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new helper: mount_subtree()

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takes vfsmount and relative path, does lookup within that vfsmount
(possibly triggering automounts) and returns the result as root
of subtree suitable for return by ->mount() (i.e. a reference to
dentry and an active reference to its superblock grabbed, superblock
locked exclusive).

btrfs and nfs switched to it instead of open-coding the sucker.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2011-11-16 21:43:59 -05:00
parent c133449587
commit ea441d1104
4 changed files with 41 additions and 53 deletions
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35
fs/btrfs/super.c
View File

@@ -825,13 +825,9 @@ static char *setup_root_args(char *args)
static struct dentry *mount_subvol(const char *subvol_name, int flags,
const char *device_name, char *data)
{
struct super_block *s;
struct dentry *root;
struct vfsmount *mnt;
struct mnt_namespace *ns_private;
char *newargs;
struct path path;
int error;
newargs = setup_root_args(data);
if (!newargs)
@@ -842,36 +838,17 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags,
if (IS_ERR(mnt))
return ERR_CAST(mnt);
ns_private = create_mnt_ns(mnt);
if (IS_ERR(ns_private))
return ERR_CAST(ns_private);
root = mount_subtree(mnt, subvol_name);
/*
* This will trigger the automount of the subvol so we can just
* drop the mnt we have here and return the dentry that we
* found.
*/
error = vfs_path_lookup(mnt->mnt_root, mnt, subvol_name,
LOOKUP_FOLLOW, &path);
put_mnt_ns(ns_private);
if (error)
return ERR_PTR(error);
if (!is_subvolume_inode(path.dentry->d_inode)) {
path_put(&path);
error = -EINVAL;
if (!IS_ERR(root) && !is_subvolume_inode(root->d_inode)) {
struct super_block *s = root->d_sb;
dput(root);
root = ERR_PTR(-EINVAL);
deactivate_locked_super(s);
printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n",
subvol_name);
return ERR_PTR(-EINVAL);
}
/* Get a ref to the sb and the dentry we found and return it */
s = path.mnt->mnt_sb;
atomic_inc(&s->s_active);
root = dget(path.dentry);
path_put(&path);
down_write(&s->s_umount);
return root;
}