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-rw-r--r--fs/namespace.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index e5e1c7d1839b..6d3a1963879b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2483,11 +2483,43 @@ struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
__mnt_make_longterm(mnt);
new_ns->root = mnt;
list_add(&new_ns->list, &new_ns->root->mnt_list);
+ } else {
+ mntput(mnt);
}
return new_ns;
}
EXPORT_SYMBOL(create_mnt_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)
{