linux-kernel - [PATCH V2 2/5] dm: ignore discard return value

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Message-Id: <20251124025737.203571-3-ckulkarnilinux@gmail.com>
Date: Sun, 23 Nov 2025 18:57:34 -0800
From: Chaitanya Kulkarni <ckulkarnilinux@...il.com>
To: axboe@...nel.dk,
	agk@...hat.com,
	snitzer@...nel.org,
	mpatocka@...hat.com,
	song@...nel.org,
	yukuai@...as.com,
	hch@....de,
	sagi@...mberg.me,
	kch@...dia.com,
	jaegeuk@...nel.org,
	chao@...nel.org,
	cem@...nel.org
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-raid@...r.kernel.org,
	linux-nvme@...ts.infradead.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-xfs@...r.kernel.org,
	bpf@...r.kernel.org,
	Chaitanya Kulkarni <ckulkarnilinux@...il.com>
Subject: [PATCH V2 2/5] dm: ignore discard return value

__blkdev_issue_discard() always returns 0, making all error checking
at call sites dead code.

For dm-thin change issue_discard() return type to void, in
passdown_double_checking_shared_status() remove the r assignment from
return value of the issue_discard(), for end_discard() hardcod value
of r to 0 that matches only value returned from
__blkdev_issue_discard().

md part is simplified to only check !discard_bio by ignoring the
__blkdev_issue_discard() value.

Signed-off-by: Chaitanya Kulkarni <ckulkarnilinux@...il.com>
---
 drivers/md/dm-thin.c | 12 +++++-------
 drivers/md/md.c      |  4 ++--
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index c84149ba4e38..77c76f75c85f 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -395,13 +395,13 @@ static void begin_discard(struct discard_op *op, struct thin_c *tc, struct bio *
 	op->bio = NULL;
 }
 
-static int issue_discard(struct discard_op *op, dm_block_t data_b, dm_block_t data_e)
+static void issue_discard(struct discard_op *op, dm_block_t data_b, dm_block_t data_e)
 {
 	struct thin_c *tc = op->tc;
 	sector_t s = block_to_sectors(tc->pool, data_b);
 	sector_t len = block_to_sectors(tc->pool, data_e - data_b);
 
-	return __blkdev_issue_discard(tc->pool_dev->bdev, s, len, GFP_NOIO, &op->bio);
+	__blkdev_issue_discard(tc->pool_dev->bdev, s, len, GFP_NOIO, &op->bio);
 }
 
 static void end_discard(struct discard_op *op, int r)
@@ -1113,9 +1113,7 @@ static void passdown_double_checking_shared_status(struct dm_thin_new_mapping *m
 				break;
 		}
 
-		r = issue_discard(&op, b, e);
-		if (r)
-			goto out;
+		issue_discard(&op, b, e);
 
 		b = e;
 	}
@@ -1188,8 +1186,8 @@ static void process_prepared_discard_passdown_pt1(struct dm_thin_new_mapping *m)
 		struct discard_op op;
 
 		begin_discard(&op, tc, discard_parent);
-		r = issue_discard(&op, m->data_block, data_end);
-		end_discard(&op, r);
+		issue_discard(&op, m->data_block, data_end);
+		end_discard(&op, 0);
 	}
 }
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7b5c5967568f..aeb62df39828 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9132,8 +9132,8 @@ void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
 {
 	struct bio *discard_bio = NULL;
 
-	if (__blkdev_issue_discard(rdev->bdev, start, size, GFP_NOIO,
-			&discard_bio) || !discard_bio)
+	__blkdev_issue_discard(rdev->bdev, start, size, GFP_NOIO, &discard_bio);
+	if (!discard_bio)
 		return;
 
 	bio_chain(discard_bio, bio);
-- 
2.40.0