Remove blkdev warning triggered by using md

As setting and clearing queue flags now requires that we hold a spinlock
on the queue, and as blk_queue_stack_limits is called without that lock,
get the lock inside blk_queue_stack_limits.

For blk_queue_stack_limits to be able to find the right lock, each md
personality needs to set q->queue_lock to point to the appropriate lock.
Those personalities which didn't previously use a spin_lock, us
q->__queue_lock.  So always initialise that lock when allocated.

With this in place, setting/clearing of the QUEUE_FLAG_PLUGGED bit will no
longer cause warnings as it will be clear that the proper lock is held.

Thanks to Dan Williams for review and fixing the silly bugs.

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Alistair John Strachan <alistair@devzero.co.uk>
Cc: Nick Piggin <npiggin@suse.de>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Jacek Luczak <difrost.kernel@gmail.com>
Cc: Prakash Punnoor <prakash@punnoor.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 9 insertions, 4 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 2987fe47b5ee..6a9cc0d22a61 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -482,6 +482,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 	kobject_init(&q->kobj, &blk_queue_ktype);
 
 	mutex_init(&q->sysfs_lock);
+	spin_lock_init(&q->__queue_lock);
 
 	return q;
 }
@@ -544,10 +545,8 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 	 * if caller didn't supply a lock, they get per-queue locking with
 	 * our embedded lock
 	 */
-	if (!lock) {
-		spin_lock_init(&q->__queue_lock);
+	if (!lock)
 		lock = &q->__queue_lock;
-	}
 
 	q->request_fn		= rfn;
 	q->prep_rq_fn		= NULL;
diff --git a/block/blk-settings.c b/block/blk-settings.c
index bb93d4c32775..8dd86418f35d 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -286,8 +286,14 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 	t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);
 	t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
 	t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
-	if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
+	if (!t->queue_lock)
+		WARN_ON_ONCE(1);
+	else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
+		unsigned long flags;
+		spin_lock_irqsave(t->queue_lock, flags);
 		queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
+		spin_unlock_irqrestore(t->queue_lock, flags);
+	}
 }
 EXPORT_SYMBOL(blk_queue_stack_limits);