linux-kernel - [PATCH 3.16.y-ckt 011/129] btrfs: unlock i_mutex after attempting to delete subvolume during send

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Date:	Fri, 22 May 2015 09:56:36 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Omar Sandoval <osandov@...ndov.com>, Chris Mason <clm@...com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 011/129] btrfs: unlock i_mutex after attempting to delete subvolume during send

3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Omar Sandoval <osandov@...ndov.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@...e.com>
Reviewed-by: David Sterba <dsterba@...e.cz>
Signed-off-by: Omar Sandoval <osandov@...ndov.com>
Signed-off-by: Chris Mason <clm@...com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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 5576abb92a23..7c5f053ee42c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2451,7 +2451,7 @@ 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;
 	}
 
 	err = d_invalidate(dentry);
@@ -2549,6 +2549,7 @@ out_unlock:
 				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);
--
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