Commit de67c139b384 for kernel

commit de67c139b3846ece6b8bbb62abf1f010ae85c083
Author: Mikulas Patocka <mpatocka@redhat.com>
Date:   Wed Nov 5 16:01:33 2025 +0100

    dm: test for REQ_ATOMIC in dm_accept_partial_bio()

    Any bio with REQ_ATOMIC flag set should never be split or partially
    completed, so BUG_ON() on this scenario in dm_accept_partial_bio() (whose
    intent is to allow partial completions).

    Also, we must reject atomic bio to targets that don't support them,
    otherwise this BUG could be triggered by stray bios that have the
    REQ_ATOMIC set.

    Signed-off-by: John Garry <john.g.garry@oracle.com>
    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Tested-by: John Garry <john.g.garry@oracle.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 557f3f52edf4..44be646574b7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1321,6 +1321,7 @@ void dm_accept_partial_bio(struct bio *bio, unsigned int n_sectors)
 	BUG_ON(dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
 	BUG_ON(bio_sectors > *tio->len_ptr);
 	BUG_ON(n_sectors > bio_sectors);
+	BUG_ON(bio->bi_opf & REQ_ATOMIC);

 	if (static_branch_unlikely(&zoned_enabled) &&
 	    unlikely(bdev_is_zoned(bio->bi_bdev))) {
@@ -1735,8 +1736,12 @@ 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;
+	if (ci->bio->bi_opf & REQ_ATOMIC) {
+		if (unlikely(!dm_target_supports_atomic_writes(ti->type)))
+			return BLK_STS_IOERR;
+		if (unlikely(len != ci->sector_count))
+			return BLK_STS_IOERR;
+	}

 	setup_split_accounting(ci, len);