linux-kernel - [RFC 06/12] bio: don't check target->bi

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Message-ID: <20251208121020.1780402-7-agruenba@redhat.com>
Date: Mon,  8 Dec 2025 12:10:13 +0000
From: Andreas Gruenbacher <agruenba@...hat.com>
To: Christoph Hellwig <hch@...radead.org>,
	Jens Axboe <axboe@...nel.dk>,
	Chris Mason <clm@...com>,
	David Sterba <dsterba@...e.com>
Cc: Andreas Gruenbacher <agruenba@...hat.com>,
	linux-block@...r.kernel.org,
	linux-btrfs@...r.kernel.org,
	linux-raid@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [RFC 06/12] bio: don't check target->bi_status on error

In a few places, target->bi_status is set to source->bi_status only if
source->bi_status is not 0 and target->bi_status is (still) 0.  Here,
checking the value of target->bi_status before setting it is an
unnecessary micro optimization because we are already on an error path.

In addition, we can be racing with other execution contexts in the case
of chained bios, so there is no guarantee that target->bi_status won't
be set concurrently.  We don't require atomic test-and-set semantics
here.

Created with Coccinelle using the following semantic patch:

@@
struct bio *source;
struct bio *target;
@@
- if (source->bi_status && !target->bi_status)
-       target->bi_status = source->bi_status;
+ bio_set_status(target, source->bi_status);

@@
struct bio *source;
struct bio target;
@@
- if (source->bi_status && !target.bi_status)
-       target.bi_status = source->bi_status;
+ bio_set_status(&target, source->bi_status);

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 block/bio.c     | 3 +--
 block/fops.c    | 3 +--
 drivers/md/md.c | 6 ++----
 3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 3f408e1ba13f..5389321872f0 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -314,8 +314,7 @@ static struct bio *__bio_chain_endio(struct bio *bio)
 {
 	struct bio *parent = bio->bi_private;
 
-	if (bio->bi_status && !parent->bi_status)
-		parent->bi_status = bio->bi_status;
+	bio_set_status(parent, bio->bi_status);
 	bio_put(bio);
 	return parent;
 }
diff --git a/block/fops.c b/block/fops.c
index b4f911273289..a4a6972cbfbf 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -135,8 +135,7 @@ static void blkdev_bio_end_io(struct bio *bio)
 	bool should_dirty = dio->flags & DIO_SHOULD_DIRTY;
 	bool is_sync = dio->flags & DIO_IS_SYNC;
 
-	if (bio->bi_status && !dio->bio.bi_status)
-		dio->bio.bi_status = bio->bi_status;
+	bio_set_status(&dio->bio, bio->bi_status);
 
 	if (bio_integrity(bio))
 		bio_integrity_unmap_user(bio);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 41c476b40c7a..f6f1aab18a8b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9084,8 +9084,7 @@ static void md_end_clone_io(struct bio *bio)
 	if (bio_data_dir(orig_bio) == WRITE && md_bitmap_enabled(mddev, false))
 		md_bitmap_end(mddev, md_io_clone);
 
-	if (bio->bi_status && !orig_bio->bi_status)
-		orig_bio->bi_status = bio->bi_status;
+	bio_set_status(orig_bio, bio->bi_status);
 
 	if (md_io_clone->start_time)
 		bio_end_io_acct(orig_bio, md_io_clone->start_time);
@@ -9136,8 +9135,7 @@ void md_free_cloned_bio(struct bio *bio)
 	if (bio_data_dir(orig_bio) == WRITE && md_bitmap_enabled(mddev, false))
 		md_bitmap_end(mddev, md_io_clone);
 
-	if (bio->bi_status && !orig_bio->bi_status)
-		orig_bio->bi_status = bio->bi_status;
+	bio_set_status(orig_bio, bio->bi_status);
 
 	if (md_io_clone->start_time)
 		bio_end_io_acct(orig_bio, md_io_clone->start_time);
-- 
2.51.0