linux-kernel - [PATCH 3/9] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr

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Date:   Wed, 14 Jul 2021 23:06:29 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <ming.lei@...hat.com>, <linux-scsi@...r.kernel.org>,
        <kashyap.desai@...adcom.com>, <hare@...e.de>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH 3/9] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()

For shared sbitmap, if the call to blk_mq_tag_update_depth() was
successful for any hctx when hctx->sched_tags is not set, then it would be
successful for all (due to nature in which blk_mq_tag_update_depth()
fails).

As such, there is no need to call blk_mq_tag_resize_shared_sbitmap() for
each hctx. So relocate the call until after the hctx iteration under the
!q->elevator check, which is equivalent (to !hctx->sched_tags).

Signed-off-by: John Garry <john.garry@...wei.com>
---
 block/blk-mq.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ae28f470893c..56e3c6fdba60 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3624,8 +3624,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		if (!hctx->sched_tags) {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
 							false);
-			if (!ret && blk_mq_is_sbitmap_shared(set->flags))
-				blk_mq_tag_resize_shared_sbitmap(set, nr);
 		} else {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
 							nr, true);
@@ -3643,9 +3641,14 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 	}
 	if (!ret) {
 		q->nr_requests = nr;
-		if (q->elevator && blk_mq_is_sbitmap_shared(set->flags))
-			sbitmap_queue_resize(&q->sched_bitmap_tags,
-					     nr - set->reserved_tags);
+		if (blk_mq_is_sbitmap_shared(set->flags)) {
+			if (q->elevator) {
+				sbitmap_queue_resize(&q->sched_bitmap_tags,
+						     nr - set->reserved_tags);
+			} else {
+				blk_mq_tag_resize_shared_sbitmap(set, nr);
+			}
+		}
 	}
 
 	blk_mq_unquiesce_queue(q);
-- 
2.26.2