[3.11.y.z extended stable] Patch "btrfs: call mnt_drop_write after interrupted subvol deletion" has been added to staging queue

[Luis Henriques]

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

    btrfs: call mnt_drop_write after interrupted subvol deletion

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From bbfe0c570d6bce71c29d8f65d47ed7a54a1eb1c6 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba at suse.cz>
Date: Fri, 6 Dec 2013 17:51:32 +0100
Subject: btrfs: call mnt_drop_write after interrupted subvol deletion

commit e43f998e47bae27e37e159915625e8d4b130153b upstream.

If btrfs_ioctl_snap_destroy blocks on the mutex and the process is
killed, mnt_write count is unbalanced and leads to unmountable
filesystem.

Signed-off-by: David Sterba <dsterba at suse.cz>
Signed-off-by: Chris Mason <clm at fb.com>
Signed-off-by: Luis Henriques <luis.henriques 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 9877a2a..6074a8e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2099,7 +2099,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,

 	err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
 	if (err == -EINTR)
-		goto out;
+		goto out_drop_write;
 	dentry = lookup_one_len(vol_args->name, parent, namelen);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
@@ -2241,6 +2241,7 @@ out_dput:
 	dput(dentry);
 out_unlock_dir:
 	mutex_unlock(&dir->i_mutex);
+out_drop_write:
 	mnt_drop_write_file(file);
 out:
 	kfree(vol_args);
--
1.8.3.2