			       unsigned long possession);
+	key_ref_t make_key_ref(const struct key *key, bool possession);
 
 	struct key *key_ref_to_ptr(const key_ref_t key_ref);
 
-	unsigned long is_key_possessed(const key_ref_t key_ref);
+	bool is_key_possessed(const key_ref_t key_ref);
 
      The first function constructs a key reference from a key pointer and
-     possession information (which must be 0 or 1 and not any other value).
+     possession information (which must be true or false).
 
      The second function retrieves the key pointer from a reference and the
      third retrieves the possession flag.
diff --git a/include/linux/key.h b/include/linux/key.h
index 4dfde11..51bce29 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -99,7 +99,7 @@ struct keyring_name;
 typedef struct __key_reference_with_attributes *key_ref_t;
 
 static inline key_ref_t make_key_ref(const struct key *key,
-				     unsigned long possession)
+				     bool possession)
 {
 	return (key_ref_t) ((unsigned long) key | possession);
 }
@@ -109,7 +109,7 @@ static inline struct key *key_ref_to_ptr(const key_ref_t key_ref)
 	return (struct key *) ((unsigned long) key_ref & ~1UL);
 }
 
-static inline unsigned long is_key_possessed(const key_ref_t key_ref)
+static inline bool is_key_possessed(const key_ref_t key_ref)
 {
 	return (unsigned long) key_ref & 1UL;
 }
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 6ece7f2..f784063 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -329,9 +329,10 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 
 	struct keyring_list *keylist;
 	struct timespec now;
-	unsigned long possessed, kflags;
+	unsigned long kflags;
 	struct key *keyring, *key;
 	key_ref_t key_ref;
+	bool possessed;
 	long err;
 	int sp, nkeys, kix;
 
@@ -542,8 +543,8 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 			       key_perm_t perm)
 {
 	struct keyring_list *klist;
-	unsigned long possessed;
 	struct key *keyring, *key;
+	bool possessed;
 	int nkeys, loop;
 
 	keyring = key_ref_to_ptr(keyring_ref);
-- 
1.8.3.1


From 4a7e7536b9b728f1d912d0e4c047c885c95e13a1 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:51 +0100
Subject: [PATCH 03/10] KEYS: key_is_dead() should take a const key pointer
 argument

key_is_dead() should take a const key pointer argument as it doesn't modify
what it points to.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 security/keys/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/keys/internal.h b/security/keys/internal.h
index df971fe..490aef5 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -203,7 +203,7 @@ extern struct key *key_get_instantiation_authkey(key_serial_t target_id);
 /*
  * Determine whether a key is dead.
  */
-static inline bool key_is_dead(struct key *key, time_t limit)
+static inline bool key_is_dead(const struct key *key, time_t limit)
 {
 	return
 		key->flags & ((1 << KEY_FLAG_DEAD) |
-- 
1.8.3.1


From 9007a0a7f8c135f0085e46db277de0cf7b944403 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:52 +0100
Subject: [PATCH 04/10] KEYS: Consolidate the concept of an 'index key' for key
 access

Consolidate the concept of an 'index key' for accessing keys.  The index key
is the search term needed to find a key directly - basically the key type and
the key description.  We can add to that the description length.

This will be useful when turning a keyring into an associative array rather
than just a pointer block.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/linux/key.h         | 21 +++++++++----
 security/keys/internal.h    |  8 ++---
 security/keys/key.c         | 72 +++++++++++++++++++++++----------------------
 security/keys/keyring.c     | 37 +++++++++++------------
 security/keys/request_key.c | 12 +++++---
 5 files changed, 83 insertions(+), 67 deletions(-)

diff --git a/include/linux/key.h b/include/linux/key.h
index 51bce29..d573e82 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -82,6 +82,12 @@ struct key_owner;
 struct keyring_list;
 struct keyring_name;
 
+struct keyring_index_key {
+	struct key_type		*type;
+	const char		*description;
+	size_t			desc_len;
+};
+
 /*****************************************************************************/
 /*
  * key reference with possession attribute handling
@@ -129,7 +135,6 @@ struct key {
 		struct list_head graveyard_link;
 		struct rb_node	serial_node;
 	};
-	struct key_type		*type;		/* type of key */
 	struct rw_semaphore	sem;		/* change vs change sem */
 	struct key_user		*user;		/* owner of this key */
 	void			*security;	/* security data for this key */
@@ -163,12 +168,18 @@ struct key {
 #define KEY_FLAG_ROOT_CAN_CLEAR	6	/* set if key can be cleared by root without permission */
 #define KEY_FLAG_INVALIDATED	7	/* set if key has been invalidated */
 
-	/* the description string
-	 * - this is used to match a key against search criteria
-	 * - this should be a printable string
+	/* the key type and key description string
+	 * - the desc is used to match a key against search criteria
+	 * - it should be a printable string
 	 * - eg: for krb5 AFS, this might be "afs@REDHAT.COM"
 	 */
-	char			*description;
+	union {
+		struct keyring_index_key index_key;
+		struct {
+			struct key_type	*type;		/* type of key */
+			char		*description;
+		};
+	};
 
 	/* type specific data
 	 * - this is used by the keyring type to index the name
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 490aef5..77441dd 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -89,19 +89,17 @@ extern struct key_type *key_type_lookup(const char *type);
 extern void key_type_put(struct key_type *ktype);
 
 extern int __key_link_begin(struct key *keyring,
-			    const struct key_type *type,
-			    const char *description,
+			    const struct keyring_index_key *index_key,
 			    unsigned long *_prealloc);
 extern int __key_link_check_live_key(struct key *keyring, struct key *key);
 extern void __key_link(struct key *keyring, struct key *key,
 		       unsigned long *_prealloc);
 extern void __key_link_end(struct key *keyring,
-			   struct key_type *type,
+			   const struct keyring_index_key *index_key,
 			   unsigned long prealloc);
 
 extern key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-				      const struct key_type *type,
-				      const char *description,
+				      const struct keyring_index_key *index_key,
 				      key_perm_t perm);
 
 extern struct key *keyring_search_instkey(struct key *keyring,
diff --git a/security/keys/key.c b/security/keys/key.c
index 8fb7c7b..7e6bc39 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -242,8 +242,8 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 		}
 	}
 
-	desclen = strlen(desc) + 1;
-	quotalen = desclen + type->def_datalen;
+	desclen = strlen(desc);
+	quotalen = desclen + 1 + type->def_datalen;
 
 	/* get hold of the key tracking for this user */
 	user = key_user_lookup(uid);
@@ -277,7 +277,8 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 		goto no_memory_2;
 
 	if (desc) {
-		key->description = kmemdup(desc, desclen, GFP_KERNEL);
+		key->index_key.desc_len = desclen;
+		key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
 		if (!key->description)
 			goto no_memory_3;
 	}
@@ -285,7 +286,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	atomic_set(&key->usage, 1);
 	init_rwsem(&key->sem);
 	lockdep_set_class(&key->sem, &type->lock_class);
-	key->type = type;
+	key->index_key.type = type;
 	key->user = user;
 	key->quotalen = quotalen;
 	key->datalen = type->def_datalen;
@@ -489,8 +490,7 @@ int key_instantiate_and_link(struct key *key,
 	}
 
 	if (keyring) {
-		ret = __key_link_begin(keyring, key->type, key->description,
-				       &prealloc);
+		ret = __key_link_begin(keyring, &key->index_key, &prealloc);
 		if (ret < 0)
 			goto error_free_preparse;
 	}
@@ -499,7 +499,7 @@ int key_instantiate_and_link(struct key *key,
 					 &prealloc);
 
 	if (keyring)
-		__key_link_end(keyring, key->type, prealloc);
+		__key_link_end(keyring, &key->index_key, prealloc);
 
 error_free_preparse:
 	if (key->type->preparse)
@@ -548,8 +548,7 @@ int key_reject_and_link(struct key *key,
 	ret = -EBUSY;
 
 	if (keyring)
-		link_ret = __key_link_begin(keyring, key->type,
-					    key->description, &prealloc);
+		link_ret = __key_link_begin(keyring, &key->index_key, &prealloc);
 
 	mutex_lock(&key_construction_mutex);
 
@@ -581,7 +580,7 @@ int key_reject_and_link(struct key *key,
 	mutex_unlock(&key_construction_mutex);
 
 	if (keyring)
-		__key_link_end(keyring, key->type, prealloc);
+		__key_link_end(keyring, &key->index_key, prealloc);
 
 	/* wake up anyone waiting for a key to be constructed */
 	if (awaken)
@@ -780,25 +779,27 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 			       key_perm_t perm,
 			       unsigned long flags)
 {
-	unsigned long prealloc;
+	struct keyring_index_key index_key = {
+		.description	= description,
+	};
 	struct key_preparsed_payload prep;
 	const struct cred *cred = current_cred();
-	struct key_type *ktype;
+	unsigned long prealloc;
 	struct key *keyring, *key = NULL;
 	key_ref_t key_ref;
 	int ret;
 
 	/* look up the key type to see if it's one of the registered kernel
 	 * types */
-	ktype = key_type_lookup(type);
-	if (IS_ERR(ktype)) {
+	index_key.type = key_type_lookup(type);
+	if (IS_ERR(index_key.type)) {
 		key_ref = ERR_PTR(-ENODEV);
 		goto error;
 	}
 
 	key_ref = ERR_PTR(-EINVAL);
-	if (!ktype->match || !ktype->instantiate ||
-	    (!description && !ktype->preparse))
+	if (!index_key.type->match || !index_key.type->instantiate ||
+	    (!index_key.description && !index_key.type->preparse))
 		goto error_put_type;
 
 	keyring = key_ref_to_ptr(keyring_ref);
@@ -812,21 +813,22 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	memset(&prep, 0, sizeof(prep));
 	prep.data = payload;
 	prep.datalen = plen;
-	prep.quotalen = ktype->def_datalen;
-	if (ktype->preparse) {
-		ret = ktype->preparse(&prep);
+	prep.quotalen = index_key.type->def_datalen;
+	if (index_key.type->preparse) {
+		ret = index_key.type->preparse(&prep);
 		if (ret < 0) {
 			key_ref = ERR_PTR(ret);
 			goto error_put_type;
 		}
-		if (!description)
-			description = prep.description;
+		if (!index_key.description)
+			index_key.description = prep.description;
 		key_ref = ERR_PTR(-EINVAL);
-		if (!description)
+		if (!index_key.description)
 			goto error_free_prep;
 	}
+	index_key.desc_len = strlen(index_key.description);
 
-	ret = __key_link_begin(keyring, ktype, description, &prealloc);
+	ret = __key_link_begin(keyring, &index_key, &prealloc);
 	if (ret < 0) {
 		key_ref = ERR_PTR(ret);
 		goto error_free_prep;
@@ -844,9 +846,8 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	 * key of the same type and description in the destination keyring and
 	 * update that instead if possible
 	 */
-	if (ktype->update) {
-		key_ref = __keyring_search_one(keyring_ref, ktype, description,
-					       0);
+	if (index_key.type->update) {
+		key_ref = __keyring_search_one(keyring_ref, &index_key, 0);
 		if (!IS_ERR(key_ref))
 			goto found_matching_key;
 	}
@@ -856,16 +857,17 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 		perm |= KEY_USR_VIEW;
 
-		if (ktype->read)
+		if (index_key.type->read)
 			perm |= KEY_POS_READ;
 
-		if (ktype == &key_type_keyring || ktype->update)
+		if (index_key.type == &key_type_keyring ||
+		    index_key.type->update)
 			perm |= KEY_POS_WRITE;
 	}
 
 	/* allocate a new key */
-	key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
-			perm, flags);
+	key = key_alloc(index_key.type, index_key.description,
+			cred->fsuid, cred->fsgid, cred, perm, flags);
 	if (IS_ERR(key)) {
 		key_ref = ERR_CAST(key);
 		goto error_link_end;
@@ -882,12 +884,12 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 
 error_link_end:
-	__key_link_end(keyring, ktype, prealloc);
+	__key_link_end(keyring, &index_key, prealloc);
 error_free_prep:
-	if (ktype->preparse)
-		ktype->free_preparse(&prep);
+	if (index_key.type->preparse)
+		index_key.type->free_preparse(&prep);
 error_put_type:
-	key_type_put(ktype);
+	key_type_put(index_key.type);
 error:
 	return key_ref;
 
@@ -895,7 +897,7 @@ error:
 	/* we found a matching key, so we're going to try to update it
 	 * - we can drop the locks first as we have the key pinned
 	 */
-	__key_link_end(keyring, ktype, prealloc);
+	__key_link_end(keyring, &index_key, prealloc);
 
 	key_ref = __key_update(key_ref, &prep);
 	goto error_free_prep;
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index f784063..c7f59f9 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -538,8 +538,7 @@ EXPORT_SYMBOL(keyring_search);
  * to the returned key reference.
  */
 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-			       const struct key_type *ktype,
-			       const char *description,
+			       const struct keyring_index_key *index_key,
 			       key_perm_t perm)
 {
 	struct keyring_list *klist;
@@ -558,9 +557,9 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 		smp_rmb();
 		for (loop = 0; loop < nkeys ; loop++) {
 			key = rcu_dereference(klist->keys[loop]);
-			if (key->type == ktype &&
+			if (key->type == index_key->type &&
 			    (!key->type->match ||
-			     key->type->match(key, description)) &&
+			     key->type->match(key, index_key->description)) &&
 			    key_permission(make_key_ref(key, possessed),
 					   perm) == 0 &&
 			    !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
@@ -747,8 +746,8 @@ static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
 /*
  * Preallocate memory so that a key can be linked into to a keyring.
  */
-int __key_link_begin(struct key *keyring, const struct key_type *type,
-		     const char *description, unsigned long *_prealloc)
+int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_key,
+		     unsigned long *_prealloc)
 	__acquires(&keyring->sem)
 	__acquires(&keyring_serialise_link_sem)
 {
@@ -759,7 +758,8 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
 	size_t size;
 	int loop, lru, ret;
 
-	kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
+	kenter("%d,%s,%s,",
+	       key_serial(keyring), index_key->type->name, index_key->description);
 
 	if (keyring->type != &key_type_keyring)
 		return -ENOTDIR;
@@ -772,7 +772,7 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
 
 	/* serialise link/link calls to prevent parallel calls causing a cycle
 	 * when linking two keyring in opposite orders */
-	if (type == &key_type_keyring)
+	if (index_key->type == &key_type_keyring)
 		down_write(&keyring_serialise_link_sem);
 
 	klist = rcu_dereference_locked_keyring(keyring);
@@ -784,8 +784,8 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
 		for (loop = klist->nkeys - 1; loop >= 0; loop--) {
 			struct key *key = rcu_deref_link_locked(klist, loop,
 								keyring);
-			if (key->type == type &&
-			    strcmp(key->description, description) == 0) {
+			if (key->type == index_key->type &&
+			    strcmp(key->description, index_key->description) == 0) {
 				/* Found a match - we'll replace the link with
 				 * one to the new key.  We record the slot
 				 * position.
@@ -865,7 +865,7 @@ error_quota:
 	key_payload_reserve(keyring,
 			    keyring->datalen - KEYQUOTA_LINK_BYTES);
 error_sem:
-	if (type == &key_type_keyring)
+	if (index_key->type == &key_type_keyring)
 		up_write(&keyring_serialise_link_sem);
 error_krsem:
 	up_write(&keyring->sem);
@@ -957,16 +957,17 @@ void __key_link(struct key *keyring, struct key *key,
  *
  * Must be called with __key_link_begin() having being called.
  */
-void __key_link_end(struct key *keyring, struct key_type *type,
+void __key_link_end(struct key *keyring,
+		    const struct keyring_index_key *index_key,
 		    unsigned long prealloc)
 	__releases(&keyring->sem)
 	__releases(&keyring_serialise_link_sem)
 {
-	BUG_ON(type == NULL);
-	BUG_ON(type->name == NULL);
-	kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
+	BUG_ON(index_key->type == NULL);
+	BUG_ON(index_key->type->name == NULL);
+	kenter("%d,%s,%lx", keyring->serial, index_key->type->name, prealloc);
 
-	if (type == &key_type_keyring)
+	if (index_key->type == &key_type_keyring)
 		up_write(&keyring_serialise_link_sem);
 
 	if (prealloc) {
@@ -1007,12 +1008,12 @@ int key_link(struct key *keyring, struct key *key)
 	key_check(keyring);
 	key_check(key);
 
-	ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
+	ret = __key_link_begin(keyring, &key->index_key, &prealloc);
 	if (ret == 0) {
 		ret = __key_link_check_live_key(keyring, key);
 		if (ret == 0)
 			__key_link(keyring, key, &prealloc);
-		__key_link_end(keyring, key->type, prealloc);
+		__key_link_end(keyring, &key->index_key, prealloc);
 	}
 
 	return ret;
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 172115b..586cb79 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -352,6 +352,11 @@ static int construct_alloc_key(struct key_type *type,
 			       struct key_user *user,
 			       struct key **_key)
 {
+	const struct keyring_index_key index_key = {
+		.type		= type,
+		.description	= description,
+		.desc_len	= strlen(description),
+	};
 	const struct cred *cred = current_cred();
 	unsigned long prealloc;
 	struct key *key;
@@ -379,8 +384,7 @@ static int construct_alloc_key(struct key_type *type,
 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 
 	if (dest_keyring) {
-		ret = __key_link_begin(dest_keyring, type, description,
-				       &prealloc);
+		ret = __key_link_begin(dest_keyring, &index_key, &prealloc);
 		if (ret < 0)
 			goto link_prealloc_failed;
 	}
@@ -400,7 +404,7 @@ static int construct_alloc_key(struct key_type *type,
 
 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
-		__key_link_end(dest_keyring, type, prealloc);
+		__key_link_end(dest_keyring, &index_key, prealloc);
 	mutex_unlock(&user->cons_lock);
 	*_key = key;
 	kleave(" = 0 [%d]", key_serial(key));
@@ -416,7 +420,7 @@ key_already_present:
 		ret = __key_link_check_live_key(dest_keyring, key);
 		if (ret == 0)
 			__key_link(dest_keyring, key, &prealloc);
-		__key_link_end(dest_keyring, type, prealloc);
+		__key_link_end(dest_keyring, &index_key, prealloc);
 		if (ret < 0)
 			goto link_check_failed;
 	}
-- 
1.8.3.1


From eca8dad5cd291d2baf2d20372fcb0af9e75e25ea Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:52 +0100
Subject: [PATCH 05/10] KEYS: Introduce a search context structure

Search functions pass around a bunch of arguments, each of which gets copied
with each call.  Introduce a search context structure to hold these.

Whilst we're at it, create a search flag that indicates whether the search
should be directly to the description or whether it should iterate through all
keys looking for a non-description match.

This will be useful when keyrings use a generic data struct with generic
routines to manage their content as the search terms can just be passed
through to the iterator callback function.

Also, for future use, the data to be supplied to the match function is
separated from the description pointer in the search context.  This makes it
clear which is being supplied.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/linux/key-type.h         |   5 ++
 security/keys/internal.h         |  40 +++++++------
 security/keys/keyring.c          |  70 +++++++++++------------
 security/keys/proc.c             |  17 ++++--
 security/keys/process_keys.c     | 117 +++++++++++++++++++--------------------
 security/keys/request_key.c      |  56 +++++++++----------
 security/keys/request_key_auth.c |  14 +++--
 security/keys/user_defined.c     |  18 +++---
 8 files changed, 179 insertions(+), 158 deletions(-)

diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index 518a53a..f58737b 100644
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -63,6 +63,11 @@ struct key_type {
 	 */
 	size_t def_datalen;
 
+	/* Default key search algorithm. */
+	unsigned def_lookup_type;
+#define KEYRING_SEARCH_LOOKUP_DIRECT	0x0000	/* Direct lookup by description. */
+#define KEYRING_SEARCH_LOOKUP_ITERATE	0x0001	/* Iterative search. */
+
 	/* vet a description */
 	int (*vet_description)(const char *description);
 
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 77441dd..f4bf938 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -107,23 +107,31 @@ extern struct key *keyring_search_instkey(struct key *keyring,
 
 typedef int (*key_match_func_t)(const struct key *, const void *);
 
+struct keyring_search_context {
+	struct keyring_index_key index_key;
+	const struct cred	*cred;
+	key_match_func_t	match;
+	const void		*match_data;
+	unsigned		flags;
+#define KEYRING_SEARCH_LOOKUP_TYPE	0x0001	/* [as type->def_lookup_type] */
+#define KEYRING_SEARCH_NO_STATE_CHECK	0x0002	/* Skip state checks */
+#define KEYRING_SEARCH_DO_STATE_CHECK	0x0004	/* Override NO_STATE_CHECK */
+#define KEYRING_SEARCH_NO_UPDATE_TIME	0x0008	/* Don't update times */
+#define KEYRING_SEARCH_NO_CHECK_PERM	0x0010	/* Don't check permissions */
+#define KEYRING_SEARCH_DETECT_TOO_DEEP	0x0020	/* Give an error on excessive depth */
+
+	/* Internal stuff */
+	int			skipped_ret;
+	bool			possessed;
+	key_ref_t		result;
+	struct timespec		now;
+};
+
 extern key_ref_t keyring_search_aux(key_ref_t keyring_ref,
-				    const struct cred *cred,
-				    struct key_type *type,
-				    const void *description,
-				    key_match_func_t match,
-				    bool no_state_check);
-
-extern key_ref_t search_my_process_keyrings(struct key_type *type,
-					    const void *description,
-					    key_match_func_t match,
-					    bool no_state_check,
-					    const struct cred *cred);
-extern key_ref_t search_process_keyrings(struct key_type *type,
-					 const void *description,
-					 key_match_func_t match,
-					 bool no_state_check,
-					 const struct cred *cred);
+				    struct keyring_search_context *ctx);
+
+extern key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx);
+extern key_ref_t search_process_keyrings(struct keyring_search_context *ctx);
 
 extern struct key *find_keyring_by_name(const char *name, bool skip_perm_check);
 
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index c7f59f9..b42f2d4 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -280,11 +280,7 @@ EXPORT_SYMBOL(keyring_alloc);
 /**
  * keyring_search_aux - Search a keyring tree for a key matching some criteria
  * @keyring_ref: A pointer to the keyring with possession indicator.
- * @cred: The credentials to use for permissions checks.
- * @type: The type of key to search for.
- * @description: Parameter for @match.
- * @match: Function to rule on whether or not a key is the one required.
- * @no_state_check: Don't check if a matching key is bad
+ * @ctx: The keyring search context.
  *
  * Search the supplied keyring tree for a key that matches the criteria given.
  * The root keyring and any linked keyrings must grant Search permission to the
@@ -314,11 +310,7 @@ EXPORT_SYMBOL(keyring_alloc);
  * @keyring_ref is propagated to the returned key reference.
  */
 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
-			     const struct cred *cred,
-			     struct key_type *type,
-			     const void *description,
-			     key_match_func_t match,
-			     bool no_state_check)
+			     struct keyring_search_context *ctx)
 {
 	struct {
 		/* Need a separate keylist pointer for RCU purposes */
@@ -328,20 +320,18 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 	} stack[KEYRING_SEARCH_MAX_DEPTH];
 
 	struct keyring_list *keylist;
-	struct timespec now;
 	unsigned long kflags;
 	struct key *keyring, *key;
 	key_ref_t key_ref;
-	bool possessed;
 	long err;
 	int sp, nkeys, kix;
 
 	keyring = key_ref_to_ptr(keyring_ref);
-	possessed = is_key_possessed(keyring_ref);
+	ctx->possessed = is_key_possessed(keyring_ref);
 	key_check(keyring);
 
 	/* top keyring must have search permission to begin the search */
-	err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
+	err = key_task_permission(keyring_ref, ctx->cred, KEY_SEARCH);
 	if (err < 0) {
 		key_ref = ERR_PTR(err);
 		goto error;
@@ -353,7 +343,7 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 
 	rcu_read_lock();
 
-	now = current_kernel_time();
+	ctx->now = current_kernel_time();
 	err = -EAGAIN;
 	sp = 0;
 
@@ -361,16 +351,17 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 	 * are looking for */
 	key_ref = ERR_PTR(-EAGAIN);
 	kflags = keyring->flags;
-	if (keyring->type == type && match(keyring, description)) {
+	if (keyring->type == ctx->index_key.type &&
+	    ctx->match(keyring, ctx->match_data)) {
 		key = keyring;
-		if (no_state_check)
+		if (ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)
 			goto found;
 
 		/* check it isn't negative and hasn't expired or been
 		 * revoked */
 		if (kflags & (1 << KEY_FLAG_REVOKED))
 			goto error_2;
-		if (key->expiry && now.tv_sec >= key->expiry)
+		if (key->expiry && ctx->now.tv_sec >= key->expiry)
 			goto error_2;
 		key_ref = ERR_PTR(key->type_data.reject_error);
 		if (kflags & (1 << KEY_FLAG_NEGATIVE))
@@ -384,7 +375,7 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 	if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
 		      (1 << KEY_FLAG_REVOKED) |
 		      (1 << KEY_FLAG_NEGATIVE)) ||
-	    (keyring->expiry && now.tv_sec >= keyring->expiry))
+	    (keyring->expiry && ctx->now.tv_sec >= keyring->expiry))
 		goto error_2;
 
 	/* start processing a new keyring */
@@ -406,29 +397,29 @@ descend:
 		kflags = key->flags;
 
 		/* ignore keys not of this type */
-		if (key->type != type)
+		if (key->type != ctx->index_key.type)
 			continue;
 
 		/* skip invalidated, revoked and expired keys */
-		if (!no_state_check) {
+		if (!(ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)) {
 			if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
 				      (1 << KEY_FLAG_REVOKED)))
 				continue;
 
-			if (key->expiry && now.tv_sec >= key->expiry)
+			if (key->expiry && ctx->now.tv_sec >= key->expiry)
 				continue;
 		}
 
 		/* keys that don't match */
-		if (!match(key, description))
+		if (!ctx->match(key, ctx->match_data))
 			continue;
 
 		/* key must have search permissions */
-		if (key_task_permission(make_key_ref(key, possessed),
-					cred, KEY_SEARCH) < 0)
+		if (key_task_permission(make_key_ref(key, ctx->possessed),
+					ctx->cred, KEY_SEARCH) < 0)
 			continue;
 
-		if (no_state_check)
+		if (ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)
 			goto found;
 
 		/* we set a different error code if we pass a negative key */
@@ -456,8 +447,8 @@ ascend:
 		if (sp >= KEYRING_SEARCH_MAX_DEPTH)
 			continue;
 
-		if (key_task_permission(make_key_ref(key, possessed),
-					cred, KEY_SEARCH) < 0)
+		if (key_task_permission(make_key_ref(key, ctx->possessed),
+					ctx->cred, KEY_SEARCH) < 0)
 			continue;
 
 		/* stack the current position */
@@ -489,12 +480,12 @@ not_this_keyring:
 	/* we found a viable match */
 found:
 	atomic_inc(&key->usage);
-	key->last_used_at = now.tv_sec;
-	keyring->last_used_at = now.tv_sec;
+	key->last_used_at = ctx->now.tv_sec;
+	keyring->last_used_at = ctx->now.tv_sec;
 	while (sp > 0)
-		stack[--sp].keyring->last_used_at = now.tv_sec;
+		stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
 	key_check(key);
-	key_ref = make_key_ref(key, possessed);
+	key_ref = make_key_ref(key, ctx->possessed);
 error_2:
 	rcu_read_unlock();
 error:
@@ -514,11 +505,20 @@ key_ref_t keyring_search(key_ref_t keyring,
 			 struct key_type *type,
 			 const char *description)
 {
-	if (!type->match)
+	struct keyring_search_context ctx = {
+		.index_key.type		= type,
+		.index_key.description	= description,
+		.cred			= current_cred(),
+		.match			= type->match,
+		.match_data		= description,
+		.flags			= (type->def_lookup_type |
+					   KEYRING_SEARCH_DO_STATE_CHECK),
+	};
+
+	if (!ctx.match)
 		return ERR_PTR(-ENOKEY);
 
-	return keyring_search_aux(keyring, current->cred,
-				  type, description, type->match, false);
+	return keyring_search_aux(keyring, &ctx);
 }
 EXPORT_SYMBOL(keyring_search);
 
diff --git a/security/keys/proc.c b/security/keys/proc.c
index 217b685..88e9a46 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -182,7 +182,6 @@ static void proc_keys_stop(struct seq_file *p, void *v)
 
 static int proc_keys_show(struct seq_file *m, void *v)
 {
-	const struct cred *cred = current_cred();
 	struct rb_node *_p = v;
 	struct key *key = rb_entry(_p, struct key, serial_node);
 	struct timespec now;
@@ -191,15 +190,23 @@ static int proc_keys_show(struct seq_file *m, void *v)
 	char xbuf[12];
 	int rc;
 
+	struct keyring_search_context ctx = {
+		.index_key.type		= key->type,
+		.index_key.description	= key->description,
+		.cred			= current_cred(),
+		.match			= lookup_user_key_possessed,
+		.match_data		= key,
+		.flags			= (KEYRING_SEARCH_NO_STATE_CHECK |
+					   KEYRING_SEARCH_LOOKUP_DIRECT),
+	};
+
 	key_ref = make_key_ref(key, 0);
 
 	/* determine if the key is possessed by this process (a test we can
 	 * skip if the key does not indicate the possessor can view it
 	 */
 	if (key->perm & KEY_POS_VIEW) {
-		skey_ref = search_my_process_keyrings(key->type, key,
-						      lookup_user_key_possessed,
-						      true, cred);
+		skey_ref = search_my_process_keyrings(&ctx);
 		if (!IS_ERR(skey_ref)) {
 			key_ref_put(skey_ref);
 			key_ref = make_key_ref(key, 1);
@@ -211,7 +218,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
 	 * - the caller holds a spinlock, and thus the RCU read lock, making our
 	 *   access to __current_cred() safe
 	 */
-	rc = key_task_permission(key_ref, cred, KEY_VIEW);
+	rc = key_task_permission(key_ref, ctx.cred, KEY_VIEW);
 	if (rc < 0)
 		return 0;
 
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index a3410d6..e68a3e0 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -319,11 +319,7 @@ void key_fsgid_changed(struct task_struct *tsk)
  * In the case of a successful return, the possession attribute is set on the
  * returned key reference.
  */
-key_ref_t search_my_process_keyrings(struct key_type *type,
-				     const void *description,
-				     key_match_func_t match,
-				     bool no_state_check,
-				     const struct cred *cred)
+key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
 {
 	key_ref_t key_ref, ret, err;
 
@@ -339,10 +335,9 @@ key_ref_t search_my_process_keyrings(struct key_type *type,
 	err = ERR_PTR(-EAGAIN);
 
 	/* search the thread keyring first */
-	if (cred->thread_keyring) {
+	if (ctx->cred->thread_keyring) {
 		key_ref = keyring_search_aux(
-			make_key_ref(cred->thread_keyring, 1),
-			cred, type, description, match, no_state_check);
+			make_key_ref(ctx->cred->thread_keyring, 1), ctx);
 		if (!IS_ERR(key_ref))
 			goto found;
 
@@ -358,10 +353,9 @@ key_ref_t search_my_process_keyrings(struct key_type *type,
 	}
 
 	/* search the process keyring second */
-	if (cred->process_keyring) {
+	if (ctx->cred->process_keyring) {
 		key_ref = keyring_search_aux(
-			make_key_ref(cred->process_keyring, 1),
-			cred, type, description, match, no_state_check);
+			make_key_ref(ctx->cred->process_keyring, 1), ctx);
 		if (!IS_ERR(key_ref))
 			goto found;
 
@@ -379,11 +373,11 @@ key_ref_t search_my_process_keyrings(struct key_type *type,
 	}
 
 	/* search the session keyring */
-	if (cred->session_keyring) {
+	if (ctx->cred->session_keyring) {
 		rcu_read_lock();
 		key_ref = keyring_search_aux(
-			make_key_ref(rcu_dereference(cred->session_keyring), 1),
-			cred, type, description, match, no_state_check);
+			make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
+			ctx);
 		rcu_read_unlock();
 
 		if (!IS_ERR(key_ref))
@@ -402,10 +396,10 @@ key_ref_t search_my_process_keyrings(struct key_type *type,
 		}
 	}
 	/* or search the user-session keyring */
-	else if (cred->user->session_keyring) {
+	else if (ctx->cred->user->session_keyring) {
 		key_ref = keyring_search_aux(
-			make_key_ref(cred->user->session_keyring, 1),
-			cred, type, description, match, no_state_check);
+			make_key_ref(ctx->cred->user->session_keyring, 1),
+			ctx);
 		if (!IS_ERR(key_ref))
 			goto found;
 
@@ -437,19 +431,14 @@ found:
  *
  * Return same as search_my_process_keyrings().
  */
-key_ref_t search_process_keyrings(struct key_type *type,
-				  const void *description,
-				  key_match_func_t match,
-				  bool no_state_check,
-				  const struct cred *cred)
+key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
 {
 	struct request_key_auth *rka;
 	key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
 
 	might_sleep();
 
-	key_ref = search_my_process_keyrings(type, description, match,
-					     no_state_check, cred);
+	key_ref = search_my_process_keyrings(ctx);
 	if (!IS_ERR(key_ref))
 		goto found;
 	err = key_ref;
@@ -458,19 +447,21 @@ key_ref_t search_process_keyrings(struct key_type *type,
 	 * search the keyrings of the process mentioned there
 	 * - we don't permit access to request_key auth keys via this method
 	 */
-	if (cred->request_key_auth &&
-	    cred == current_cred() &&
-	    type != &key_type_request_key_auth
+	if (ctx->cred->request_key_auth &&
+	    ctx->cred == current_cred() &&
+	    ctx->index_key.type != &key_type_request_key_auth
 	    ) {
+		const struct cred *cred = ctx->cred;
+
 		/* defend against the auth key being revoked */
 		down_read(&cred->request_key_auth->sem);
 
-		if (key_validate(cred->request_key_auth) == 0) {
-			rka = cred->request_key_auth->payload.data;
+		if (key_validate(ctx->cred->request_key_auth) == 0) {
+			rka = ctx->cred->request_key_auth->payload.data;
 
-			key_ref = search_process_keyrings(type, description,
-							  match, no_state_check,
-							  rka->cred);
+			ctx->cred = rka->cred;
+			key_ref = search_process_keyrings(ctx);
+			ctx->cred = cred;
 
 			up_read(&cred->request_key_auth->sem);
 
@@ -524,19 +515,23 @@ int lookup_user_key_possessed(const struct key *key, const void *target)
 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
 			  key_perm_t perm)
 {
+	struct keyring_search_context ctx = {
+		.match	= lookup_user_key_possessed,
+		.flags	= (KEYRING_SEARCH_NO_STATE_CHECK |
+			   KEYRING_SEARCH_LOOKUP_DIRECT),
+	};
 	struct request_key_auth *rka;
-	const struct cred *cred;
 	struct key *key;
 	key_ref_t key_ref, skey_ref;
 	int ret;
 
 try_again:
-	cred = get_current_cred();
+	ctx.cred = get_current_cred();
 	key_ref = ERR_PTR(-ENOKEY);
 
 	switch (id) {
 	case KEY_SPEC_THREAD_KEYRING:
-		if (!cred->thread_keyring) {
+		if (!ctx.cred->thread_keyring) {
 			if (!(lflags & KEY_LOOKUP_CREATE))
 				goto error;
 
@@ -548,13 +543,13 @@ try_again:
 			goto reget_creds;
 		}
 
-		key = cred->thread_keyring;
+		key = ctx.cred->thread_keyring;
 		atomic_inc(&key->usage);
 		key_ref = make_key_ref(key, 1);
 		break;
 
 	case KEY_SPEC_PROCESS_KEYRING:
-		if (!cred->process_keyring) {
+		if (!ctx.cred->process_keyring) {
 			if (!(lflags & KEY_LOOKUP_CREATE))
 				goto error;
 
@@ -566,13 +561,13 @@ try_again:
 			goto reget_creds;
 		}
 
-		key = cred->process_keyring;
+		key = ctx.cred->process_keyring;
 		atomic_inc(&key->usage);
 		key_ref = make_key_ref(key, 1);
 		break;
 
 	case KEY_SPEC_SESSION_KEYRING:
-		if (!cred->session_keyring) {
+		if (!ctx.cred->session_keyring) {
 			/* always install a session keyring upon access if one
 			 * doesn't exist yet */
 			ret = install_user_keyrings();
@@ -582,13 +577,13 @@ try_again:
 				ret = join_session_keyring(NULL);
 			else
 				ret = install_session_keyring(
-					cred->user->session_keyring);
+					ctx.cred->user->session_keyring);
 
 			if (ret < 0)
 				goto error;
 			goto reget_creds;
-		} else if (cred->session_keyring ==
-			   cred->user->session_keyring &&
+		} else if (ctx.cred->session_keyring ==
+			   ctx.cred->user->session_keyring &&
 			   lflags & KEY_LOOKUP_CREATE) {
 			ret = join_session_keyring(NULL);
 			if (ret < 0)
@@ -597,32 +592,32 @@ try_again:
 		}
 
 		rcu_read_lock();
-		key = rcu_dereference(cred->session_keyring);
+		key = rcu_dereference(ctx.cred->session_keyring);
 		atomic_inc(&key->usage);
 		rcu_read_unlock();
 		key_ref = make_key_ref(key, 1);
 		break;
 
 	case KEY_SPEC_USER_KEYRING:
-		if (!cred->user->uid_keyring) {
+		if (!ctx.cred->user->uid_keyring) {
 			ret = install_user_keyrings();
 			if (ret < 0)
 				goto error;
 		}
 
-		key = cred->user->uid_keyring;
+		key = ctx.cred->user->uid_keyring;
 		atomic_inc(&key->usage);
 		key_ref = make_key_ref(key, 1);
 		break;
 
 	case KEY_SPEC_USER_SESSION_KEYRING:
-		if (!cred->user->session_keyring) {
+		if (!ctx.cred->user->session_keyring) {
 			ret = install_user_keyrings();
 			if (ret < 0)
 				goto error;
 		}
 
-		key = cred->user->session_keyring;
+		key = ctx.cred->user->session_keyring;
 		atomic_inc(&key->usage);
 		key_ref = make_key_ref(key, 1);
 		break;
@@ -633,7 +628,7 @@ try_again:
 		goto error;
 
 	case KEY_SPEC_REQKEY_AUTH_KEY:
-		key = cred->request_key_auth;
+		key = ctx.cred->request_key_auth;
 		if (!key)
 			goto error;
 
@@ -642,20 +637,20 @@ try_again:
 		break;
 
 	case KEY_SPEC_REQUESTOR_KEYRING:
-		if (!cred->request_key_auth)
+		if (!ctx.cred->request_key_auth)
 			goto error;
 
-		down_read(&cred->request_key_auth->sem);
+		down_read(&ctx.cred->request_key_auth->sem);
 		if (test_bit(KEY_FLAG_REVOKED,
-			     &cred->request_key_auth->flags)) {
+			     &ctx.cred->request_key_auth->flags)) {
 			key_ref = ERR_PTR(-EKEYREVOKED);
 			key = NULL;
 		} else {
-			rka = cred->request_key_auth->payload.data;
+			rka = ctx.cred->request_key_auth->payload.data;
 			key = rka->dest_keyring;
 			atomic_inc(&key->usage);
 		}
-		up_read(&cred->request_key_auth->sem);
+		up_read(&ctx.cred->request_key_auth->sem);
 		if (!key)
 			goto error;
 		key_ref = make_key_ref(key, 1);
@@ -675,9 +670,13 @@ try_again:
 		key_ref = make_key_ref(key, 0);
 
 		/* check to see if we possess the key */
-		skey_ref = search_process_keyrings(key->type, key,
-						   lookup_user_key_possessed,
-						   true, cred);
+		ctx.index_key.type		= key->type;
+		ctx.index_key.description	= key->description;
+		ctx.index_key.desc_len		= strlen(key->description);
+		ctx.match_data			= key;
+		kdebug("check possessed");
+		skey_ref = search_process_keyrings(&ctx);
+		kdebug("possessed=%p", skey_ref);
 
 		if (!IS_ERR(skey_ref)) {
 			key_put(key);
@@ -717,14 +716,14 @@ try_again:
 		goto invalid_key;
 
 	/* check the permissions */
-	ret = key_task_permission(key_ref, cred, perm);
+	ret = key_task_permission(key_ref, ctx.cred, perm);
 	if (ret < 0)
 		goto invalid_key;
 
 	key->last_used_at = current_kernel_time().tv_sec;
 
 error:
-	put_cred(cred);
+	put_cred(ctx.cred);
 	return key_ref;
 
 invalid_key:
@@ -735,7 +734,7 @@ invalid_key:
 	/* if we attempted to install a keyring, then it may have caused new
 	 * creds to be installed */
 reget_creds:
-	put_cred(cred);
+	put_cred(ctx.cred);
 	goto try_again;
 }
 
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 586cb79..ab75df4 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -345,38 +345,34 @@ static void construct_get_dest_keyring(struct key **_dest_keyring)
  * May return a key that's already under construction instead if there was a
  * race between two thread calling request_key().
  */
-static int construct_alloc_key(struct key_type *type,
-			       const char *description,
+static int construct_alloc_key(struct keyring_search_context *ctx,
 			       struct key *dest_keyring,
 			       unsigned long flags,
 			       struct key_user *user,
 			       struct key **_key)
 {
-	const struct keyring_index_key index_key = {
-		.type		= type,
-		.description	= description,
-		.desc_len	= strlen(description),
-	};
-	const struct cred *cred = current_cred();
 	unsigned long prealloc;
 	struct key *key;
 	key_perm_t perm;
 	key_ref_t key_ref;
 	int ret;
 
-	kenter("%s,%s,,,", type->name, description);
+	kenter("%s,%s,,,",
+	       ctx->index_key.type->name, ctx->index_key.description);
 
 	*_key = NULL;
 	mutex_lock(&user->cons_lock);
 
 	perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 	perm |= KEY_USR_VIEW;
-	if (type->read)
+	if (ctx->index_key.type->read)
 		perm |= KEY_POS_READ;
-	if (type == &key_type_keyring || type->update)
+	if (ctx->index_key.type == &key_type_keyring ||
+	    ctx->index_key.type->update)
 		perm |= KEY_POS_WRITE;
 
-	key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
+	key = key_alloc(ctx->index_key.type, ctx->index_key.description,
+			ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
 			perm, flags);
 	if (IS_ERR(key))
 		goto alloc_failed;
@@ -384,7 +380,7 @@ static int construct_alloc_key(struct key_type *type,
 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 
 	if (dest_keyring) {
-		ret = __key_link_begin(dest_keyring, &index_key, &prealloc);
+		ret = __key_link_begin(dest_keyring, &ctx->index_key, &prealloc);
 		if (ret < 0)
 			goto link_prealloc_failed;
 	}
@@ -394,8 +390,7 @@ static int construct_alloc_key(struct key_type *type,
 	 * waited for locks */
 	mutex_lock(&key_construction_mutex);
 
-	key_ref = search_process_keyrings(type, description, type->match,
-					  false, cred);
+	key_ref = search_process_keyrings(ctx);
 	if (!IS_ERR(key_ref))
 		goto key_already_present;
 
@@ -404,7 +399,7 @@ static int construct_alloc_key(struct key_type *type,
 
 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
-		__key_link_end(dest_keyring, &index_key, prealloc);
+		__key_link_end(dest_keyring, &ctx->index_key, prealloc);
 	mutex_unlock(&user->cons_lock);
 	*_key = key;
 	kleave(" = 0 [%d]", key_serial(key));
@@ -420,7 +415,7 @@ key_already_present:
 		ret = __key_link_check_live_key(dest_keyring, key);
 		if (ret == 0)
 			__key_link(dest_keyring, key, &prealloc);
-		__key_link_end(dest_keyring, &index_key, prealloc);
+		__key_link_end(dest_keyring, &ctx->index_key, prealloc);
 		if (ret < 0)
 			goto link_check_failed;
 	}
@@ -449,8 +444,7 @@ alloc_failed:
 /*
  * Commence key construction.
  */
-static struct key *construct_key_and_link(struct key_type *type,
-					  const char *description,
+static struct key *construct_key_and_link(struct keyring_search_context *ctx,
 					  const char *callout_info,
 					  size_t callout_len,
 					  void *aux,
@@ -469,8 +463,7 @@ static struct key *construct_key_and_link(struct key_type *type,
 
 	construct_get_dest_keyring(&dest_keyring);
 
-	ret = construct_alloc_key(type, description, dest_keyring, flags, user,
-				  &key);
+	ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
 	key_user_put(user);
 
 	if (ret == 0) {
@@ -534,18 +527,24 @@ struct key *request_key_and_link(struct key_type *type,
 				 struct key *dest_keyring,
 				 unsigned long flags)
 {
-	const struct cred *cred = current_cred();
+	struct keyring_search_context ctx = {
+		.index_key.type		= type,
+		.index_key.description	= description,
+		.cred			= current_cred(),
+		.match			= type->match,
+		.match_data		= description,
+		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
+	};
 	struct key *key;
 	key_ref_t key_ref;
 	int ret;
 
 	kenter("%s,%s,%p,%zu,%p,%p,%lx",
-	       type->name, description, callout_info, callout_len, aux,
-	       dest_keyring, flags);
+	       ctx.index_key.type->name, ctx.index_key.description,
+	       callout_info, callout_len, aux, dest_keyring, flags);
 
 	/* search all the process keyrings for a key */
-	key_ref = search_process_keyrings(type, description, type->match,
-					  false, cred);
+	key_ref = search_process_keyrings(&ctx);
 
 	if (!IS_ERR(key_ref)) {
 		key = key_ref_to_ptr(key_ref);
@@ -568,9 +567,8 @@ struct key *request_key_and_link(struct key_type *type,
 		if (!callout_info)
 			goto error;
 
-		key = construct_key_and_link(type, description, callout_info,
-					     callout_len, aux, dest_keyring,
-					     flags);
+		key = construct_key_and_link(&ctx, callout_info, callout_len,
+					     aux, dest_keyring, flags);
 	}
 
 error:
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 92077de..8d09852 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -239,15 +239,17 @@ static int key_get_instantiation_authkey_match(const struct key *key,
  */
 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 {
-	const struct cred *cred = current_cred();
+	struct keyring_search_context ctx = {
+		.index_key.type		= &key_type_request_key_auth,
+		.cred			= current_cred(),
+		.match			= key_get_instantiation_authkey_match,
+		.match_data		= (void *)(unsigned long)target_id,
+		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
+	};
 	struct key *authkey;
 	key_ref_t authkey_ref;
 
-	authkey_ref = search_process_keyrings(
-		&key_type_request_key_auth,
-		(void *) (unsigned long) target_id,
-		key_get_instantiation_authkey_match,
-		false, cred);
+	authkey_ref = search_process_keyrings(&ctx);
 
 	if (IS_ERR(authkey_ref)) {
 		authkey = ERR_CAST(authkey_ref);
diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index 55dc889..faa2cae 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -25,14 +25,15 @@ static int logon_vet_description(const char *desc);
  * arbitrary blob of data as the payload
  */
 struct key_type key_type_user = {
-	.name		= "user",
-	.instantiate	= user_instantiate,
-	.update		= user_update,
-	.match		= user_match,
-	.revoke		= user_revoke,
-	.destroy	= user_destroy,
-	.describe	= user_describe,
-	.read		= user_read,
+	.name			= "user",
+	.def_lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
+	.instantiate		= user_instantiate,
+	.update			= user_update,
+	.match			= user_match,
+	.revoke			= user_revoke,
+	.destroy		= user_destroy,
+	.describe		= user_describe,
+	.read			= user_read,
 };
 
 EXPORT_SYMBOL_GPL(key_type_user);
@@ -45,6 +46,7 @@ EXPORT_SYMBOL_GPL(key_type_user);
  */
 struct key_type key_type_logon = {
 	.name			= "logon",
+	.def_lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
 	.instantiate		= user_instantiate,
 	.update			= user_update,
 	.match			= user_match,
-- 
1.8.3.1


From 4dffed72b92a305bcdbb73b719570d8f4ec53f46 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:52 +0100
Subject: [PATCH 06/10] KEYS: Search for auth-key by name rather than target
 key ID

Search for auth-key by name rather than by target key ID as, in a future
patch, we'll by searching directly by index key in preference to iteration
over all keys.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 security/keys/request_key_auth.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 8d09852..7495a93 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <asm/uaccess.h>
 #include "internal.h"
+#include <keys/user-type.h>
 
 static int request_key_auth_instantiate(struct key *,
 					struct key_preparsed_payload *);
@@ -222,33 +223,25 @@ error_alloc:
 }
 
 /*
- * See if an authorisation key is associated with a particular key.
- */
-static int key_get_instantiation_authkey_match(const struct key *key,
-					       const void *_id)
-{
-	struct request_key_auth *rka = key->payload.data;
-	key_serial_t id = (key_serial_t)(unsigned long) _id;
-
-	return rka->target_key->serial == id;
-}
-
-/*
  * Search the current process's keyrings for the authorisation key for
  * instantiation of a key.
  */
 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 {
+	char description[16];
 	struct keyring_search_context ctx = {
 		.index_key.type		= &key_type_request_key_auth,
+		.index_key.description	= description,
 		.cred			= current_cred(),
-		.match			= key_get_instantiation_authkey_match,
-		.match_data		= (void *)(unsigned long)target_id,
+		.match			= user_match,
+		.match_data		= description,
 		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
 	};
 	struct key *authkey;
 	key_ref_t authkey_ref;
 
+	sprintf(description, "%x", target_id);
+
 	authkey_ref = search_process_keyrings(&ctx);
 
 	if (IS_ERR(authkey_ref)) {
-- 
1.8.3.1


From 5f3c76b0923620ddd5294270ac478819f06f21d1 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:53 +0100
Subject: [PATCH 07/10] KEYS: Define a __key_get() wrapper to use rather than
 atomic_inc()

Define a __key_get() wrapper to use rather than atomic_inc() on the key usage
count as this makes it easier to hook in refcount error debugging.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 Documentation/security/keys.txt | 13 ++++++++-----
 include/linux/key.h             | 10 +++++++---
 security/keys/key.c             |  2 +-
 security/keys/keyring.c         |  6 +++---
 security/keys/process_keys.c    | 16 ++++++++--------
 5 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 9ede670..a4c33f1 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -960,14 +960,17 @@ payload contents" for more information.
     the argument will not be parsed.
 
 
-(*) Extra references can be made to a key by calling the following function:
+(*) Extra references can be made to a key by calling one of the following
+    functions:
 
+	struct key *__key_get(struct key *key);
 	struct key *key_get(struct key *key);
 
-    These need to be disposed of by calling key_put() when they've been
-    finished with. The key pointer passed in will be returned. If the pointer
-    is NULL or CONFIG_KEYS is not set then the key will not be dereferenced and
-    no increment will take place.
+    Keys so references will need to be disposed of by calling key_put() when
+    they've been finished with.  The key pointer passed in will be returned.
+
+    In the case of key_get(), if the pointer is NULL or CONFIG_KEYS is not set
+    then the key will not be dereferenced and no increment will take place.
 
 
 (*) A key's serial number can be obtained by calling:
diff --git a/include/linux/key.h b/include/linux/key.h
index d573e82..ef596c7 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -219,13 +219,17 @@ extern void key_revoke(struct key *key);
 extern void key_invalidate(struct key *key);
 extern void key_put(struct key *key);
 
-static inline struct key *key_get(struct key *key)
+static inline struct key *__key_get(struct key *key)
 {
-	if (key)
-		atomic_inc(&key->usage);
+	atomic_inc(&key->usage);
 	return key;
 }
 
+static inline struct key *key_get(struct key *key)
+{
+	return key ? __key_get(key) : key;
+}
+
 static inline void key_ref_put(key_ref_t key_ref)
 {
 	key_put(key_ref_to_ptr(key_ref));
diff --git a/security/keys/key.c b/security/keys/key.c
index 7e6bc39..1e23cc2 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -644,7 +644,7 @@ found:
 	/* this races with key_put(), but that doesn't matter since key_put()
 	 * doesn't actually change the key
 	 */
-	atomic_inc(&key->usage);
+	__key_get(key);
 
 error:
 	spin_unlock(&key_serial_lock);
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index b42f2d4..87eff32 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -479,7 +479,7 @@ not_this_keyring:
 
 	/* we found a viable match */
 found:
-	atomic_inc(&key->usage);
+	__key_get(key);
 	key->last_used_at = ctx->now.tv_sec;
 	keyring->last_used_at = ctx->now.tv_sec;
 	while (sp > 0)
@@ -573,7 +573,7 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 	return ERR_PTR(-ENOKEY);
 
 found:
-	atomic_inc(&key->usage);
+	__key_get(key);
 	keyring->last_used_at = key->last_used_at =
 		current_kernel_time().tv_sec;
 	rcu_read_unlock();
@@ -909,7 +909,7 @@ void __key_link(struct key *keyring, struct key *key,
 
 	klist = rcu_dereference_locked_keyring(keyring);
 
-	atomic_inc(&key->usage);
+	__key_get(key);
 	keyring->last_used_at = key->last_used_at =
 		current_kernel_time().tv_sec;
 
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index e68a3e0..68548ea 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -235,7 +235,7 @@ int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
 		if (IS_ERR(keyring))
 			return PTR_ERR(keyring);
 	} else {
-		atomic_inc(&keyring->usage);
+		__key_get(keyring);
 	}
 
 	/* install the keyring */
@@ -544,7 +544,7 @@ try_again:
 		}
 
 		key = ctx.cred->thread_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -562,7 +562,7 @@ try_again:
 		}
 
 		key = ctx.cred->process_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -593,7 +593,7 @@ try_again:
 
 		rcu_read_lock();
 		key = rcu_dereference(ctx.cred->session_keyring);
-		atomic_inc(&key->usage);
+		__key_get(key);
 		rcu_read_unlock();
 		key_ref = make_key_ref(key, 1);
 		break;
@@ -606,7 +606,7 @@ try_again:
 		}
 
 		key = ctx.cred->user->uid_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -618,7 +618,7 @@ try_again:
 		}
 
 		key = ctx.cred->user->session_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -632,7 +632,7 @@ try_again:
 		if (!key)
 			goto error;
 
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -648,7 +648,7 @@ try_again:
 		} else {
 			rka = ctx.cred->request_key_auth->payload.data;
 			key = rka->dest_keyring;
-			atomic_inc(&key->usage);
+			__key_get(key);
 		}
 		up_read(&ctx.cred->request_key_auth->sem);
 		if (!key)
-- 
1.8.3.1


From 99b0f3185570bb92a61952673b9933d9c1999508 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:53 +0100
Subject: [PATCH 08/10] KEYS: Drop the permissions argument from
 __keyring_search_one()

Drop the permissions argument from __keyring_search_one() as the only caller
passes 0 here - which causes all checks to be skipped.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 security/keys/internal.h | 3 +--
 security/keys/key.c      | 2 +-
 security/keys/keyring.c  | 9 +++------
 3 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/security/keys/internal.h b/security/keys/internal.h
index f4bf938..73950bf 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -99,8 +99,7 @@ extern void __key_link_end(struct key *keyring,
 			   unsigned long prealloc);
 
 extern key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-				      const struct keyring_index_key *index_key,
-				      key_perm_t perm);
+				      const struct keyring_index_key *index_key);
 
 extern struct key *keyring_search_instkey(struct key *keyring,
 					  key_serial_t target_id);
diff --git a/security/keys/key.c b/security/keys/key.c
index 1e23cc2..7d716b8 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -847,7 +847,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	 * update that instead if possible
 	 */
 	if (index_key.type->update) {
-		key_ref = __keyring_search_one(keyring_ref, &index_key, 0);
+		key_ref = __keyring_search_one(keyring_ref, &index_key);
 		if (!IS_ERR(key_ref))
 			goto found_matching_key;
 	}
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 87eff32..eeef1a0 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -531,15 +531,14 @@ EXPORT_SYMBOL(keyring_search);
  * RCU is used to make it unnecessary to lock the keyring key list here.
  *
  * Returns a pointer to the found key with usage count incremented if
- * successful and returns -ENOKEY if not found.  Revoked keys and keys not
- * providing the requested permission are skipped over.
+ * successful and returns -ENOKEY if not found.  Revoked and invalidated keys
+ * are skipped over.
  *
  * If successful, the possession indicator is propagated from the keyring ref
  * to the returned key reference.
  */
 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-			       const struct keyring_index_key *index_key,
-			       key_perm_t perm)
+			       const struct keyring_index_key *index_key)
 {
 	struct keyring_list *klist;
 	struct key *keyring, *key;
@@ -560,8 +559,6 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 			if (key->type == index_key->type &&
 			    (!key->type->match ||
 			     key->type->match(key, index_key->description)) &&
-			    key_permission(make_key_ref(key, possessed),
-					   perm) == 0 &&
 			    !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
 					    (1 << KEY_FLAG_REVOKED)))
 			    )
-- 
1.8.3.1


From cb720b39e41e62d55bf1e5f8243d78643d31154d Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:53 +0100
Subject: [PATCH 09/10] Add a generic associative array implementation.

Add a generic associative array implementation that can be used as the
container for keyrings, thereby massively increasing the capacity available
whilst also speeding up searching in keyrings that contain a lot of keys.

This may also be useful in FS-Cache for tracking cookies.

Documentation is added into Documentation/associative_array.txt

Some of the properties of the implementation are:

 (1) Objects are opaque pointers.  The implementation does not care where they
     point (if anywhere) or what they point to (if anything).

     [!] NOTE: Pointers to objects _must_ be zero in the two least significant
     	       bits.

 (2) Objects do not need to contain linkage blocks for use by the array.  This
     permits an object to be located in multiple arrays simultaneously.
     Rather, the array is made up of metadata blocks that point to objects.

 (3) Objects are labelled as being one of two types (the type is a bool value).
     This information is stored in the array, but has no consequence to the
     array itself or its algorithms.

 (4) Objects require index keys to locate them within the array.

 (5) Index keys must be unique.  Inserting an object with the same key as one
     already in the array will replace the old object.

 (6) Index keys can be of any length and can be of different lengths.

 (7) Index keys should encode the length early on, before any variation due to
     length is seen.

 (8) Index keys can include a hash to scatter objects throughout the array.

 (9) The array can iterated over.  The objects will not necessarily come out in
     key order.

(10) The array can be iterated whilst it is being modified, provided the RCU
     readlock is being held by the iterator.  Note, however, under these
     circumstances, some objects may be seen more than once.  If this is a
     problem, the iterator should lock against modification.  Objects will not
     be missed, however, unless deleted.

(11) Objects in the array can be looked up by means of their index key.

(12) Objects can be looked up whilst the array is being modified, provided the
     RCU readlock is being held by the thread doing the look up.

The implementation uses a tree of 16-pointer nodes internally that are indexed
on each level by nibbles from the index key.  To improve memory efficiency,
shortcuts can be emplaced to skip over what would otherwise be a series of
single-occupancy nodes.  Further, nodes pack leaf object pointers into spare
space in the node rather than making an extra branch until as such time an
object needs to be added to a full node.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 Documentation/assoc_array.txt    |  574 +++++++++++++
 include/linux/assoc_array.h      |   92 ++
 include/linux/assoc_array_priv.h |  182 ++++
 lib/Kconfig                      |   14 +
 lib/Makefile                     |    1 +
 lib/assoc_array.c                | 1745 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 2608 insertions(+)
 create mode 100644 Documentation/assoc_array.txt
 create mode 100644 include/linux/assoc_array.h
 create mode 100644 include/linux/assoc_array_priv.h
 create mode 100644 lib/assoc_array.c

diff --git a/Documentation/assoc_array.txt b/Documentation/assoc_array.txt
new file mode 100644
index 0000000..f4faec0
--- /dev/null
+++ b/Documentation/assoc_array.txt
@@ -0,0 +1,574 @@
+		   ========================================
+		   GENERIC ASSOCIATIVE ARRAY IMPLEMENTATION
+		   ========================================
+
+Contents:
+
+ - Overview.
+
+ - The public API.
+   - Edit script.
+   - Operations table.
+   - Manipulation functions.
+   - Access functions.
+   - Index key form.
+
+ - Internal workings.
+   - Basic internal tree layout.
+   - Shortcuts.
+   - Splitting and collapsing nodes.
+   - Non-recursive iteration.
+   - Simultaneous alteration and iteration.
+
+
+========
+OVERVIEW
+========
+
+This associative array implementation is an object container with the following
+properties:
+
+ (1) Objects are opaque pointers.  The implementation does not care where they
+     point (if anywhere) or what they point to (if anything).
+
+     [!] NOTE: Pointers to objects _must_ be zero in the least significant bit.
+
+ (2) Objects do not need to contain linkage blocks for use by the array.  This
+     permits an object to be located in multiple arrays simultaneously.
+     Rather, the array is made up of metadata blocks that point to objects.
+
+ (3) Objects require index keys to locate them within the array.
+
+ (4) Index keys must be unique.  Inserting an object with the same key as one
+     already in the array will replace the old object.
+
+ (5) Index keys can be of any length and can be of different lengths.
+
+ (6) Index keys should encode the length early on, before any variation due to
+     length is seen.
+
+ (7) Index keys can include a hash to scatter objects throughout the array.
+
+ (8) The array can iterated over.  The objects will not necessarily come out in
+     key order.
+
+ (9) The array can be iterated over whilst it is being modified, provided the
+     RCU readlock is being held by the iterator.  Note, however, under these
+     circumstances, some objects may be seen more than once.  If this is a
+     problem, the iterator should lock against modification.  Objects will not
+     be missed, however, unless deleted.
+
+(10) Objects in the array can be looked up by means of their index key.
+
+(11) Objects can be looked up whilst the array is being modified, provided the
+     RCU readlock is being held by the thread doing the look up.
+
+The implementation uses a tree of 16-pointer nodes internally that are indexed
+on each level by nibbles from the index key in the same manner as in a radix
+tree.  To improve memory efficiency, shortcuts can be emplaced to skip over
+what would otherwise be a series of single-occupancy nodes.  Further, nodes
+pack leaf object pointers into spare space in the node rather than making an
+extra branch until as such time an object needs to be added to a full node.
+
+
+==============
+THE PUBLIC API
+==============
+
+The public API can be found in <linux/assoc_array.h>.  The associative array is
+rooted on the following structure:
+
+	struct assoc_array {
+		...
+	};
+
+The code is selected by enabling CONFIG_ASSOCIATIVE_ARRAY.
+
+
+EDIT SCRIPT
+-----------
+
+The insertion and deletion functions produce an 'edit script' that can later be
+applied to effect the changes without risking ENOMEM.  This retains the
+preallocated metadata blocks that will be installed in the internal tree and
+keeps track of the metadata blocks that will be removed from the tree when the
+script is applied.
+
+This is also used to keep track of dead blocks and dead objects after the
+script has been applied so that they can be freed later.  The freeing is done
+after an RCU grace period has passed - thus allowing access functions to
+proceed under the RCU read lock.
+
+The script appears as outside of the API as a pointer of the type:
+
+	struct assoc_array_edit;
+
+There are two functions for dealing with the script:
+
+ (1) Apply an edit script.
+
+	void assoc_array_apply_edit(struct assoc_array_edit *edit);
+
+     This will perform the edit functions, interpolating various write barriers
+     to permit accesses under the RCU read lock to continue.  The edit script
+     will then be passed to call_rcu() to free it and any dead stuff it points
+     to.
+
+ (2) Cancel an edit script.
+
+	void assoc_array_cancel_edit(struct assoc_array_edit *edit);
+
+     This frees the edit script and all preallocated memory immediately.  If
+     this was for insertion, the new object is _not_ released by this function,
+     but must rather be released by the caller.
+
+These functions are guaranteed not to fail.
+
+
+OPERATIONS TABLE
+----------------
+
+Various functions take a table of operations:
+
+	struct assoc_array_ops {
+		...
+	};
+
+This points to a number of methods, all of which need to be provided:
+
+ (1) Get a chunk of index key from caller data:
+
+	unsigned long (*get_key_chunk)(const void *index_key, int level);
+
+     This should return a chunk of caller-supplied index key starting at the
+     *bit* position given by the level argument.  The level argument will be a
+     multiple of ASSOC_ARRAY_KEY_CHUNK_SIZE and the function should return
+     ASSOC_ARRAY_KEY_CHUNK_SIZE bits.  No error is possible.
+
+
+ (2) Get a chunk of an object's index key.
+
+	unsigned long (*get_object_key_chunk)(const void *object, int level);
+
+     As the previous function, but gets its data from an object in the array
+     rather than from a caller-supplied index key.
+
+
+ (3) See if this is the object we're looking for.
+
+	bool (*compare_object)(const void *object, const void *index_key);
+
+     Compare the object against an index key and return true if it matches and
+     false if it doesn't.
+
+
+ (4) Diff the index keys of two objects.
+
+	int (*diff_objects)(const void *a, const void *b);
+
+     Return the bit position at which the index keys of two objects differ or
+     -1 if they are the same.
+
+
+ (5) Free an object.
+
+	void (*free_object)(void *object);
+
+     Free the specified object.  Note that this may be called an RCU grace
+     period after assoc_array_apply_edit() was called, so synchronize_rcu() may
+     be necessary on module unloading.
+
+
+MANIPULATION FUNCTIONS
+----------------------
+
+There are a number of functions for manipulating an associative array:
+
+ (1) Initialise an associative array.
+
+	void assoc_array_init(struct assoc_array *array);
+
+     This initialises the base structure for an associative array.  It can't
+     fail.
+
+
+ (2) Insert/replace an object in an associative array.
+
+	struct assoc_array_edit *
+	assoc_array_insert(struct assoc_array *array,
+			   const struct assoc_array_ops *ops,
+			   const void *index_key,
+			   void *object);
+
+     This inserts the given object into the array.  Note that the least
+     significant bit of the pointer must be zero as it's used to type-mark
+     pointers internally.
+
+     If an object already exists for that key then it will be replaced with the
+     new object and the old one will be freed automatically.
+
+     The index_key argument should hold index key information and is
+     passed to the methods in the ops table when they are called.
+
+     This function makes no alteration to the array itself, but rather returns
+     an edit script that must be applied.  -ENOMEM is returned in the case of
+     an out-of-memory error.
+
+     The caller should lock exclusively against other modifiers of the array.
+
+
+ (3) Delete an object from an associative array.
+
+	struct assoc_array_edit *
+	assoc_array_delete(struct assoc_array *array,
+			   const struct assoc_array_ops *ops,
+			   const void *index_key);
+
+     This deletes an object that matches the specified data from the array.
+
+     The index_key argument should hold index key information and is
+     passed to the methods in the ops table when they are called.
+
+     This function makes no alteration to the array itself, but rather returns
+     an edit script that must be applied.  -ENOMEM is returned in the case of
+     an out-of-memory error.  NULL will be returned if the specified object is
+     not found within the array.
+
+     The caller should lock exclusively against other modifiers of the array.
+
+
+ (4) Delete all objects from an associative array.
+
+	struct assoc_array_edit *
+	assoc_array_clear(struct assoc_array *array,
+			  const struct assoc_array_ops *ops);
+
+     This deletes all the objects from an associative array and leaves it
+     completely empty.
+
+     This function makes no alteration to the array itself, but rather returns
+     an edit script that must be applied.  -ENOMEM is returned in the case of
+     an out-of-memory error.
+
+     The caller should lock exclusively against other modifiers of the array.
+
+
+ (5) Destroy an associative array, deleting all objects.
+
+	void assoc_array_destroy(struct assoc_array *array,
+				 const struct assoc_array_ops *ops);
+
+     This destroys the contents of the associative array and leaves it
+     completely empty.  It is not permitted for another thread to be traversing
+     the array under the RCU read lock at the same time as this function is
+     destroying it as no RCU deferral is performed on memory release -
+     something that would require memory to be allocated.
+
+     The caller should lock exclusively against other modifiers and accessors
+     of the array.
+
+
+ (6) Garbage collect an associative array.
+
+	int assoc_array_gc(struct assoc_array *array,
+			   const struct assoc_array_ops *ops,
+			   bool (*iterator)(void *object, void *iterator_data),
+			   void *iterator_data);
+
+     This iterates over the objects in an associative array and passes each one
+     to iterator().  If iterator() returns true, the object is kept.  If it
+     returns false, the object will be freed.  If the iterator() function
+     returns true, it must perform any appropriate refcount incrementing on the
+     object before returning.
+
+     The internal tree will be packed down if possible as part of the iteration
+     to reduce the number of nodes in it.
+
+     The iterator_data is passed directly to iterator() and is otherwise
+     ignored by the function.
+
+     The function will return 0 if successful and -ENOMEM if there wasn't
+     enough memory.
+
+     It is possible for other threads to iterate over or search the array under
+     the RCU read lock whilst this function is in progress.  The caller should
+     lock exclusively against other modifiers of the array.
+
+
+ACCESS FUNCTIONS
+----------------
+
+There are two functions for accessing an associative array:
+
+ (1) Iterate over all the objects in an associative array.
+
+	int assoc_array_iterate(const struct assoc_array *array,
+				int (*iterator)(const void *object,
+						void *iterator_data),
+				void *iterator_data);
+
+     This passes each object in the array to the iterator callback function.
+     iterator_data is private data for that function.
+
+     This may be used on an array at the same time as the array is being
+     modified, provided the RCU read lock is held.  Under such circumstances,
+     it is possible for the iteration function to see some objects twice.  If
+     this is a problem, then modification should be locked against.  The
+     iteration algorithm should not, however, miss any objects.
+
+     The function will return 0 if no objects were in the array or else it will
+     return the result of the last iterator function called.  Iteration stops
+     immediately if any call to the iteration function results in a non-zero
+     return.
+
+
+ (2) Find an object in an associative array.
+
+	void *assoc_array_find(const struct assoc_array *array,
+			       const struct assoc_array_ops *ops,
+			       const void *index_key);
+
+     This walks through the array's internal tree directly to the object
+     specified by the index key..
+
+     This may be used on an array at the same time as the array is being
+     modified, provided the RCU read lock is held.
+
+     The function will return the object if found (and set *_type to the object
+     type) or will return NULL if the object was not found.
+
+
+INDEX KEY FORM
+--------------
+
+The index key can be of any form, but since the algorithms aren't told how long
+the key is, it is strongly recommended that the index key includes its length
+very early on before any variation due to the length would have an effect on
+comparisons.
+
+This will cause leaves with different length keys to scatter away from each
+other - and those with the same length keys to cluster together.
+
+It is also recommended that the index key begin with a hash of the rest of the
+key to maximise scattering throughout keyspace.
+
+The better the scattering, the wider and lower the internal tree will be.
+
+Poor scattering isn't too much of a problem as there are shortcuts and nodes
+can contain mixtures of leaves and metadata pointers.
+
+The index key is read in chunks of machine word.  Each chunk is subdivided into
+one nibble (4 bits) per level, so on a 32-bit CPU this is good for 8 levels and
+on a 64-bit CPU, 16 levels.  Unless the scattering is really poor, it is
+unlikely that more than one word of any particular index key will have to be
+used.
+
+
+=================
+INTERNAL WORKINGS
+=================
+
+The associative array data structure has an internal tree.  This tree is
+constructed of two types of metadata blocks: nodes and shortcuts.
+
+A node is an array of slots.  Each slot can contain one of four things:
+
+ (*) A NULL pointer, indicating that the slot is empty.
+
+ (*) A pointer to an object (a leaf).
+
+ (*) A pointer to a node at the next level.
+
+ (*) A pointer to a shortcut.
+
+
+BASIC INTERNAL TREE LAYOUT
+--------------------------
+
+Ignoring shortcuts for the moment, the nodes form a multilevel tree.  The index
+key space is strictly subdivided by the nodes in the tree and nodes occur on
+fixed levels.  For example:
+
+ Level:	0		1		2		3
+	===============	===============	===============	===============
+							NODE D
+			NODE B		NODE C	+------>+---+
+		+------>+---+	+------>+---+	|	| 0 |
+	NODE A	|	| 0 |	|	| 0 |	|	+---+
+	+---+	|	+---+	|	+---+	|	:   :
+	| 0 |	|	:   :	|	:   :	|	+---+
+	+---+	|	+---+	|	+---+	|	| f |
+	| 1 |---+	| 3 |---+	| 7 |---+	+---+
+	+---+		+---+		+---+
+	:   :		:   :		| 8 |---+
+	+---+		+---+		+---+	|	NODE E
+	| e |---+	| f |		:   :   +------>+---+
+	+---+	|	+---+		+---+		| 0 |
+	| f |	|			| f |		+---+
+	+---+	|			+---+		:   :
+		|	NODE F				+---+
+		+------>+---+				| f |
+			| 0 |		NODE G		+---+
+			+---+	+------>+---+
+			:   :	|	| 0 |
+			+---+	|	+---+
+			| 6 |---+	:   :
+			+---+		+---+
+			:   :		| f |
+			+---+		+---+
+			| f |
+			+---+
+
+In the above example, there are 7 nodes (A-G), each with 16 slots (0-f).
+Assuming no other meta data nodes in the tree, the key space is divided thusly:
+
+	KEY PREFIX	NODE
+	==========	====
+	137*		D
+	138*		E
+	13[0-69-f]*	C
+	1[0-24-f]*	B
+	e6*		G
+	e[0-57-f]*	F
+	[02-df]*	A
+
+So, for instance, keys with the following example index keys will be found in
+the appropriate nodes:
+
+	INDEX KEY	PREFIX	NODE
+	===============	=======	====
+	13694892892489	13	C
+	13795289025897	137	D
+	13889dde88793	138	E
+	138bbb89003093	138	E
+	1394879524789	12	C
+	1458952489	1	B
+	9431809de993ba	-	A
+	b4542910809cd	-	A
+	e5284310def98	e	F
+	e68428974237	e6	G
+	e7fffcbd443	e	F
+	f3842239082	-	A
+
+To save memory, if a node can hold all the leaves in its portion of keyspace,
+then the node will have all those leaves in it and will not have any metadata
+pointers - even if some of those leaves would like to be in the same slot.
+
+A node can contain a heterogeneous mix of leaves and metadata pointers.
+Metadata pointers must be in the slots that match their subdivisions of key
+space.  The leaves can be in any slot not occupied by a metadata pointer.  It
+is guaranteed that none of the leaves in a node will match a slot occupied by a
+metadata pointer.  If the metadata pointer is there, any leaf whose key matches
+the metadata key prefix must be in the subtree that the metadata pointer points
+to.
+
+In the above example list of index keys, node A will contain:
+
+	SLOT	CONTENT		INDEX KEY (PREFIX)
+	====	===============	==================
+	1	PTR TO NODE B	1*
+	any	LEAF		9431809de993ba
+	any	LEAF		b4542910809cd
+	e	PTR TO NODE F	e*
+	any	LEAF		f3842239082
+
+and node B:
+
+	3	PTR TO NODE C	13*
+	any	LEAF		1458952489
+
+
+SHORTCUTS
+---------
+
+Shortcuts are metadata records that jump over a piece of keyspace.  A shortcut
+is a replacement for a series of single-occupancy nodes ascending through the
+levels.  Shortcuts exist to save memory and to speed up traversal.
+
+It is possible for the root of the tree to be a shortcut - say, for example,
+the tree contains at least 17 nodes all with key prefix '1111'.  The insertion
+algorithm will insert a shortcut to skip over the '1111' keyspace in a single
+bound and get to the fourth level where these actually become different.
+
+
+SPLITTING AND COLLAPSING NODES
+------------------------------
+
+Each node has a maximum capacity of 16 leaves and metadata pointers.  If the
+insertion algorithm finds that it is trying to insert a 17th object into a
+node, that node will be split such that at least two leaves that have a common
+key segment at that level end up in a separate node rooted on that slot for
+that common key segment.
+
+If the leaves in a full node and the leaf that is being inserted are
+sufficiently similar, then a shortcut will be inserted into the tree.
+
+When the number of objects in the subtree rooted at a node falls to 16 or
+fewer, then the subtree will be collapsed down to a single node - and this will
+ripple towards the root if possible.
+
+
+NON-RECURSIVE ITERATION
+-----------------------
+
+Each node and shortcut contains a back pointer to its parent and the number of
+slot in that parent that points to it.  None-recursive iteration uses these to
+proceed rootwards through the tree, going to the parent node, slot N + 1 to
+make sure progress is made without the need for a stack.
+
+The backpointers, however, make simultaneous alteration and iteration tricky.
+
+
+SIMULTANEOUS ALTERATION AND ITERATION
+-------------------------------------
+
+There are a number of cases to consider:
+
+ (1) Simple insert/replace.  This involves simply replacing a NULL or old
+     matching leaf pointer with the pointer to the new leaf after a barrier.
+     The metadata blocks don't change otherwise.  An old leaf won't be freed
+     until after the RCU grace period.
+
+ (2) Simple delete.  This involves just clearing an old matching leaf.  The
+     metadata blocks don't change otherwise.  The old leaf won't be freed until
+     after the RCU grace period.
+
+ (3) Insertion replacing part of a subtree that we haven't yet entered.  This
+     may involve replacement of part of that subtree - but that won't affect
+     the iteration as we won't have reached the pointer to it yet and the
+     ancestry blocks are not replaced (the layout of those does not change).
+
+ (4) Insertion replacing nodes that we're actively processing.  This isn't a
+     problem as we've passed the anchoring pointer and won't switch onto the
+     new layout until we follow the back pointers - at which point we've
+     already examined the leaves in the replaced node (we iterate over all the
+     leaves in a node before following any of its metadata pointers).
+
+     We might, however, re-see some leaves that have been split out into a new
+     branch that's in a slot further along than we were at.
+
+ (5) Insertion replacing nodes that we're processing a dependent branch of.
+     This won't affect us until we follow the back pointers.  Similar to (4).
+
+ (6) Deletion collapsing a branch under us.  This doesn't affect us because the
+     back pointers will get us back to the parent of the new node before we
+     could see the new node.  The entire collapsed subtree is thrown away
+     unchanged - and will still be rooted on the same slot, so we shouldn't
+     process it a second time as we'll go back to slot + 1.
+
+Note:
+
+ (*) Under some circumstances, we need to simultaneously change the parent
+     pointer and the parent slot pointer on a node (say, for example, we
+     inserted another node before it and moved it up a level).  We cannot do
+     this without locking against a read - so we have to replace that node too.
+
+     However, when we're changing a shortcut into a node this isn't a problem
+     as shortcuts only have one slot and so the parent slot number isn't used
+     when traversing backwards over one.  This means that it's okay to change
+     the slot number first - provided suitable barriers are used to make sure
+     the parent slot number is read after the back pointer.
+
+Obsolete blocks and leaves are freed up after an RCU grace period has passed,
+so as long as anyone doing walking or iteration holds the RCU read lock, the
+old superstructure should not go away on them.
diff --git a/include/linux/assoc_array.h b/include/linux/assoc_array.h
new file mode 100644
index 0000000..9a193b8
--- /dev/null
+++ b/include/linux/assoc_array.h
@@ -0,0 +1,92 @@
+/* Generic associative array implementation.
+ *
+ * See Documentation/assoc_array.txt for information.
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_ASSOC_ARRAY_H
+#define _LINUX_ASSOC_ARRAY_H
+
+#ifdef CONFIG_ASSOCIATIVE_ARRAY
+
+#include <linux/types.h>
+
+#define ASSOC_ARRAY_KEY_CHUNK_SIZE BITS_PER_LONG /* Key data retrieved in chunks of this size */
+
+/*
+ * Generic associative array.
+ */
+struct assoc_array {
+	struct assoc_array_ptr	*root;		/* The node at the root of the tree */
+	unsigned long		nr_leaves_on_tree;
+};
+
+/*
+ * Operations on objects and index keys for use by array manipulation routines.
+ */
+struct assoc_array_ops {
+	/* Method to get a chunk of an index key from caller-supplied data */
+	unsigned long (*get_key_chunk)(const void *index_key, int level);
+
+	/* Method to get a piece of an object's index key */
+	unsigned long (*get_object_key_chunk)(const void *object, int level);
+
+	/* Is this the object we're looking for? */
+	bool (*compare_object)(const void *object, const void *index_key);
+
+	/* How different are two objects, to a bit position in their keys? (or
+	 * -1 if they're the same)
+	 */
+	int (*diff_objects)(const void *a, const void *b);
+
+	/* Method to free an object. */
+	void (*free_object)(void *object);
+};
+
+/*
+ * Access and manipulation functions.
+ */
+struct assoc_array_edit;
+
+static inline void assoc_array_init(struct assoc_array *array)
+{
+	array->root = NULL;
+	array->nr_leaves_on_tree = 0;
+}
+
+extern int assoc_array_iterate(const struct assoc_array *array,
+			       int (*iterator)(const void *object,
+					       void *iterator_data),
+			       void *iterator_data);
+extern void *assoc_array_find(const struct assoc_array *array,
+			      const struct assoc_array_ops *ops,
+			      const void *index_key);
+extern void assoc_array_destroy(struct assoc_array *array,
+				const struct assoc_array_ops *ops);
+extern struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
+						   const struct assoc_array_ops *ops,
+						   const void *index_key,
+						   void *object);
+extern void assoc_array_insert_set_object(struct assoc_array_edit *edit,
+					  void *object);
+extern struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
+						   const struct assoc_array_ops *ops,
+						   const void *index_key);
+extern struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
+						  const struct assoc_array_ops *ops);
+extern void assoc_array_apply_edit(struct assoc_array_edit *edit);
+extern void assoc_array_cancel_edit(struct assoc_array_edit *edit);
+extern int assoc_array_gc(struct assoc_array *array,
+			  const struct assoc_array_ops *ops,
+			  bool (*iterator)(void *object, void *iterator_data),
+			  void *iterator_data);
+
+#endif /* CONFIG_ASSOCIATIVE_ARRAY */
+#endif /* _LINUX_ASSOC_ARRAY_H */
diff --git a/include/linux/assoc_array_priv.h b/include/linux/assoc_array_priv.h
new file mode 100644
index 0000000..711275e
--- /dev/null
+++ b/include/linux/assoc_array_priv.h
@@ -0,0 +1,182 @@
+/* Private definitions for the generic associative array implementation.
+ *
+ * See Documentation/assoc_array.txt for information.
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_ASSOC_ARRAY_PRIV_H
+#define _LINUX_ASSOC_ARRAY_PRIV_H
+
+#ifdef CONFIG_ASSOCIATIVE_ARRAY
+
+#include <linux/assoc_array.h>
+
+#define ASSOC_ARRAY_FAN_OUT		16	/* Number of slots per node */
+#define ASSOC_ARRAY_FAN_MASK		(ASSOC_ARRAY_FAN_OUT - 1)
+#define ASSOC_ARRAY_LEVEL_STEP		(ilog2(ASSOC_ARRAY_FAN_OUT))
+#define ASSOC_ARRAY_LEVEL_STEP_MASK	(ASSOC_ARRAY_LEVEL_STEP - 1)
+#define ASSOC_ARRAY_KEY_CHUNK_MASK	(ASSOC_ARRAY_KEY_CHUNK_SIZE - 1)
+#define ASSOC_ARRAY_KEY_CHUNK_SHIFT	(ilog2(BITS_PER_LONG))
+
+/*
+ * Undefined type representing a pointer with type information in the bottom
+ * two bits.
+ */
+struct assoc_array_ptr;
+
+/*
+ * An N-way node in the tree.
+ *
+ * Each slot contains one of four things:
+ *
+ *	(1) Nothing (NULL).
+ *
+ *	(2) A leaf object (pointer types 0).
+ *
+ *	(3) A next-level node (pointer type 1, subtype 0).
+ *
+ *	(4) A shortcut (pointer type 1, subtype 1).
+ *
+ * The tree is optimised for search-by-ID, but permits reasonable iteration
+ * also.
+ *
+ * The tree is navigated by constructing an index key consisting of an array of
+ * segments, where each segment is ilog2(ASSOC_ARRAY_FAN_OUT) bits in size.
+ *
+ * The segments correspond to levels of the tree (the first segment is used at
+ * level 0, the second at level 1, etc.).
+ */
+struct assoc_array_node {
+	struct assoc_array_ptr	*back_pointer;
+	u8			parent_slot;
+	struct assoc_array_ptr	*slots[ASSOC_ARRAY_FAN_OUT];
+	unsigned long		nr_leaves_on_branch;
+};
+
+/*
+ * A shortcut through the index space out to where a collection of nodes/leaves
+ * with the same IDs live.
+ */
+struct assoc_array_shortcut {
+	struct assoc_array_ptr	*back_pointer;
+	int			parent_slot;
+	int			skip_to_level;
+	struct assoc_array_ptr	*next_node;
+	unsigned long		index_key[];
+};
+
+/*
+ * Preallocation cache.
+ */
+struct assoc_array_edit {
+	struct rcu_head			rcu;
+	struct assoc_array		*array;
+	const struct assoc_array_ops	*ops;
+	const struct assoc_array_ops	*ops_for_excised_subtree;
+	struct assoc_array_ptr		*leaf;
+	struct assoc_array_ptr		**leaf_p;
+	struct assoc_array_ptr		*dead_leaf;
+	struct assoc_array_ptr		*new_meta[3];
+	struct assoc_array_ptr		*excised_meta[1];
+	struct assoc_array_ptr		*excised_subtree;
+	struct assoc_array_ptr		**set_backpointers[ASSOC_ARRAY_FAN_OUT];
+	struct assoc_array_ptr		*set_backpointers_to;
+	struct assoc_array_node		*adjust_count_on;
+	long				adjust_count_by;
+	struct {
+		struct assoc_array_ptr	**ptr;
+		struct assoc_array_ptr	*to;
+	} set[2];
+	struct {
+		u8			*p;
+		u8			to;
+	} set_parent_slot[1];
+	u8				segment_cache[ASSOC_ARRAY_FAN_OUT + 1];
+};
+
+/*
+ * Internal tree member pointers are marked in the bottom one or two bits to
+ * indicate what type they are so that we don't have to look behind every
+ * pointer to see what it points to.
+ *
+ * We provide functions to test type annotations and to create and translate
+ * the annotated pointers.
+ */
+#define ASSOC_ARRAY_PTR_TYPE_MASK 0x1UL
+#define ASSOC_ARRAY_PTR_LEAF_TYPE 0x0UL	/* Points to leaf (or nowhere) */
+#define ASSOC_ARRAY_PTR_META_TYPE 0x1UL	/* Points to node or shortcut */
+#define ASSOC_ARRAY_PTR_SUBTYPE_MASK	0x2UL
+#define ASSOC_ARRAY_PTR_NODE_SUBTYPE	0x0UL
+#define ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE 0x2UL
+
+static inline bool assoc_array_ptr_is_meta(const struct assoc_array_ptr *x)
+{
+	return (unsigned long)x & ASSOC_ARRAY_PTR_TYPE_MASK;
+}
+static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
+{
+	return !assoc_array_ptr_is_meta(x);
+}
+static inline bool assoc_array_ptr_is_shortcut(const struct assoc_array_ptr *x)
+{
+	return (unsigned long)x & ASSOC_ARRAY_PTR_SUBTYPE_MASK;
+}
+static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
+{
+	return !assoc_array_ptr_is_shortcut(x);
+}
+
+static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
+{
+	return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
+}
+
+static inline
+unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
+{
+	return (unsigned long)x &
+		~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
+}
+static inline
+struct assoc_array_node *assoc_array_ptr_to_node(const struct assoc_array_ptr *x)
+{
+	return (struct assoc_array_node *)__assoc_array_ptr_to_meta(x);
+}
+static inline
+struct assoc_array_shortcut *assoc_array_ptr_to_shortcut(const struct assoc_array_ptr *x)
+{
+	return (struct assoc_array_shortcut *)__assoc_array_ptr_to_meta(x);
+}
+
+static inline
+struct assoc_array_ptr *__assoc_array_x_to_ptr(const void *p, unsigned long t)
+{
+	return (struct assoc_array_ptr *)((unsigned long)p | t);
+}
+static inline
+struct assoc_array_ptr *assoc_array_leaf_to_ptr(const void *p)
+{
+	return __assoc_array_x_to_ptr(p, ASSOC_ARRAY_PTR_LEAF_TYPE);
+}
+static inline
+struct assoc_array_ptr *assoc_array_node_to_ptr(const struct assoc_array_node *p)
+{
+	return __assoc_array_x_to_ptr(
+		p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_NODE_SUBTYPE);
+}
+static inline
+struct assoc_array_ptr *assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut *p)
+{
+	return __assoc_array_x_to_ptr(
+		p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE);
+}
+
+#endif /* CONFIG_ASSOCIATIVE_ARRAY */
+#endif /* _LINUX_ASSOC_ARRAY_PRIV_H */
diff --git a/lib/Kconfig b/lib/Kconfig
index 35da513..b7d3234 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -312,6 +312,20 @@ config TEXTSEARCH_FSM
 config BTREE
 	boolean
 
+config ASSOCIATIVE_ARRAY
+	bool
+	help
+	  Generic associative array.  Can be searched and iterated over whilst
+	  it is being modified.  It is also reasonably quick to search and
+	  modify.  The algorithms are non-recursive, and the trees are highly
+	  capacious.
+
+	  See:
+
+		Documentation/assoc_array.txt
+
+	  for more information.
+
 config HAS_IOMEM
 	boolean
 	depends on !NO_IOMEM
diff --git a/lib/Makefile b/lib/Makefile
index 7baccfd..2c59891 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -49,6 +49,7 @@ CFLAGS_hweight.o = $(subst $(quote),,$(CONFIG_ARCH_HWEIGHT_CFLAGS))
 obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
 
 obj-$(CONFIG_BTREE) += btree.o
+obj-$(CONFIG_ASSOCIATIVE_ARRAY) += assoc_array.o
 obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
 obj-$(CONFIG_DEBUG_LIST) += list_debug.o
 obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
new file mode 100644
index 0000000..a095281
--- /dev/null
+++ b/lib/assoc_array.c
@@ -0,0 +1,1745 @@
+/* Generic associative array implementation.
+ *
+ * See Documentation/assoc_array.txt for information.
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+//#define DEBUG
+#include <linux/slab.h>
+#include <linux/assoc_array_priv.h>
+
+/*
+ * Iterate over an associative array.  The caller must hold the RCU read lock
+ * or better.
+ */
+static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
+				       const struct assoc_array_ptr *stop,
+				       int (*iterator)(const void *leaf,
+						       void *iterator_data),
+				       void *iterator_data)
+{
+	const struct assoc_array_shortcut *shortcut;
+	const struct assoc_array_node *node;
+	const struct assoc_array_ptr *cursor, *ptr, *parent;
+	unsigned long has_meta;
+	int slot, ret;
+
+	cursor = root;
+
+begin_node:
+	if (assoc_array_ptr_is_shortcut(cursor)) {
+		/* Descend through a shortcut */
+		shortcut = assoc_array_ptr_to_shortcut(cursor);
+		smp_read_barrier_depends();
+		cursor = ACCESS_ONCE(shortcut->next_node);
+	}
+
+	node = assoc_array_ptr_to_node(cursor);
+	smp_read_barrier_depends();
+	slot = 0;
+
+	/* We perform two passes of each node.
+	 *
+	 * The first pass does all the leaves in this node.  This means we
+	 * don't miss any leaves if the node is split up by insertion whilst
+	 * we're iterating over the branches rooted here (we may, however, see
+	 * some leaves twice).
+	 */
+	has_meta = 0;
+	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = ACCESS_ONCE(node->slots[slot]);
+		has_meta |= (unsigned long)ptr;
+		if (ptr && assoc_array_ptr_is_leaf(ptr)) {
+			/* We need a barrier between the read of the pointer
+			 * and dereferencing the pointer - but only if we are
+			 * actually going to dereference it.
+			 */
+			smp_read_barrier_depends();
+
+			/* Invoke the callback */
+			ret = iterator(assoc_array_ptr_to_leaf(ptr),
+				       iterator_data);
+			if (ret)
+				return ret;
+		}
+	}
+
+	/* The second pass attends to all the metadata pointers.  If we follow
+	 * one of these we may find that we don't come back here, but rather go
+	 * back to a replacement node with the leaves in a different layout.
+	 *
+	 * We are guaranteed to make progress, however, as the slot number for
+	 * a particular portion of the key space cannot change - and we
+	 * continue at the back pointer + 1.
+	 */
+	if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
+		goto finished_node;
+	slot = 0;
+
+continue_node:
+	node = assoc_array_ptr_to_node(cursor);
+	smp_read_barrier_depends();
+
+	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = ACCESS_ONCE(node->slots[slot]);
+		if (assoc_array_ptr_is_meta(ptr)) {
+			cursor = ptr;
+			goto begin_node;
+		}
+	}
+
+finished_node:
+	/* Move up to the parent (may need to skip back over a shortcut) */
+	parent = ACCESS_ONCE(node->back_pointer);
+	slot = node->parent_slot;
+	if (parent == stop)
+		return 0;
+
+	if (assoc_array_ptr_is_shortcut(parent)) {
+		shortcut = assoc_array_ptr_to_shortcut(parent);
+		smp_read_barrier_depends();
+		cursor = parent;
+		parent = ACCESS_ONCE(shortcut->back_pointer);
+		slot = shortcut->parent_slot;
+		if (parent == stop)
+			return 0;
+	}
+
+	/* Ascend to next slot in parent node */
+	cursor = parent;
+	slot++;
+	goto continue_node;
+}
+
+/**
+ * assoc_array_iterate - Pass all objects in the array to a callback
+ * @array: The array to iterate over.
+ * @iterator: The callback function.
+ * @iterator_data: Private data for the callback function.
+ *
+ * Iterate over all the objects in an associative array.  Each one will be
+ * presented to the iterator function.
+ *
+ * If the array is being modified concurrently with the iteration then it is
+ * possible that some objects in the array will be passed to the iterator
+ * callback more than once - though every object should be passed at least
+ * once.  If this is undesirable then the caller must lock against modification
+ * for the duration of this function.
+ *
+ * The function will return 0 if no objects were in the array or else it will
+ * return the result of the last iterator function called.  Iteration stops
+ * immediately if any call to the iteration function results in a non-zero
+ * return.
+ *
+ * The caller should hold the RCU read lock or better if concurrent
+ * modification is possible.
+ */
+int assoc_array_iterate(const struct assoc_array *array,
+			int (*iterator)(const void *object,
+					void *iterator_data),
+			void *iterator_data)
+{
+	struct assoc_array_ptr *root = ACCESS_ONCE(array->root);
+
+	if (!root)
+		return 0;
+	return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);
+}
+
+enum assoc_array_walk_status {
+	assoc_array_walk_tree_empty,
+	assoc_array_walk_found_terminal_node,
+	assoc_array_walk_found_wrong_shortcut,
+} status;
+
+struct assoc_array_walk_result {
+	struct {
+		struct assoc_array_node	*node;	/* Node in which leaf might be found */
+		int		level;
+		int		slot;
+	} terminal_node;
+	struct {
+		struct assoc_array_shortcut *shortcut;
+		int		level;
+		int		sc_level;
+		unsigned long	sc_segments;
+		unsigned long	dissimilarity;
+	} wrong_shortcut;
+};
+
+/*
+ * Navigate through the internal tree looking for the closest node to the key.
+ */
+static enum assoc_array_walk_status
+assoc_array_walk(const struct assoc_array *array,
+		 const struct assoc_array_ops *ops,
+		 const void *index_key,
+		 struct assoc_array_walk_result *result)
+{
+	struct assoc_array_shortcut *shortcut;
+	struct assoc_array_node *node;
+	struct assoc_array_ptr *cursor, *ptr;
+	unsigned long sc_segments, dissimilarity;
+	unsigned long segments;
+	int level, sc_level, next_sc_level;
+	int slot;
+
+	pr_devel("-->%s()\n", __func__);
+
+	cursor = ACCESS_ONCE(array->root);
+	if (!cursor)
+		return assoc_array_walk_tree_empty;
+
+	level = 0;
+
+	/* Use segments from the key for the new leaf to navigate through the
+	 * internal tree, skipping through nodes and shortcuts that are on
+	 * route to the destination.  Eventually we'll come to a slot that is
+	 * either empty or contains a leaf at which point we've found a node in
+	 * which the leaf we're looking for might be found or into which it
+	 * should be inserted.
+	 */
+jumped:
+	segments = ops->get_key_chunk(index_key, level);
+	pr_devel("segments[%d]: %lx\n", level, segments);
+
+	if (assoc_array_ptr_is_shortcut(cursor))
+		goto follow_shortcut;
+
+consider_node:
+	node = assoc_array_ptr_to_node(cursor);
+	smp_read_barrier_depends();
+
+	slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
+	slot &= ASSOC_ARRAY_FAN_MASK;
+	ptr = ACCESS_ONCE(node->slots[slot]);
+
+	pr_devel("consider slot %x [ix=%d type=%lu]\n",
+		 slot, level, (unsigned long)ptr & 3);
+
+	if (!assoc_array_ptr_is_meta(ptr)) {
+		/* The node doesn't have a node/shortcut pointer in the slot
+		 * corresponding to the index key that we have to follow.
+		 */
+		result->terminal_node.node = node;
+		result->terminal_node.level = level;
+		result->terminal_node.slot = slot;
+		pr_devel("<--%s() = terminal_node\n", __func__);
+		return assoc_array_walk_found_terminal_node;
+	}
+
+	if (assoc_array_ptr_is_node(ptr)) {
+		/* There is a pointer to a node in the slot corresponding to
+		 * this index key segment, so we need to follow it.
+		 */
+		cursor = ptr;
+		level += ASSOC_ARRAY_LEVEL_STEP;
+		if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)
+			goto consider_node;
+		goto jumped;
+	}
+
+	/* There is a shortcut in the slot corresponding to the index key
+	 * segment.  We follow the shortcut if its partial index key matches
+	 * this leaf's.  Otherwise we need to split the shortcut.
+	 */
+	cursor = ptr;
+follow_shortcut:
+	shortcut = assoc_array_ptr_to_shortcut(cursor);
+	smp_read_barrier_depends();
+	pr_devel("shortcut to %d\n", shortcut->skip_to_level);
+	sc_level = level + ASSOC_ARRAY_LEVEL_STEP;
+	BUG_ON(sc_level > shortcut->skip_to_level);
+
+	do {
+		/* Check the leaf against the shortcut's index key a word at a
+		 * time, trimming the final word (the shortcut stores the index
+		 * key completely from the root to the shortcut's target).
+		 */
+		if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)
+			segments = ops->get_key_chunk(index_key, sc_level);
+
+		sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];
+		dissimilarity = segments ^ sc_segments;
+
+		if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) {
+			/* Trim segments that are beyond the shortcut */
+			int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK;
+			dissimilarity &= ~(ULONG_MAX << shift);
+			next_sc_level = shortcut->skip_to_level;
+		} else {
+			next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE;
+			next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
+		}
+
+		if (dissimilarity != 0) {
+			/* This shortcut points elsewhere */
+			result->wrong_shortcut.shortcut = shortcut;
+			result->wrong_shortcut.level = level;
+			result->wrong_shortcut.sc_level = sc_level;
+			result->wrong_shortcut.sc_segments = sc_segments;
+			result->wrong_shortcut.dissimilarity = dissimilarity;
+			return assoc_array_walk_found_wrong_shortcut;
+		}
+
+		sc_level = next_sc_level;
+	} while (sc_level < shortcut->skip_to_level);
+
+	/* The shortcut matches the leaf's index to this point. */
+	cursor = ACCESS_ONCE(shortcut->next_node);
+	if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {
+		level = sc_level;
+		goto jumped;
+	} else {
+		level = sc_level;
+		goto consider_node;
+	}
+}
+
+/**
+ * assoc_array_find - Find an object by index key
+ * @array: The associative array to search.
+ * @ops: The operations to use.
+ * @index_key: The key to the object.
+ *
+ * Find an object in an associative array by walking through the internal tree
+ * to the node that should contain the object and then searching the leaves
+ * there.  NULL is returned if the requested object was not found in the array.
+ *
+ * The caller must hold the RCU read lock or better.
+ */
+void *assoc_array_find(const struct assoc_array *array,
+		       const struct assoc_array_ops *ops,
+		       const void *index_key)
+{
+	struct assoc_array_walk_result result;
+	const struct assoc_array_node *node;
+	const struct assoc_array_ptr *ptr;
+	const void *leaf;
+	int slot;
+
+	if (assoc_array_walk(array, ops, index_key, &result) !=
+	    assoc_array_walk_found_terminal_node)
+		return NULL;
+
+	node = result.terminal_node.node;
+	smp_read_barrier_depends();
+
+	/* If the target key is available to us, it's has to be pointed to by
+	 * the terminal node.
+	 */
+	for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = ACCESS_ONCE(node->slots[slot]);
+		if (ptr && assoc_array_ptr_is_leaf(ptr)) {
+			/* We need a barrier between the read of the pointer
+			 * and dereferencing the pointer - but only if we are
+			 * actually going to dereference it.
+			 */
+			leaf = assoc_array_ptr_to_leaf(ptr);
+			smp_read_barrier_depends();
+			if (ops->compare_object(leaf, index_key))
+				return (void *)leaf;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Destructively iterate over an associative array.  The caller must prevent
+ * other simultaneous accesses.
+ */
+static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,
+					const struct assoc_array_ops *ops)
+{
+	struct assoc_array_shortcut *shortcut;
+	struct assoc_array_node *node;
+	struct assoc_array_ptr *cursor, *parent = NULL;
+	int slot = -1;
+
+	pr_devel("-->%s()\n", __func__);
+
+	cursor = root;
+	if (!cursor) {
+		pr_devel("empty\n");
+		return;
+	}
+
+move_to_meta:
+	if (assoc_array_ptr_is_shortcut(cursor)) {
+		/* Descend through a shortcut */
+		pr_devel("[%d] shortcut\n", slot);
+		BUG_ON(!assoc_array_ptr_is_shortcut(cursor));
+		shortcut = assoc_array_ptr_to_shortcut(cursor);
+		BUG_ON(shortcut->back_pointer != parent);
+		BUG_ON(slot != -1 && shortcut->parent_slot != slot);
+		parent = cursor;
+		cursor = shortcut->next_node;
+		slot = -1;
+		BUG_ON(!assoc_array_ptr_is_node(cursor));
+	}
+
+	pr_devel("[%d] node\n", slot);
+	node = assoc_array_ptr_to_node(cursor);
+	BUG_ON(node->back_pointer != parent);
+	BUG_ON(slot != -1 && node->parent_slot != slot);
+	slot = 0;
+
+continue_node:
+	pr_devel("Node %p [back=%p]\n", node, node->back_pointer);
+	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		struct assoc_array_ptr *ptr = node->slots[slot];
+		if (!ptr)
+			continue;
+		if (assoc_array_ptr_is_meta(ptr)) {
+			parent = cursor;
+			cursor = ptr;
+			goto move_to_meta;
+		}
+
+		if (ops) {
+			pr_devel("[%d] free leaf\n", slot);
+			ops->free_object(assoc_array_ptr_to_leaf(ptr));
+		}
+	}
+
+	parent = node->back_pointer;
+	slot = node->parent_slot;
+	pr_devel("free node\n");
+	kfree(node);
+	if (!parent)
+		return; /* Done */
+
+	/* Move back up to the parent (may need to free a shortcut on
+	 * the way up) */
+	if (assoc_array_ptr_is_shortcut(parent)) {
+		shortcut = assoc_array_ptr_to_shortcut(parent);
+		BUG_ON(shortcut->next_node != cursor);
+		cursor = parent;
+		parent = shortcut->back_pointer;
+		slot = shortcut->parent_slot;
+		pr_devel("free shortcut\n");
+		kfree(shortcut);
+		if (!parent)
+			return;
+
+		BUG_ON(!assoc_array_ptr_is_node(parent));
+	}
+
+	/* Ascend to next slot in parent node */
+	pr_devel("ascend to %p[%d]\n", parent, slot);
+	cursor = parent;
+	node = assoc_array_ptr_to_node(cursor);
+	slot++;
+	goto continue_node;
+}
+
+/**
+ * assoc_array_destroy - Destroy an associative array
+ * @array: The array to destroy.
+ * @ops: The operations to use.
+ *
+ * Discard all metadata and free all objects in an associative array.  The
+ * array will be empty and ready to use again upon completion.  This function
+ * cannot fail.
+ *
+ * The caller must prevent all other accesses whilst this takes place as no
+ * attempt is made to adjust pointers gracefully to permit RCU readlock-holding
+ * accesses to continue.  On the other hand, no memory allocation is required.
+ */
+void assoc_array_destroy(struct assoc_array *array,
+			 const struct assoc_array_ops *ops)
+{
+	assoc_array_destroy_subtree(array->root, ops);
+	array->root = NULL;
+}
+
+/*
+ * Handle insertion into an empty tree.
+ */
+static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)
+{
+	struct assoc_array_node *new_n0;
+
+	pr_devel("-->%s()\n", __func__);
+
+	new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+	if (!new_n0)
+		return false;
+
+	edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
+	edit->leaf_p = &new_n0->slots[0];
+	edit->adjust_count_on = new_n0;
+	edit->set[0].ptr = &edit->array->root;
+	edit->set[0].to = assoc_array_node_to_ptr(new_n0);
+
+	pr_devel("<--%s() = ok [no root]\n", __func__);
+	return true;
+}
+
+/*
+ * Handle insertion into a terminal node.
+ */
+static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
+						  const struct assoc_array_ops *ops,
+						  const void *index_key,
+						  struct assoc_array_walk_result *result)
+{
+	struct assoc_array_shortcut *shortcut, *new_s0;
+	struct assoc_array_node *node, *new_n0, *new_n1, *side;
+	struct assoc_array_ptr *ptr;
+	unsigned long dissimilarity, base_seg, blank;
+	size_t keylen;
+	bool have_meta;
+	int level, diff;
+	int slot, next_slot, free_slot, i, j;
+
+	node	= result->terminal_node.node;
+	level	= result->terminal_node.level;
+	edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;
+
+	pr_devel("-->%s()\n", __func__);
+
+	/* We arrived at a node which doesn't have an onward node or shortcut
+	 * pointer that we have to follow.  This means that (a) the leaf we
+	 * want must go here (either by insertion or replacement) or (b) we
+	 * need to split this node and insert in one of the fragments.
+	 */
+	free_slot = -1;
+
+	/* Firstly, we have to check the leaves in this node to see if there's
+	 * a matching one we should replace in place.
+	 */
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		ptr = node->slots[i];
+		if (!ptr) {
+			free_slot = i;
+			continue;
+		}
+		if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) {
+			pr_devel("replace in slot %d\n", i);
+			edit->leaf_p = &node->slots[i];
+			edit->dead_leaf = node->slots[i];
+			pr_devel("<--%s() = ok [replace]\n", __func__);
+			return true;
+		}
+	}
+
+	/* If there is a free slot in this node then we can just insert the
+	 * leaf here.
+	 */
+	if (free_slot >= 0) {
+		pr_devel("insert in free slot %d\n", free_slot);
+		edit->leaf_p = &node->slots[free_slot];
+		edit->adjust_count_on = node;
+		pr_devel("<--%s() = ok [insert]\n", __func__);
+		return true;
+	}
+
+	/* The node has no spare slots - so we're either going to have to split
+	 * it or insert another node before it.
+	 *
+	 * Whatever, we're going to need at least two new nodes - so allocate
+	 * those now.  We may also need a new shortcut, but we deal with that
+	 * when we need it.
+	 */
+	new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+	if (!new_n0)
+		return false;
+	edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
+	new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+	if (!new_n1)
+		return false;
+	edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);
+
+	/* We need to find out how similar the leaves are. */
+	pr_devel("no spare slots\n");
+	have_meta = false;
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		ptr = node->slots[i];
+		if (assoc_array_ptr_is_meta(ptr)) {
+			edit->segment_cache[i] = 0xff;
+			have_meta = true;
+			continue;
+		}
+		base_seg = ops->get_object_key_chunk(
+			assoc_array_ptr_to_leaf(ptr), level);
+		base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
+		edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
+	}
+
+	if (have_meta) {
+		pr_devel("have meta\n");
+		goto split_node;
+	}
+
+	/* The node contains only leaves */
+	dissimilarity = 0;
+	base_seg = edit->segment_cache[0];
+	for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)
+		dissimilarity |= edit->segment_cache[i] ^ base_seg;
+
+	pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);
+
+	if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {
+		/* The old leaves all cluster in the same slot.  We will need
+		 * to insert a shortcut if the new node wants to cluster with them.
+		 */
+		if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)
+			goto all_leaves_cluster_together;
+
+		/* Otherwise we can just insert a new node ahead of the old
+		 * one.
+		 */
+		goto present_leaves_cluster_but_not_new_leaf;
+	}
+
+split_node:
+	pr_devel("split node\n");
+
+	/* We need to split the current node; we know that the node doesn't
+	 * simply contain a full set of leaves that cluster together (it
+	 * contains meta pointers and/or non-clustering leaves).
+	 *
+	 * We need to expel at least two leaves out of a set consisting of the
+	 * leaves in the node and the new leaf.
+	 *
+	 * We need a new node (n0) to replace the current one and a new node to
+	 * take the expelled nodes (n1).
+	 */
+	edit->set[0].to = assoc_array_node_to_ptr(new_n0);
+	new_n0->back_pointer = node->back_pointer;
+	new_n0->parent_slot = node->parent_slot;
+	new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
+	new_n1->parent_slot = -1; /* Need to calculate this */
+
+do_split_node:
+	pr_devel("do_split_node\n");
+
+	new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
+	new_n1->nr_leaves_on_branch = 0;
+
+	/* Begin by finding two matching leaves.  There have to be at least two
+	 * that match - even if there are meta pointers - because any leaf that
+	 * would match a slot with a meta pointer in it must be somewhere
+	 * behind that meta pointer and cannot be here.  Further, given N
+	 * remaining leaf slots, we now have N+1 leaves to go in them.
+	 */
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		slot = edit->segment_cache[i];
+		if (slot != 0xff)
+			for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
+				if (edit->segment_cache[j] == slot)
+					goto found_slot_for_multiple_occupancy;
+	}
+found_slot_for_multiple_occupancy:
+	pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
+	BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
+	BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
+	BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
+
+	new_n1->parent_slot = slot;
+
+	/* Metadata pointers cannot change slot */
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
+		if (assoc_array_ptr_is_meta(node->slots[i]))
+			new_n0->slots[i] = node->slots[i];
+		else
+			new_n0->slots[i] = NULL;
+	BUG_ON(new_n0->slots[slot] != NULL);
+	new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
+
+	/* Filter the leaf pointers between the new nodes */
+	free_slot = -1;
+	next_slot = 0;
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		if (assoc_array_ptr_is_meta(node->slots[i]))
+			continue;
+		if (edit->segment_cache[i] == slot) {
+			new_n1->slots[next_slot++] = node->slots[i];
+			new_n1->nr_leaves_on_branch++;
+		} else {
+			do {
+				free_slot++;
+			} while (new_n0->slots[free_slot] != NULL);
+			new_n0->slots[free_slot] = node->slots[i];
+		}
+	}
+
+	pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
+
+	if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
+		do {
+			free_slot++;
+		} while (new_n0->slots[free_slot] != NULL);
+		edit->leaf_p = &new_n0->slots[free_slot];
+		edit->adjust_count_on = new_n0;
+	} else {
+		edit->leaf_p = &new_n1->slots[next_slot++];
+		edit->adjust_count_on = new_n1;
+	}
+
+	BUG_ON(next_slot <= 1);
+
+	edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		if (edit->segment_cache[i] == 0xff) {
+			ptr = node->slots[i];
+			BUG_ON(assoc_array_ptr_is_leaf(ptr));
+			if (assoc_array_ptr_is_node(ptr)) {
+				side = assoc_array_ptr_to_node(ptr);
+				edit->set_backpointers[i] = &side->back_pointer;
+			} else {
+				shortcut = assoc_array_ptr_to_shortcut(ptr);
+				edit->set_backpointers[i] = &shortcut->back_pointer;
+			}
+		}
+	}
+
+	ptr = node->back_pointer;
+	if (!ptr)
+		edit->set[0].ptr = &edit->array->root;
+	else if (assoc_array_ptr_is_node(ptr))
+		edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
+	else
+		edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
+	edit->excised_meta[0] = assoc_array_node_to_ptr(node);
+	pr_devel("<--%s() = ok [split node]\n", __func__);
+	return true;
+
+present_leaves_cluster_but_not_new_leaf:
+	/* All the old leaves cluster in the same slot, but the new leaf wants
+	 * to go into a different slot, so we create a new node to hold the new
+	 * leaf and a pointer to a new node holding all the old leaves.
+	 */
+	pr_devel("present leaves cluster but not new leaf\n");
+
+	new_n0->back_pointer = node->back_pointer;
+	new_n0->parent_slot = node->parent_slot;
+	new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
+	new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
+	new_n1->parent_slot = edit->segment_cache[0];
+	new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch;
+	edit->adjust_count_on = new_n0;
+
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
+		new_n1->slots[i] = node->slots[i];
+
+	new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0);
+	edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]];
+
+	edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot];
+	edit->set[0].to = assoc_array_node_to_ptr(new_n0);
+	edit->excised_meta[0] = assoc_array_node_to_ptr(node);
+	pr_devel("<--%s() = ok [insert node before]\n", __func__);
+	return true;
+
+all_leaves_cluster_together:
+	/* All the leaves, new and old, want to cluster together in this node
+	 * in the same slot, so we have to replace this node with a shortcut to
+	 * skip over the identical parts of the key and then place a pair of
+	 * nodes, one inside the other, at the end of the shortcut and
+	 * distribute the keys between them.
+	 *
+	 * Firstly we need to work out where the leaves start diverging as a
+	 * bit position into their keys so that we know how big the shortcut
+	 * needs to be.
+	 *
+	 * We only need to make a single pass of N of the N+1 leaves because if
+	 * any keys differ between themselves at bit X then at least one of
+	 * them must also differ with the base key at bit X or before.
+	 */
+	pr_devel("all leaves cluster together\n");
+	diff = INT_MAX;
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		int x = ops->diff_objects(assoc_array_ptr_to_leaf(edit->leaf),
+					  assoc_array_ptr_to_leaf(node->slots[i]));
+		if (x < diff) {
+			BUG_ON(x < 0);
+			diff = x;
+		}
+	}
+	BUG_ON(diff == INT_MAX);
+	BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
+
+	keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
+	keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
+
+	new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
+			 keylen * sizeof(unsigned long), GFP_KERNEL);
+	if (!new_s0)
+		return false;
+	edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
+
+	edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
+	new_s0->back_pointer = node->back_pointer;
+	new_s0->parent_slot = node->parent_slot;
+	new_s0->next_node = assoc_array_node_to_ptr(new_n0);
+	new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
+	new_n0->parent_slot = 0;
+	new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
+	new_n1->parent_slot = -1; /* Need to calculate this */
+
+	new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
+	pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
+	BUG_ON(level <= 0);
+
+	for (i = 0; i < keylen; i++)
+		new_s0->index_key[i] =
+			ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
+
+	blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
+	pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
+	new_s0->index_key[keylen - 1] &= ~blank;
+
+	/* This now reduces to a node splitting exercise for which we'll need
+	 * to regenerate the disparity table.
+	 */
+	for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+		ptr = node->slots[i];
+		base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
+						     level);
+		base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
+		edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
+	}
+
+	base_seg = ops->get_key_chunk(index_key, level);
+	base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
+	edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
+	goto do_split_node;
+}
+
+/*
+ * Handle insertion into the middle of a shortcut.
+ */
+static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
+					    const struct assoc_array_ops *ops,
+					    struct assoc_array_walk_result *result)
+{
+	struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
+	struct assoc_array_node *node, *new_n0, *side;
+	unsigned long sc_segments, dissimilarity, blank;
+	size_t keylen;
+	int level, sc_level, diff;
+	int sc_slot;
+
+	shortcut	= result->wrong_shortcut.shortcut;
+	level		= result->wrong_shortcut.level;
+	sc_level	= result->wrong_shortcut.sc_level;
+	sc_segments	= result->wrong_shortcut.sc_segments;
+	dissimilarity	= result->wrong_shortcut.dissimilarity;
+
+	pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
+		 __func__, level, dissimilarity, sc_level);
+
+	/* We need to split a shortcut and insert a node between the two
+	 * pieces.  Zero-length pieces will be dispensed with entirely.
+	 *
+	 * First of all, we need to find out in which level the first
+	 * difference was.
+	 */
+	diff = __ffs(dissimilarity);
+	diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
+	diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
+	pr_devel("diff=%d\n", diff);
+
+	if (!shortcut->back_pointer) {
+		edit->set[0].ptr = &edit->array->root;
+	} else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
+		node = assoc_array_ptr_to_node(shortcut->back_pointer);
+		edit->set[0].ptr = &node->slots[shortcut->parent_slot];
+	} else {
+		BUG();
+	}
+
+	edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
+
+	/* Create a new node now since we're going to need it anyway */
+	new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+	if (!new_n0)
+		return false;
+	edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
+	edit->adjust_count_on = new_n0;
+
+	/* Insert a new shortcut before the new node if this segment isn't of
+	 * zero length - otherwise we just connect the new node directly to the
+	 * parent.
+	 */
+	level += ASSOC_ARRAY_LEVEL_STEP;
+	if (diff > level) {
+		pr_devel("pre-shortcut %d...%d\n", level, diff);
+		keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
+		keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
+
+		new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
+				 keylen * sizeof(unsigned long), GFP_KERNEL);
+		if (!new_s0)
+			return false;
+		edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
+		edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
+		new_s0->back_pointer = shortcut->back_pointer;
+		new_s0->parent_slot = shortcut->parent_slot;
+		new_s0->next_node = assoc_array_node_to_ptr(new_n0);
+		new_s0->skip_to_level = diff;
+
+		new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
+		new_n0->parent_slot = 0;
+
+		memcpy(new_s0->index_key, shortcut->index_key,
+		       keylen * sizeof(unsigned long));
+
+		blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
+		pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
+		new_s0->index_key[keylen - 1] &= ~blank;
+	} else {
+		pr_devel("no pre-shortcut\n");
+		edit->set[0].to = assoc_array_node_to_ptr(new_n0);
+		new_n0->back_pointer = shortcut->back_pointer;
+		new_n0->parent_slot = shortcut->parent_slot;
+	}
+
+	side = assoc_array_ptr_to_node(shortcut->next_node);
+	new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
+
+	/* We need to know which slot in the new node is going to take a
+	 * metadata pointer.
+	 */
+	sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
+	sc_slot &= ASSOC_ARRAY_FAN_MASK;
+
+	pr_devel("new slot %lx >> %d -> %d\n",
+		 sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
+
+	/* Determine whether we need to follow the new node with a replacement
+	 * for the current shortcut.  We could in theory reuse the current
+	 * shortcut if its parent slot number doesn't change - but that's a
+	 * 1-in-16 chance so not worth expending the code upon.
+	 */
+	level = diff + ASSOC_ARRAY_LEVEL_STEP;
+	if (level < shortcut->skip_to_level) {
+		pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
+		keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
+		keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
+
+		new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
+				 keylen * sizeof(unsigned long), GFP_KERNEL);
+		if (!new_s1)
+			return false;
+		edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
+
+		new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
+		new_s1->parent_slot = sc_slot;
+		new_s1->next_node = shortcut->next_node;
+		new_s1->skip_to_level = shortcut->skip_to_level;
+
+		new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
+
+		memcpy(new_s1->index_key, shortcut->index_key,
+		       keylen * sizeof(unsigned long));
+
+		edit->set[1].ptr = &side->back_pointer;
+		edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
+	} else {
+		pr_devel("no post-shortcut\n");
+
+		/* We don't have to replace the pointed-to node as long as we
+		 * use memory barriers to make sure the parent slot number is
+		 * changed before the back pointer (the parent slot number is
+		 * irrelevant to the old parent shortcut).
+		 */
+		new_n0->slots[sc_slot] = shortcut->next_node;
+		edit->set_parent_slot[0].p = &side->parent_slot;
+		edit->set_parent_slot[0].to = sc_slot;
+		edit->set[1].ptr = &side->back_pointer;
+		edit->set[1].to = assoc_array_node_to_ptr(new_n0);
+	}
+
+	/* Install the new leaf in a spare slot in the new node. */
+	if (sc_slot == 0)
+		edit->leaf_p = &new_n0->slots[1];
+	else
+		edit->leaf_p = &new_n0->slots[0];
+
+	pr_devel("<--%s() = ok [split shortcut]\n", __func__);
+	return edit;
+}
+
+/**
+ * assoc_array_insert - Script insertion of an object into an associative array
+ * @array: The array to insert into.
+ * @ops: The operations to use.
+ * @index_key: The key to insert at.
+ * @object: The object to insert.
+ *
+ * Precalculate and preallocate a script for the insertion or replacement of an
+ * object in an associative array.  This results in an edit script that can
+ * either be applied or cancelled.
+ *
+ * The function returns a pointer to an edit script or -ENOMEM.
+ *
+ * The caller should lock against other modifications and must continue to hold
+ * the lock until assoc_array_apply_edit() has been called.
+ *
+ * Accesses to the tree may take place concurrently with this function,
+ * provided they hold the RCU read lock.
+ */
+struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
+					    const struct assoc_array_ops *ops,
+					    const void *index_key,
+					    void *object)
+{
+	struct assoc_array_walk_result result;
+	struct assoc_array_edit *edit;
+
+	pr_devel("-->%s()\n", __func__);
+
+	/* The leaf pointer we're given must not have the bottom bit set as we
+	 * use those for type-marking the pointer.  NULL pointers are also not
+	 * allowed as they indicate an empty slot but we have to allow them
+	 * here as they can be updated later.
+	 */
+	BUG_ON(assoc_array_ptr_is_meta(object));
+
+	edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
+	if (!edit)
+		return ERR_PTR(-ENOMEM);
+	edit->array = array;
+	edit->ops = ops;
+	edit->leaf = assoc_array_leaf_to_ptr(object);
+	edit->adjust_count_by = 1;
+
+	switch (assoc_array_walk(array, ops, index_key, &result)) {
+	case assoc_array_walk_tree_empty:
+		/* Allocate a root node if there isn't one yet */
+		if (!assoc_array_insert_in_empty_tree(edit))
+			goto enomem;
+		return edit;
+
+	case assoc_array_walk_found_terminal_node:
+		/* We found a node that doesn't have a node/shortcut pointer in
+		 * the slot corresponding to the index key that we have to
+		 * follow.
+		 */
+		if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
+							   &result))
+			goto enomem;
+		return edit;
+
+	case assoc_array_walk_found_wrong_shortcut:
+		/* We found a shortcut that didn't match our key in a slot we
+		 * needed to follow.
+		 */
+		if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
+			goto enomem;
+		return edit;
+	}
+
+enomem:
+	/* Clean up after an out of memory error */
+	pr_devel("enomem\n");
+	assoc_array_cancel_edit(edit);
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * assoc_array_insert_set_object - Set the new object pointer in an edit script
+ * @edit: The edit script to modify.
+ * @object: The object pointer to set.
+ *
+ * Change the object to be inserted in an edit script.  The object pointed to
+ * by the old object is not freed.  This must be done prior to applying the
+ * script.
+ */
+void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
+{
+	BUG_ON(!object);
+	edit->leaf = assoc_array_leaf_to_ptr(object);
+}
+
+struct assoc_array_delete_collapse_context {
+	struct assoc_array_node	*node;
+	const void		*skip_leaf;
+	int			slot;
+};
+
+/*
+ * Subtree collapse to node iterator.
+ */
+static int assoc_array_delete_collapse_iterator(const void *leaf,
+						void *iterator_data)
+{
+	struct assoc_array_delete_collapse_context *collapse = iterator_data;
+
+	if (leaf == collapse->skip_leaf)
+		return 0;
+
+	BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
+
+	collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
+	return 0;
+}
+
+/**
+ * assoc_array_delete - Script deletion of an object from an associative array
+ * @array: The array to search.
+ * @ops: The operations to use.
+ * @index_key: The key to the object.
+ *
+ * Precalculate and preallocate a script for the deletion of an object from an
+ * associative array.  This results in an edit script that can either be
+ * applied or cancelled.
+ *
+ * The function returns a pointer to an edit script if the object was found,
+ * NULL if the object was not found or -ENOMEM.
+ *
+ * The caller should lock against other modifications and must continue to hold
+ * the lock until assoc_array_apply_edit() has been called.
+ *
+ * Accesses to the tree may take place concurrently with this function,
+ * provided they hold the RCU read lock.
+ */
+struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
+					    const struct assoc_array_ops *ops,
+					    const void *index_key)
+{
+	struct assoc_array_delete_collapse_context collapse;
+	struct assoc_array_walk_result result;
+	struct assoc_array_node *node, *new_n0;
+	struct assoc_array_edit *edit;
+	struct assoc_array_ptr *ptr;
+	bool has_meta;
+	int slot, i;
+
+	pr_devel("-->%s()\n", __func__);
+
+	edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
+	if (!edit)
+		return ERR_PTR(-ENOMEM);
+	edit->array = array;
+	edit->ops = ops;
+	edit->adjust_count_by = -1;
+
+	switch (assoc_array_walk(array, ops, index_key, &result)) {
+	case assoc_array_walk_found_terminal_node:
+		/* We found a node that should contain the leaf we've been
+		 * asked to remove - *if* it's in the tree.
+		 */
+		pr_devel("terminal_node\n");
+		node = result.terminal_node.node;
+
+		for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+			ptr = node->slots[slot];
+			if (ptr &&
+			    assoc_array_ptr_is_leaf(ptr) &&
+			    ops->compare_object(assoc_array_ptr_to_leaf(ptr),
+						index_key))
+				goto found_leaf;
+		}
+	case assoc_array_walk_tree_empty:
+	case assoc_array_walk_found_wrong_shortcut:
+	default:
+		assoc_array_cancel_edit(edit);
+		pr_devel("not found\n");
+		return NULL;
+	}
+
+found_leaf:
+	BUG_ON(array->nr_leaves_on_tree <= 0);
+
+	/* In the simplest form of deletion we just clear the slot and release
+	 * the leaf after a suitable interval.
+	 */
+	edit->dead_leaf = node->slots[slot];
+	edit->set[0].ptr = &node->slots[slot];
+	edit->set[0].to = NULL;
+	edit->adjust_count_on = node;
+
+	/* If that concludes erasure of the last leaf, then delete the entire
+	 * internal array.
+	 */
+	if (array->nr_leaves_on_tree == 1) {
+		edit->set[1].ptr = &array->root;
+		edit->set[1].to = NULL;
+		edit->adjust_count_on = NULL;
+		edit->excised_subtree = array->root;
+		pr_devel("all gone\n");
+		return edit;
+	}
+
+	/* However, we'd also like to clear up some metadata blocks if we
+	 * possibly can.
+	 *
+	 * We go for a simple algorithm of: if this node has FAN_OUT or fewer
+	 * leaves in it, then attempt to collapse it - and attempt to
+	 * recursively collapse up the tree.
+	 *
+	 * We could also try and collapse in partially filled subtrees to take
+	 * up space in this node.
+	 */
+	if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
+		struct assoc_array_node *parent, *grandparent;
+		struct assoc_array_ptr *ptr;
+
+		/* First of all, we need to know if this node has metadata so
+		 * that we don't try collapsing if all the leaves are already
+		 * here.
+		 */
+		has_meta = false;
+		for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+			ptr = node->slots[i];
+			if (assoc_array_ptr_is_meta(ptr)) {
+				has_meta = true;
+				break;
+			}
+		}
+
+		pr_devel("leaves: %ld [m=%d]\n",
+			 node->nr_leaves_on_branch - 1, has_meta);
+
+		/* Look further up the tree to see if we can collapse this node
+		 * into a more proximal node too.
+		 */
+		parent = node;
+	collapse_up:
+		pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
+
+		ptr = parent->back_pointer;
+		if (!ptr)
+			goto do_collapse;
+		if (assoc_array_ptr_is_shortcut(ptr)) {
+			struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
+			ptr = s->back_pointer;
+			if (!ptr)
+				goto do_collapse;
+		}
+
+		grandparent = assoc_array_ptr_to_node(ptr);
+		if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
+			parent = grandparent;
+			goto collapse_up;
+		}
+
+	do_collapse:
+		/* There's no point collapsing if the original node has no meta
+		 * pointers to discard and if we didn't merge into one of that
+		 * node's ancestry.
+		 */
+		if (has_meta || parent != node) {
+			node = parent;
+
+			/* Create a new node to collapse into */
+			new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+			if (!new_n0)
+				goto enomem;
+			edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
+
+			new_n0->back_pointer = node->back_pointer;
+			new_n0->parent_slot = node->parent_slot;
+			new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
+			edit->adjust_count_on = new_n0;
+
+			collapse.node = new_n0;
+			collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
+			collapse.slot = 0;
+			assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
+						    node->back_pointer,
+						    assoc_array_delete_collapse_iterator,
+						    &collapse);
+			pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
+			BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
+
+			if (!node->back_pointer) {
+				edit->set[1].ptr = &array->root;
+			} else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
+				BUG();
+			} else if (assoc_array_ptr_is_node(node->back_pointer)) {
+				struct assoc_array_node *p =
+					assoc_array_ptr_to_node(node->back_pointer);
+				edit->set[1].ptr = &p->slots[node->parent_slot];
+			} else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
+				struct assoc_array_shortcut *s =
+					assoc_array_ptr_to_shortcut(node->back_pointer);
+				edit->set[1].ptr = &s->next_node;
+			}
+			edit->set[1].to = assoc_array_node_to_ptr(new_n0);
+			edit->excised_subtree = assoc_array_node_to_ptr(node);
+		}
+	}
+
+	return edit;
+
+enomem:
+	/* Clean up after an out of memory error */
+	pr_devel("enomem\n");
+	assoc_array_cancel_edit(edit);
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * assoc_array_clear - Script deletion of all objects from an associative array
+ * @array: The array to clear.
+ * @ops: The operations to use.
+ *
+ * Precalculate and preallocate a script for the deletion of all the objects
+ * from an associative array.  This results in an edit script that can either
+ * be applied or cancelled.
+ *
+ * The function returns a pointer to an edit script if there are objects to be
+ * deleted, NULL if there are no objects in the array or -ENOMEM.
+ *
+ * The caller should lock against other modifications and must continue to hold
+ * the lock until assoc_array_apply_edit() has been called.
+ *
+ * Accesses to the tree may take place concurrently with this function,
+ * provided they hold the RCU read lock.
+ */
+struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
+					   const struct assoc_array_ops *ops)
+{
+	struct assoc_array_edit *edit;
+
+	pr_devel("-->%s()\n", __func__);
+
+	if (!array->root)
+		return NULL;
+
+	edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
+	if (!edit)
+		return ERR_PTR(-ENOMEM);
+	edit->array = array;
+	edit->ops = ops;
+	edit->set[1].ptr = &array->root;
+	edit->set[1].to = NULL;
+	edit->excised_subtree = array->root;
+	edit->ops_for_excised_subtree = ops;
+	pr_devel("all gone\n");
+	return edit;
+}
+
+/*
+ * Handle the deferred destruction after an applied edit.
+ */
+static void assoc_array_rcu_cleanup(struct rcu_head *head)
+{
+	struct assoc_array_edit *edit =
+		container_of(head, struct assoc_array_edit, rcu);
+	int i;
+
+	pr_devel("-->%s()\n", __func__);
+
+	if (edit->dead_leaf)
+		edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
+	for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
+		if (edit->excised_meta[i])
+			kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
+
+	if (edit->excised_subtree) {
+		BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
+		if (assoc_array_ptr_is_node(edit->excised_subtree)) {
+			struct assoc_array_node *n =
+				assoc_array_ptr_to_node(edit->excised_subtree);
+			n->back_pointer = NULL;
+		} else {
+			struct assoc_array_shortcut *s =
+				assoc_array_ptr_to_shortcut(edit->excised_subtree);
+			s->back_pointer = NULL;
+		}
+		assoc_array_destroy_subtree(edit->excised_subtree,
+					    edit->ops_for_excised_subtree);
+	}
+
+	kfree(edit);
+}
+
+/**
+ * assoc_array_apply_edit - Apply an edit script to an associative array
+ * @edit: The script to apply.
+ *
+ * Apply an edit script to an associative array to effect an insertion,
+ * deletion or clearance.  As the edit script includes preallocated memory,
+ * this is guaranteed not to fail.
+ *
+ * The edit script, dead objects and dead metadata will be scheduled for
+ * destruction after an RCU grace period to permit those doing read-only
+ * accesses on the array to continue to do so under the RCU read lock whilst
+ * the edit is taking place.
+ */
+void assoc_array_apply_edit(struct assoc_array_edit *edit)
+{
+	struct assoc_array_shortcut *shortcut;
+	struct assoc_array_node *node;
+	struct assoc_array_ptr *ptr;
+	int i;
+
+	pr_devel("-->%s()\n", __func__);
+
+	smp_wmb();
+	if (edit->leaf_p)
+		*edit->leaf_p = edit->leaf;
+
+	smp_wmb();
+	for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
+		if (edit->set_parent_slot[i].p)
+			*edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
+
+	smp_wmb();
+	for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
+		if (edit->set_backpointers[i])
+			*edit->set_backpointers[i] = edit->set_backpointers_to;
+
+	smp_wmb();
+	for (i = 0; i < ARRAY_SIZE(edit->set); i++)
+		if (edit->set[i].ptr)
+			*edit->set[i].ptr = edit->set[i].to;
+
+	if (edit->array->root == NULL) {
+		edit->array->nr_leaves_on_tree = 0;
+	} else if (edit->adjust_count_on) {
+		node = edit->adjust_count_on;
+		for (;;) {
+			node->nr_leaves_on_branch += edit->adjust_count_by;
+
+			ptr = node->back_pointer;
+			if (!ptr)
+				break;
+			if (assoc_array_ptr_is_shortcut(ptr)) {
+				shortcut = assoc_array_ptr_to_shortcut(ptr);
+				ptr = shortcut->back_pointer;
+				if (!ptr)
+					break;
+			}
+			BUG_ON(!assoc_array_ptr_is_node(ptr));
+			node = assoc_array_ptr_to_node(ptr);
+		}
+
+		edit->array->nr_leaves_on_tree += edit->adjust_count_by;
+	}
+
+	call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
+}
+
+/**
+ * assoc_array_cancel_edit - Discard an edit script.
+ * @edit: The script to discard.
+ *
+ * Free an edit script and all the preallocated data it holds without making
+ * any changes to the associative array it was intended for.
+ *
+ * NOTE!  In the case of an insertion script, this does _not_ release the leaf
+ * that was to be inserted.  That is left to the caller.
+ */
+void assoc_array_cancel_edit(struct assoc_array_edit *edit)
+{
+	struct assoc_array_ptr *ptr;
+	int i;
+
+	pr_devel("-->%s()\n", __func__);
+
+	/* Clean up after an out of memory error */
+	for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
+		ptr = edit->new_meta[i];
+		if (ptr) {
+			if (assoc_array_ptr_is_node(ptr))
+				kfree(assoc_array_ptr_to_node(ptr));
+			else
+				kfree(assoc_array_ptr_to_shortcut(ptr));
+		}
+	}
+	kfree(edit);
+}
+
+/**
+ * assoc_array_gc - Garbage collect an associative array.
+ * @array: The array to clean.
+ * @ops: The operations to use.
+ * @iterator: A callback function to pass judgement on each object.
+ * @iterator_data: Private data for the callback function.
+ *
+ * Collect garbage from an associative array and pack down the internal tree to
+ * save memory.
+ *
+ * The iterator function is asked to pass judgement upon each object in the
+ * array.  If it returns false, the object is discard and if it returns true,
+ * the object is kept.  If it returns true, it must increment the object's
+ * usage count (or whatever it needs to do to retain it) before returning.
+ *
+ * This function returns 0 if successful or -ENOMEM if out of memory.  In the
+ * latter case, the array is not changed.
+ *
+ * The caller should lock against other modifications and must continue to hold
+ * the lock until assoc_array_apply_edit() has been called.
+ *
+ * Accesses to the tree may take place concurrently with this function,
+ * provided they hold the RCU read lock.
+ */
+int assoc_array_gc(struct assoc_array *array,
+		   const struct assoc_array_ops *ops,
+		   bool (*iterator)(void *object, void *iterator_data),
+		   void *iterator_data)
+{
+	struct assoc_array_shortcut *shortcut, *new_s;
+	struct assoc_array_node *node, *new_n;
+	struct assoc_array_edit *edit;
+	struct assoc_array_ptr *cursor, *ptr;
+	struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
+	unsigned long nr_leaves_on_tree;
+	int keylen, slot, nr_free, next_slot, i;
+
+	pr_devel("-->%s()\n", __func__);
+
+	if (!array->root)
+		return 0;
+
+	edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
+	if (!edit)
+		return -ENOMEM;
+	edit->array = array;
+	edit->ops = ops;
+	edit->ops_for_excised_subtree = ops;
+	edit->set[0].ptr = &array->root;
+	edit->excised_subtree = array->root;
+
+	new_root = new_parent = NULL;
+	new_ptr_pp = &new_root;
+	cursor = array->root;
+
+descend:
+	/* If this point is a shortcut, then we need to duplicate it and
+	 * advance the target cursor.
+	 */
+	if (assoc_array_ptr_is_shortcut(cursor)) {
+		shortcut = assoc_array_ptr_to_shortcut(cursor);
+		keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
+		keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
+		new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
+				keylen * sizeof(unsigned long), GFP_KERNEL);
+		if (!new_s)
+			goto enomem;
+		pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
+		memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
+					 keylen * sizeof(unsigned long)));
+		new_s->back_pointer = new_parent;
+		new_s->parent_slot = shortcut->parent_slot;
+		*new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
+		new_ptr_pp = &new_s->next_node;
+		cursor = shortcut->next_node;
+	}
+
+	/* Duplicate the node at this position */
+	node = assoc_array_ptr_to_node(cursor);
+	new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
+	if (!new_n)
+		goto enomem;
+	pr_devel("dup node %p -> %p\n", node, new_n);
+	new_n->back_pointer = new_parent;
+	new_n->parent_slot = node->parent_slot;
+	*new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
+	new_ptr_pp = NULL;
+	slot = 0;
+
+continue_node:
+	/* Filter across any leaves and gc any subtrees */
+	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = node->slots[slot];
+		if (!ptr)
+			continue;
+
+		if (assoc_array_ptr_is_leaf(ptr)) {
+			if (iterator(assoc_array_ptr_to_leaf(ptr),
+				     iterator_data))
+				/* The iterator will have done any reference
+				 * counting on the object for us.
+				 */
+				new_n->slots[slot] = ptr;
+			continue;
+		}
+
+		new_ptr_pp = &new_n->slots[slot];
+		cursor = ptr;
+		goto descend;
+	}
+
+	pr_devel("-- compress node %p --\n", new_n);
+
+	/* Count up the number of empty slots in this node and work out the
+	 * subtree leaf count.
+	 */
+	new_n->nr_leaves_on_branch = 0;
+	nr_free = 0;
+	for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = new_n->slots[slot];
+		if (!ptr)
+			nr_free++;
+		else if (assoc_array_ptr_is_leaf(ptr))
+			new_n->nr_leaves_on_branch++;
+	}
+	pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
+
+	/* See what we can fold in */
+	next_slot = 0;
+	for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		struct assoc_array_shortcut *s;
+		struct assoc_array_node *child;
+
+		ptr = new_n->slots[slot];
+		if (!ptr || assoc_array_ptr_is_leaf(ptr))
+			continue;
+
+		s = NULL;
+		if (assoc_array_ptr_is_shortcut(ptr)) {
+			s = assoc_array_ptr_to_shortcut(ptr);
+			ptr = s->next_node;
+		}
+
+		child = assoc_array_ptr_to_node(ptr);
+		new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
+
+		if (child->nr_leaves_on_branch <= nr_free + 1) {
+			/* Fold the child node into this one */
+			pr_devel("[%d] fold node %lu/%d [nx %d]\n",
+				 slot, child->nr_leaves_on_branch, nr_free + 1,
+				 next_slot);
+
+			/* We would already have reaped an intervening shortcut
+			 * on the way back up the tree.
+			 */
+			BUG_ON(s);
+
+			new_n->slots[slot] = NULL;
+			nr_free++;
+			if (slot < next_slot)
+				next_slot = slot;
+			for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
+				struct assoc_array_ptr *p = child->slots[i];
+				if (!p)
+					continue;
+				BUG_ON(assoc_array_ptr_is_meta(p));
+				while (new_n->slots[next_slot])
+					next_slot++;
+				BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
+				new_n->slots[next_slot++] = p;
+				nr_free--;
+			}
+			kfree(child);
+		} else {
+			pr_devel("[%d] retain node %lu/%d [nx %d]\n",
+				 slot, child->nr_leaves_on_branch, nr_free + 1,
+				 next_slot);
+		}
+	}
+
+	pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
+
+	nr_leaves_on_tree = new_n->nr_leaves_on_branch;
+
+	/* Excise this node if it is singly occupied by a shortcut */
+	if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
+		for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
+			if ((ptr = new_n->slots[slot]))
+				break;
+
+		if (assoc_array_ptr_is_meta(ptr) &&
+		    assoc_array_ptr_is_shortcut(ptr)) {
+			pr_devel("excise node %p with 1 shortcut\n", new_n);
+			new_s = assoc_array_ptr_to_shortcut(ptr);
+			new_parent = new_n->back_pointer;
+			slot = new_n->parent_slot;
+			kfree(new_n);
+			if (!new_parent) {
+				new_s->back_pointer = NULL;
+				new_s->parent_slot = 0;
+				new_root = ptr;
+				goto gc_complete;
+			}
+
+			if (assoc_array_ptr_is_shortcut(new_parent)) {
+				/* We can discard any preceding shortcut also */
+				struct assoc_array_shortcut *s =
+					assoc_array_ptr_to_shortcut(new_parent);
+
+				pr_devel("excise preceding shortcut\n");
+
+				new_parent = new_s->back_pointer = s->back_pointer;
+				slot = new_s->parent_slot = s->parent_slot;
+				kfree(s);
+				if (!new_parent) {
+					new_s->back_pointer = NULL;
+					new_s->parent_slot = 0;
+					new_root = ptr;
+					goto gc_complete;
+				}
+			}
+
+			new_s->back_pointer = new_parent;
+			new_s->parent_slot = slot;
+			new_n = assoc_array_ptr_to_node(new_parent);
+			new_n->slots[slot] = ptr;
+			goto ascend_old_tree;
+		}
+	}
+
+	/* Excise any shortcuts we might encounter that point to nodes that
+	 * only contain leaves.
+	 */
+	ptr = new_n->back_pointer;
+	if (!ptr)
+		goto gc_complete;
+
+	if (assoc_array_ptr_is_shortcut(ptr)) {
+		new_s = assoc_array_ptr_to_shortcut(ptr);
+		new_parent = new_s->back_pointer;
+		slot = new_s->parent_slot;
+
+		if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
+			struct assoc_array_node *n;
+
+			pr_devel("excise shortcut\n");
+			new_n->back_pointer = new_parent;
+			new_n->parent_slot = slot;
+			kfree(new_s);
+			if (!new_parent) {
+				new_root = assoc_array_node_to_ptr(new_n);
+				goto gc_complete;
+			}
+
+			n = assoc_array_ptr_to_node(new_parent);
+			n->slots[slot] = assoc_array_node_to_ptr(new_n);
+		}
+	} else {
+		new_parent = ptr;
+	}
+	new_n = assoc_array_ptr_to_node(new_parent);
+
+ascend_old_tree:
+	ptr = node->back_pointer;
+	if (assoc_array_ptr_is_shortcut(ptr)) {
+		shortcut = assoc_array_ptr_to_shortcut(ptr);
+		slot = shortcut->parent_slot;
+		cursor = shortcut->back_pointer;
+	} else {
+		slot = node->parent_slot;
+		cursor = ptr;
+	}
+	BUG_ON(!ptr);
+	node = assoc_array_ptr_to_node(cursor);
+	slot++;
+	goto continue_node;
+
+gc_complete:
+	edit->set[0].to = new_root;
+	assoc_array_apply_edit(edit);
+	edit->array->nr_leaves_on_tree = nr_leaves_on_tree;
+	return 0;
+
+enomem:
+	pr_devel("enomem\n");
+	assoc_array_destroy_subtree(new_root, edit->ops);
+	kfree(edit);
+	return -ENOMEM;
+}
-- 
1.8.3.1


From 03ac60b84587fa8e57e7ec5cd3d59b7fa8d97c79 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 30 Aug 2013 15:37:54 +0100
Subject: [PATCH 10/10] KEYS: Expand the capacity of a keyring

Expand the capacity of a keyring to be able to hold a lot more keys by using
the previously added associative array implementation.  Currently the maximum
capacity is:

	(PAGE_SIZE - sizeof(header)) / sizeof(struct key *)

which, on a 64-bit system, is a little more 500.  However, since this is being
used for the NFS uid mapper, we need more than that.  The new implementation
gives us effectively unlimited capacity.

With some alterations, the keyutils testsuite runs successfully to completion
after this patch is applied.  The alterations are because (a) keyrings that
are simply added to no longer appear ordered and (b) some of the errors have
changed a bit.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/keys/keyring-type.h |   17 +-
 include/linux/key.h         |   13 +-
 lib/assoc_array.c           |    1 +
 security/keys/Kconfig       |    1 +
 security/keys/gc.c          |   33 +-
 security/keys/internal.h    |   17 +-
 security/keys/key.c         |   35 +-
 security/keys/keyring.c     | 1436 ++++++++++++++++++++++---------------------
 security/keys/request_key.c |   12 +-
 9 files changed, 803 insertions(+), 762 deletions(-)

diff --git a/include/keys/keyring-type.h b/include/keys/keyring-type.h
index cf49159..fca5c62 100644
--- a/include/keys/keyring-type.h
+++ b/include/keys/keyring-type.h
@@ -1,6 +1,6 @@
 /* Keyring key type
  *
- * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2008, 2013 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
@@ -13,19 +13,6 @@
 #define _KEYS_KEYRING_TYPE_H
 
 #include <linux/key.h>
-#include <linux/rcupdate.h>
-
-/*
- * the keyring payload contains a list of the keys to which the keyring is
- * subscribed
- */
-struct keyring_list {
-	struct rcu_head	rcu;		/* RCU deletion hook */
-	unsigned short	maxkeys;	/* max keys this list can hold */
-	unsigned short	nkeys;		/* number of keys currently held */
-	unsigned short	delkey;		/* key to be unlinked by RCU */
-	struct key __rcu *keys[0];
-};
-
+#include <linux/assoc_array.h>
 
 #endif /* _KEYS_KEYRING_TYPE_H */
diff --git a/include/linux/key.h b/include/linux/key.h
index ef596c7..2417f78 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -22,6 +22,7 @@
 #include <linux/sysctl.h>
 #include <linux/rwsem.h>
 #include <linux/atomic.h>
+#include <linux/assoc_array.h>
 
 #ifdef __KERNEL__
 #include <linux/uidgid.h>
@@ -196,11 +197,13 @@ struct key {
 	 *   whatever
 	 */
 	union {
-		unsigned long		value;
-		void __rcu		*rcudata;
-		void			*data;
-		struct keyring_list __rcu *subscriptions;
-	} payload;
+		union {
+			unsigned long		value;
+			void __rcu		*rcudata;
+			void			*data;
+		} payload;
+		struct assoc_array keys;
+	};
 };
 
 extern struct key *key_alloc(struct key_type *type,
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index a095281..17edeaf 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -12,6 +12,7 @@
  */
 //#define DEBUG
 #include <linux/slab.h>
+#include <linux/err.h>
 #include <linux/assoc_array_priv.h>
 
 /*
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index a90d6d3..15e0dfe 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -4,6 +4,7 @@
 
 config KEYS
 	bool "Enable access key retention support"
+	select ASSOCIATIVE_ARRAY
 	help
 	  This option provides support for retaining authentication tokens and
 	  access keys in the kernel.
diff --git a/security/keys/gc.c b/security/keys/gc.c
index d67c97b..cce621c 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -130,6 +130,13 @@ void key_gc_keytype(struct key_type *ktype)
 	kleave("");
 }
 
+static int key_gc_keyring_func(const void *object, void *iterator_data)
+{
+	const struct key *key = object;
+	time_t *limit = iterator_data;
+	return key_is_dead(key, *limit);
+}
+
 /*
  * Garbage collect pointers from a keyring.
  *
@@ -138,10 +145,9 @@ void key_gc_keytype(struct key_type *ktype)
  */
 static void key_gc_keyring(struct key *keyring, time_t limit)
 {
-	struct keyring_list *klist;
-	int loop;
+	int result;
 
-	kenter("%x", key_serial(keyring));
+	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
 
 	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
 			      (1 << KEY_FLAG_REVOKED)))
@@ -149,27 +155,17 @@ static void key_gc_keyring(struct key *keyring, time_t limit)
 
 	/* scan the keyring looking for dead keys */
 	rcu_read_lock();
-	klist = rcu_dereference(keyring->payload.subscriptions);
-	if (!klist)
-		goto unlock_dont_gc;
-
-	loop = klist->nkeys;
-	smp_rmb();
-	for (loop--; loop >= 0; loop--) {
-		struct key *key = rcu_dereference(klist->keys[loop]);
-		if (key_is_dead(key, limit))
-			goto do_gc;
-	}
-
-unlock_dont_gc:
+	result = assoc_array_iterate(&keyring->keys,
+				     key_gc_keyring_func, &limit);
 	rcu_read_unlock();
+	if (result == true)
+		goto do_gc;
+
 dont_gc:
 	kleave(" [no gc]");
 	return;
 
 do_gc:
-	rcu_read_unlock();
-
 	keyring_gc(keyring, limit);
 	kleave(" [gc]");
 }
@@ -392,7 +388,6 @@ found_unreferenced_key:
 	 */
 found_keyring:
 	spin_unlock(&key_serial_lock);
-	kdebug("scan keyring %d", key->serial);
 	key_gc_keyring(key, limit);
 	goto maybe_resched;
 
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 73950bf..581c6f6 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -90,20 +90,23 @@ extern void key_type_put(struct key_type *ktype);
 
 extern int __key_link_begin(struct key *keyring,
 			    const struct keyring_index_key *index_key,
-			    unsigned long *_prealloc);
+			    struct assoc_array_edit **_edit);
 extern int __key_link_check_live_key(struct key *keyring, struct key *key);
-extern void __key_link(struct key *keyring, struct key *key,
-		       unsigned long *_prealloc);
+extern void __key_link(struct key *key, struct assoc_array_edit **_edit);
 extern void __key_link_end(struct key *keyring,
 			   const struct keyring_index_key *index_key,
-			   unsigned long prealloc);
+			   struct assoc_array_edit *edit);
 
-extern key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-				      const struct keyring_index_key *index_key);
+extern key_ref_t find_key_to_update(key_ref_t keyring_ref,
+				    const struct keyring_index_key *index_key);
 
 extern struct key *keyring_search_instkey(struct key *keyring,
 					  key_serial_t target_id);
 
+extern int iterate_over_keyring(const struct key *keyring,
+				int (*func)(const struct key *key, void *data),
+				void *data);
+
 typedef int (*key_match_func_t)(const struct key *, const void *);
 
 struct keyring_search_context {
@@ -119,6 +122,8 @@ struct keyring_search_context {
 #define KEYRING_SEARCH_NO_CHECK_PERM	0x0010	/* Don't check permissions */
 #define KEYRING_SEARCH_DETECT_TOO_DEEP	0x0020	/* Give an error on excessive depth */
 
+	int (*iterator)(const void *object, void *iterator_data);
+
 	/* Internal stuff */
 	int			skipped_ret;
 	bool			possessed;
diff --git a/security/keys/key.c b/security/keys/key.c
index 7d716b8..a819b5c 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -409,7 +409,7 @@ static int __key_instantiate_and_link(struct key *key,
 				      struct key_preparsed_payload *prep,
 				      struct key *keyring,
 				      struct key *authkey,
-				      unsigned long *_prealloc)
+				      struct assoc_array_edit **_edit)
 {
 	int ret, awaken;
 
@@ -436,7 +436,7 @@ static int __key_instantiate_and_link(struct key *key,
 
 			/* and link it into the destination keyring */
 			if (keyring)
-				__key_link(keyring, key, _prealloc);
+				__key_link(key, _edit);
 
 			/* disable the authorisation key */
 			if (authkey)
@@ -476,7 +476,7 @@ int key_instantiate_and_link(struct key *key,
 			     struct key *authkey)
 {
 	struct key_preparsed_payload prep;
-	unsigned long prealloc;
+	struct assoc_array_edit *edit;
 	int ret;
 
 	memset(&prep, 0, sizeof(prep));
@@ -490,16 +490,15 @@ int key_instantiate_and_link(struct key *key,
 	}
 
 	if (keyring) {
-		ret = __key_link_begin(keyring, &key->index_key, &prealloc);
+		ret = __key_link_begin(keyring, &key->index_key, &edit);
 		if (ret < 0)
 			goto error_free_preparse;
 	}
 
-	ret = __key_instantiate_and_link(key, &prep, keyring, authkey,
-					 &prealloc);
+	ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit);
 
 	if (keyring)
-		__key_link_end(keyring, &key->index_key, prealloc);
+		__key_link_end(keyring, &key->index_key, edit);
 
 error_free_preparse:
 	if (key->type->preparse)
@@ -537,7 +536,7 @@ int key_reject_and_link(struct key *key,
 			struct key *keyring,
 			struct key *authkey)
 {
-	unsigned long prealloc;
+	struct assoc_array_edit *edit;
 	struct timespec now;
 	int ret, awaken, link_ret = 0;
 
@@ -548,7 +547,7 @@ int key_reject_and_link(struct key *key,
 	ret = -EBUSY;
 
 	if (keyring)
-		link_ret = __key_link_begin(keyring, &key->index_key, &prealloc);
+		link_ret = __key_link_begin(keyring, &key->index_key, &edit);
 
 	mutex_lock(&key_construction_mutex);
 
@@ -570,7 +569,7 @@ int key_reject_and_link(struct key *key,
 
 		/* and link it into the destination keyring */
 		if (keyring && link_ret == 0)
-			__key_link(keyring, key, &prealloc);
+			__key_link(key, &edit);
 
 		/* disable the authorisation key */
 		if (authkey)
@@ -580,7 +579,7 @@ int key_reject_and_link(struct key *key,
 	mutex_unlock(&key_construction_mutex);
 
 	if (keyring)
-		__key_link_end(keyring, &key->index_key, prealloc);
+		__key_link_end(keyring, &key->index_key, edit);
 
 	/* wake up anyone waiting for a key to be constructed */
 	if (awaken)
@@ -783,8 +782,8 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 		.description	= description,
 	};
 	struct key_preparsed_payload prep;
+	struct assoc_array_edit *edit;
 	const struct cred *cred = current_cred();
-	unsigned long prealloc;
 	struct key *keyring, *key = NULL;
 	key_ref_t key_ref;
 	int ret;
@@ -828,7 +827,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	}
 	index_key.desc_len = strlen(index_key.description);
 
-	ret = __key_link_begin(keyring, &index_key, &prealloc);
+	ret = __key_link_begin(keyring, &index_key, &edit);
 	if (ret < 0) {
 		key_ref = ERR_PTR(ret);
 		goto error_free_prep;
@@ -847,8 +846,8 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	 * update that instead if possible
 	 */
 	if (index_key.type->update) {
-		key_ref = __keyring_search_one(keyring_ref, &index_key);
-		if (!IS_ERR(key_ref))
+		key_ref = find_key_to_update(keyring_ref, &index_key);
+		if (key_ref)
 			goto found_matching_key;
 	}
 
@@ -874,7 +873,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	}
 
 	/* instantiate it and link it into the target keyring */
-	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &prealloc);
+	ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &edit);
 	if (ret < 0) {
 		key_put(key);
 		key_ref = ERR_PTR(ret);
@@ -884,7 +883,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 
 error_link_end:
-	__key_link_end(keyring, &index_key, prealloc);
+	__key_link_end(keyring, &index_key, edit);
 error_free_prep:
 	if (index_key.type->preparse)
 		index_key.type->free_preparse(&prep);
@@ -897,7 +896,7 @@ error:
 	/* we found a matching key, so we're going to try to update it
 	 * - we can drop the locks first as we have the key pinned
 	 */
-	__key_link_end(keyring, &index_key, prealloc);
+	__key_link_end(keyring, &index_key, edit);
 
 	key_ref = __key_update(key_ref, &prep);
 	goto error_free_prep;
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index eeef1a0..f7cdea2 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1,6 +1,6 @@
 /* Keyring handling
  *
- * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
@@ -17,25 +17,11 @@
 #include <linux/seq_file.h>
 #include <linux/err.h>
 #include <keys/keyring-type.h>
+#include <keys/user-type.h>
+#include <linux/assoc_array_priv.h>
 #include <linux/uaccess.h>
 #include "internal.h"
 
-#define rcu_dereference_locked_keyring(keyring)				\
-	(rcu_dereference_protected(					\
-		(keyring)->payload.subscriptions,			\
-		rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
-
-#define rcu_deref_link_locked(klist, index, keyring)			\
-	(rcu_dereference_protected(					\
-		(klist)->keys[index],					\
-		rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
-
-#define MAX_KEYRING_LINKS						\
-	min_t(size_t, USHRT_MAX - 1,					\
-	      ((PAGE_SIZE - sizeof(struct keyring_list)) / sizeof(struct key *)))
-
-#define KEY_LINK_FIXQUOTA 1UL
-
 /*
  * When plumbing the depths of the key tree, this sets a hard limit
  * set on how deep we're willing to go.
@@ -47,6 +33,28 @@
  */
 #define KEYRING_NAME_HASH_SIZE	(1 << 5)
 
+/*
+ * We mark pointers we pass to the associative array with bit 1 set if
+ * they're keyrings and clear otherwise.
+ */
+#define KEYRING_PTR_SUBTYPE	0x2UL
+
+static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
+{
+	return (unsigned long)x & KEYRING_PTR_SUBTYPE;
+}
+static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
+{
+	void *object = assoc_array_ptr_to_leaf(x);
+	return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
+}
+static inline void *keyring_key_to_ptr(struct key *key)
+{
+	if (key->type == &key_type_keyring)
+		return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
+	return key;
+}
+
 static struct list_head	keyring_name_hash[KEYRING_NAME_HASH_SIZE];
 static DEFINE_RWLOCK(keyring_name_lock);
 
@@ -67,7 +75,6 @@ static inline unsigned keyring_hash(const char *desc)
  */
 static int keyring_instantiate(struct key *keyring,
 			       struct key_preparsed_payload *prep);
-static int keyring_match(const struct key *keyring, const void *criterion);
 static void keyring_revoke(struct key *keyring);
 static void keyring_destroy(struct key *keyring);
 static void keyring_describe(const struct key *keyring, struct seq_file *m);
@@ -76,9 +83,9 @@ static long keyring_read(const struct key *keyring,
 
 struct key_type key_type_keyring = {
 	.name		= "keyring",
-	.def_datalen	= sizeof(struct keyring_list),
+	.def_datalen	= 0,
 	.instantiate	= keyring_instantiate,
-	.match		= keyring_match,
+	.match		= user_match,
 	.revoke		= keyring_revoke,
 	.destroy	= keyring_destroy,
 	.describe	= keyring_describe,
@@ -127,6 +134,7 @@ static int keyring_instantiate(struct key *keyring,
 
 	ret = -EINVAL;
 	if (prep->datalen == 0) {
+		assoc_array_init(&keyring->keys);
 		/* make the keyring available by name if it has one */
 		keyring_publish_name(keyring);
 		ret = 0;
@@ -136,15 +144,226 @@ static int keyring_instantiate(struct key *keyring,
 }
 
 /*
- * Match keyrings on their name
+ * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
+ * fold the carry back too, but that requires inline asm.
+ */
+static u64 mult_64x32_and_fold(u64 x, u32 y)
+{
+	u64 hi = (u64)(u32)(x >> 32) * y;
+	u64 lo = (u64)(u32)(x) * y;
+	return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
+}
+
+/*
+ * Hash a key type and description.
+ */
+static unsigned long hash_key_type_and_desc(const struct keyring_index_key *index_key)
+{
+	const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
+	const unsigned long level_mask = ASSOC_ARRAY_LEVEL_STEP_MASK;
+	const char *description = index_key->description;
+	unsigned long hash, type;
+	u32 piece;
+	u64 acc;
+	int n, desc_len = index_key->desc_len;
+
+	type = (unsigned long)index_key->type;
+
+	acc = mult_64x32_and_fold(type, desc_len + 13);
+	acc = mult_64x32_and_fold(acc, 9207);
+	for (;;) {
+		n = desc_len;
+		if (n <= 0)
+			break;
+		if (n > 4)
+			n = 4;
+		piece = 0;
+		memcpy(&piece, description, n);
+		description += n;
+		desc_len -= n;
+		acc = mult_64x32_and_fold(acc, piece);
+		acc = mult_64x32_and_fold(acc, 9207);
+	}
+
+	/* Fold the hash down to 32 bits if need be. */
+	hash = acc;
+	if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
+		hash ^= acc >> 32;
+
+	/* Squidge all the keyrings into a separate part of the tree to
+	 * ordinary keys by making sure the lowest level segment in the hash is
+	 * zero for keyrings and non-zero otherwise.
+	 */
+	if (index_key->type != &key_type_keyring && (hash & level_mask) == 0)
+		return hash | (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
+	if (index_key->type == &key_type_keyring && (hash & level_mask) != 0)
+		return (hash + (hash << level_shift)) & ~level_mask;
+	return hash;
+}
+
+/*
+ * Build the next index key chunk.
+ *
+ * On 32-bit systems the index key is laid out as:
+ *
+ *	0	4	5	9...
+ *	hash	desclen	typeptr	desc[]
+ *
+ * On 64-bit systems:
+ *
+ *	0	8	9	17...
+ *	hash	desclen	typeptr	desc[]
+ *
+ * We return it one word-sized chunk at a time.
  */
-static int keyring_match(const struct key *keyring, const void *description)
+static unsigned long keyring_get_key_chunk(const void *data, int level)
+{
+	const struct keyring_index_key *index_key = data;
+	unsigned long chunk = 0;
+	long offset = 0;
+	int desc_len = index_key->desc_len, n = sizeof(chunk);
+
+	level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
+	switch (level) {
+	case 0:
+		return hash_key_type_and_desc(index_key);
+	case 1:
+		return ((unsigned long)index_key->type << 8) | desc_len;
+	case 2:
+		if (desc_len == 0)
+			return (u8)((unsigned long)index_key->type >>
+				    (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
+		n--;
+		offset = 1;
+	default:
+		offset += sizeof(chunk) - 1;
+		offset += (level - 3) * sizeof(chunk);
+		if (offset >= desc_len)
+			return 0;
+		desc_len -= offset;
+		if (desc_len > n)
+			desc_len = n;
+		offset += desc_len;
+		do {
+			chunk <<= 8;
+			chunk |= ((u8*)index_key->description)[--offset];
+		} while (--desc_len > 0);
+
+		if (level == 2) {
+			chunk <<= 8;
+			chunk |= (u8)((unsigned long)index_key->type >>
+				      (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
+		}
+		return chunk;
+	}
+}
+
+static unsigned long keyring_get_object_key_chunk(const void *object, int level)
+{
+	const struct key *key = keyring_ptr_to_key(object);
+	return keyring_get_key_chunk(&key->index_key, level);
+}
+
+static bool keyring_compare_object(const void *object, const void *data)
 {
-	return keyring->description &&
-		strcmp(keyring->description, description) == 0;
+	const struct keyring_index_key *index_key = data;
+	const struct key *key = keyring_ptr_to_key(object);
+
+	return key->index_key.type == index_key->type &&
+		key->index_key.desc_len == index_key->desc_len &&
+		memcmp(key->index_key.description, index_key->description,
+		       index_key->desc_len) == 0;
 }
 
 /*
+ * Compare the index keys of a pair of objects and determine the bit position
+ * at which they differ - if they differ.
+ */
+static int keyring_diff_objects(const void *_a, const void *_b)
+{
+	const struct key *key_a = keyring_ptr_to_key(_a);
+	const struct key *key_b = keyring_ptr_to_key(_b);
+	const struct keyring_index_key *a = &key_a->index_key;
+	const struct keyring_index_key *b = &key_b->index_key;
+	unsigned long seg_a, seg_b;
+	int level, i;
+
+	level = 0;
+	seg_a = hash_key_type_and_desc(a);
+	seg_b = hash_key_type_and_desc(b);
+	if ((seg_a ^ seg_b) != 0)
+		goto differ;
+
+	/* The number of bits contributed by the hash is controlled by a
+	 * constant in the assoc_array headers.  Everything else thereafter we
+	 * can deal with as being machine word-size dependent.
+	 */
+	level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
+	seg_a = a->desc_len;
+	seg_b = b->desc_len;
+	if ((seg_a ^ seg_b) != 0)
+		goto differ;
+
+	/* The next bit may not work on big endian */
+	level++;
+	seg_a = (unsigned long)a->type;
+	seg_b = (unsigned long)b->type;
+	if ((seg_a ^ seg_b) != 0)
+		goto differ;
+
+	level += sizeof(unsigned long);
+	if (a->desc_len == 0)
+		goto same;
+
+	i = 0;
+	if (((unsigned long)a->description | (unsigned long)b->description) &
+	    (sizeof(unsigned long) - 1)) {
+		do {
+			seg_a = *(unsigned long *)(a->description + i);
+			seg_b = *(unsigned long *)(b->description + i);
+			if ((seg_a ^ seg_b) != 0)
+				goto differ_plus_i;
+			i += sizeof(unsigned long);
+		} while (i < (a->desc_len & (sizeof(unsigned long) - 1)));
+	}
+
+	for (; i < a->desc_len; i++) {
+		seg_a = *(unsigned char *)(a->description + i);
+		seg_b = *(unsigned char *)(b->description + i);
+		if ((seg_a ^ seg_b) != 0)
+			goto differ_plus_i;
+	}
+
+same:
+	return -1;
+
+differ_plus_i:
+	level += i;
+differ:
+	i = level * 8 + __ffs(seg_a ^ seg_b);
+	return i;
+}
+
+/*
+ * Free an object after stripping the keyring flag off of the pointer.
+ */
+static void keyring_free_object(void *object)
+{
+	key_put(keyring_ptr_to_key(object));
+}
+
+/*
+ * Operations for keyring management by the index-tree routines.
+ */
+static const struct assoc_array_ops keyring_assoc_array_ops = {
+	.get_key_chunk		= keyring_get_key_chunk,
+	.get_object_key_chunk	= keyring_get_object_key_chunk,
+	.compare_object		= keyring_compare_object,
+	.diff_objects		= keyring_diff_objects,
+	.free_object		= keyring_free_object,
+};
+
+/*
  * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
  * and dispose of its data.
  *
@@ -155,9 +374,6 @@ static int keyring_match(const struct key *keyring, const void *description)
  */
 static void keyring_destroy(struct key *keyring)
 {
-	struct keyring_list *klist;
-	int loop;
-
 	if (keyring->description) {
 		write_lock(&keyring_name_lock);
 
@@ -168,12 +384,7 @@ static void keyring_destroy(struct key *keyring)
 		write_unlock(&keyring_name_lock);
 	}
 
-	klist = rcu_access_pointer(keyring->payload.subscriptions);
-	if (klist) {
-		for (loop = klist->nkeys - 1; loop >= 0; loop--)
-			key_put(rcu_access_pointer(klist->keys[loop]));
-		kfree(klist);
-	}
+	assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
 }
 
 /*
@@ -181,76 +392,88 @@ static void keyring_destroy(struct key *keyring)
  */
 static void keyring_describe(const struct key *keyring, struct seq_file *m)
 {
-	struct keyring_list *klist;
-
 	if (keyring->description)
 		seq_puts(m, keyring->description);
 	else
 		seq_puts(m, "[anon]");
 
 	if (key_is_instantiated(keyring)) {
-		rcu_read_lock();
-		klist = rcu_dereference(keyring->payload.subscriptions);
-		if (klist)
-			seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
+		if (keyring->keys.nr_leaves_on_tree != 0)
+			seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
 		else
 			seq_puts(m, ": empty");
-		rcu_read_unlock();
 	}
 }
 
+struct keyring_read_iterator_context {
+	size_t			qty;
+	size_t			count;
+	key_serial_t __user	*buffer;
+};
+
+static int keyring_read_iterator(const void *object, void *data)
+{
+	struct keyring_read_iterator_context *ctx = data;
+	const struct key *key = keyring_ptr_to_key(object);
+	int ret;
+
+	kenter("{%s,%d},,{%zu/%zu}",
+	       key->type->name, key->serial, ctx->count, ctx->qty);
+
+	if (ctx->count >= ctx->qty)
+		return 1;
+
+	ret = put_user(key->serial, ctx->buffer);
+	if (ret < 0)
+		return ret;
+	ctx->buffer++;
+	ctx->count += sizeof(key->serial);
+	return 0;
+}
+
 /*
  * Read a list of key IDs from the keyring's contents in binary form
  *
- * The keyring's semaphore is read-locked by the caller.
+ * The keyring's semaphore is read-locked by the caller.  This prevents someone
+ * from modifying it under us - which could cause us to read key IDs multiple
+ * times.
  */
 static long keyring_read(const struct key *keyring,
 			 char __user *buffer, size_t buflen)
 {
-	struct keyring_list *klist;
-	struct key *key;
-	size_t qty, tmp;
-	int loop, ret;
+	struct keyring_read_iterator_context ctx;
+	unsigned long nr_keys;
+	int ret;
 
-	ret = 0;
-	klist = rcu_dereference_locked_keyring(keyring);
-	if (klist) {
-		/* calculate how much data we could return */
-		qty = klist->nkeys * sizeof(key_serial_t);
-
-		if (buffer && buflen > 0) {
-			if (buflen > qty)
-				buflen = qty;
-
-			/* copy the IDs of the subscribed keys into the
-			 * buffer */
-			ret = -EFAULT;
-
-			for (loop = 0; loop < klist->nkeys; loop++) {
-				key = rcu_deref_link_locked(klist, loop,
-							    keyring);
-
-				tmp = sizeof(key_serial_t);
-				if (tmp > buflen)
-					tmp = buflen;
-
-				if (copy_to_user(buffer,
-						 &key->serial,
-						 tmp) != 0)
-					goto error;
-
-				buflen -= tmp;
-				if (buflen == 0)
-					break;
-				buffer += tmp;
-			}
-		}
+	kenter("{%d},,%zu", key_serial(keyring), buflen);
+
+	if (buflen & (sizeof(key_serial_t) - 1))
+		return -EINVAL;
+
+	nr_keys = keyring->keys.nr_leaves_on_tree;
+	if (nr_keys == 0)
+		return 0;
 
-		ret = qty;
+	/* Calculate how much data we could return */
+	ctx.qty = nr_keys * sizeof(key_serial_t);
+
+	if (!buffer || !buflen)
+		return ctx.qty;
+
+	if (buflen > ctx.qty)
+		ctx.qty = buflen;
+
+	/* Copy the IDs of the subscribed keys into the buffer */
+	ctx.buffer = (key_serial_t __user *)buffer;
+	ctx.count = 0;
+	ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
+	if (ret < 0) {
+		kleave(" = %d [iterate]", ret);
+		return ret;
 	}
 
-error:
-	return ret;
+	kleave(" = %zu [ok]", ctx.count);
+	return ctx.count;
 }
 
 /*
@@ -277,219 +500,360 @@ struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
 }
 EXPORT_SYMBOL(keyring_alloc);
 
-/**
- * keyring_search_aux - Search a keyring tree for a key matching some criteria
- * @keyring_ref: A pointer to the keyring with possession indicator.
- * @ctx: The keyring search context.
- *
- * Search the supplied keyring tree for a key that matches the criteria given.
- * The root keyring and any linked keyrings must grant Search permission to the
- * caller to be searchable and keys can only be found if they too grant Search
- * to the caller. The possession flag on the root keyring pointer controls use
- * of the possessor bits in permissions checking of the entire tree.  In
- * addition, the LSM gets to forbid keyring searches and key matches.
- *
- * The search is performed as a breadth-then-depth search up to the prescribed
- * limit (KEYRING_SEARCH_MAX_DEPTH).
- *
- * Keys are matched to the type provided and are then filtered by the match
- * function, which is given the description to use in any way it sees fit.  The
- * match function may use any attributes of a key that it wishes to to
- * determine the match.  Normally the match function from the key type would be
- * used.
- *
- * RCU is used to prevent the keyring key lists from disappearing without the
- * need to take lots of locks.
- *
- * Returns a pointer to the found key and increments the key usage count if
- * successful; -EAGAIN if no matching keys were found, or if expired or revoked
- * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
- * specified keyring wasn't a keyring.
- *
- * In the case of a successful return, the possession attribute from
- * @keyring_ref is propagated to the returned key reference.
+/*
+ * Iteration function to consider each key found.
  */
-key_ref_t keyring_search_aux(key_ref_t keyring_ref,
-			     struct keyring_search_context *ctx)
+static int keyring_search_iterator(const void *object, void *iterator_data)
 {
-	struct {
-		/* Need a separate keylist pointer for RCU purposes */
-		struct key *keyring;
-		struct keyring_list *keylist;
-		int kix;
-	} stack[KEYRING_SEARCH_MAX_DEPTH];
-
-	struct keyring_list *keylist;
-	unsigned long kflags;
-	struct key *keyring, *key;
-	key_ref_t key_ref;
-	long err;
-	int sp, nkeys, kix;
+	struct keyring_search_context *ctx = iterator_data;
+	const struct key *key = keyring_ptr_to_key(object);
+	unsigned long kflags = key->flags;
 
-	keyring = key_ref_to_ptr(keyring_ref);
-	ctx->possessed = is_key_possessed(keyring_ref);
-	key_check(keyring);
+	kenter("{%d}", key->serial);
 
-	/* top keyring must have search permission to begin the search */
-	err = key_task_permission(keyring_ref, ctx->cred, KEY_SEARCH);
-	if (err < 0) {
-		key_ref = ERR_PTR(err);
-		goto error;
+	/* ignore keys not of this type */
+	if (key->type != ctx->index_key.type) {
+		kleave(" = 0 [!type]");
+		return 0;
 	}
 
-	key_ref = ERR_PTR(-ENOTDIR);
-	if (keyring->type != &key_type_keyring)
-		goto error;
+	/* skip invalidated, revoked and expired keys */
+	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
+		if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
+			      (1 << KEY_FLAG_REVOKED))) {
+			ctx->result = ERR_PTR(-EKEYREVOKED);
+			kleave(" = %d [invrev]", ctx->skipped_ret);
+			goto skipped;
+		}
 
-	rcu_read_lock();
+		if (key->expiry && ctx->now.tv_sec >= key->expiry) {
+			ctx->result = ERR_PTR(-EKEYEXPIRED);
+			kleave(" = %d [expire]", ctx->skipped_ret);
+			goto skipped;
+		}
+	}
 
-	ctx->now = current_kernel_time();
-	err = -EAGAIN;
-	sp = 0;
-
-	/* firstly we should check to see if this top-level keyring is what we
-	 * are looking for */
-	key_ref = ERR_PTR(-EAGAIN);
-	kflags = keyring->flags;
-	if (keyring->type == ctx->index_key.type &&
-	    ctx->match(keyring, ctx->match_data)) {
-		key = keyring;
-		if (ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)
-			goto found;
+	/* keys that don't match */
+	if (!ctx->match(key, ctx->match_data)) {
+		kleave(" = 0 [!match]");
+		return 0;
+	}
 
-		/* check it isn't negative and hasn't expired or been
-		 * revoked */
-		if (kflags & (1 << KEY_FLAG_REVOKED))
-			goto error_2;
-		if (key->expiry && ctx->now.tv_sec >= key->expiry)
-			goto error_2;
-		key_ref = ERR_PTR(key->type_data.reject_error);
-		if (kflags & (1 << KEY_FLAG_NEGATIVE))
-			goto error_2;
-		goto found;
+	/* key must have search permissions */
+	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
+	    key_task_permission(make_key_ref(key, ctx->possessed),
+				ctx->cred, KEY_SEARCH) < 0) {
+		ctx->result = ERR_PTR(-EACCES);
+		kleave(" = %d [!perm]", ctx->skipped_ret);
+		goto skipped;
 	}
 
-	/* otherwise, the top keyring must not be revoked, expired, or
-	 * negatively instantiated if we are to search it */
-	key_ref = ERR_PTR(-EAGAIN);
-	if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
-		      (1 << KEY_FLAG_REVOKED) |
-		      (1 << KEY_FLAG_NEGATIVE)) ||
-	    (keyring->expiry && ctx->now.tv_sec >= keyring->expiry))
-		goto error_2;
-
-	/* start processing a new keyring */
-descend:
-	kflags = keyring->flags;
-	if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
-		      (1 << KEY_FLAG_REVOKED)))
-		goto not_this_keyring;
+	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
+		/* we set a different error code if we pass a negative key */
+		if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
+			ctx->result = ERR_PTR(key->type_data.reject_error);
+			kleave(" = %d [neg]", ctx->skipped_ret);
+			goto skipped;
+		}
+	}
 
-	keylist = rcu_dereference(keyring->payload.subscriptions);
-	if (!keylist)
-		goto not_this_keyring;
+	/* Found */
+	ctx->result = make_key_ref(key, ctx->possessed);
+	kleave(" = 1 [found]");
+	return 1;
 
-	/* iterate through the keys in this keyring first */
-	nkeys = keylist->nkeys;
-	smp_rmb();
-	for (kix = 0; kix < nkeys; kix++) {
-		key = rcu_dereference(keylist->keys[kix]);
-		kflags = key->flags;
+skipped:
+	return ctx->skipped_ret;
+}
 
-		/* ignore keys not of this type */
-		if (key->type != ctx->index_key.type)
-			continue;
+/*
+ * Search inside a keyring for a key.  We can search by walking to it
+ * directly based on its index-key or we can iterate over the entire
+ * tree looking for it, based on the match function.
+ */
+static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
+{
+	if ((ctx->flags & KEYRING_SEARCH_LOOKUP_TYPE) ==
+	    KEYRING_SEARCH_LOOKUP_DIRECT) {
+		const void *object;
+
+		object = assoc_array_find(&keyring->keys,
+					  &keyring_assoc_array_ops,
+					  &ctx->index_key);
+		return object ? ctx->iterator(object, ctx) : 0;
+	}
+	return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
+}
 
-		/* skip invalidated, revoked and expired keys */
-		if (!(ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)) {
-			if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
-				      (1 << KEY_FLAG_REVOKED)))
-				continue;
+/*
+ * Search a tree of keyrings that point to other keyrings up to the maximum
+ * depth.
+ */
+static bool search_nested_keyrings(struct key *keyring,
+				   struct keyring_search_context *ctx)
+{
+	struct {
+		struct key *keyring;
+		struct assoc_array_node *node;
+		int slot;
+	} stack[KEYRING_SEARCH_MAX_DEPTH];
 
-			if (key->expiry && ctx->now.tv_sec >= key->expiry)
-				continue;
-		}
+	struct assoc_array_shortcut *shortcut;
+	struct assoc_array_node *node;
+	struct assoc_array_ptr *ptr;
+	struct key *key;
+	int sp = 0, slot;
 
-		/* keys that don't match */
-		if (!ctx->match(key, ctx->match_data))
-			continue;
+	kenter("{%d},{%s,%s}",
+	       keyring->serial,
+	       ctx->index_key.type->name,
+	       ctx->index_key.description);
 
-		/* key must have search permissions */
-		if (key_task_permission(make_key_ref(key, ctx->possessed),
-					ctx->cred, KEY_SEARCH) < 0)
-			continue;
+	if (ctx->index_key.description)
+		ctx->index_key.desc_len = strlen(ctx->index_key.description);
 
-		if (ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)
+	/* Check to see if this top-level keyring is what we are looking for
+	 * and whether it is valid or not.
+	 */
+	if (ctx->flags & KEYRING_SEARCH_LOOKUP_ITERATE ||
+	    keyring_compare_object(keyring, &ctx->index_key)) {
+		ctx->skipped_ret = 2;
+		ctx->flags |= KEYRING_SEARCH_DO_STATE_CHECK;
+		switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
+		case 1:
 			goto found;
-
-		/* we set a different error code if we pass a negative key */
-		if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
-			err = key->type_data.reject_error;
-			continue;
+		case 2:
+			return false;
+		default:
+			break;
 		}
+	}
 
+	ctx->skipped_ret = 0;
+	if (ctx->flags & KEYRING_SEARCH_NO_STATE_CHECK)
+		ctx->flags &= ~KEYRING_SEARCH_DO_STATE_CHECK;
+
+	/* Start processing a new keyring */
+descend_to_keyring:
+	kdebug("descend to %d", keyring->serial);
+	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
+			      (1 << KEY_FLAG_REVOKED)))
+		goto not_this_keyring;
+
+	/* Search through the keys in this keyring before its searching its
+	 * subtrees.
+	 */
+	if (search_keyring(keyring, ctx))
 		goto found;
-	}
 
-	/* search through the keyrings nested in this one */
-	kix = 0;
-ascend:
-	nkeys = keylist->nkeys;
-	smp_rmb();
-	for (; kix < nkeys; kix++) {
-		key = rcu_dereference(keylist->keys[kix]);
-		if (key->type != &key_type_keyring)
-			continue;
+	/* Then manually iterate through the keyrings nested in this one.
+	 *
+	 * Start from the root node of the index tree.  Because of the way the
+	 * hash function has been set up, keyrings cluster on the leftmost
+	 * branch of the root node (root slot 0) or in the root node itself.
+	 * Non-keyrings avoid the leftmost branch of the root entirely (root
+	 * slots 1-15).
+	 */
+	ptr = ACCESS_ONCE(keyring->keys.root);
+	if (!ptr)
+		goto not_this_keyring;
 
-		/* recursively search nested keyrings
-		 * - only search keyrings for which we have search permission
+	if (assoc_array_ptr_is_shortcut(ptr)) {
+		/* If the root is a shortcut, either the keyring only contains
+		 * keyring pointers (everything clusters behind root slot 0) or
+		 * doesn't contain any keyring pointers.
 		 */
-		if (sp >= KEYRING_SEARCH_MAX_DEPTH)
+		shortcut = assoc_array_ptr_to_shortcut(ptr);
+		smp_read_barrier_depends();
+		if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
+			goto not_this_keyring;
+
+		ptr = ACCESS_ONCE(shortcut->next_node);
+		node = assoc_array_ptr_to_node(ptr);
+		goto begin_node;
+	}
+
+	node = assoc_array_ptr_to_node(ptr);
+	smp_read_barrier_depends();
+
+	ptr = node->slots[0];
+	if (!assoc_array_ptr_is_meta(ptr))
+		goto begin_node;
+
+descend_to_node:
+	/* Descend to a more distal node in this keyring's content tree and go
+	 * through that.
+	 */
+	kdebug("descend");
+	if (assoc_array_ptr_is_shortcut(ptr)) {
+		shortcut = assoc_array_ptr_to_shortcut(ptr);
+		smp_read_barrier_depends();
+		ptr = ACCESS_ONCE(shortcut->next_node);
+		BUG_ON(!assoc_array_ptr_is_node(ptr));
+		node = assoc_array_ptr_to_node(ptr);
+	}
+
+begin_node:
+	kdebug("begin_node");
+	smp_read_barrier_depends();
+	slot = 0;
+ascend_to_node:
+	/* Go through the slots in a node */
+	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
+		ptr = ACCESS_ONCE(node->slots[slot]);
+
+		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
+			goto descend_to_node;
+
+		if (!keyring_ptr_is_keyring(ptr))
 			continue;
 
-		if (key_task_permission(make_key_ref(key, ctx->possessed),
+		key = keyring_ptr_to_key(ptr);
+
+		if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
+			if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
+				ctx->result = ERR_PTR(-ELOOP);
+				return false;
+			}
+			goto not_this_keyring;
+		}
+
+		/* Search a nested keyring */
+		if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
+		    key_task_permission(make_key_ref(key, ctx->possessed),
 					ctx->cred, KEY_SEARCH) < 0)
 			continue;
 
 		/* stack the current position */
 		stack[sp].keyring = keyring;
-		stack[sp].keylist = keylist;
-		stack[sp].kix = kix;
+		stack[sp].node = node;
+		stack[sp].slot = slot;
 		sp++;
 
 		/* begin again with the new keyring */
 		keyring = key;
-		goto descend;
+		goto descend_to_keyring;
+	}
+
+	/* We've dealt with all the slots in the current node, so now we need
+	 * to ascend to the parent and continue processing there.
+	 */
+	ptr = ACCESS_ONCE(node->back_pointer);
+	slot = node->parent_slot;
+
+	if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
+		shortcut = assoc_array_ptr_to_shortcut(ptr);
+		smp_read_barrier_depends();
+		ptr = ACCESS_ONCE(shortcut->back_pointer);
+		slot = shortcut->parent_slot;
+	}
+	if (!ptr)
+		goto not_this_keyring;
+	node = assoc_array_ptr_to_node(ptr);
+	smp_read_barrier_depends();
+	slot++;
+
+	/* If we've ascended to the root (zero backpointer), we must have just
+	 * finished processing the leftmost branch rather than the root slots -
+	 * so there can't be any more keyrings for us to find.
+	 */
+	if (node->back_pointer) {
+		kdebug("ascend %d", slot);
+		goto ascend_to_node;
 	}
 
-	/* the keyring we're looking at was disqualified or didn't contain a
-	 * matching key */
+	/* The keyring we're looking at was disqualified or didn't contain a
+	 * matching key.
+	 */
 not_this_keyring:
-	if (sp > 0) {
-		/* resume the processing of a keyring higher up in the tree */
-		sp--;
-		keyring = stack[sp].keyring;
-		keylist = stack[sp].keylist;
-		kix = stack[sp].kix + 1;
-		goto ascend;
+	kdebug("not_this_keyring %d", sp);
+	if (sp <= 0) {
+		kleave(" = false");
+		return false;
 	}
 
-	key_ref = ERR_PTR(err);
-	goto error_2;
+	/* Resume the processing of a keyring higher up in the tree */
+	sp--;
+	keyring = stack[sp].keyring;
+	node = stack[sp].node;
+	slot = stack[sp].slot + 1;
+	kdebug("ascend to %d [%d]", keyring->serial, slot);
+	goto ascend_to_node;
 
-	/* we found a viable match */
+	/* We found a viable match */
 found:
-	__key_get(key);
-	key->last_used_at = ctx->now.tv_sec;
-	keyring->last_used_at = ctx->now.tv_sec;
-	while (sp > 0)
-		stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
+	key = key_ref_to_ptr(ctx->result);
 	key_check(key);
-	key_ref = make_key_ref(key, ctx->possessed);
-error_2:
+	if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
+		key->last_used_at = ctx->now.tv_sec;
+		keyring->last_used_at = ctx->now.tv_sec;
+		while (sp > 0)
+			stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
+	}
+	kleave(" = true");
+	return true;
+}
+
+/**
+ * keyring_search_aux - Search a keyring tree for a key matching some criteria
+ * @keyring_ref: A pointer to the keyring with possession indicator.
+ * @ctx: The keyring search context.
+ *
+ * Search the supplied keyring tree for a key that matches the criteria given.
+ * The root keyring and any linked keyrings must grant Search permission to the
+ * caller to be searchable and keys can only be found if they too grant Search
+ * to the caller. The possession flag on the root keyring pointer controls use
+ * of the possessor bits in permissions checking of the entire tree.  In
+ * addition, the LSM gets to forbid keyring searches and key matches.
+ *
+ * The search is performed as a breadth-then-depth search up to the prescribed
+ * limit (KEYRING_SEARCH_MAX_DEPTH).
+ *
+ * Keys are matched to the type provided and are then filtered by the match
+ * function, which is given the description to use in any way it sees fit.  The
+ * match function may use any attributes of a key that it wishes to to
+ * determine the match.  Normally the match function from the key type would be
+ * used.
+ *
+ * RCU can be used to prevent the keyring key lists from disappearing without
+ * the need to take lots of locks.
+ *
+ * Returns a pointer to the found key and increments the key usage count if
+ * successful; -EAGAIN if no matching keys were found, or if expired or revoked
+ * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
+ * specified keyring wasn't a keyring.
+ *
+ * In the case of a successful return, the possession attribute from
+ * @keyring_ref is propagated to the returned key reference.
+ */
+key_ref_t keyring_search_aux(key_ref_t keyring_ref,
+			     struct keyring_search_context *ctx)
+{
+	struct key *keyring;
+	long err;
+
+	ctx->iterator = keyring_search_iterator;
+	ctx->possessed = is_key_possessed(keyring_ref);
+	ctx->result = ERR_PTR(-EAGAIN);
+
+	keyring = key_ref_to_ptr(keyring_ref);
+	key_check(keyring);
+
+	if (keyring->type != &key_type_keyring)
+		return ERR_PTR(-ENOTDIR);
+
+	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
+		err = key_task_permission(keyring_ref, ctx->cred, KEY_SEARCH);
+		if (err < 0)
+			return ERR_PTR(err);
+	}
+
+	rcu_read_lock();
+	ctx->now = current_kernel_time();
+	if (search_nested_keyrings(keyring, ctx))
+		__key_get(key_ref_to_ptr(ctx->result));
 	rcu_read_unlock();
-error:
-	return key_ref;
+	return ctx->result;
 }
 
 /**
@@ -499,7 +863,7 @@ error:
  * @description: The name of the keyring we want to find.
  *
  * As keyring_search_aux() above, but using the current task's credentials and
- * type's default matching function.
+ * type's default matching function and preferred search method.
  */
 key_ref_t keyring_search(key_ref_t keyring,
 			 struct key_type *type,
@@ -523,58 +887,49 @@ key_ref_t keyring_search(key_ref_t keyring,
 EXPORT_SYMBOL(keyring_search);
 
 /*
- * Search the given keyring only (no recursion).
+ * Search the given keyring for a key that might be updated.
  *
  * The caller must guarantee that the keyring is a keyring and that the
- * permission is granted to search the keyring as no check is made here.
- *
- * RCU is used to make it unnecessary to lock the keyring key list here.
+ * permission is granted to modify the keyring as no check is made here.  The
+ * caller must also hold a lock on the keyring semaphore.
  *
  * Returns a pointer to the found key with usage count incremented if
- * successful and returns -ENOKEY if not found.  Revoked and invalidated keys
- * are skipped over.
+ * successful and returns NULL if not found.  Revoked and invalidated keys are
+ * skipped over.
  *
  * If successful, the possession indicator is propagated from the keyring ref
  * to the returned key reference.
  */
-key_ref_t __keyring_search_one(key_ref_t keyring_ref,
-			       const struct keyring_index_key *index_key)
+key_ref_t find_key_to_update(key_ref_t keyring_ref,
+			     const struct keyring_index_key *index_key)
 {
-	struct keyring_list *klist;
 	struct key *keyring, *key;
-	bool possessed;
-	int nkeys, loop;
+	const void *object;
 
 	keyring = key_ref_to_ptr(keyring_ref);
-	possessed = is_key_possessed(keyring_ref);
 
-	rcu_read_lock();
+	kenter("{%d},{%s,%s}",
+	       keyring->serial, index_key->type->name, index_key->description);
 
-	klist = rcu_dereference(keyring->payload.subscriptions);
-	if (klist) {
-		nkeys = klist->nkeys;
-		smp_rmb();
-		for (loop = 0; loop < nkeys ; loop++) {
-			key = rcu_dereference(klist->keys[loop]);
-			if (key->type == index_key->type &&
-			    (!key->type->match ||
-			     key->type->match(key, index_key->description)) &&
-			    !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
-					    (1 << KEY_FLAG_REVOKED)))
-			    )
-				goto found;
-		}
-	}
+	object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
+				  index_key);
 
-	rcu_read_unlock();
-	return ERR_PTR(-ENOKEY);
+	if (object)
+		goto found;
+
+	kleave(" = NULL");
+	return NULL;
 
 found:
+	key = keyring_ptr_to_key(object);
+	if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
+			  (1 << KEY_FLAG_REVOKED))) {
+		kleave(" = NULL [x]");
+		return NULL;
+	}
 	__key_get(key);
-	keyring->last_used_at = key->last_used_at =
-		current_kernel_time().tv_sec;
-	rcu_read_unlock();
-	return make_key_ref(key, possessed);
+	kleave(" = {%d}", key->serial);
+	return make_key_ref(key, is_key_possessed(keyring_ref));
 }
 
 /*
@@ -637,6 +992,19 @@ out:
 	return keyring;
 }
 
+static int keyring_detect_cycle_iterator(const void *object,
+					 void *iterator_data)
+{
+	struct keyring_search_context *ctx = iterator_data;
+	const struct key *key = keyring_ptr_to_key(object);
+
+	kenter("{%d}", key->serial);
+
+	BUG_ON(key != ctx->match_data);
+	ctx->result = ERR_PTR(-EDEADLK);
+	return 1;
+}
+
 /*
  * See if a cycle will will be created by inserting acyclic tree B in acyclic
  * tree A at the topmost level (ie: as a direct child of A).
@@ -646,117 +1014,39 @@ out:
  */
 static int keyring_detect_cycle(struct key *A, struct key *B)
 {
-	struct {
-		struct keyring_list *keylist;
-		int kix;
-	} stack[KEYRING_SEARCH_MAX_DEPTH];
-
-	struct keyring_list *keylist;
-	struct key *subtree, *key;
-	int sp, nkeys, kix, ret;
+	struct keyring_search_context ctx = {
+		.index_key	= A->index_key,
+		.match_data	= A,
+		.iterator	= keyring_detect_cycle_iterator,
+		.flags		= (KEYRING_SEARCH_LOOKUP_DIRECT |
+				   KEYRING_SEARCH_NO_STATE_CHECK |
+				   KEYRING_SEARCH_NO_UPDATE_TIME |
+				   KEYRING_SEARCH_NO_CHECK_PERM |
+				   KEYRING_SEARCH_DETECT_TOO_DEEP),
+	};
 
 	rcu_read_lock();
-
-	ret = -EDEADLK;
-	if (A == B)
-		goto cycle_detected;
-
-	subtree = B;
-	sp = 0;
-
-	/* start processing a new keyring */
-descend:
-	if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
-		goto not_this_keyring;
-
-	keylist = rcu_dereference(subtree->payload.subscriptions);
-	if (!keylist)
-		goto not_this_keyring;
-	kix = 0;
-
-ascend:
-	/* iterate through the remaining keys in this keyring */
-	nkeys = keylist->nkeys;
-	smp_rmb();
-	for (; kix < nkeys; kix++) {
-		key = rcu_dereference(keylist->keys[kix]);
-
-		if (key == A)
-			goto cycle_detected;
-
-		/* recursively check nested keyrings */
-		if (key->type == &key_type_keyring) {
-			if (sp >= KEYRING_SEARCH_MAX_DEPTH)
-				goto too_deep;
-
-			/* stack the current position */
-			stack[sp].keylist = keylist;
-			stack[sp].kix = kix;
-			sp++;
-
-			/* begin again with the new keyring */
-			subtree = key;
-			goto descend;
-		}
-	}
-
-	/* the keyring we're looking at was disqualified or didn't contain a
-	 * matching key */
-not_this_keyring:
-	if (sp > 0) {
-		/* resume the checking of a keyring higher up in the tree */
-		sp--;
-		keylist = stack[sp].keylist;
-		kix = stack[sp].kix + 1;
-		goto ascend;
-	}
-
-	ret = 0; /* no cycles detected */
-
-error:
+	search_nested_keyrings(B, &ctx);
 	rcu_read_unlock();
-	return ret;
-
-too_deep:
-	ret = -ELOOP;
-	goto error;
-
-cycle_detected:
-	ret = -EDEADLK;
-	goto error;
-}
-
-/*
- * Dispose of a keyring list after the RCU grace period, freeing the unlinked
- * key
- */
-static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
-{
-	struct keyring_list *klist =
-		container_of(rcu, struct keyring_list, rcu);
-
-	if (klist->delkey != USHRT_MAX)
-		key_put(rcu_access_pointer(klist->keys[klist->delkey]));
-	kfree(klist);
+	return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
 }
 
 /*
  * Preallocate memory so that a key can be linked into to a keyring.
  */
-int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_key,
-		     unsigned long *_prealloc)
+int __key_link_begin(struct key *keyring,
+		     const struct keyring_index_key *index_key,
+		     struct assoc_array_edit **_edit)
 	__acquires(&keyring->sem)
 	__acquires(&keyring_serialise_link_sem)
 {
-	struct keyring_list *klist, *nklist;
-	unsigned long prealloc;
-	unsigned max;
-	time_t lowest_lru;
-	size_t size;
-	int loop, lru, ret;
+	struct assoc_array_edit *edit;
+	int ret;
 
 	kenter("%d,%s,%s,",
-	       key_serial(keyring), index_key->type->name, index_key->description);
+	       keyring->serial, index_key->type->name, index_key->description);
+
+	BUG_ON(index_key->desc_len == 0);
 
 	if (keyring->type != &key_type_keyring)
 		return -ENOTDIR;
@@ -772,88 +1062,25 @@ int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_
 	if (index_key->type == &key_type_keyring)
 		down_write(&keyring_serialise_link_sem);
 
-	klist = rcu_dereference_locked_keyring(keyring);
-
-	/* see if there's a matching key we can displace */
-	lru = -1;
-	if (klist && klist->nkeys > 0) {
-		lowest_lru = TIME_T_MAX;
-		for (loop = klist->nkeys - 1; loop >= 0; loop--) {
-			struct key *key = rcu_deref_link_locked(klist, loop,
-								keyring);
-			if (key->type == index_key->type &&
-			    strcmp(key->description, index_key->description) == 0) {
-				/* Found a match - we'll replace the link with
-				 * one to the new key.  We record the slot
-				 * position.
-				 */
-				klist->delkey = loop;
-				prealloc = 0;
-				goto done;
-			}
-			if (key->last_used_at < lowest_lru) {
-				lowest_lru = key->last_used_at;
-				lru = loop;
-			}
-		}
-	}
-
-	/* If the keyring is full then do an LRU discard */
-	if (klist &&
-	    klist->nkeys == klist->maxkeys &&
-	    klist->maxkeys >= MAX_KEYRING_LINKS) {
-		kdebug("LRU discard %d\n", lru);
-		klist->delkey = lru;
-		prealloc = 0;
-		goto done;
-	}
-
 	/* check that we aren't going to overrun the user's quota */
 	ret = key_payload_reserve(keyring,
 				  keyring->datalen + KEYQUOTA_LINK_BYTES);
 	if (ret < 0)
 		goto error_sem;
 
-	if (klist && klist->nkeys < klist->maxkeys) {
-		/* there's sufficient slack space to append directly */
-		klist->delkey = klist->nkeys;
-		prealloc = KEY_LINK_FIXQUOTA;
-	} else {
-		/* grow the key list */
-		max = 4;
-		if (klist) {
-			max += klist->maxkeys;
-			if (max > MAX_KEYRING_LINKS)
-				max = MAX_KEYRING_LINKS;
-			BUG_ON(max <= klist->maxkeys);
-		}
-
-		size = sizeof(*klist) + sizeof(struct key *) * max;
-
-		ret = -ENOMEM;
-		nklist = kmalloc(size, GFP_KERNEL);
-		if (!nklist)
-			goto error_quota;
-
-		nklist->maxkeys = max;
-		if (klist) {
-			memcpy(nklist->keys, klist->keys,
-			       sizeof(struct key *) * klist->nkeys);
-			nklist->delkey = klist->nkeys;
-			nklist->nkeys = klist->nkeys + 1;
-			klist->delkey = USHRT_MAX;
-		} else {
-			nklist->nkeys = 1;
-			nklist->delkey = 0;
-		}
-
-		/* add the key into the new space */
-		RCU_INIT_POINTER(nklist->keys[nklist->delkey], NULL);
-		prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
+	/* Create an edit script that will insert/replace the key in the
+	 * keyring tree.
+	 */
+	edit = assoc_array_insert(&keyring->keys,
+				  &keyring_assoc_array_ops,
+				  index_key,
+				  NULL);
+	if (IS_ERR(edit)) {
+		ret = PTR_ERR(edit);
+		goto error_quota;
 	}
 
-done:
-	*_prealloc = prealloc;
+	*_edit = edit;
 	kleave(" = 0");
 	return 0;
 
@@ -893,60 +1120,12 @@ int __key_link_check_live_key(struct key *keyring, struct key *key)
  * holds at most one link to any given key of a particular type+description
  * combination.
  */
-void __key_link(struct key *keyring, struct key *key,
-		unsigned long *_prealloc)
+void __key_link(struct key *key, struct assoc_array_edit **_edit)
 {
-	struct keyring_list *klist, *nklist;
-	struct key *discard;
-
-	nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
-	*_prealloc = 0;
-
-	kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
-
-	klist = rcu_dereference_locked_keyring(keyring);
-
 	__key_get(key);
-	keyring->last_used_at = key->last_used_at =
-		current_kernel_time().tv_sec;
-
-	/* there's a matching key we can displace or an empty slot in a newly
-	 * allocated list we can fill */
-	if (nklist) {
-		kdebug("reissue %hu/%hu/%hu",
-		       nklist->delkey, nklist->nkeys, nklist->maxkeys);
-
-		RCU_INIT_POINTER(nklist->keys[nklist->delkey], key);
-
-		rcu_assign_pointer(keyring->payload.subscriptions, nklist);
-
-		/* dispose of the old keyring list and, if there was one, the
-		 * displaced key */
-		if (klist) {
-			kdebug("dispose %hu/%hu/%hu",
-			       klist->delkey, klist->nkeys, klist->maxkeys);
-			call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
-		}
-	} else if (klist->delkey < klist->nkeys) {
-		kdebug("replace %hu/%hu/%hu",
-		       klist->delkey, klist->nkeys, klist->maxkeys);
-
-		discard = rcu_dereference_protected(
-			klist->keys[klist->delkey],
-			rwsem_is_locked(&keyring->sem));
-		rcu_assign_pointer(klist->keys[klist->delkey], key);
-		/* The garbage collector will take care of RCU
-		 * synchronisation */
-		key_put(discard);
-	} else {
-		/* there's sufficient slack space to append directly */
-		kdebug("append %hu/%hu/%hu",
-		       klist->delkey, klist->nkeys, klist->maxkeys);
-
-		RCU_INIT_POINTER(klist->keys[klist->delkey], key);
-		smp_wmb();
-		klist->nkeys++;
-	}
+	assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
+	assoc_array_apply_edit(*_edit);
+	*_edit = NULL;
 }
 
 /*
@@ -956,23 +1135,20 @@ void __key_link(struct key *keyring, struct key *key,
  */
 void __key_link_end(struct key *keyring,
 		    const struct keyring_index_key *index_key,
-		    unsigned long prealloc)
+		    struct assoc_array_edit *edit)
 	__releases(&keyring->sem)
 	__releases(&keyring_serialise_link_sem)
 {
 	BUG_ON(index_key->type == NULL);
-	BUG_ON(index_key->type->name == NULL);
-	kenter("%d,%s,%lx", keyring->serial, index_key->type->name, prealloc);
+	kenter("%d,%s,", keyring->serial, index_key->type->name);
 
 	if (index_key->type == &key_type_keyring)
 		up_write(&keyring_serialise_link_sem);
 
-	if (prealloc) {
-		if (prealloc & KEY_LINK_FIXQUOTA)
-			key_payload_reserve(keyring,
-					    keyring->datalen -
-					    KEYQUOTA_LINK_BYTES);
-		kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
+	if (edit) {
+		key_payload_reserve(keyring,
+				    keyring->datalen - KEYQUOTA_LINK_BYTES);
+		assoc_array_cancel_edit(edit);
 	}
 	up_write(&keyring->sem);
 }
@@ -999,20 +1175,24 @@ void __key_link_end(struct key *keyring,
  */
 int key_link(struct key *keyring, struct key *key)
 {
-	unsigned long prealloc;
+	struct assoc_array_edit *edit;
 	int ret;
 
+	kenter("{%d,%d}", keyring->serial, atomic_read(&keyring->usage));
+
 	key_check(keyring);
 	key_check(key);
 
-	ret = __key_link_begin(keyring, &key->index_key, &prealloc);
+	ret = __key_link_begin(keyring, &key->index_key, &edit);
 	if (ret == 0) {
+		kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage));
 		ret = __key_link_check_live_key(keyring, key);
 		if (ret == 0)
-			__key_link(keyring, key, &prealloc);
-		__key_link_end(keyring, &key->index_key, prealloc);
+			__key_link(key, &edit);
+		__key_link_end(keyring, &key->index_key, edit);
 	}
 
+	kleave(" = %d {%d,%d}", ret, keyring->serial, atomic_read(&keyring->usage));
 	return ret;
 }
 EXPORT_SYMBOL(key_link);
@@ -1036,90 +1216,36 @@ EXPORT_SYMBOL(key_link);
  */
 int key_unlink(struct key *keyring, struct key *key)
 {
-	struct keyring_list *klist, *nklist;
-	int loop, ret;
+	struct assoc_array_edit *edit;
+	int ret;
 
 	key_check(keyring);
 	key_check(key);
 
-	ret = -ENOTDIR;
 	if (keyring->type != &key_type_keyring)
-		goto error;
+		return -ENOTDIR;
 
 	down_write(&keyring->sem);
 
-	klist = rcu_dereference_locked_keyring(keyring);
-	if (klist) {
-		/* search the keyring for the key */
-		for (loop = 0; loop < klist->nkeys; loop++)
-			if (rcu_access_pointer(klist->keys[loop]) == key)
-				goto key_is_present;
+	edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
+				  &key->index_key);
+	if (IS_ERR(edit)) {
+		ret = PTR_ERR(edit);
+		goto error;
 	}
-
-	up_write(&keyring->sem);
 	ret = -ENOENT;
-	goto error;
-
-key_is_present:
-	/* we need to copy the key list for RCU purposes */
-	nklist = kmalloc(sizeof(*klist) +
-			 sizeof(struct key *) * klist->maxkeys,
-			 GFP_KERNEL);
-	if (!nklist)
-		goto nomem;
-	nklist->maxkeys = klist->maxkeys;
-	nklist->nkeys = klist->nkeys - 1;
-
-	if (loop > 0)
-		memcpy(&nklist->keys[0],
-		       &klist->keys[0],
-		       loop * sizeof(struct key *));
-
-	if (loop < nklist->nkeys)
-		memcpy(&nklist->keys[loop],
-		       &klist->keys[loop + 1],
-		       (nklist->nkeys - loop) * sizeof(struct key *));
-
-	/* adjust the user's quota */
-	key_payload_reserve(keyring,
-			    keyring->datalen - KEYQUOTA_LINK_BYTES);
-
-	rcu_assign_pointer(keyring->payload.subscriptions, nklist);
-
-	up_write(&keyring->sem);
-
-	/* schedule for later cleanup */
-	klist->delkey = loop;
-	call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
+	if (edit == NULL)
+		goto error;
 
+	assoc_array_apply_edit(edit);
 	ret = 0;
 
 error:
-	return ret;
-nomem:
-	ret = -ENOMEM;
 	up_write(&keyring->sem);
-	goto error;
+	return ret;
 }
 EXPORT_SYMBOL(key_unlink);
 
-/*
- * Dispose of a keyring list after the RCU grace period, releasing the keys it
- * links to.
- */
-static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
-{
-	struct keyring_list *klist;
-	int loop;
-
-	klist = container_of(rcu, struct keyring_list, rcu);
-
-	for (loop = klist->nkeys - 1; loop >= 0; loop--)
-		key_put(rcu_access_pointer(klist->keys[loop]));
-
-	kfree(klist);
-}
-
 /**
  * keyring_clear - Clear a keyring
  * @keyring: The keyring to clear.
@@ -1130,33 +1256,25 @@ static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
  */
 int keyring_clear(struct key *keyring)
 {
-	struct keyring_list *klist;
+	struct assoc_array_edit *edit;
 	int ret;
 
-	ret = -ENOTDIR;
-	if (keyring->type == &key_type_keyring) {
-		/* detach the pointer block with the locks held */
-		down_write(&keyring->sem);
-
-		klist = rcu_dereference_locked_keyring(keyring);
-		if (klist) {
-			/* adjust the quota */
-			key_payload_reserve(keyring,
-					    sizeof(struct keyring_list));
-
-			rcu_assign_pointer(keyring->payload.subscriptions,
-					   NULL);
-		}
-
-		up_write(&keyring->sem);
+	if (keyring->type != &key_type_keyring)
+		return -ENOTDIR;
 
-		/* free the keys after the locks have been dropped */
-		if (klist)
-			call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
+	down_write(&keyring->sem);
 
+	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
+	if (IS_ERR(edit)) {
+		ret = PTR_ERR(edit);
+	} else {
+		if (edit)
+			assoc_array_apply_edit(edit);
+		key_payload_reserve(keyring, 0);
 		ret = 0;
 	}
 
+	up_write(&keyring->sem);
 	return ret;
 }
 EXPORT_SYMBOL(keyring_clear);
@@ -1168,17 +1286,25 @@ EXPORT_SYMBOL(keyring_clear);
  */
 static void keyring_revoke(struct key *keyring)
 {
-	struct keyring_list *klist;
+	struct assoc_array_edit *edit;
 
-	klist = rcu_dereference_locked_keyring(keyring);
+	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
+	if (!IS_ERR(edit)) {
+		if (edit)
+			assoc_array_apply_edit(edit);
+		key_payload_reserve(keyring, 0);
+	}
+}
 
-	/* adjust the quota */
-	key_payload_reserve(keyring, 0);
+static bool gc_iterator(void *object, void *iterator_data)
+{
+	struct key *key = keyring_ptr_to_key(object);
+	time_t *limit = iterator_data;
 
-	if (klist) {
-		rcu_assign_pointer(keyring->payload.subscriptions, NULL);
-		call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
-	}
+	if (key_is_dead(key, *limit))
+		return false;
+	key_get(key);
+	return true;
 }
 
 /*
@@ -1191,88 +1317,12 @@ static void keyring_revoke(struct key *keyring)
  */
 void keyring_gc(struct key *keyring, time_t limit)
 {
-	struct keyring_list *klist, *new;
-	struct key *key;
-	int loop, keep, max;
-
 	kenter("{%x,%s}", key_serial(keyring), keyring->description);
 
 	down_write(&keyring->sem);
-
-	klist = rcu_dereference_locked_keyring(keyring);
-	if (!klist)
-		goto no_klist;
-
-	/* work out how many subscriptions we're keeping */
-	keep = 0;
-	for (loop = klist->nkeys - 1; loop >= 0; loop--)
-		if (!key_is_dead(rcu_deref_link_locked(klist, loop, keyring),
-				 limit))
-			keep++;
-
-	if (keep == klist->nkeys)
-		goto just_return;
-
-	/* allocate a new keyring payload */
-	max = roundup(keep, 4);
-	new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
-		      GFP_KERNEL);
-	if (!new)
-		goto nomem;
-	new->maxkeys = max;
-	new->nkeys = 0;
-	new->delkey = 0;
-
-	/* install the live keys
-	 * - must take care as expired keys may be updated back to life
-	 */
-	keep = 0;
-	for (loop = klist->nkeys - 1; loop >= 0; loop--) {
-		key = rcu_deref_link_locked(klist, loop, keyring);
-		if (!key_is_dead(key, limit)) {
-			if (keep >= max)
-				goto discard_new;
-			RCU_INIT_POINTER(new->keys[keep++], key_get(key));
-		}
-	}
-	new->nkeys = keep;
-
-	/* adjust the quota */
-	key_payload_reserve(keyring,
-			    sizeof(struct keyring_list) +
-			    KEYQUOTA_LINK_BYTES * keep);
-
-	if (keep == 0) {
-		rcu_assign_pointer(keyring->payload.subscriptions, NULL);
-		kfree(new);
-	} else {
-		rcu_assign_pointer(keyring->payload.subscriptions, new);
-	}
-
-	up_write(&keyring->sem);
-
-	call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
-	kleave(" [yes]");
-	return;
-
-discard_new:
-	new->nkeys = keep;
-	keyring_clear_rcu_disposal(&new->rcu);
+	assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
+		       gc_iterator, &limit);
 	up_write(&keyring->sem);
-	kleave(" [discard]");
-	return;
 
-just_return:
-	up_write(&keyring->sem);
-	kleave(" [no dead]");
-	return;
-
-no_klist:
-	up_write(&keyring->sem);
-	kleave(" [no_klist]");
-	return;
-
-nomem:
-	up_write(&keyring->sem);
-	kleave(" [oom]");
+	kleave("");
 }
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index ab75df4..df94827 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -351,7 +351,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
 			       struct key_user *user,
 			       struct key **_key)
 {
-	unsigned long prealloc;
+	struct assoc_array_edit *edit;
 	struct key *key;
 	key_perm_t perm;
 	key_ref_t key_ref;
@@ -380,7 +380,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 
 	if (dest_keyring) {
-		ret = __key_link_begin(dest_keyring, &ctx->index_key, &prealloc);
+		ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit);
 		if (ret < 0)
 			goto link_prealloc_failed;
 	}
@@ -395,11 +395,11 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
 		goto key_already_present;
 
 	if (dest_keyring)
-		__key_link(dest_keyring, key, &prealloc);
+		__key_link(key, &edit);
 
 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
-		__key_link_end(dest_keyring, &ctx->index_key, prealloc);
+		__key_link_end(dest_keyring, &ctx->index_key, edit);
 	mutex_unlock(&user->cons_lock);
 	*_key = key;
 	kleave(" = 0 [%d]", key_serial(key));
@@ -414,8 +414,8 @@ key_already_present:
 	if (dest_keyring) {
 		ret = __key_link_check_live_key(dest_keyring, key);
 		if (ret == 0)
-			__key_link(dest_keyring, key, &prealloc);
-		__key_link_end(dest_keyring, &ctx->index_key, prealloc);
+			__key_link(key, &edit);
+		__key_link_end(dest_keyring, &ctx->index_key, edit);
 		if (ret < 0)
 			goto link_check_failed;
 	}
-- 
1.8.3.1