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authorAnton Arapov <anton@redhat.com>2012-04-16 10:05:28 +0200
committerAnton Arapov <anton@redhat.com>2012-04-16 10:05:28 +0200
commitb4b6116a13633898cf868f2f103c96a90c4c20f8 (patch)
tree93d1b7e2cfcdf473d8d4ff3ad141fa864f8491f6 /fs/namespace.c
parentedd4be777c953e5faafc80d091d3084b4343f5d3 (diff)
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fedora kernel: d9aad82f3319f3cfd1aebc01234254ef0c37ad84v3.3.2-1
Signed-off-by: Anton Arapov <anton@redhat.com>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c2635
1 files changed, 2635 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
new file mode 100644
index 00000000000..e6081996c9a
--- /dev/null
+++ b/fs/namespace.c
@@ -0,0 +1,2635 @@
+/*
+ * linux/fs/namespace.c
+ *
+ * (C) Copyright Al Viro 2000, 2001
+ * Released under GPL v2.
+ *
+ * Based on code from fs/super.c, copyright Linus Torvalds and others.
+ * Heavily rewritten.
+ */
+
+#include <linux/syscalls.h>
+#include <linux/export.h>
+#include <linux/capability.h>
+#include <linux/mnt_namespace.h>
+#include <linux/namei.h>
+#include <linux/security.h>
+#include <linux/idr.h>
+#include <linux/acct.h> /* acct_auto_close_mnt */
+#include <linux/ramfs.h> /* init_rootfs */
+#include <linux/fs_struct.h> /* get_fs_root et.al. */
+#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
+#include <linux/uaccess.h>
+#include "pnode.h"
+#include "internal.h"
+
+#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
+#define HASH_SIZE (1UL << HASH_SHIFT)
+
+static int event;
+static DEFINE_IDA(mnt_id_ida);
+static DEFINE_IDA(mnt_group_ida);
+static DEFINE_SPINLOCK(mnt_id_lock);
+static int mnt_id_start = 0;
+static int mnt_group_start = 1;
+
+static struct list_head *mount_hashtable __read_mostly;
+static struct kmem_cache *mnt_cache __read_mostly;
+static struct rw_semaphore namespace_sem;
+
+/* /sys/fs */
+struct kobject *fs_kobj;
+EXPORT_SYMBOL_GPL(fs_kobj);
+
+/*
+ * vfsmount lock may be taken for read to prevent changes to the
+ * vfsmount hash, ie. during mountpoint lookups or walking back
+ * up the tree.
+ *
+ * It should be taken for write in all cases where the vfsmount
+ * tree or hash is modified or when a vfsmount structure is modified.
+ */
+DEFINE_BRLOCK(vfsmount_lock);
+
+static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
+{
+ unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
+ tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
+ tmp = tmp + (tmp >> HASH_SHIFT);
+ return tmp & (HASH_SIZE - 1);
+}
+
+#define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
+
+/*
+ * allocation is serialized by namespace_sem, but we need the spinlock to
+ * serialize with freeing.
+ */
+static int mnt_alloc_id(struct mount *mnt)
+{
+ int res;
+
+retry:
+ ida_pre_get(&mnt_id_ida, GFP_KERNEL);
+ spin_lock(&mnt_id_lock);
+ res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
+ if (!res)
+ mnt_id_start = mnt->mnt_id + 1;
+ spin_unlock(&mnt_id_lock);
+ if (res == -EAGAIN)
+ goto retry;
+
+ return res;
+}
+
+static void mnt_free_id(struct mount *mnt)
+{
+ int id = mnt->mnt_id;
+ spin_lock(&mnt_id_lock);
+ ida_remove(&mnt_id_ida, id);
+ if (mnt_id_start > id)
+ mnt_id_start = id;
+ spin_unlock(&mnt_id_lock);
+}
+
+/*
+ * Allocate a new peer group ID
+ *
+ * mnt_group_ida is protected by namespace_sem
+ */
+static int mnt_alloc_group_id(struct mount *mnt)
+{
+ int res;
+
+ if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
+ return -ENOMEM;
+
+ res = ida_get_new_above(&mnt_group_ida,
+ mnt_group_start,
+ &mnt->mnt_group_id);
+ if (!res)
+ mnt_group_start = mnt->mnt_group_id + 1;
+
+ return res;
+}
+
+/*
+ * Release a peer group ID
+ */
+void mnt_release_group_id(struct mount *mnt)
+{
+ int id = mnt->mnt_group_id;
+ ida_remove(&mnt_group_ida, id);
+ if (mnt_group_start > id)
+ mnt_group_start = id;
+ mnt->mnt_group_id = 0;
+}
+
+/*
+ * vfsmount lock must be held for read
+ */
+static inline void mnt_add_count(struct mount *mnt, int n)
+{
+#ifdef CONFIG_SMP
+ this_cpu_add(mnt->mnt_pcp->mnt_count, n);
+#else
+ preempt_disable();
+ mnt->mnt_count += n;
+ preempt_enable();
+#endif
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+unsigned int mnt_get_count(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ unsigned int count = 0;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
+ }
+
+ return count;
+#else
+ return mnt->mnt_count;
+#endif
+}
+
+static struct mount *alloc_vfsmnt(const char *name)
+{
+ struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
+ if (mnt) {
+ int err;
+
+ err = mnt_alloc_id(mnt);
+ if (err)
+ goto out_free_cache;
+
+ if (name) {
+ mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
+ if (!mnt->mnt_devname)
+ goto out_free_id;
+ }
+
+#ifdef CONFIG_SMP
+ mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
+ if (!mnt->mnt_pcp)
+ goto out_free_devname;
+
+ this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
+#else
+ mnt->mnt_count = 1;
+ mnt->mnt_writers = 0;
+#endif
+
+ INIT_LIST_HEAD(&mnt->mnt_hash);
+ INIT_LIST_HEAD(&mnt->mnt_child);
+ INIT_LIST_HEAD(&mnt->mnt_mounts);
+ INIT_LIST_HEAD(&mnt->mnt_list);
+ INIT_LIST_HEAD(&mnt->mnt_expire);
+ INIT_LIST_HEAD(&mnt->mnt_share);
+ INIT_LIST_HEAD(&mnt->mnt_slave_list);
+ INIT_LIST_HEAD(&mnt->mnt_slave);
+#ifdef CONFIG_FSNOTIFY
+ INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
+#endif
+ }
+ return mnt;
+
+#ifdef CONFIG_SMP
+out_free_devname:
+ kfree(mnt->mnt_devname);
+#endif
+out_free_id:
+ mnt_free_id(mnt);
+out_free_cache:
+ kmem_cache_free(mnt_cache, mnt);
+ return NULL;
+}
+
+/*
+ * Most r/o checks on a fs are for operations that take
+ * discrete amounts of time, like a write() or unlink().
+ * We must keep track of when those operations start
+ * (for permission checks) and when they end, so that
+ * we can determine when writes are able to occur to
+ * a filesystem.
+ */
+/*
+ * __mnt_is_readonly: check whether a mount is read-only
+ * @mnt: the mount to check for its write status
+ *
+ * This shouldn't be used directly ouside of the VFS.
+ * It does not guarantee that the filesystem will stay
+ * r/w, just that it is right *now*. This can not and
+ * should not be used in place of IS_RDONLY(inode).
+ * mnt_want/drop_write() will _keep_ the filesystem
+ * r/w.
+ */
+int __mnt_is_readonly(struct vfsmount *mnt)
+{
+ if (mnt->mnt_flags & MNT_READONLY)
+ return 1;
+ if (mnt->mnt_sb->s_flags & MS_RDONLY)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__mnt_is_readonly);
+
+static inline void mnt_inc_writers(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ this_cpu_inc(mnt->mnt_pcp->mnt_writers);
+#else
+ mnt->mnt_writers++;
+#endif
+}
+
+static inline void mnt_dec_writers(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ this_cpu_dec(mnt->mnt_pcp->mnt_writers);
+#else
+ mnt->mnt_writers--;
+#endif
+}
+
+static unsigned int mnt_get_writers(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ unsigned int count = 0;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
+ }
+
+ return count;
+#else
+ return mnt->mnt_writers;
+#endif
+}
+
+static int mnt_is_readonly(struct vfsmount *mnt)
+{
+ if (mnt->mnt_sb->s_readonly_remount)
+ return 1;
+ /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
+ smp_rmb();
+ return __mnt_is_readonly(mnt);
+}
+
+/*
+ * Most r/o checks on a fs are for operations that take
+ * discrete amounts of time, like a write() or unlink().
+ * We must keep track of when those operations start
+ * (for permission checks) and when they end, so that
+ * we can determine when writes are able to occur to
+ * a filesystem.
+ */
+/**
+ * mnt_want_write - get write access to a mount
+ * @m: the mount on which to take a write
+ *
+ * This tells the low-level filesystem that a write is
+ * about to be performed to it, and makes sure that
+ * writes are allowed before returning success. When
+ * the write operation is finished, mnt_drop_write()
+ * must be called. This is effectively a refcount.
+ */
+int mnt_want_write(struct vfsmount *m)
+{
+ struct mount *mnt = real_mount(m);
+ int ret = 0;
+
+ preempt_disable();
+ mnt_inc_writers(mnt);
+ /*
+ * The store to mnt_inc_writers must be visible before we pass
+ * MNT_WRITE_HOLD loop below, so that the slowpath can see our
+ * incremented count after it has set MNT_WRITE_HOLD.
+ */
+ smp_mb();
+ while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
+ cpu_relax();
+ /*
+ * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
+ * be set to match its requirements. So we must not load that until
+ * MNT_WRITE_HOLD is cleared.
+ */
+ smp_rmb();
+ if (mnt_is_readonly(m)) {
+ mnt_dec_writers(mnt);
+ ret = -EROFS;
+ }
+ preempt_enable();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(mnt_want_write);
+
+/**
+ * mnt_clone_write - get write access to a mount
+ * @mnt: the mount on which to take a write
+ *
+ * This is effectively like mnt_want_write, except
+ * it must only be used to take an extra write reference
+ * on a mountpoint that we already know has a write reference
+ * on it. This allows some optimisation.
+ *
+ * After finished, mnt_drop_write must be called as usual to
+ * drop the reference.
+ */
+int mnt_clone_write(struct vfsmount *mnt)
+{
+ /* superblock may be r/o */
+ if (__mnt_is_readonly(mnt))
+ return -EROFS;
+ preempt_disable();
+ mnt_inc_writers(real_mount(mnt));
+ preempt_enable();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mnt_clone_write);
+
+/**
+ * mnt_want_write_file - get write access to a file's mount
+ * @file: the file who's mount on which to take a write
+ *
+ * This is like mnt_want_write, but it takes a file and can
+ * do some optimisations if the file is open for write already
+ */
+int mnt_want_write_file(struct file *file)
+{
+ struct inode *inode = file->f_dentry->d_inode;
+ if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
+ return mnt_want_write(file->f_path.mnt);
+ else
+ return mnt_clone_write(file->f_path.mnt);
+}
+EXPORT_SYMBOL_GPL(mnt_want_write_file);
+
+/**
+ * mnt_drop_write - give up write access to a mount
+ * @mnt: the mount on which to give up write access
+ *
+ * Tells the low-level filesystem that we are done
+ * performing writes to it. Must be matched with
+ * mnt_want_write() call above.
+ */
+void mnt_drop_write(struct vfsmount *mnt)
+{
+ preempt_disable();
+ mnt_dec_writers(real_mount(mnt));
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(mnt_drop_write);
+
+void mnt_drop_write_file(struct file *file)
+{
+ mnt_drop_write(file->f_path.mnt);
+}
+EXPORT_SYMBOL(mnt_drop_write_file);
+
+static int mnt_make_readonly(struct mount *mnt)
+{
+ int ret = 0;
+
+ br_write_lock(vfsmount_lock);
+ mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
+ /*
+ * After storing MNT_WRITE_HOLD, we'll read the counters. This store
+ * should be visible before we do.
+ */
+ smp_mb();
+
+ /*
+ * With writers on hold, if this value is zero, then there are
+ * definitely no active writers (although held writers may subsequently
+ * increment the count, they'll have to wait, and decrement it after
+ * seeing MNT_READONLY).
+ *
+ * It is OK to have counter incremented on one CPU and decremented on
+ * another: the sum will add up correctly. The danger would be when we
+ * sum up each counter, if we read a counter before it is incremented,
+ * but then read another CPU's count which it has been subsequently
+ * decremented from -- we would see more decrements than we should.
+ * MNT_WRITE_HOLD protects against this scenario, because
+ * mnt_want_write first increments count, then smp_mb, then spins on
+ * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
+ * we're counting up here.
+ */
+ if (mnt_get_writers(mnt) > 0)
+ ret = -EBUSY;
+ else
+ mnt->mnt.mnt_flags |= MNT_READONLY;
+ /*
+ * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
+ * that become unheld will see MNT_READONLY.
+ */
+ smp_wmb();
+ mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
+ br_write_unlock(vfsmount_lock);
+ return ret;
+}
+
+static void __mnt_unmake_readonly(struct mount *mnt)
+{
+ br_write_lock(vfsmount_lock);
+ mnt->mnt.mnt_flags &= ~MNT_READONLY;
+ br_write_unlock(vfsmount_lock);
+}
+
+int sb_prepare_remount_readonly(struct super_block *sb)
+{
+ struct mount *mnt;
+ int err = 0;
+
+ /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
+ if (atomic_long_read(&sb->s_remove_count))
+ return -EBUSY;
+
+ br_write_lock(vfsmount_lock);
+ list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
+ if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
+ mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
+ smp_mb();
+ if (mnt_get_writers(mnt) > 0) {
+ err = -EBUSY;
+ break;
+ }
+ }
+ }
+ if (!err && atomic_long_read(&sb->s_remove_count))
+ err = -EBUSY;
+
+ if (!err) {
+ sb->s_readonly_remount = 1;
+ smp_wmb();
+ }
+ list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
+ if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
+ mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
+ }
+ br_write_unlock(vfsmount_lock);
+
+ return err;
+}
+
+static void free_vfsmnt(struct mount *mnt)
+{
+ kfree(mnt->mnt_devname);
+ mnt_free_id(mnt);
+#ifdef CONFIG_SMP
+ free_percpu(mnt->mnt_pcp);
+#endif
+ kmem_cache_free(mnt_cache, mnt);
+}
+
+/*
+ * find the first or last mount at @dentry on vfsmount @mnt depending on
+ * @dir. If @dir is set return the first mount else return the last mount.
+ * vfsmount_lock must be held for read or write.
+ */
+struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
+ int dir)
+{
+ struct list_head *head = mount_hashtable + hash(mnt, dentry);
+ struct list_head *tmp = head;
+ struct mount *p, *found = NULL;
+
+ for (;;) {
+ tmp = dir ? tmp->next : tmp->prev;
+ p = NULL;
+ if (tmp == head)
+ break;
+ p = list_entry(tmp, struct mount, mnt_hash);
+ if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
+ found = p;
+ break;
+ }
+ }
+ return found;
+}
+
+/*
+ * lookup_mnt increments the ref count before returning
+ * the vfsmount struct.
+ */
+struct vfsmount *lookup_mnt(struct path *path)
+{
+ struct mount *child_mnt;
+
+ br_read_lock(vfsmount_lock);
+ child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
+ if (child_mnt) {
+ mnt_add_count(child_mnt, 1);
+ br_read_unlock(vfsmount_lock);
+ return &child_mnt->mnt;
+ } else {
+ br_read_unlock(vfsmount_lock);
+ return NULL;
+ }
+}
+
+static inline int check_mnt(struct mount *mnt)
+{
+ return mnt->mnt_ns == current->nsproxy->mnt_ns;
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void touch_mnt_namespace(struct mnt_namespace *ns)
+{
+ if (ns) {
+ ns->event = ++event;
+ wake_up_interruptible(&ns->poll);
+ }
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void __touch_mnt_namespace(struct mnt_namespace *ns)
+{
+ if (ns && ns->event != event) {
+ ns->event = event;
+ wake_up_interruptible(&ns->poll);
+ }
+}
+
+/*
+ * Clear dentry's mounted state if it has no remaining mounts.
+ * vfsmount_lock must be held for write.
+ */
+static void dentry_reset_mounted(struct dentry *dentry)
+{
+ unsigned u;
+
+ for (u = 0; u < HASH_SIZE; u++) {
+ struct mount *p;
+
+ list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
+ if (p->mnt_mountpoint == dentry)
+ return;
+ }
+ }
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags &= ~DCACHE_MOUNTED;
+ spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void detach_mnt(struct mount *mnt, struct path *old_path)
+{
+ old_path->dentry = mnt->mnt_mountpoint;
+ old_path->mnt = &mnt->mnt_parent->mnt;
+ mnt->mnt_parent = mnt;
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ list_del_init(&mnt->mnt_child);
+ list_del_init(&mnt->mnt_hash);
+ dentry_reset_mounted(old_path->dentry);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry,
+ struct mount *child_mnt)
+{
+ mnt_add_count(mnt, 1); /* essentially, that's mntget */
+ child_mnt->mnt_mountpoint = dget(dentry);
+ child_mnt->mnt_parent = mnt;
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_MOUNTED;
+ spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void attach_mnt(struct mount *mnt, struct path *path)
+{
+ mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt);
+ list_add_tail(&mnt->mnt_hash, mount_hashtable +
+ hash(path->mnt, path->dentry));
+ list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
+}
+
+static inline void __mnt_make_longterm(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ atomic_inc(&mnt->mnt_longterm);
+#endif
+}
+
+/* needs vfsmount lock for write */
+static inline void __mnt_make_shortterm(struct mount *mnt)
+{
+#ifdef CONFIG_SMP
+ atomic_dec(&mnt->mnt_longterm);
+#endif
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void commit_tree(struct mount *mnt)
+{
+ struct mount *parent = mnt->mnt_parent;
+ struct mount *m;
+ LIST_HEAD(head);
+ struct mnt_namespace *n = parent->mnt_ns;
+
+ BUG_ON(parent == mnt);
+
+ list_add_tail(&head, &mnt->mnt_list);
+ list_for_each_entry(m, &head, mnt_list) {
+ m->mnt_ns = n;
+ __mnt_make_longterm(m);
+ }
+
+ list_splice(&head, n->list.prev);
+
+ list_add_tail(&mnt->mnt_hash, mount_hashtable +
+ hash(&parent->mnt, mnt->mnt_mountpoint));
+ list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ touch_mnt_namespace(n);
+}
+
+static struct mount *next_mnt(struct mount *p, struct mount *root)
+{
+ struct list_head *next = p->mnt_mounts.next;
+ if (next == &p->mnt_mounts) {
+ while (1) {
+ if (p == root)
+ return NULL;
+ next = p->mnt_child.next;
+ if (next != &p->mnt_parent->mnt_mounts)
+ break;
+ p = p->mnt_parent;
+ }
+ }
+ return list_entry(next, struct mount, mnt_child);
+}
+
+static struct mount *skip_mnt_tree(struct mount *p)
+{
+ struct list_head *prev = p->mnt_mounts.prev;
+ while (prev != &p->mnt_mounts) {
+ p = list_entry(prev, struct mount, mnt_child);
+ prev = p->mnt_mounts.prev;
+ }
+ return p;
+}
+
+struct vfsmount *
+vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
+{
+ struct mount *mnt;
+ struct dentry *root;
+
+ if (!type)
+ return ERR_PTR(-ENODEV);
+
+ mnt = alloc_vfsmnt(name);
+ if (!mnt)
+ return ERR_PTR(-ENOMEM);
+
+ if (flags & MS_KERNMOUNT)
+ mnt->mnt.mnt_flags = MNT_INTERNAL;
+
+ root = mount_fs(type, flags, name, data);
+ if (IS_ERR(root)) {
+ free_vfsmnt(mnt);
+ return ERR_CAST(root);
+ }
+
+ mnt->mnt.mnt_root = root;
+ mnt->mnt.mnt_sb = root->d_sb;
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
+ br_write_unlock(vfsmount_lock);
+ return &mnt->mnt;
+}
+EXPORT_SYMBOL_GPL(vfs_kern_mount);
+
+static struct mount *clone_mnt(struct mount *old, struct dentry *root,
+ int flag)
+{
+ struct super_block *sb = old->mnt.mnt_sb;
+ struct mount *mnt = alloc_vfsmnt(old->mnt_devname);
+
+ if (mnt) {
+ if (flag & (CL_SLAVE | CL_PRIVATE))
+ mnt->mnt_group_id = 0; /* not a peer of original */
+ else
+ mnt->mnt_group_id = old->mnt_group_id;
+
+ if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
+ int err = mnt_alloc_group_id(mnt);
+ if (err)
+ goto out_free;
+ }
+
+ mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
+ atomic_inc(&sb->s_active);
+ mnt->mnt.mnt_sb = sb;
+ mnt->mnt.mnt_root = dget(root);
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
+ br_write_unlock(vfsmount_lock);
+
+ if (flag & CL_SLAVE) {
+ list_add(&mnt->mnt_slave, &old->mnt_slave_list);
+ mnt->mnt_master = old;
+ CLEAR_MNT_SHARED(mnt);
+ } else if (!(flag & CL_PRIVATE)) {
+ if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
+ list_add(&mnt->mnt_share, &old->mnt_share);
+ if (IS_MNT_SLAVE(old))
+ list_add(&mnt->mnt_slave, &old->mnt_slave);
+ mnt->mnt_master = old->mnt_master;
+ }
+ if (flag & CL_MAKE_SHARED)
+ set_mnt_shared(mnt);
+
+ /* stick the duplicate mount on the same expiry list
+ * as the original if that was on one */
+ if (flag & CL_EXPIRE) {
+ if (!list_empty(&old->mnt_expire))
+ list_add(&mnt->mnt_expire, &old->mnt_expire);
+ }
+ }
+ return mnt;
+
+ out_free:
+ free_vfsmnt(mnt);
+ return NULL;
+}
+
+static inline void mntfree(struct mount *mnt)
+{
+ struct vfsmount *m = &mnt->mnt;
+ struct super_block *sb = m->mnt_sb;
+
+ /*
+ * This probably indicates that somebody messed
+ * up a mnt_want/drop_write() pair. If this
+ * happens, the filesystem was probably unable
+ * to make r/w->r/o transitions.
+ */
+ /*
+ * The locking used to deal with mnt_count decrement provides barriers,
+ * so mnt_get_writers() below is safe.
+ */
+ WARN_ON(mnt_get_writers(mnt));
+ fsnotify_vfsmount_delete(m);
+ dput(m->mnt_root);
+ free_vfsmnt(mnt);
+ deactivate_super(sb);
+}
+
+static void mntput_no_expire(struct mount *mnt)
+{
+put_again:
+#ifdef CONFIG_SMP
+ br_read_lock(vfsmount_lock);
+ if (likely(atomic_read(&mnt->mnt_longterm))) {
+ mnt_add_count(mnt, -1);
+ br_read_unlock(vfsmount_lock);
+ return;
+ }
+ br_read_unlock(vfsmount_lock);
+
+ br_write_lock(vfsmount_lock);
+ mnt_add_count(mnt, -1);
+ if (mnt_get_count(mnt)) {
+ br_write_unlock(vfsmount_lock);
+ return;
+ }
+#else
+ mnt_add_count(mnt, -1);
+ if (likely(mnt_get_count(mnt)))
+ return;
+ br_write_lock(vfsmount_lock);
+#endif
+ if (unlikely(mnt->mnt_pinned)) {
+ mnt_add_count(mnt, mnt->mnt_pinned + 1);
+ mnt->mnt_pinned = 0;
+ br_write_unlock(vfsmount_lock);
+ acct_auto_close_mnt(&mnt->mnt);
+ goto put_again;
+ }
+ list_del(&mnt->mnt_instance);
+ br_write_unlock(vfsmount_lock);
+ mntfree(mnt);
+}
+
+void mntput(struct vfsmount *mnt)
+{
+ if (mnt) {
+ struct mount *m = real_mount(mnt);
+ /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
+ if (unlikely(m->mnt_expiry_mark))
+ m->mnt_expiry_mark = 0;
+ mntput_no_expire(m);
+ }
+}
+EXPORT_SYMBOL(mntput);
+
+struct vfsmount *mntget(struct vfsmount *mnt)
+{
+ if (mnt)
+ mnt_add_count(real_mount(mnt), 1);
+ return mnt;
+}
+EXPORT_SYMBOL(mntget);
+
+void mnt_pin(struct vfsmount *mnt)
+{
+ br_write_lock(vfsmount_lock);
+ real_mount(mnt)->mnt_pinned++;
+ br_write_unlock(vfsmount_lock);
+}
+EXPORT_SYMBOL(mnt_pin);
+
+void mnt_unpin(struct vfsmount *m)
+{
+ struct mount *mnt = real_mount(m);
+ br_write_lock(vfsmount_lock);
+ if (mnt->mnt_pinned) {
+ mnt_add_count(mnt, 1);
+ mnt->mnt_pinned--;
+ }
+ br_write_unlock(vfsmount_lock);
+}
+EXPORT_SYMBOL(mnt_unpin);
+
+static inline void mangle(struct seq_file *m, const char *s)
+{
+ seq_escape(m, s, " \t\n\\");
+}
+
+/*
+ * Simple .show_options callback for filesystems which don't want to
+ * implement more complex mount option showing.
+ *
+ * See also save_mount_options().
+ */
+int generic_show_options(struct seq_file *m, struct dentry *root)
+{
+ const char *options;
+
+ rcu_read_lock();
+ options = rcu_dereference(root->d_sb->s_options);
+
+ if (options != NULL && options[0]) {
+ seq_putc(m, ',');
+ mangle(m, options);
+ }
+ rcu_read_unlock();
+
+ return 0;
+}
+EXPORT_SYMBOL(generic_show_options);
+
+/*
+ * If filesystem uses generic_show_options(), this function should be
+ * called from the fill_super() callback.
+ *
+ * The .remount_fs callback usually needs to be handled in a special
+ * way, to make sure, that previous options are not overwritten if the
+ * remount fails.
+ *
+ * Also note, that if the filesystem's .remount_fs function doesn't
+ * reset all options to their default value, but changes only newly
+ * given options, then the displayed options will not reflect reality
+ * any more.
+ */
+void save_mount_options(struct super_block *sb, char *options)
+{
+ BUG_ON(sb->s_options);
+ rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
+}
+EXPORT_SYMBOL(save_mount_options);
+
+void replace_mount_options(struct super_block *sb, char *options)
+{
+ char *old = sb->s_options;
+ rcu_assign_pointer(sb->s_options, options);
+ if (old) {
+ synchronize_rcu();
+ kfree(old);
+ }
+}
+EXPORT_SYMBOL(replace_mount_options);
+
+#ifdef CONFIG_PROC_FS
+/* iterator; we want it to have access to namespace_sem, thus here... */
+static void *m_start(struct seq_file *m, loff_t *pos)
+{
+ struct proc_mounts *p = container_of(m, struct proc_mounts, m);
+
+ down_read(&namespace_sem);
+ return seq_list_start(&p->ns->list, *pos);
+}
+
+static void *m_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct proc_mounts *p = container_of(m, struct proc_mounts, m);
+
+ return seq_list_next(v, &p->ns->list, pos);
+}
+
+static void m_stop(struct seq_file *m, void *v)
+{
+ up_read(&namespace_sem);
+}
+
+static int m_show(struct seq_file *m, void *v)
+{
+ struct proc_mounts *p = container_of(m, struct proc_mounts, m);
+ struct mount *r = list_entry(v, struct mount, mnt_list);
+ return p->show(m, &r->mnt);
+}
+
+const struct seq_operations mounts_op = {
+ .start = m_start,
+ .next = m_next,
+ .stop = m_stop,
+ .show = m_show,
+};
+#endif /* CONFIG_PROC_FS */
+
+/**
+ * may_umount_tree - check if a mount tree is busy
+ * @mnt: root of mount tree
+ *
+ * This is called to check if a tree of mounts has any
+ * open files, pwds, chroots or sub mounts that are
+ * busy.
+ */
+int may_umount_tree(struct vfsmount *m)
+{
+ struct mount *mnt = real_mount(m);
+ int actual_refs = 0;
+ int minimum_refs = 0;
+ struct mount *p;
+ BUG_ON(!m);
+
+ /* write lock needed for mnt_get_count */
+ br_write_lock(vfsmount_lock);
+ for (p = mnt; p; p = next_mnt(p, mnt)) {
+ actual_refs += mnt_get_count(p);
+ minimum_refs += 2;
+ }
+ br_write_unlock(vfsmount_lock);
+
+ if (actual_refs > minimum_refs)
+ return 0;
+
+ return 1;
+}
+
+EXPORT_SYMBOL(may_umount_tree);
+
+/**
+ * may_umount - check if a mount point is busy
+ * @mnt: root of mount
+ *
+ * This is called to check if a mount point has any
+ * open files, pwds, chroots or sub mounts. If the
+ * mount has sub mounts this will return busy
+ * regardless of whether the sub mounts are busy.
+ *
+ * Doesn't take quota and stuff into account. IOW, in some cases it will
+ * give false negatives. The main reason why it's here is that we need
+ * a non-destructive way to look for easily umountable filesystems.
+ */
+int may_umount(struct vfsmount *mnt)
+{
+ int ret = 1;
+ down_read(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+ if (propagate_mount_busy(real_mount(mnt), 2))
+ ret = 0;
+ br_write_unlock(vfsmount_lock);
+ up_read(&namespace_sem);
+ return ret;
+}
+
+EXPORT_SYMBOL(may_umount);
+
+void release_mounts(struct list_head *head)
+{
+ struct mount *mnt;
+ while (!list_empty(head)) {
+ mnt = list_first_entry(head, struct mount, mnt_hash);
+ list_del_init(&mnt->mnt_hash);
+ if (mnt_has_parent(mnt)) {
+ struct dentry *dentry;
+ struct mount *m;
+
+ br_write_lock(vfsmount_lock);
+ dentry = mnt->mnt_mountpoint;
+ m = mnt->mnt_parent;
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+ m->mnt_ghosts--;
+ br_write_unlock(vfsmount_lock);
+ dput(dentry);
+ mntput(&m->mnt);
+ }
+ mntput(&mnt->mnt);
+ }
+}
+
+/*
+ * vfsmount lock must be held for write
+ * namespace_sem must be held for write
+ */
+void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
+{
+ LIST_HEAD(tmp_list);
+ struct mount *p;
+
+ for (p = mnt; p; p = next_mnt(p, mnt))
+ list_move(&p->mnt_hash, &tmp_list);
+
+ if (propagate)
+ propagate_umount(&tmp_list);
+
+ list_for_each_entry(p, &tmp_list, mnt_hash) {
+ list_del_init(&p->mnt_expire);
+ list_del_init(&p->mnt_list);
+ __touch_mnt_namespace(p->mnt_ns);
+ p->mnt_ns = NULL;
+ __mnt_make_shortterm(p);
+ list_del_init(&p->mnt_child);
+ if (mnt_has_parent(p)) {
+ p->mnt_parent->mnt_ghosts++;
+ dentry_reset_mounted(p->mnt_mountpoint);
+ }
+ change_mnt_propagation(p, MS_PRIVATE);
+ }
+ list_splice(&tmp_list, kill);
+}
+
+static void shrink_submounts(struct mount *mnt, struct list_head *umounts);
+
+static int do_umount(struct mount *mnt, int flags)
+{
+ struct super_block *sb = mnt->mnt.mnt_sb;
+ int retval;
+ LIST_HEAD(umount_list);
+
+ retval = security_sb_umount(&mnt->mnt, flags);
+ if (retval)
+ return retval;
+
+ /*
+ * Allow userspace to request a mountpoint be expired rather than
+ * unmounting unconditionally. Unmount only happens if:
+ * (1) the mark is already set (the mark is cleared by mntput())
+ * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
+ */
+ if (flags & MNT_EXPIRE) {
+ if (&mnt->mnt == current->fs->root.mnt ||
+ flags & (MNT_FORCE | MNT_DETACH))
+ return -EINVAL;
+
+ /*
+ * probably don't strictly need the lock here if we examined
+ * all race cases, but it's a slowpath.
+ */
+ br_write_lock(vfsmount_lock);
+ if (mnt_get_count(mnt) != 2) {
+ br_write_unlock(vfsmount_lock);
+ return -EBUSY;
+ }
+ br_write_unlock(vfsmount_lock);
+
+ if (!xchg(&mnt->mnt_expiry_mark, 1))
+ return -EAGAIN;
+ }
+
+ /*
+ * If we may have to abort operations to get out of this
+ * mount, and they will themselves hold resources we must
+ * allow the fs to do things. In the Unix tradition of
+ * 'Gee thats tricky lets do it in userspace' the umount_begin
+ * might fail to complete on the first run through as other tasks
+ * must return, and the like. Thats for the mount program to worry
+ * about for the moment.
+ */
+
+ if (flags & MNT_FORCE && sb->s_op->umount_begin) {
+ sb->s_op->umount_begin(sb);
+ }
+
+ /*
+ * No sense to grab the lock for this test, but test itself looks
+ * somewhat bogus. Suggestions for better replacement?
+ * Ho-hum... In principle, we might treat that as umount + switch
+ * to rootfs. GC would eventually take care of the old vfsmount.
+ * Actually it makes sense, especially if rootfs would contain a
+ * /reboot - static binary that would close all descriptors and
+ * call reboot(9). Then init(8) could umount root and exec /reboot.
+ */
+ if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
+ /*
+ * Special case for "unmounting" root ...
+ * we just try to remount it readonly.
+ */
+ down_write(&sb->s_umount);
+ if (!(sb->s_flags & MS_RDONLY))
+ retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
+ up_write(&sb->s_umount);
+ return retval;
+ }
+
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+ event++;
+
+ if (!(flags & MNT_DETACH))
+ shrink_submounts(mnt, &umount_list);
+
+ retval = -EBUSY;
+ if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
+ if (!list_empty(&mnt->mnt_list))
+ umount_tree(mnt, 1, &umount_list);
+ retval = 0;
+ }
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+ release_mounts(&umount_list);
+ return retval;
+}
+
+/*
+ * Now umount can handle mount points as well as block devices.
+ * This is important for filesystems which use unnamed block devices.
+ *
+ * We now support a flag for forced unmount like the other 'big iron'
+ * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
+ */
+
+SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
+{
+ struct path path;
+ struct mount *mnt;
+ int retval;
+ int lookup_flags = 0;
+
+ if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
+ return -EINVAL;
+
+ if (!(flags & UMOUNT_NOFOLLOW))
+ lookup_flags |= LOOKUP_FOLLOW;
+
+ retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
+ if (retval)
+ goto out;
+ mnt = real_mount(path.mnt);
+ retval = -EINVAL;
+ if (path.dentry != path.mnt->mnt_root)
+ goto dput_and_out;
+ if (!check_mnt(mnt))
+ goto dput_and_out;
+
+ retval = -EPERM;
+ if (!capable(CAP_SYS_ADMIN))
+ goto dput_and_out;
+
+ retval = do_umount(mnt, flags);
+dput_and_out:
+ /* we mustn't call path_put() as that would clear mnt_expiry_mark */
+ dput(path.dentry);
+ mntput_no_expire(mnt);
+out:
+ return retval;
+}
+
+#ifdef __ARCH_WANT_SYS_OLDUMOUNT
+
+/*
+ * The 2.0 compatible umount. No flags.
+ */
+SYSCALL_DEFINE1(oldumount, char __user *, name)
+{
+ return sys_umount(name, 0);
+}
+
+#endif
+
+static int mount_is_safe(struct path *path)
+{
+ if (capable(CAP_SYS_ADMIN))
+ return 0;
+ return -EPERM;
+#ifdef notyet
+ if (S_ISLNK(path->dentry->d_inode->i_mode))
+ return -EPERM;
+ if (path->dentry->d_inode->i_mode & S_ISVTX) {
+ if (current_uid() != path->dentry->d_inode->i_uid)
+ return -EPERM;
+ }
+ if (inode_permission(path->dentry->d_inode, MAY_WRITE))
+ return -EPERM;
+ return 0;
+#endif
+}
+
+struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
+ int flag)
+{
+ struct mount *res, *p, *q, *r;
+ struct path path;
+
+ if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
+ return NULL;
+
+ res = q = clone_mnt(mnt, dentry, flag);
+ if (!q)
+ goto Enomem;
+ q->mnt_mountpoint = mnt->mnt_mountpoint;
+
+ p = mnt;
+ list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
+ struct mount *s;
+ if (!is_subdir(r->mnt_mountpoint, dentry))
+ continue;
+
+ for (s = r; s; s = next_mnt(s, r)) {
+ if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
+ s = skip_mnt_tree(s);
+ continue;
+ }
+ while (p != s->mnt_parent) {
+ p = p->mnt_parent;
+ q = q->mnt_parent;
+ }
+ p = s;
+ path.mnt = &q->mnt;
+ path.dentry = p->mnt_mountpoint;
+ q = clone_mnt(p, p->mnt.mnt_root, flag);
+ if (!q)
+ goto Enomem;
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&q->mnt_list, &res->mnt_list);
+ attach_mnt(q, &path);
+ br_write_unlock(vfsmount_lock);
+ }
+ }
+ return res;
+Enomem:
+ if (res) {
+ LIST_HEAD(umount_list);
+ br_write_lock(vfsmount_lock);
+ umount_tree(res, 0, &umount_list);
+ br_write_unlock(vfsmount_lock);
+ release_mounts(&umount_list);
+ }
+ return NULL;
+}
+
+struct vfsmount *collect_mounts(struct path *path)
+{
+ struct mount *tree;
+ down_write(&namespace_sem);
+ tree = copy_tree(real_mount(path->mnt), path->dentry,
+ CL_COPY_ALL | CL_PRIVATE);
+ up_write(&namespace_sem);
+ return tree ? &tree->mnt : NULL;
+}
+
+void drop_collected_mounts(struct vfsmount *mnt)
+{
+ LIST_HEAD(umount_list);
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+ umount_tree(real_mount(mnt), 0, &umount_list);
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+ release_mounts(&umount_list);
+}
+
+int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
+ struct vfsmount *root)
+{
+ struct mount *mnt;
+ int res = f(root, arg);
+ if (res)
+ return res;
+ list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
+ res = f(&mnt->mnt, arg);
+ if (res)
+ return res;
+ }
+ return 0;
+}
+
+static void cleanup_group_ids(struct mount *mnt, struct mount *end)
+{
+ struct mount *p;
+
+ for (p = mnt; p != end; p = next_mnt(p, mnt)) {
+ if (p->mnt_group_id && !IS_MNT_SHARED(p))
+ mnt_release_group_id(p);
+ }
+}
+
+static int invent_group_ids(struct mount *mnt, bool recurse)
+{
+ struct mount *p;
+
+ for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
+ if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
+ int err = mnt_alloc_group_id(p);
+ if (err) {
+ cleanup_group_ids(mnt, p);
+ return err;
+ }
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * @source_mnt : mount tree to be attached
+ * @nd : place the mount tree @source_mnt is attached
+ * @parent_nd : if non-null, detach the source_mnt from its parent and
+ * store the parent mount and mountpoint dentry.
+ * (done when source_mnt is moved)
+ *
+ * NOTE: in the table below explains the semantics when a source mount
+ * of a given type is attached to a destination mount of a given type.
+ * ---------------------------------------------------------------------------
+ * | BIND MOUNT OPERATION |
+ * |**************************************************************************
+ * | source-->| shared | private | slave | unbindable |
+ * | dest | | | | |
+ * | | | | | | |
+ * | v | | | | |
+ * |**************************************************************************
+ * | shared | shared (++) | shared (+) | shared(+++)| invalid |
+ * | | | | | |
+ * |non-shared| shared (+) | private | slave (*) | invalid |
+ * ***************************************************************************
+ * A bind operation clones the source mount and mounts the clone on the
+ * destination mount.
+ *
+ * (++) the cloned mount is propagated to all the mounts in the propagation
+ * tree of the destination mount and the cloned mount is added to
+ * the peer group of the source mount.
+ * (+) the cloned mount is created under the destination mount and is marked
+ * as shared. The cloned mount is added to the peer group of the source
+ * mount.
+ * (+++) the mount is propagated to all the mounts in the propagation tree
+ * of the destination mount and the cloned mount is made slave
+ * of the same master as that of the source mount. The cloned mount
+ * is marked as 'shared and slave'.
+ * (*) the cloned mount is made a slave of the same master as that of the
+ * source mount.
+ *
+ * ---------------------------------------------------------------------------
+ * | MOVE MOUNT OPERATION |
+ * |**************************************************************************
+ * | source-->| shared | private | slave | unbindable |
+ * | dest | | | | |
+ * | | | | | | |
+ * | v | | | | |
+ * |**************************************************************************
+ * | shared | shared (+) | shared (+) | shared(+++) | invalid |
+ * | | | | | |
+ * |non-shared| shared (+*) | private | slave (*) | unbindable |
+ * ***************************************************************************
+ *
+ * (+) the mount is moved to the destination. And is then propagated to
+ * all the mounts in the propagation tree of the destination mount.
+ * (+*) the mount is moved to the destination.
+ * (+++) the mount is moved to the destination and is then propagated to
+ * all the mounts belonging to the destination mount's propagation tree.
+ * the mount is marked as 'shared and slave'.
+ * (*) the mount continues to be a slave at the new location.
+ *
+ * if the source mount is a tree, the operations explained above is
+ * applied to each mount in the tree.
+ * Must be called without spinlocks held, since this function can sleep
+ * in allocations.
+ */
+static int attach_recursive_mnt(struct mount *source_mnt,
+ struct path *path, struct path *parent_path)
+{
+ LIST_HEAD(tree_list);
+ struct mount *dest_mnt = real_mount(path->mnt);
+ struct dentry *dest_dentry = path->dentry;
+ struct mount *child, *p;
+ int err;
+
+ if (IS_MNT_SHARED(dest_mnt)) {
+ err = invent_group_ids(source_mnt, true);
+ if (err)
+ goto out;
+ }
+ err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
+ if (err)
+ goto out_cleanup_ids;
+
+ br_write_lock(vfsmount_lock);
+
+ if (IS_MNT_SHARED(dest_mnt)) {
+ for (p = source_mnt; p; p = next_mnt(p, source_mnt))
+ set_mnt_shared(p);
+ }
+ if (parent_path) {
+ detach_mnt(source_mnt, parent_path);
+ attach_mnt(source_mnt, path);
+ touch_mnt_namespace(source_mnt->mnt_ns);
+ } else {
+ mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
+ commit_tree(source_mnt);
+ }
+
+ list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
+ list_del_init(&child->mnt_hash);
+ commit_tree(child);
+ }
+ br_write_unlock(vfsmount_lock);
+
+ return 0;
+
+ out_cleanup_ids:
+ if (IS_MNT_SHARED(dest_mnt))
+ cleanup_group_ids(source_mnt, NULL);
+ out:
+ return err;
+}
+
+static int lock_mount(struct path *path)
+{
+ struct vfsmount *mnt;
+retry:
+ mutex_lock(&path->dentry->d_inode->i_mutex);
+ if (unlikely(cant_mount(path->dentry))) {
+ mutex_unlock(&path->dentry->d_inode->i_mutex);
+ return -ENOENT;
+ }
+ down_write(&namespace_sem);
+ mnt = lookup_mnt(path);
+ if (likely(!mnt))
+ return 0;
+ up_write(&namespace_sem);
+ mutex_unlock(&path->dentry->d_inode->i_mutex);
+ path_put(path);
+ path->mnt = mnt;
+ path->dentry = dget(mnt->mnt_root);
+ goto retry;
+}
+
+static void unlock_mount(struct path *path)
+{
+ up_write(&namespace_sem);
+ mutex_unlock(&path->dentry->d_inode->i_mutex);
+}
+
+static int graft_tree(struct mount *mnt, struct path *path)
+{
+ if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
+ return -EINVAL;
+
+ if (S_ISDIR(path->dentry->d_inode->i_mode) !=
+ S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
+ return -ENOTDIR;
+
+ if (d_unlinked(path->dentry))
+ return -ENOENT;
+
+ return attach_recursive_mnt(mnt, path, NULL);
+}
+
+/*
+ * Sanity check the flags to change_mnt_propagation.
+ */
+
+static int flags_to_propagation_type(int flags)
+{
+ int type = flags & ~(MS_REC | MS_SILENT);
+
+ /* Fail if any non-propagation flags are set */
+ if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+ return 0;
+ /* Only one propagation flag should be set */
+ if (!is_power_of_2(type))
+ return 0;
+ return type;
+}
+
+/*
+ * recursively change the type of the mountpoint.
+ */
+static int do_change_type(struct path *path, int flag)
+{
+ struct mount *m;
+ struct mount *mnt = real_mount(path->mnt);
+ int recurse = flag & MS_REC;
+ int type;
+ int err = 0;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (path->dentry != path->mnt->mnt_root)
+ return -EINVAL;
+
+ type = flags_to_propagation_type(flag);
+ if (!type)
+ return -EINVAL;
+
+ down_write(&namespace_sem);
+ if (type == MS_SHARED) {
+ err = invent_group_ids(mnt, recurse);
+ if (err)
+ goto out_unlock;
+ }
+
+ br_write_lock(vfsmount_lock);
+ for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
+ change_mnt_propagation(m, type);
+ br_write_unlock(vfsmount_lock);
+
+ out_unlock:
+ up_write(&namespace_sem);
+ return err;
+}
+
+/*
+ * do loopback mount.
+ */
+static int do_loopback(struct path *path, char *old_name,
+ int recurse)
+{
+ LIST_HEAD(umount_list);
+ struct path old_path;
+ struct mount *mnt = NULL, *old;
+ int err = mount_is_safe(path);
+ if (err)
+ return err;
+ if (!old_name || !*old_name)
+ return -EINVAL;
+ err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
+ if (err)
+ return err;
+
+ err = lock_mount(path);
+ if (err)
+ goto out;
+
+ old = real_mount(old_path.mnt);
+
+ err = -EINVAL;
+ if (IS_MNT_UNBINDABLE(old))
+ goto out2;
+
+ if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old))
+ goto out2;
+
+ err = -ENOMEM;
+ if (recurse)
+ mnt = copy_tree(old, old_path.dentry, 0);
+ else
+ mnt = clone_mnt(old, old_path.dentry, 0);
+
+ if (!mnt)
+ goto out2;
+
+ err = graft_tree(mnt, path);
+ if (err) {
+ br_write_lock(vfsmount_lock);
+ umount_tree(mnt, 0, &umount_list);
+ br_write_unlock(vfsmount_lock);
+ }
+out2:
+ unlock_mount(path);
+ release_mounts(&umount_list);
+out:
+ path_put(&old_path);
+ return err;
+}
+
+static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
+{
+ int error = 0;
+ int readonly_request = 0;
+
+ if (ms_flags & MS_RDONLY)
+ readonly_request = 1;
+ if (readonly_request == __mnt_is_readonly(mnt))
+ return 0;
+
+ if (readonly_request)
+ error = mnt_make_readonly(real_mount(mnt));
+ else
+ __mnt_unmake_readonly(real_mount(mnt));
+ return error;
+}
+
+/*
+ * change filesystem flags. dir should be a physical root of filesystem.
+ * If you've mounted a non-root directory somewhere and want to do remount
+ * on it - tough luck.
+ */
+static int do_remount(struct path *path, int flags, int mnt_flags,
+ void *data)
+{
+ int err;
+ struct super_block *sb = path->mnt->mnt_sb;
+ struct mount *mnt = real_mount(path->mnt);
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (!check_mnt(mnt))
+ return -EINVAL;
+
+ if (path->dentry != path->mnt->mnt_root)
+ return -EINVAL;
+
+ err = security_sb_remount(sb, data);
+ if (err)
+ return err;
+
+ down_write(&sb->s_umount);
+ if (flags & MS_BIND)
+ err = change_mount_flags(path->mnt, flags);
+ else
+ err = do_remount_sb(sb, flags, data, 0);
+ if (!err) {
+ br_write_lock(vfsmount_lock);
+ mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
+ mnt->mnt.mnt_flags = mnt_flags;
+ br_write_unlock(vfsmount_lock);
+ }
+ up_write(&sb->s_umount);
+ if (!err) {
+ br_write_lock(vfsmount_lock);
+ touch_mnt_namespace(mnt->mnt_ns);
+ br_write_unlock(vfsmount_lock);
+ }
+ return err;
+}
+
+static inline int tree_contains_unbindable(struct mount *mnt)
+{
+ struct mount *p;
+ for (p = mnt; p; p = next_mnt(p, mnt)) {
+ if (IS_MNT_UNBINDABLE(p))
+ return 1;
+ }
+ return 0;
+}
+
+static int do_move_mount(struct path *path, char *old_name)
+{
+ struct path old_path, parent_path;
+ struct mount *p;
+ struct mount *old;
+ int err = 0;
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (!old_name || !*old_name)
+ return -EINVAL;
+ err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
+ if (err)
+ return err;
+
+ err = lock_mount(path);
+ if (err < 0)
+ goto out;
+
+ old = real_mount(old_path.mnt);
+ p = real_mount(path->mnt);
+
+ err = -EINVAL;
+ if (!check_mnt(p) || !check_mnt(old))
+ goto out1;
+
+ if (d_unlinked(path->dentry))
+ goto out1;
+
+ err = -EINVAL;
+ if (old_path.dentry != old_path.mnt->mnt_root)
+ goto out1;
+
+ if (!mnt_has_parent(old))
+ goto out1;
+
+ if (S_ISDIR(path->dentry->d_inode->i_mode) !=
+ S_ISDIR(old_path.dentry->d_inode->i_mode))
+ goto out1;
+ /*
+ * Don't move a mount residing in a shared parent.
+ */
+ if (IS_MNT_SHARED(old->mnt_parent))
+ goto out1;
+ /*
+ * Don't move a mount tree containing unbindable mounts to a destination
+ * mount which is shared.
+ */
+ if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
+ goto out1;
+ err = -ELOOP;
+ for (; mnt_has_parent(p); p = p->mnt_parent)
+ if (p == old)
+ goto out1;
+
+ err = attach_recursive_mnt(old, path, &parent_path);
+ if (err)
+ goto out1;
+
+ /* if the mount is moved, it should no longer be expire
+ * automatically */
+ list_del_init(&old->mnt_expire);
+out1:
+ unlock_mount(path);
+out:
+ if (!err)
+ path_put(&parent_path);
+ path_put(&old_path);
+ return err;
+}
+
+static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
+{
+ int err;
+ const char *subtype = strchr(fstype, '.');
+ if (subtype) {
+ subtype++;
+ err = -EINVAL;
+ if (!subtype[0])
+ goto err;
+ } else
+ subtype = "";
+
+ mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
+ err = -ENOMEM;
+ if (!mnt->mnt_sb->s_subtype)
+ goto err;
+ return mnt;
+
+ err:
+ mntput(mnt);
+ return ERR_PTR(err);
+}
+
+static struct vfsmount *
+do_kern_mount(const char *fstype, int flags, const char *name, void *data)
+{
+ struct file_system_type *type = get_fs_type(fstype);
+ struct vfsmount *mnt;
+ if (!type)
+ return ERR_PTR(-ENODEV);
+ mnt = vfs_kern_mount(type, flags, name, data);
+ if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
+ !mnt->mnt_sb->s_subtype)
+ mnt = fs_set_subtype(mnt, fstype);
+ put_filesystem(type);
+ return mnt;
+}
+
+/*
+ * add a mount into a namespace's mount tree
+ */
+static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
+{
+ int err;
+
+ mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
+
+ err = lock_mount(path);
+ if (err)
+ return err;
+
+ err = -EINVAL;
+ if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(real_mount(path->mnt)))
+ goto unlock;
+
+ /* Refuse the same filesystem on the same mount point */
+ err = -EBUSY;
+ if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
+ path->mnt->mnt_root == path->dentry)
+ goto unlock;
+
+ err = -EINVAL;
+ if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
+ goto unlock;
+
+ newmnt->mnt.mnt_flags = mnt_flags;
+ err = graft_tree(newmnt, path);
+
+unlock:
+ unlock_mount(path);
+ return err;
+}
+
+/*
+ * create a new mount for userspace and request it to be added into the
+ * namespace's tree
+ */
+static int do_new_mount(struct path *path, char *type, int flags,
+ int mnt_flags, char *name, void *data)
+{
+ struct vfsmount *mnt;
+ int err;
+
+ if (!type)
+ return -EINVAL;
+
+ /* we need capabilities... */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ mnt = do_kern_mount(type, flags, name, data);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
+ err = do_add_mount(real_mount(mnt), path, mnt_flags);
+ if (err)
+ mntput(mnt);
+ return err;
+}
+
+int finish_automount(struct vfsmount *m, struct path *path)
+{
+ struct mount *mnt = real_mount(m);
+ int err;
+ /* The new mount record should have at least 2 refs to prevent it being
+ * expired before we get a chance to add it
+ */
+ BUG_ON(mnt_get_count(mnt) < 2);
+
+ if (m->mnt_sb == path->mnt->mnt_sb &&
+ m->mnt_root == path->dentry) {
+ err = -ELOOP;
+ goto fail;
+ }
+
+ err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
+ if (!err)
+ return 0;
+fail:
+ /* remove m from any expiration list it may be on */
+ if (!list_empty(&mnt->mnt_expire)) {
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+ list_del_init(&mnt->mnt_expire);
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+ }
+ mntput(m);
+ mntput(m);
+ return err;
+}
+
+/**
+ * mnt_set_expiry - Put a mount on an expiration list
+ * @mnt: The mount to list.
+ * @expiry_list: The list to add the mount to.
+ */
+void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
+{
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+
+ list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
+
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+}
+EXPORT_SYMBOL(mnt_set_expiry);
+
+/*
+ * process a list of expirable mountpoints with the intent of discarding any
+ * mountpoints that aren't in use and haven't been touched since last we came
+ * here
+ */
+void mark_mounts_for_expiry(struct list_head *mounts)
+{
+ struct mount *mnt, *next;
+ LIST_HEAD(graveyard);
+ LIST_HEAD(umounts);
+
+ if (list_empty(mounts))
+ return;
+
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+
+ /* extract from the expiration list every vfsmount that matches the
+ * following criteria:
+ * - only referenced by its parent vfsmount
+ * - still marked for expiry (marked on the last call here; marks are
+ * cleared by mntput())
+ */
+ list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
+ if (!xchg(&mnt->mnt_expiry_mark, 1) ||
+ propagate_mount_busy(mnt, 1))
+ continue;
+ list_move(&mnt->mnt_expire, &graveyard);
+ }
+ while (!list_empty(&graveyard)) {
+ mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
+ touch_mnt_namespace(mnt->mnt_ns);
+ umount_tree(mnt, 1, &umounts);
+ }
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+
+ release_mounts(&umounts);
+}
+
+EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
+
+/*
+ * Ripoff of 'select_parent()'
+ *
+ * search the list of submounts for a given mountpoint, and move any
+ * shrinkable submounts to the 'graveyard' list.
+ */
+static int select_submounts(struct mount *parent, struct list_head *graveyard)
+{
+ struct mount *this_parent = parent;
+ struct list_head *next;
+ int found = 0;
+
+repeat:
+ next = this_parent->mnt_mounts.next;
+resume:
+ while (next != &this_parent->mnt_mounts) {
+ struct list_head *tmp = next;
+ struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
+
+ next = tmp->next;
+ if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
+ continue;
+ /*
+ * Descend a level if the d_mounts list is non-empty.
+ */
+ if (!list_empty(&mnt->mnt_mounts)) {
+ this_parent = mnt;
+ goto repeat;
+ }
+
+ if (!propagate_mount_busy(mnt, 1)) {
+ list_move_tail(&mnt->mnt_expire, graveyard);
+ found++;
+ }
+ }
+ /*
+ * All done at this level ... ascend and resume the search
+ */
+ if (this_parent != parent) {
+ next = this_parent->mnt_child.next;
+ this_parent = this_parent->mnt_parent;
+ goto resume;
+ }
+ return found;
+}
+
+/*
+ * process a list of expirable mountpoints with the intent of discarding any
+ * submounts of a specific parent mountpoint
+ *
+ * vfsmount_lock must be held for write
+ */
+static void shrink_submounts(struct mount *mnt, struct list_head *umounts)
+{
+ LIST_HEAD(graveyard);
+ struct mount *m;
+
+ /* extract submounts of 'mountpoint' from the expiration list */
+ while (select_submounts(mnt, &graveyard)) {
+ while (!list_empty(&graveyard)) {
+ m = list_first_entry(&graveyard, struct mount,
+ mnt_expire);
+ touch_mnt_namespace(m->mnt_ns);
+ umount_tree(m, 1, umounts);
+ }
+ }
+}
+
+/*
+ * Some copy_from_user() implementations do not return the exact number of
+ * bytes remaining to copy on a fault. But copy_mount_options() requires that.
+ * Note that this function differs from copy_from_user() in that it will oops
+ * on bad values of `to', rather than returning a short copy.
+ */
+static long exact_copy_from_user(void *to, const void __user * from,
+ unsigned long n)
+{
+ char *t = to;
+ const char __user *f = from;
+ char c;
+
+ if (!access_ok(VERIFY_READ, from, n))
+ return n;
+
+ while (n) {
+ if (__get_user(c, f)) {
+ memset(t, 0, n);
+ break;
+ }
+ *t++ = c;
+ f++;
+ n--;
+ }
+ return n;
+}
+
+int copy_mount_options(const void __user * data, unsigned long *where)
+{
+ int i;
+ unsigned long page;
+ unsigned long size;
+
+ *where = 0;
+ if (!data)
+ return 0;
+
+ if (!(page = __get_free_page(GFP_KERNEL)))
+ return -ENOMEM;
+
+ /* We only care that *some* data at the address the user
+ * gave us is valid. Just in case, we'll zero
+ * the remainder of the page.
+ */
+ /* copy_from_user cannot cross TASK_SIZE ! */
+ size = TASK_SIZE - (unsigned long)data;
+ if (size > PAGE_SIZE)
+ size = PAGE_SIZE;
+
+ i = size - exact_copy_from_user((void *)page, data, size);
+ if (!i) {
+ free_page(page);
+ return -EFAULT;
+ }
+ if (i != PAGE_SIZE)
+ memset((char *)page + i, 0, PAGE_SIZE - i);
+ *where = page;
+ return 0;
+}
+
+int copy_mount_string(const void __user *data, char **where)
+{
+ char *tmp;
+
+ if (!data) {
+ *where = NULL;
+ return 0;
+ }
+
+ tmp = strndup_user(data, PAGE_SIZE);
+ if (IS_ERR(tmp))
+ return PTR_ERR(tmp);
+
+ *where = tmp;
+ return 0;
+}
+
+/*
+ * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
+ * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
+ *
+ * data is a (void *) that can point to any structure up to
+ * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
+ * information (or be NULL).
+ *
+ * Pre-0.97 versions of mount() didn't have a flags word.
+ * When the flags word was introduced its top half was required
+ * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
+ * Therefore, if this magic number is present, it carries no information
+ * and must be discarded.
+ */
+long do_mount(char *dev_name, char *dir_name, char *type_page,
+ unsigned long flags, void *data_page)
+{
+ struct path path;
+ int retval = 0;
+ int mnt_flags = 0;
+
+ /* Discard magic */
+ if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
+ flags &= ~MS_MGC_MSK;
+
+ /* Basic sanity checks */
+
+ if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
+ return -EINVAL;
+
+ if (data_page)
+ ((char *)data_page)[PAGE_SIZE - 1] = 0;
+
+ /* ... and get the mountpoint */
+ retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
+ if (retval)
+ return retval;
+
+ retval = security_sb_mount(dev_name, &path,
+ type_page, flags, data_page);
+ if (retval)
+ goto dput_out;
+
+ /* Default to relatime unless overriden */
+ if (!(flags & MS_NOATIME))
+ mnt_flags |= MNT_RELATIME;
+
+ /* Separate the per-mountpoint flags */
+ if (flags & MS_NOSUID)
+ mnt_flags |= MNT_NOSUID;
+ if (flags & MS_NODEV)
+ mnt_flags |= MNT_NODEV;
+ if (flags & MS_NOEXEC)
+ mnt_flags |= MNT_NOEXEC;
+ if (flags & MS_NOATIME)
+ mnt_flags |= MNT_NOATIME;
+ if (flags & MS_NODIRATIME)
+ mnt_flags |= MNT_NODIRATIME;
+ if (flags & MS_STRICTATIME)
+ mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
+ if (flags & MS_RDONLY)
+ mnt_flags |= MNT_READONLY;
+
+ flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
+ MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
+ MS_STRICTATIME);
+
+ if (flags & MS_REMOUNT)
+ retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
+ data_page);
+ else if (flags & MS_BIND)
+ retval = do_loopback(&path, dev_name, flags & MS_REC);
+ else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+ retval = do_change_type(&path, flags);
+ else if (flags & MS_MOVE)
+ retval = do_move_mount(&path, dev_name);
+ else
+ retval = do_new_mount(&path, type_page, flags, mnt_flags,
+ dev_name, data_page);
+dput_out:
+ path_put(&path);
+ return retval;
+}
+
+static struct mnt_namespace *alloc_mnt_ns(void)
+{
+ struct mnt_namespace *new_ns;
+
+ new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+ if (!new_ns)
+ return ERR_PTR(-ENOMEM);
+ atomic_set(&new_ns->count, 1);
+ new_ns->root = NULL;
+ INIT_LIST_HEAD(&new_ns->list);
+ init_waitqueue_head(&new_ns->poll);
+ new_ns->event = 0;
+ return new_ns;
+}
+
+void mnt_make_longterm(struct vfsmount *mnt)
+{
+ __mnt_make_longterm(real_mount(mnt));
+}
+
+void mnt_make_shortterm(struct vfsmount *m)
+{
+#ifdef CONFIG_SMP
+ struct mount *mnt = real_mount(m);
+ if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
+ return;
+ br_write_lock(vfsmount_lock);
+ atomic_dec(&mnt->mnt_longterm);
+ br_write_unlock(vfsmount_lock);
+#endif
+}
+
+/*
+ * Allocate a new namespace structure and populate it with contents
+ * copied from the namespace of the passed in task structure.
+ */
+static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
+ struct fs_struct *fs)
+{
+ struct mnt_namespace *new_ns;
+ struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
+ struct mount *p, *q;
+ struct mount *old = mnt_ns->root;
+ struct mount *new;
+
+ new_ns = alloc_mnt_ns();
+ if (IS_ERR(new_ns))
+ return new_ns;
+
+ down_write(&namespace_sem);
+ /* First pass: copy the tree topology */
+ new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE);
+ if (!new) {
+ up_write(&namespace_sem);
+ kfree(new_ns);
+ return ERR_PTR(-ENOMEM);
+ }
+ new_ns->root = new;
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&new_ns->list, &new->mnt_list);
+ br_write_unlock(vfsmount_lock);
+
+ /*
+ * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
+ * as belonging to new namespace. We have already acquired a private
+ * fs_struct, so tsk->fs->lock is not needed.
+ */
+ p = old;
+ q = new;
+ while (p) {
+ q->mnt_ns = new_ns;
+ __mnt_make_longterm(q);
+ if (fs) {
+ if (&p->mnt == fs->root.mnt) {
+ fs->root.mnt = mntget(&q->mnt);
+ __mnt_make_longterm(q);
+ mnt_make_shortterm(&p->mnt);
+ rootmnt = &p->mnt;
+ }
+ if (&p->mnt == fs->pwd.mnt) {
+ fs->pwd.mnt = mntget(&q->mnt);
+ __mnt_make_longterm(q);
+ mnt_make_shortterm(&p->mnt);
+ pwdmnt = &p->mnt;
+ }
+ }
+ p = next_mnt(p, old);
+ q = next_mnt(q, new);
+ }
+ up_write(&namespace_sem);
+
+ if (rootmnt)
+ mntput(rootmnt);
+ if (pwdmnt)
+ mntput(pwdmnt);
+
+ return new_ns;
+}
+
+struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
+ struct fs_struct *new_fs)
+{
+ struct mnt_namespace *new_ns;
+
+ BUG_ON(!ns);
+ get_mnt_ns(ns);
+
+ if (!(flags & CLONE_NEWNS))
+ return ns;
+
+ new_ns = dup_mnt_ns(ns, new_fs);
+
+ put_mnt_ns(ns);
+ return new_ns;
+}
+
+/**
+ * create_mnt_ns - creates a private namespace and adds a root filesystem
+ * @mnt: pointer to the new root filesystem mountpoint
+ */
+static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
+{
+ struct mnt_namespace *new_ns = alloc_mnt_ns();
+ if (!IS_ERR(new_ns)) {
+ struct mount *mnt = real_mount(m);
+ mnt->mnt_ns = new_ns;
+ __mnt_make_longterm(mnt);
+ new_ns->root = mnt;
+ list_add(&new_ns->list, &mnt->mnt_list);
+ } else {
+ mntput(m);
+ }
+ return new_ns;
+}
+
+struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
+{
+ struct mnt_namespace *ns;
+ struct super_block *s;
+ struct path path;
+ int err;
+
+ ns = create_mnt_ns(mnt);
+ if (IS_ERR(ns))
+ return ERR_CAST(ns);
+
+ err = vfs_path_lookup(mnt->mnt_root, mnt,
+ name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
+
+ put_mnt_ns(ns);
+
+ if (err)
+ return ERR_PTR(err);
+
+ /* trade a vfsmount reference for active sb one */
+ s = path.mnt->mnt_sb;
+ atomic_inc(&s->s_active);
+ mntput(path.mnt);
+ /* lock the sucker */
+ down_write(&s->s_umount);
+ /* ... and return the root of (sub)tree on it */
+ return path.dentry;
+}
+EXPORT_SYMBOL(mount_subtree);
+
+SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
+ char __user *, type, unsigned long, flags, void __user *, data)
+{
+ int ret;
+ char *kernel_type;
+ char *kernel_dir;
+ char *kernel_dev;
+ unsigned long data_page;
+
+ ret = copy_mount_string(type, &kernel_type);
+ if (ret < 0)
+ goto out_type;
+
+ kernel_dir = getname(dir_name);
+ if (IS_ERR(kernel_dir)) {
+ ret = PTR_ERR(kernel_dir);
+ goto out_dir;
+ }
+
+ ret = copy_mount_string(dev_name, &kernel_dev);
+ if (ret < 0)
+ goto out_dev;
+
+ ret = copy_mount_options(data, &data_page);
+ if (ret < 0)
+ goto out_data;
+
+ ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags,
+ (void *) data_page);
+
+ free_page(data_page);
+out_data:
+ kfree(kernel_dev);
+out_dev:
+ putname(kernel_dir);
+out_dir:
+ kfree(kernel_type);
+out_type:
+ return ret;
+}
+
+/*
+ * Return true if path is reachable from root
+ *
+ * namespace_sem or vfsmount_lock is held
+ */
+bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
+ const struct path *root)
+{
+ while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
+ dentry = mnt->mnt_mountpoint;
+ mnt = mnt->mnt_parent;
+ }
+ return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
+}
+
+int path_is_under(struct path *path1, struct path *path2)
+{
+ int res;
+ br_read_lock(vfsmount_lock);
+ res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
+ br_read_unlock(vfsmount_lock);
+ return res;
+}
+EXPORT_SYMBOL(path_is_under);
+
+/*
+ * pivot_root Semantics:
+ * Moves the root file system of the current process to the directory put_old,
+ * makes new_root as the new root file system of the current process, and sets
+ * root/cwd of all processes which had them on the current root to new_root.
+ *
+ * Restrictions:
+ * The new_root and put_old must be directories, and must not be on the
+ * same file system as the current process root. The put_old must be
+ * underneath new_root, i.e. adding a non-zero number of /.. to the string
+ * pointed to by put_old must yield the same directory as new_root. No other
+ * file system may be mounted on put_old. After all, new_root is a mountpoint.
+ *
+ * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
+ * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
+ * in this situation.
+ *
+ * Notes:
+ * - we don't move root/cwd if they are not at the root (reason: if something
+ * cared enough to change them, it's probably wrong to force them elsewhere)
+ * - it's okay to pick a root that isn't the root of a file system, e.g.
+ * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
+ * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
+ * first.
+ */
+SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
+ const char __user *, put_old)
+{
+ struct path new, old, parent_path, root_parent, root;
+ struct mount *new_mnt, *root_mnt;
+ int error;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ error = user_path_dir(new_root, &new);
+ if (error)
+ goto out0;
+
+ error = user_path_dir(put_old, &old);
+ if (error)
+ goto out1;
+
+ error = security_sb_pivotroot(&old, &new);
+ if (error)
+ goto out2;
+
+ get_fs_root(current->fs, &root);
+ error = lock_mount(&old);
+ if (error)
+ goto out3;
+
+ error = -EINVAL;
+ new_mnt = real_mount(new.mnt);
+ root_mnt = real_mount(root.mnt);
+ if (IS_MNT_SHARED(real_mount(old.mnt)) ||
+ IS_MNT_SHARED(new_mnt->mnt_parent) ||
+ IS_MNT_SHARED(root_mnt->mnt_parent))
+ goto out4;
+ if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
+ goto out4;
+ error = -ENOENT;
+ if (d_unlinked(new.dentry))
+ goto out4;
+ if (d_unlinked(old.dentry))
+ goto out4;
+ error = -EBUSY;
+ if (new.mnt == root.mnt ||
+ old.mnt == root.mnt)
+ goto out4; /* loop, on the same file system */
+ error = -EINVAL;
+ if (root.mnt->mnt_root != root.dentry)
+ goto out4; /* not a mountpoint */
+ if (!mnt_has_parent(root_mnt))
+ goto out4; /* not attached */
+ if (new.mnt->mnt_root != new.dentry)
+ goto out4; /* not a mountpoint */
+ if (!mnt_has_parent(new_mnt))
+ goto out4; /* not attached */
+ /* make sure we can reach put_old from new_root */
+ if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new))
+ goto out4;
+ br_write_lock(vfsmount_lock);
+ detach_mnt(new_mnt, &parent_path);
+ detach_mnt(root_mnt, &root_parent);
+ /* mount old root on put_old */
+ attach_mnt(root_mnt, &old);
+ /* mount new_root on / */
+ attach_mnt(new_mnt, &root_parent);
+ touch_mnt_namespace(current->nsproxy->mnt_ns);
+ br_write_unlock(vfsmount_lock);
+ chroot_fs_refs(&root, &new);
+ error = 0;
+out4:
+ unlock_mount(&old);
+ if (!error) {
+ path_put(&root_parent);
+ path_put(&parent_path);
+ }
+out3:
+ path_put(&root);
+out2:
+ path_put(&old);
+out1:
+ path_put(&new);
+out0:
+ return error;
+}
+
+static void __init init_mount_tree(void)
+{
+ struct vfsmount *mnt;
+ struct mnt_namespace *ns;
+ struct path root;
+
+ mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
+ if (IS_ERR(mnt))
+ panic("Can't create rootfs");
+
+ ns = create_mnt_ns(mnt);
+ if (IS_ERR(ns))
+ panic("Can't allocate initial namespace");
+
+ init_task.nsproxy->mnt_ns = ns;
+ get_mnt_ns(ns);
+
+ root.mnt = mnt;
+ root.dentry = mnt->mnt_root;
+
+ set_fs_pwd(current->fs, &root);
+ set_fs_root(current->fs, &root);
+}
+
+void __init mnt_init(void)
+{
+ unsigned u;
+ int err;
+
+ init_rwsem(&namespace_sem);
+
+ mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
+ 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+
+ mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
+
+ if (!mount_hashtable)
+ panic("Failed to allocate mount hash table\n");
+
+ printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
+
+ for (u = 0; u < HASH_SIZE; u++)
+ INIT_LIST_HEAD(&mount_hashtable[u]);
+
+ br_lock_init(vfsmount_lock);
+
+ err = sysfs_init();
+ if (err)
+ printk(KERN_WARNING "%s: sysfs_init error: %d\n",
+ __func__, err);
+ fs_kobj = kobject_create_and_add("fs", NULL);
+ if (!fs_kobj)
+ printk(KERN_WARNING "%s: kobj create error\n", __func__);
+ init_rootfs();
+ init_mount_tree();
+}
+
+void put_mnt_ns(struct mnt_namespace *ns)
+{
+ LIST_HEAD(umount_list);
+
+ if (!atomic_dec_and_test(&ns->count))
+ return;
+ down_write(&namespace_sem);
+ br_write_lock(vfsmount_lock);
+ umount_tree(ns->root, 0, &umount_list);
+ br_write_unlock(vfsmount_lock);
+ up_write(&namespace_sem);
+ release_mounts(&umount_list);
+ kfree(ns);
+}
+
+struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
+{
+ struct vfsmount *mnt;
+ mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
+ if (!IS_ERR(mnt)) {
+ /*
+ * it is a longterm mount, don't release mnt until
+ * we unmount before file sys is unregistered
+ */
+ mnt_make_longterm(mnt);
+ }
+ return mnt;
+}
+EXPORT_SYMBOL_GPL(kern_mount_data);
+
+void kern_unmount(struct vfsmount *mnt)
+{
+ /* release long term mount so mount point can be released */
+ if (!IS_ERR_OR_NULL(mnt)) {
+ mnt_make_shortterm(mnt);
+ mntput(mnt);
+ }
+}
+EXPORT_SYMBOL(kern_unmount);
+
+bool our_mnt(struct vfsmount *mnt)
+{
+ return check_mnt(real_mount(mnt));
+}