[dm-devel] [PATCH v2] dm raid1: "mirror" target doesn't use all available legs on multiple failures

[Heinz Mauelshagen]

In case legs of a mirror target fail, any read will cause a new,
operational default leg to be selected and the read be resubmitted
to it. If that new default leg fails the read too, no other still
accessible legs are used to resubmit the read again thus failing
the io.

Fix by allowing the read to get resubmitted until there's no
operational legs any more.

Removes any details.bi_dev use as a flag.

Resolves: rhbz1383444

Signed-off-by: Heinz Mauelshagen <heinzm at redhat.com>
---
 drivers/md/dm-raid1.c | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 7a6254d..a7fe697 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -145,7 +145,6 @@ static void dispatch_bios(void *context, struct bio_list *bio_list)
 
 struct dm_raid1_bio_record {
 	struct mirror *m;
-	/* if details->bi_bdev == NULL, details were not saved */
 	struct dm_bio_details details;
 	region_t write_region;
 };
@@ -1200,8 +1199,6 @@ static int mirror_map(struct dm_target *ti, struct bio *bio)
 	struct dm_raid1_bio_record *bio_record =
 	  dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
 
-	bio_record->details.bi_bdev = NULL;
-
 	if (rw == WRITE) {
 		/* Save region for mirror_end_io() handler */
 		bio_record->write_region = dm_rh_bio_to_region(ms->rh, bio);
@@ -1266,16 +1263,6 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
 		goto out;
 
 	if (unlikely(error)) {
-		if (!bio_record->details.bi_bdev) {
-			/*
-			 * There wasn't enough memory to record necessary
-			 * information for a retry or there was no other
-			 * mirror in-sync.
-			 */
-			DMERR_LIMIT("Mirror read failed.");
-			return -EIO;
-		}
-
 		m = bio_record->m;
 
 		DMERR("Mirror read failed from %s. Trying alternative device.",
@@ -1291,7 +1278,6 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
 			bd = &bio_record->details;
 
 			dm_bio_restore(bd, bio);
-			bio_record->details.bi_bdev = NULL;
 			bio->bi_error = 0;
 
 			queue_bio(ms, bio, rw);
@@ -1301,8 +1287,6 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
 	}
 
 out:
-	bio_record->details.bi_bdev = NULL;
-
 	return error;
 }
 
-- 
2.7.4