md: avoid spinlock problem in blk_throtl_exit

blk_throtl_exit assumes that ->queue_lock still exists,
so make sure that it does.
To do this, we stop redirecting ->queue_lock to conf->device_lock
and leave it pointing where it is initialised - __queue_lock.

As the blk_plug functions check the ->queue_lock is held, we now
take that spin_lock explicitly around the plug functions.  We don't
need the locking, just the warning removal.

This is needed for any kernel with the blk_throtl code, which is
which is 2.6.37 and later.

Cc: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 0 insertions, 1 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 75671dfee551..c0ac457f1218 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -361,7 +361,6 @@ static int raid0_run(mddev_t *mddev)
         if (md_check_no_bitmap(mddev))
                 return -EINVAL;
         blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
-        mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 
         /* if private is not null, we are here after takeover */
         if (mddev->private == NULL) {