[3.19.y-ckt stable] Patch "btrfs: unlock i_mutex after attempting to delete subvolume during send" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    btrfs: unlock i_mutex after attempting to delete subvolume during send

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From db1d2367b0b5db03de5ac7db9c7d88858586a6d0 Mon Sep 17 00:00:00 2001
From: Omar Sandoval <osandov at osandov.com>
Date: Fri, 10 Apr 2015 14:20:40 -0700
Subject: btrfs: unlock i_mutex after attempting to delete subvolume during
 send

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 at suse.com>
Reviewed-by: David Sterba <dsterba at suse.cz>
Signed-off-by: Omar Sandoval <osandov at osandov.com>
Signed-off-by: Chris Mason <clm at fb.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/btrfs/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 09a566a..334b0a9 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2403,7 +2403,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 			"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);
--
1.9.1