md/raid1,raid10: don't handle IO error for REQ_RAHEAD and REQ_NOWAIT

IO with REQ_RAHEAD or REQ_NOWAIT can fail early, even if the storage medium
is fine, hence record badblocks or remove the disk from array does not
make sense.

This problem if found by lvm2 test lvcreate-large-raid, where dm-zero
will fail read ahead IO directly.

Fixes: e879a0d ("md/raid1,raid10: don't ignore IO flags")
Reported-and-tested-by: Mikulas Patocka <mpatocka@redhat.com>
Closes: https://lore.kernel.org/all/34fa755d-62c8-4588-8ee1-33cb1249bdf2@redhat.com/
Link: https://lore.kernel.org/linux-raid/20250527081407.3004055-1-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Author: YuKuai-huawei

drivers/md/raid1-10.c

@@ -293,3 +293,13 @@ static inline bool raid1_should_read_first(struct mddev *mddev,
 
 	return false;
 }
+
+/*
+ * bio with REQ_RAHEAD or REQ_NOWAIT can fail at anytime, before such IO is
+ * submitted to the underlying disks, hence don't record badblocks or retry
+ * in this case.
+ */
+static inline bool raid1_should_handle_error(struct bio *bio)
+{
+	return !(bio->bi_opf & (REQ_RAHEAD | REQ_NOWAIT));
+}

drivers/md/raid1.c

@@ -373,14 +373,16 @@ static void raid1_end_read_request(struct bio *bio)
 	 */
 	update_head_pos(r1_bio->read_disk, r1_bio);
 
-	if (uptodate)
+	if (uptodate) {
 		set_bit(R1BIO_Uptodate, &r1_bio->state);
-	else if (test_bit(FailFast, &rdev->flags) &&
-		 test_bit(R1BIO_FailFast, &r1_bio->state))
+	} else if (test_bit(FailFast, &rdev->flags) &&
+		 test_bit(R1BIO_FailFast, &r1_bio->state)) {
 		/* This was a fail-fast read so we definitely
 		 * want to retry */
 		;
-	else {
+	} else if (!raid1_should_handle_error(bio)) {
+		uptodate = 1;
+	} else {
 		/* If all other devices have failed, we want to return
 		 * the error upwards rather than fail the last device.
 		 * Here we redefine "uptodate" to mean "Don't want to retry"
@@ -451,16 +453,15 @@ static void raid1_end_write_request(struct bio *bio)
 	struct bio *to_put = NULL;
 	int mirror = find_bio_disk(r1_bio, bio);
 	struct md_rdev *rdev = conf->mirrors[mirror].rdev;
-	bool discard_error;
 	sector_t lo = r1_bio->sector;
 	sector_t hi = r1_bio->sector + r1_bio->sectors;
-
-	discard_error = bio->bi_status && bio_op(bio) == REQ_OP_DISCARD;
+	bool ignore_error = !raid1_should_handle_error(bio) ||
+		(bio->bi_status && bio_op(bio) == REQ_OP_DISCARD);
 
 	/*
 	 * 'one mirror IO has finished' event handler:
 	 */
-	if (bio->bi_status && !discard_error) {
+	if (bio->bi_status && !ignore_error) {
 		set_bit(WriteErrorSeen,	&rdev->flags);
 		if (!test_and_set_bit(WantReplacement, &rdev->flags))
 			set_bit(MD_RECOVERY_NEEDED, &
@@ -511,7 +512,7 @@ static void raid1_end_write_request(struct bio *bio)
 
 		/* Maybe we can clear some bad blocks. */
 		if (rdev_has_badblock(rdev, r1_bio->sector, r1_bio->sectors) &&
-		    !discard_error) {
+		    !ignore_error) {
 			r1_bio->bios[mirror] = IO_MADE_GOOD;
 			set_bit(R1BIO_MadeGood, &r1_bio->state);
 		}

drivers/md/raid10.c

@@ -399,6 +399,8 @@ static void raid10_end_read_request(struct bio *bio)
 		 * wait for the 'master' bio.
 		 */
 		set_bit(R10BIO_Uptodate, &r10_bio->state);
+	} else if (!raid1_should_handle_error(bio)) {
+		uptodate = 1;
 	} else {
 		/* If all other devices that store this block have
 		 * failed, we want to return the error upwards rather
@@ -456,9 +458,8 @@ static void raid10_end_write_request(struct bio *bio)
 	int slot, repl;
 	struct md_rdev *rdev = NULL;
 	struct bio *to_put = NULL;
-	bool discard_error;
-
-	discard_error = bio->bi_status && bio_op(bio) == REQ_OP_DISCARD;
+	bool ignore_error = !raid1_should_handle_error(bio) ||
+		(bio->bi_status && bio_op(bio) == REQ_OP_DISCARD);
 
 	dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
 
@@ -472,7 +473,7 @@ static void raid10_end_write_request(struct bio *bio)
 	/*
 	 * this branch is our 'one mirror IO has finished' event handler:
 	 */
-	if (bio->bi_status && !discard_error) {
+	if (bio->bi_status && !ignore_error) {
 		if (repl)
 			/* Never record new bad blocks to replacement,
 			 * just fail it.
@@ -527,7 +528,7 @@ static void raid10_end_write_request(struct bio *bio)
 		/* Maybe we can clear some bad blocks. */
 		if (rdev_has_badblock(rdev, r10_bio->devs[slot].addr,
 				      r10_bio->sectors) &&
-		    !discard_error) {
+		    !ignore_error) {
 			bio_put(bio);
 			if (repl)
 				r10_bio->devs[slot].repl_bio = IO_MADE_GOOD;