blk-mq: support concurrent queue quiesce/unquiesce

blk_mq_quiesce_queue() has been used a bit wide now, so far we don't support
concurrent/nested quiesce. One biggest issue is that unquiesce can happen
unexpectedly in case that quiesce/unquiesce are run concurrently from
more than one context.

This patch introduces q->mq_quiesce_depth to deal concurrent quiesce,
and we only unquiesce queue when it is the last/outer-most one of all
contexts.

Several kernel panic issue has been reported[1][2][3] when running stress
quiesce test. And this patch has been verified in these reports.

[1] https://lore.kernel.org/linux-block/9b21c797-e505-3821-4f5b-df7bf9380328@huawei.com/T/#m1fc52431fad7f33b1ffc3f12c4450e4238540787
[2] https://lore.kernel.org/linux-block/9b21c797-e505-3821-4f5b-df7bf9380328@huawei.com/T/#m10ad90afeb9c8cc318334190a7c24c8b5c5e0722
[3] https://listman.redhat.com/archives/dm-devel/2021-September/msg00189.html

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211014081710.1871747-7-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index bf5936d..31d9e61 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -241,7 +241,12 @@ EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
  */
 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
 {
-       blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+       unsigned long flags;
+
+       spin_lock_irqsave(&q->queue_lock, flags);
+       if (!q->quiesce_depth++)
+               blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+       spin_unlock_irqrestore(&q->queue_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
 
@@ -282,10 +287,21 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
  */
 void blk_mq_unquiesce_queue(struct request_queue *q)
 {
-       blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+       unsigned long flags;
+       bool run_queue = false;
+
+       spin_lock_irqsave(&q->queue_lock, flags);
+       if (WARN_ON_ONCE(q->quiesce_depth <= 0)) {
+               ;
+       } else if (!--q->quiesce_depth) {
+               blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+               run_queue = true;
+       }
+       spin_unlock_irqrestore(&q->queue_lock, flags);
 
        /* dispatch requests which are inserted during quiescing */
-       blk_mq_run_hw_queues(q, true);
+       if (run_queue)
+               blk_mq_run_hw_queues(q, true);
 }
 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
 

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f13091d..2b22fa3 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -315,6 +315,8 @@ struct request_queue {
         */
        struct mutex            mq_freeze_lock;
 
+       int                     quiesce_depth;
+
        struct blk_mq_tag_set   *tag_set;
        struct list_head        tag_set_list;
        struct bio_set          bio_split;