[V7,2/6] block: tracking request allocation with q_usage_counter

Commit Message

Ming Lei Sept. 30, 2017, 6:12 a.m. UTC

This usage is basically same with blk-mq, so that we can
support to freeze legacy queue easily.

Also 'wake_up_all(&q->mq_freeze_wq)' has to be moved
into blk_set_queue_dying() since both legacy and blk-mq
may wait on the wait queue of .mq_freeze_wq.

Tested-by: Oleksandr Natalenko <[e-mail]>
Tested-by: Martin Steigerwald <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Cc: Bart Van Assche <[e-mail]>
Signed-off-by: Ming Lei <[e-mail]>
---
 block/blk-core.c | 14 ++++++++++++++
 block/blk-mq.c   |  7 -------
 2 files changed, 14 insertions(+), 7 deletions(-)

Comments

Christoph Hellwig Oct. 2, 2017, 1:32 p.m. UTC | #1

I think I already gate it to basically the same patch as queued
up by Bart, but here again:

Reviewed-by: Christoph Hellwig <[e-mail]>

Bart Van Assche Oct. 2, 2017, 4:01 p.m. UTC | #2

On Sat, 2017-09-30 at 14:12 +0800, Ming Lei wrote:
> @@ -1395,16 +1401,21 @@ static struct request *blk_old_get_request(struct request_queue *q,

>  					   unsigned int op, gfp_t gfp_mask)

>  {

>  	struct request *rq;

> +	int ret = 0;

>  

>  	WARN_ON_ONCE(q->mq_ops);

>  

>  	/* create ioc upfront */

>  	create_io_context(gfp_mask, q->node);

>  

> +	ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM));

> +	if (ret)

> +		return ERR_PTR(ret);


Can the above blk_queue_enter() call block if the REQ_NOWAIT flag has been
set in the op argument and e.g. gfp_mask == GFP_KERNEL? If so, isn't that a
bug?

Bart.

Patch

diff --git a/block/blk-core.c b/block/blk-core.c
index 048be4aa6024..a5011c824ac6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -610,6 +610,12 @@  void blk_set_queue_dying(struct request_queue *q)
 		}
 		spin_unlock_irq(q->queue_lock);
 	}
+
+	/*
+	 * We need to ensure that processes currently waiting on
+	 * the queue are notified as well.
+	 */
+	wake_up_all(&q->mq_freeze_wq);
 }
 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
 
@@ -1395,16 +1401,21 @@  static struct request *blk_old_get_request(struct request_queue *q,
 					   unsigned int op, gfp_t gfp_mask)
 {
 	struct request *rq;
+	int ret = 0;
 
 	WARN_ON_ONCE(q->mq_ops);
 
 	/* create ioc upfront */
 	create_io_context(gfp_mask, q->node);
 
+	ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM));
+	if (ret)
+		return ERR_PTR(ret);
 	spin_lock_irq(q->queue_lock);
 	rq = get_request(q, op, NULL, gfp_mask);
 	if (IS_ERR(rq)) {
 		spin_unlock_irq(q->queue_lock);
+		blk_queue_exit(q);
 		return rq;
 	}
 
@@ -1576,6 +1587,7 @@  void __blk_put_request(struct request_queue *q, struct request *req)
 		blk_free_request(rl, req);
 		freed_request(rl, sync, rq_flags);
 		blk_put_rl(rl);
+		blk_queue_exit(q);
 	}
 }
 EXPORT_SYMBOL_GPL(__blk_put_request);
@@ -1857,8 +1869,10 @@  static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
 	 * Grab a free request. This is might sleep but can not fail.
 	 * Returns with the queue unlocked.
 	 */
+	blk_queue_enter_live(q);
 	req = get_request(q, bio->bi_opf, bio, GFP_NOIO);
 	if (IS_ERR(req)) {
+		blk_queue_exit(q);
 		__wbt_done(q->rq_wb, wb_acct);
 		if (PTR_ERR(req) == -ENOMEM)
 			bio->bi_status = BLK_STS_RESOURCE;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6fd9f86fc86d..10c1f49f663d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -256,13 +256,6 @@  void blk_mq_wake_waiters(struct request_queue *q)
 	queue_for_each_hw_ctx(q, hctx, i)
 		if (blk_mq_hw_queue_mapped(hctx))
 			blk_mq_tag_wakeup_all(hctx->tags, true);
-
-	/*
-	 * If we are called because the queue has now been marked as
-	 * dying, we need to ensure that processes currently waiting on
-	 * the queue are notified as well.
-	 */
-	wake_up_all(&q->mq_freeze_wq);
 }
 
 bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)