dm-table: Set BLK_FEAT_ATOMIC_WRITES for target queue limits

JIRA: https://issues.redhat.com/browse/RHEL-119009
Upstream Status: kernel/git/torvalds/linux.git

commit b7c18b1
Author: John Garry <john.g.garry@oracle.com>
Date:   Sun May 4 11:26:45 2025 +0200

    dm-table: Set BLK_FEAT_ATOMIC_WRITES for target queue limits

    Feature flag BLK_FEAT_ATOMIC_WRITES is not being properly set for the
    target queue limits, and this means that atomic writes are not being
    enabled for any dm personalities.

    When calling dm_set_device_limits() -> blk_stack_limits() ->
    ... -> blk_stack_atomic_writes_limits(), the bottom device limits
    (which corresponds to intermediate target queue limits) does not have
    BLK_FEAT_ATOMIC_WRITES set, and so atomic writes can never be enabled.

    Typically such a flag would be inherited from the stacked device in
    dm_set_device_limits() -> blk_stack_limits() via BLK_FEAT_INHERIT_MASK,
    but BLK_FEAT_ATOMIC_WRITES is not inherited as it's preferred to manually
    enable on a per-personality basis.

    Set BLK_FEAT_ATOMIC_WRITES manually for the intermediate target queue
    limits from the stacked device to get atomic writes working.

    Fixes: 3194e36 ("dm-table: atomic writes support")
    Cc: stable@vger.kernel.org      # v6.14
    Signed-off-by: John Garry <john.g.garry@oracle.com>
    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>

Author: bmarzins

drivers/md/dm-table.c

@@ -430,6 +430,12 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
 		return 0;
 	}
 
+	/*
+	 * BLK_FEAT_ATOMIC_WRITES is not inherited from the bottom device in
+	 * blk_stack_limits(), so do it manually.
+	 */
+	limits->features |= (q->limits.features & BLK_FEAT_ATOMIC_WRITES);
+
 	mutex_lock(&q->limits_lock);
 	if (blk_stack_limits(limits, &q->limits,
 			get_start_sect(bdev) + start) < 0)