linux-kernel - [PATCH RFC 4/5] dm: Ensure cloned bio is same length for atomic write

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Message-Id: <20250106124119.1318428-5-john.g.garry@oracle.com>
Date: Mon,  6 Jan 2025 12:41:18 +0000
From: John Garry <john.g.garry@...cle.com>
To: axboe@...nel.dk, agk@...hat.com, snitzer@...nel.org, hch@....de
Cc: mpatocka@...hat.com, martin.petersen@...cle.com,
        linux-block@...r.kernel.org, dm-devel@...ts.linux.dev,
        linux-kernel@...r.kernel.org, John Garry <john.g.garry@...cle.com>
Subject: [PATCH RFC 4/5] dm: Ensure cloned bio is same length for atomic write

For an atomic writes, a cloned bio must be same length as the original bio,
i.e. no splitting.

Error in case it is not.

Per-dm device queue limits should be setup to ensure that this does not
happen, but error this case as an insurance policy.

Signed-off-by: John Garry <john.g.garry@...cle.com>
---
 drivers/md/dm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 12ecf07a3841..e26c73fb365a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1746,6 +1746,9 @@ static blk_status_t __split_and_process_bio(struct clone_info *ci)
 	ci->submit_as_polled = !!(ci->bio->bi_opf & REQ_POLLED);
 
 	len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count);
+	if (ci->bio->bi_opf & REQ_ATOMIC && len != ci->sector_count)
+		return BLK_STS_IOERR;
+
 	setup_split_accounting(ci, len);
 
 	if (unlikely(ci->bio->bi_opf & REQ_NOWAIT)) {
-- 
2.31.1