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, 4 insertions, 2 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a23ffa397ba9..06cd712807d0 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -593,7 +593,10 @@ static int flush_pending_writes(conf_t *conf)
         if (conf->pending_bio_list.head) {
                 struct bio *bio;
                 bio = bio_list_get(&conf->pending_bio_list);
+                /* Only take the spinlock to quiet a warning */
+                spin_lock(conf->mddev->queue->queue_lock);
                 blk_remove_plug(conf->mddev->queue);
+                spin_unlock(conf->mddev->queue->queue_lock);
                 spin_unlock_irq(&conf->device_lock);
                 /* flush any pending bitmap writes to
                  * disk before proceeding w/ I/O */
@@ -959,7 +962,7 @@ static int make_request(mddev_t *mddev, struct bio * bio)
                 atomic_inc(&r1_bio->remaining);
                 spin_lock_irqsave(&conf->device_lock, flags);
                 bio_list_add(&conf->pending_bio_list, mbio);
-                blk_plug_device(mddev->queue);
+                blk_plug_device_unlocked(mddev->queue);
                 spin_unlock_irqrestore(&conf->device_lock, flags);
         }
         r1_bio_write_done(r1_bio, bio->bi_vcnt, behind_pages, behind_pages != NULL);
@@ -2021,7 +2024,6 @@ static int run(mddev_t *mddev)
         if (IS_ERR(conf))
                 return PTR_ERR(conf);
 
-        mddev->queue->queue_lock = &conf->device_lock;
         list_for_each_entry(rdev, &mddev->disks, same_set) {
                 disk_stack_limits(mddev->gendisk, rdev->bdev,
                                   rdev->data_offset << 9);