Add NFS fix

This was present on F29 but is applicable for all 5.0 branches.

2 files changed, 263 insertions, 0 deletions

diff --git a/kernel.spec b/kernel.spec
index 129895bde..221dfd133 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -622,6 +622,9 @@ Patch511: 0001-virt-vbox-Implement-passing-requestor-info-to-the-ho.patch
 # rhbz 1688283
 Patch512: v3-tpm-fix-an-invalid-condition-in-tpm_common_poll.patch
 
+# rhbz 1683382
+Patch515: nfsv4.1-avoid-false-retries.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
diff --git a/nfsv4.1-avoid-false-retries.patch b/nfsv4.1-avoid-false-retries.patch
new file mode 100644
index 000000000..ebec54dab
--- /dev/null
+++ b/nfsv4.1-avoid-false-retries.patch
@@ -0,0 +1,260 @@
+From 675f11241a9f5b434effc7aee9eb84bf3d17d685 Mon Sep 17 00:00:00 2001
+From: Trond Myklebust <trond.myklebust@hammerspace.com>
+Date: Wed, 20 Jun 2018 17:53:34 -0400
+Subject: [PATCH] NFSv4.1: Avoid false retries when RPC calls are interrupted
+
+A 'false retry' in NFSv4.1 occurs when the client attempts to transmit a
+new RPC call using a slot+sequence number combination that references an
+already cached one. Currently, the Linux NFS client will do this if a
+user process interrupts an RPC call that is in progress.
+The problem with doing so is that we defeat the main mechanism used by
+the server to differentiate between a new call and a replayed one. Even
+if the server is able to perfectly cache the arguments of the old call,
+it cannot know if the client intended to replay or send a new call.
+
+The obvious fix is to bump the sequence number pre-emptively if an
+RPC call is interrupted, but in order to deal with the corner cases
+where the interrupted call is not actually received and processed by
+the server, we need to interpret the error NFS4ERR_SEQ_MISORDERED
+as a sign that we need to either wait or locate a correct sequence
+number that lies between the value we sent, and the last value that
+was acked by a SEQUENCE call on that slot.
+
+Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
+---
+ fs/nfs/nfs4proc.c    | 105 ++++++++++++++++++++-----------------------
+ fs/nfs/nfs4session.c |   5 ++-
+ fs/nfs/nfs4session.h |   5 ++-
+ 3 files changed, 55 insertions(+), 60 deletions(-)
+
+diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
+index 64ac80ec6b7b..3a6a9c9ee369 100644
+--- a/fs/nfs/nfs4proc.c
++++ b/fs/nfs/nfs4proc.c
+@@ -730,13 +730,25 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
+ 	res->sr_slot = NULL;
+ }
+ 
++static void nfs4_slot_sequence_record_sent(struct nfs4_slot *slot,
++		u32 seqnr)
++{
++	if ((s32)(seqnr - slot->seq_nr_highest_sent) > 0)
++		slot->seq_nr_highest_sent = seqnr;
++}
++static void nfs4_slot_sequence_acked(struct nfs4_slot *slot,
++		u32 seqnr)
++{
++	slot->seq_nr_highest_sent = seqnr;
++	slot->seq_nr_last_acked = seqnr;
++}
++
+ static int nfs41_sequence_process(struct rpc_task *task,
+ 		struct nfs4_sequence_res *res)
+ {
+ 	struct nfs4_session *session;
+ 	struct nfs4_slot *slot = res->sr_slot;
+ 	struct nfs_client *clp;
+-	bool interrupted = false;
+ 	int ret = 1;
+ 
+ 	if (slot == NULL)
+@@ -747,16 +759,12 @@ static int nfs41_sequence_process(struct rpc_task *task,
+ 
+ 	session = slot->table->session;
+ 
+-	if (slot->interrupted) {
+-		if (res->sr_status != -NFS4ERR_DELAY)
+-			slot->interrupted = 0;
+-		interrupted = true;
+-	}
+-
+ 	trace_nfs4_sequence_done(session, res);
+ 	/* Check the SEQUENCE operation status */
+ 	switch (res->sr_status) {
+ 	case 0:
++		/* Mark this sequence number as having been acked */
++		nfs4_slot_sequence_acked(slot, slot->seq_nr);
+ 		/* Update the slot's sequence and clientid lease timer */
+ 		slot->seq_done = 1;
+ 		clp = session->clp;
+@@ -771,9 +779,9 @@ static int nfs41_sequence_process(struct rpc_task *task,
+ 		 * sr_status remains 1 if an RPC level error occurred.
+ 		 * The server may or may not have processed the sequence
+ 		 * operation..
+-		 * Mark the slot as having hosted an interrupted RPC call.
+ 		 */
+-		slot->interrupted = 1;
++		nfs4_slot_sequence_record_sent(slot, slot->seq_nr);
++		slot->seq_done = 1;
+ 		goto out;
+ 	case -NFS4ERR_DELAY:
+ 		/* The server detected a resend of the RPC call and
+@@ -784,6 +792,7 @@ static int nfs41_sequence_process(struct rpc_task *task,
+ 			__func__,
+ 			slot->slot_nr,
+ 			slot->seq_nr);
++		nfs4_slot_sequence_acked(slot, slot->seq_nr);
+ 		goto out_retry;
+ 	case -NFS4ERR_RETRY_UNCACHED_REP:
+ 	case -NFS4ERR_SEQ_FALSE_RETRY:
+@@ -791,6 +800,7 @@ static int nfs41_sequence_process(struct rpc_task *task,
+ 		 * The server thinks we tried to replay a request.
+ 		 * Retry the call after bumping the sequence ID.
+ 		 */
++		nfs4_slot_sequence_acked(slot, slot->seq_nr);
+ 		goto retry_new_seq;
+ 	case -NFS4ERR_BADSLOT:
+ 		/*
+@@ -801,21 +811,28 @@ static int nfs41_sequence_process(struct rpc_task *task,
+ 			goto session_recover;
+ 		goto retry_nowait;
+ 	case -NFS4ERR_SEQ_MISORDERED:
++		nfs4_slot_sequence_record_sent(slot, slot->seq_nr);
+ 		/*
+-		 * Was the last operation on this sequence interrupted?
+-		 * If so, retry after bumping the sequence number.
++		 * Were one or more calls using this slot interrupted?
++		 * If the server never received the request, then our
++		 * transmitted slot sequence number may be too high.
+ 		 */
+-		if (interrupted)
+-			goto retry_new_seq;
+-		/*
+-		 * Could this slot have been previously retired?
+-		 * If so, then the server may be expecting seq_nr = 1!
+-		 */
+-		if (slot->seq_nr != 1) {
+-			slot->seq_nr = 1;
++		if ((s32)(slot->seq_nr - slot->seq_nr_last_acked) > 1) {
++			slot->seq_nr--;
+ 			goto retry_nowait;
+ 		}
+-		goto session_recover;
++		/*
++		 * RFC5661:
++		 * A retry might be sent while the original request is
++		 * still in progress on the replier. The replier SHOULD
++		 * deal with the issue by returning NFS4ERR_DELAY as the
++		 * reply to SEQUENCE or CB_SEQUENCE operation, but
++		 * implementations MAY return NFS4ERR_SEQ_MISORDERED.
++		 *
++		 * Restart the search after a delay.
++		 */
++		slot->seq_nr = slot->seq_nr_highest_sent;
++		goto out_retry;
+ 	default:
+ 		/* Just update the slot sequence no. */
+ 		slot->seq_done = 1;
+@@ -906,17 +923,6 @@ static const struct rpc_call_ops nfs41_call_sync_ops = {
+ 	.rpc_call_done = nfs41_call_sync_done,
+ };
+ 
+-static void
+-nfs4_sequence_process_interrupted(struct nfs_client *client,
+-		struct nfs4_slot *slot, const struct cred *cred)
+-{
+-	struct rpc_task *task;
+-
+-	task = _nfs41_proc_sequence(client, cred, slot, true);
+-	if (!IS_ERR(task))
+-		rpc_put_task_async(task);
+-}
+-
+ #else	/* !CONFIG_NFS_V4_1 */
+ 
+ static int nfs4_sequence_process(struct rpc_task *task, struct nfs4_sequence_res *res)
+@@ -937,14 +943,6 @@ int nfs4_sequence_done(struct rpc_task *task,
+ }
+ EXPORT_SYMBOL_GPL(nfs4_sequence_done);
+ 
+-static void
+-nfs4_sequence_process_interrupted(struct nfs_client *client,
+-		struct nfs4_slot *slot, const struct cred *cred)
+-{
+-	WARN_ON_ONCE(1);
+-	slot->interrupted = 0;
+-}
+-
+ #endif	/* !CONFIG_NFS_V4_1 */
+ 
+ static void nfs41_sequence_res_init(struct nfs4_sequence_res *res)
+@@ -985,26 +983,19 @@ int nfs4_setup_sequence(struct nfs_client *client,
+ 		task->tk_timeout = 0;
+ 	}
+ 
+-	for (;;) {
+-		spin_lock(&tbl->slot_tbl_lock);
+-		/* The state manager will wait until the slot table is empty */
+-		if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
+-			goto out_sleep;
+-
+-		slot = nfs4_alloc_slot(tbl);
+-		if (IS_ERR(slot)) {
+-			/* Try again in 1/4 second */
+-			if (slot == ERR_PTR(-ENOMEM))
+-				task->tk_timeout = HZ >> 2;
+-			goto out_sleep;
+-		}
+-		spin_unlock(&tbl->slot_tbl_lock);
++	spin_lock(&tbl->slot_tbl_lock);
++	/* The state manager will wait until the slot table is empty */
++	if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
++		goto out_sleep;
+ 
+-		if (likely(!slot->interrupted))
+-			break;
+-		nfs4_sequence_process_interrupted(client,
+-				slot, task->tk_msg.rpc_cred);
++	slot = nfs4_alloc_slot(tbl);
++	if (IS_ERR(slot)) {
++		/* Try again in 1/4 second */
++		if (slot == ERR_PTR(-ENOMEM))
++			task->tk_timeout = HZ >> 2;
++		goto out_sleep;
+ 	}
++	spin_unlock(&tbl->slot_tbl_lock);
+ 
+ 	nfs4_sequence_attach_slot(args, res, slot);
+ 
+diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
+index a5489d70a724..39962c19744f 100644
+--- a/fs/nfs/nfs4session.c
++++ b/fs/nfs/nfs4session.c
+@@ -110,6 +110,8 @@ static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
+ 		slot->table = tbl;
+ 		slot->slot_nr = slotid;
+ 		slot->seq_nr = seq_init;
++		slot->seq_nr_highest_sent = seq_init;
++		slot->seq_nr_last_acked = seq_init - 1;
+ 	}
+ 	return slot;
+ }
+@@ -276,7 +278,8 @@ static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
+ 	p = &tbl->slots;
+ 	while (*p) {
+ 		(*p)->seq_nr = ivalue;
+-		(*p)->interrupted = 0;
++		(*p)->seq_nr_highest_sent = ivalue;
++		(*p)->seq_nr_last_acked = ivalue - 1;
+ 		p = &(*p)->next;
+ 	}
+ 	tbl->highest_used_slotid = NFS4_NO_SLOT;
+diff --git a/fs/nfs/nfs4session.h b/fs/nfs/nfs4session.h
+index 3c550f297561..230509b77121 100644
+--- a/fs/nfs/nfs4session.h
++++ b/fs/nfs/nfs4session.h
+@@ -23,8 +23,9 @@ struct nfs4_slot {
+ 	unsigned long		generation;
+ 	u32			slot_nr;
+ 	u32		 	seq_nr;
+-	unsigned int		interrupted : 1,
+-				privileged : 1,
++	u32		 	seq_nr_last_acked;
++	u32		 	seq_nr_highest_sent;
++	unsigned int		privileged : 1,
+ 				seq_done : 1;
+ };
+ 
+-- 
+2.20.1
+