[PATCH 4.0 47/72] btrfs: unlock i_mutex after attempting to delete subvolume during send

Greg Kroah-Hartman
2015-05-11T18:50:31Z

From: Omar Sandoval <osandov@osandov.com>

commit 909e26dce3f7600f5e293ac0522c28790a0c8c9c upstream.

Whenever the check for a send in progress introduced in commit
521e0546c970 (btrfs: protect snapshots from deleting during send) is
hit, we return without unlocking inode->i_mutex. This is easy to see
with lockdep enabled:

[ +0.000059] ================================================
[ +0.000028] [ BUG: lock held when returning to user space! ]
[ +0.000029] 4.0.0-rc5-00096-g3c435c1 #93 Not tainted
[ +0.000026] ------------------------------------------------
[ +0.000029] btrfs/211 is leaving the kernel with locks still held!
[ +0.000029] 1 lock held by btrfs/211:
[ +0.000023] #0: (&type->i_mutex_dir_key){+.+.+.}, at: [<ffffffff8135b8df>] btrfs_ioctl_snap_destroy+0x2df/0x7a0

Make sure we unlock it in the error path.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/ioctl.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2403,7 +2403,7 @@ static noinline int btrfs_ioctl_snap_des
"Attempt to delete subvolume %llu during send",
dest->root_key.objectid);
err = -EPERM;
- goto out_dput;
+ goto out_unlock_inode;
}

d_invalidate(dentry);
@@ -2498,6 +2498,7 @@ out_up_write:
root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
spin_unlock(&dest->root_item_lock);
}
+out_unlock_inode:
mutex_unlock(&inode->i_mutex);
if (!err) {
shrink_dcache_sb(root->fs_info->sb);