Merge branch 'cgroup/for-3.7-fixes' into cgroup/for-3.8

This is to receive device_cgroup fixes so that further device_cgroup
changes can be made in cgroup/for-3.8.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index e9d594fd12cb..54046e51160a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -976,8 +976,21 @@ static int loop_clr_fd(struct loop_device *lo)
 	if (lo->lo_state != Lo_bound)
 		return -ENXIO;
 
-	if (lo->lo_refcnt > 1)	/* we needed one fd for the ioctl */
-		return -EBUSY;
+	/*
+	 * If we've explicitly asked to tear down the loop device,
+	 * and it has an elevated reference count, set it for auto-teardown when
+	 * the last reference goes away. This stops $!~#$@ udev from
+	 * preventing teardown because it decided that it needs to run blkid on
+	 * the loopback device whenever they appear. xfstests is notorious for
+	 * failing tests because blkid via udev races with a losetup
+	 * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
+	 * command to fail with EBUSY.
+	 */
+	if (lo->lo_refcnt > 1) {
+		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
+		mutex_unlock(&lo->lo_ctl_mutex);
+		return 0;
+	}
 
 	if (filp == NULL)
 		return -EINVAL;