linux-kernel - [PATCH -next RFC 3/6] blk-mq: record how many tags are needed for splited bio

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Date:   Tue, 29 Mar 2022 17:40:45 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <axboe@...nel.dk>, <andriy.shevchenko@...ux.intel.com>,
        <john.garry@...wei.com>, <ming.lei@...hat.com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yukuai3@...wei.com>, <yi.zhang@...wei.com>
Subject: [PATCH -next RFC 3/6] blk-mq: record how many tags are needed for splited bio

Prepare to wake up number of threads based on required tags.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-mq-tag.c      | 1 +
 block/blk-mq.c          | 1 +
 block/blk-mq.h          | 1 +
 include/linux/sbitmap.h | 2 ++
 4 files changed, 5 insertions(+)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 68ac23d0b640..83dfbe2f1cfc 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -155,6 +155,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 	if (data->flags & BLK_MQ_REQ_NOWAIT)
 		return BLK_MQ_NO_TAG;
 
+	wait.nr_tags += data->nr_split;
 	ws = bt_wait_ptr(bt, data->hctx);
 	do {
 		struct sbitmap_queue *bt_prev;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index cad207d2079e..9bace9e2c5ca 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2737,6 +2737,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
 		.q		= q,
 		.nr_tags	= 1,
 		.cmd_flags	= bio->bi_opf,
+		.nr_split	= bio->bi_nr_split,
 	};
 	struct request *rq;
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 1a084b3b6097..3eabe394a5a9 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -156,6 +156,7 @@ struct blk_mq_alloc_data {
 
 	/* allocate multiple requests/tags in one go */
 	unsigned int nr_tags;
+	unsigned int nr_split;
 	struct request **cached_rq;
 
 	/* input & output parameter */
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 8f5a86e210b9..9c8c6da3d820 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -591,11 +591,13 @@ void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
 struct sbq_wait {
 	struct sbitmap_queue *sbq;	/* if set, sbq_wait is accounted */
 	struct wait_queue_entry wait;
+	unsigned int nr_tags;
 };
 
 #define DEFINE_SBQ_WAIT(name)							\
 	struct sbq_wait name = {						\
 		.sbq = NULL,							\
+		.nr_tags = 1,							\
 		.wait = {							\
 			.private	= current,				\
 			.func		= autoremove_wake_function,		\
-- 
2.31.1