md/raid1: Atomic write support

JIRA: https://issues.redhat.com/browse/RHEL-73514

commit f2a38ab
Author: John Garry <john.g.garry@oracle.com>
Date:   Mon Nov 18 10:50:17 2024 +0000

    md/raid1: Atomic write support

    Set BLK_FEAT_ATOMIC_WRITES_STACKED to enable atomic writes.

    For an attempt to atomic write to a region which has bad blocks, error
    the write as we just cannot do this. It is unlikely to find devices which
    support atomic writes and bad blocks.

    Reviewed-by: Yu Kuai <yukuai3@huawei.com>
    Signed-off-by: John Garry <john.g.garry@oracle.com>
    Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
    Link: https://lore.kernel.org/r/20241118105018.1870052-5-john.g.garry@oracle.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>

Author: ncroxon

drivers/md/raid1.c

@@ -1571,7 +1571,21 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 				continue;
 			}
 			if (is_bad) {
-				int good_sectors = first_bad - r1_bio->sector;
+				int good_sectors;
+
+				/*
+				 * We cannot atomically write this, so just
+				 * error in that case. It could be possible to
+				 * atomically write other mirrors, but the
+				 * complexity of supporting that is not worth
+				 * the benefit.
+				 */
+				if (bio->bi_opf & REQ_ATOMIC) {
+					error = -EIO;
+					goto err_handle;
+				}
+
+				good_sectors = first_bad - r1_bio->sector;
 				if (good_sectors < max_sectors)
 					max_sectors = good_sectors;
 			}
@@ -1657,7 +1671,8 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 
 		mbio->bi_iter.bi_sector	= (r1_bio->sector + rdev->data_offset);
 		mbio->bi_end_io	= raid1_end_write_request;
-		mbio->bi_opf = bio_op(bio) | (bio->bi_opf & (REQ_SYNC | REQ_FUA));
+		mbio->bi_opf = bio_op(bio) |
+			(bio->bi_opf & (REQ_SYNC | REQ_FUA | REQ_ATOMIC));
 		if (test_bit(FailFast, &rdev->flags) &&
 		    !test_bit(WriteMostly, &rdev->flags) &&
 		    conf->raid_disks - mddev->degraded > 1)
@@ -3224,6 +3239,7 @@ static int raid1_set_limits(struct mddev *mddev)
 
 	md_init_stacking_limits(&lim);
 	lim.max_write_zeroes_sectors = 0;
+	lim.features |= BLK_FEAT_ATOMIC_WRITES_STACKED;
 	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
 	if (err) {
 		queue_limits_cancel_update(mddev->gendisk->queue);