block: use an atomic_t for mq_freeze_depth

lockdep gets unhappy about the not disabling irqs when using the queue_lock
around it.  Instead of trying to fix that up just switch to an atomic_t
and get rid of the lock.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

2 files changed, 11 insertions, 15 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 31df47443699..c382a34fe5ac 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -89,7 +89,8 @@ static int blk_mq_queue_enter(struct request_queue *q, gfp_t gfp)
                         return -EBUSY;
 
                 ret = wait_event_interruptible(q->mq_freeze_wq,
-                                !q->mq_freeze_depth || blk_queue_dying(q));
+                                !atomic_read(&q->mq_freeze_depth) ||
+                                blk_queue_dying(q));
                 if (blk_queue_dying(q))
                         return -ENODEV;
                 if (ret)
@@ -112,13 +113,10 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref)
 
 void blk_mq_freeze_queue_start(struct request_queue *q)
 {
-        bool freeze;
+        int freeze_depth;
 
-        spin_lock_irq(q->queue_lock);
-        freeze = !q->mq_freeze_depth++;
-        spin_unlock_irq(q->queue_lock);
-
-        if (freeze) {
+        freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
+        if (freeze_depth == 1) {
                 percpu_ref_kill(&q->mq_usage_counter);
                 blk_mq_run_hw_queues(q, false);
         }
@@ -143,13 +141,11 @@ EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 
 void blk_mq_unfreeze_queue(struct request_queue *q)
 {
-        bool wake;
+        int freeze_depth;
 
-        spin_lock_irq(q->queue_lock);
-        wake = !--q->mq_freeze_depth;
-        WARN_ON_ONCE(q->mq_freeze_depth < 0);
-        spin_unlock_irq(q->queue_lock);
-        if (wake) {
+        freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
+        WARN_ON_ONCE(freeze_depth < 0);
+        if (!freeze_depth) {
                 percpu_ref_reinit(&q->mq_usage_counter);
                 wake_up_all(&q->mq_freeze_wq);
         }
@@ -2081,7 +2077,7 @@ void blk_mq_free_queue(struct request_queue *q)
 /* Basically redo blk_mq_init_queue with queue frozen */
 static void blk_mq_queue_reinit(struct request_queue *q)
 {
-        WARN_ON_ONCE(!q->mq_freeze_depth);
+        WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth));
 
         blk_mq_sysfs_unregister(q);
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2da818a48097..bc917956a6d0 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -444,7 +444,7 @@ struct request_queue {
         struct mutex            sysfs_lock;
 
         int                     bypass_depth;
-        int                     mq_freeze_depth;
+        atomic_t                mq_freeze_depth;
 
 #if defined(CONFIG_BLK_DEV_BSG)
         bsg_job_fn              *bsg_job_fn;