Patch "btrfs: unlock i_mutex after attempting to delete subvolume during send" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

btrfs: unlock i_mutex after attempting to delete subvolume during send

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
btrfs-unlock-i_mutex-after-attempting-to-delete-subvolume-during-send.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Omar Sandoval <[email protected]>
Date: Fri, 10 Apr 2015 14:20:40 -0700
Subject: btrfs: unlock i_mutex after attempting to delete subvolume during send

From: Omar Sandoval <[email protected]>

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.

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

@@ -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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/btrfs-unlock-i_mutex-after-attempting-to-delete-subvolume-during-send.patch