linux-kernel - [PATCH RFC v2 08/10] block: skip unnecessary checks for split bio

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Message-Id: <20250828065733.556341-9-yukuai1@huaweicloud.com>
Date: Thu, 28 Aug 2025 14:57:31 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: axboe@...nel.dk,
	tj@...nel.org,
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Cc: linux-block@...r.kernel.org,
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Subject: [PATCH RFC v2 08/10] block: skip unnecessary checks for split bio

From: Yu Kuai <yukuai3@...wei.com>

Lots of checks are already done while submitting this bio the first
time, and there is no need to check them again when this bio is
resubmitted after split.

Hence factor out a helper submit_split_bio_noacct() for resubmitting
bio after splitting, only should_fail_bio() and blk_throtl_bio() are
keeped.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-core.c  | 15 +++++++++++++++
 block/blk-merge.c |  2 +-
 block/blk.h       |  1 +
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 4201504158a1..37836446f365 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -765,6 +765,21 @@ static blk_status_t blk_validate_atomic_write_op_size(struct request_queue *q,
 	return BLK_STS_OK;
 }
 
+void submit_split_bio_noacct(struct bio *bio)
+{
+	might_sleep();
+
+	if (should_fail_bio(bio)) {
+		bio_io_error(bio);
+		return;
+	}
+
+	if (blk_throtl_bio(bio))
+		return;
+
+	submit_bio_noacct_nocheck(bio);
+}
+
 /**
  * submit_bio_noacct - re-submit a bio to the block device layer for I/O
  * @bio:  The bio describing the location in memory and on the device.
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 3d6dc9cc4f61..fa2c3d98b277 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -131,7 +131,7 @@ struct bio *bio_submit_split_bioset(struct bio *bio, int split_sectors,
 	bio_chain(split, bio);
 	trace_block_split(split, bio->bi_iter.bi_sector);
 	WARN_ON_ONCE(bio_zone_write_plugging(bio));
-	submit_bio_noacct(bio);
+	submit_split_bio_noacct(bio);
 
 	return split;
 }
diff --git a/block/blk.h b/block/blk.h
index 46f566f9b126..80375374ef55 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -54,6 +54,7 @@ bool blk_queue_start_drain(struct request_queue *q);
 bool __blk_freeze_queue_start(struct request_queue *q,
 			      struct task_struct *owner);
 int __bio_queue_enter(struct request_queue *q, struct bio *bio);
+void submit_split_bio_noacct(struct bio *bio);
 void submit_bio_noacct_nocheck(struct bio *bio);
 void bio_await_chain(struct bio *bio);
 
-- 
2.39.2