From 8d3ca83dcf9ca3d58822eddd279918d46f41e9ff Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 18 Nov 2016 16:16:12 +1100 Subject: [PATCH] md/raid10: add failfast handling for reads. If a device is marked FailFast, and it is not the only device we can read from, we mark the bio as MD_FAILFAST. If this does fail-fast, we don't try read repair but just allow failure. If it was the last device, it doesn't get marked Faulty so the retry happens on the same device - this time without FAILFAST. A subsequent failure will not retry but will just pass up the error. During resync we may use FAILFAST requests, and on a failure we will simply use the other device(s). During recovery we will only use FAILFAST in the unusual case were there are multiple places to read from - i.e. if there are > 2 devices. If we get a failure we will fail the device and complete the resync/recovery with remaining devices. Signed-off-by: NeilBrown Signed-off-by: Shaohua Li --- drivers/md/raid10.c | 49 ++++++++++++++++++++++++++++++++++++++++----- drivers/md/raid10.h | 2 ++ 2 files changed, 46 insertions(+), 5 deletions(-) diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index af50866f5ffb..7cdc9bcd21b0 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -719,6 +719,7 @@ static struct md_rdev *read_balance(struct r10conf *conf, best_dist = MaxSector; best_good_sectors = 0; do_balance = 1; + clear_bit(R10BIO_FailFast, &r10_bio->state); /* * Check if we can balance. We can balance on the whole * device if no resync is going on (recovery is ok), or below @@ -783,15 +784,18 @@ static struct md_rdev *read_balance(struct r10conf *conf, if (!do_balance) break; + if (best_slot >= 0) + /* At least 2 disks to choose from so failfast is OK */ + set_bit(R10BIO_FailFast, &r10_bio->state); /* This optimisation is debatable, and completely destroys * sequential read speed for 'far copies' arrays. So only * keep it for 'near' arrays, and review those later. */ if (geo->near_copies > 1 && !atomic_read(&rdev->nr_pending)) - break; + new_distance = 0; /* for far > 1 always use the lowest address */ - if (geo->far_copies > 1) + else if (geo->far_copies > 1) new_distance = r10_bio->devs[slot].addr; else new_distance = abs(r10_bio->devs[slot].addr - @@ -1170,6 +1174,9 @@ read_again: read_bio->bi_bdev = rdev->bdev; read_bio->bi_end_io = raid10_end_read_request; bio_set_op_attrs(read_bio, op, do_sync); + if (test_bit(FailFast, &rdev->flags) && + test_bit(R10BIO_FailFast, &r10_bio->state)) + read_bio->bi_opf |= MD_FAILFAST; read_bio->bi_private = r10_bio; if (mddev->gendisk) @@ -1988,6 +1995,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio) /* now find blocks with errors */ for (i=0 ; i < conf->copies ; i++) { int j, d; + struct md_rdev *rdev; tbio = r10_bio->devs[i].bio; @@ -1995,6 +2003,8 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio) continue; if (i == first) continue; + d = r10_bio->devs[i].devnum; + rdev = conf->mirrors[d].rdev; if (!r10_bio->devs[i].bio->bi_error) { /* We know that the bi_io_vec layout is the same for * both 'first' and 'i', so we just compare them. @@ -2017,6 +2027,10 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio) if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)) /* Don't fix anything. */ continue; + } else if (test_bit(FailFast, &rdev->flags)) { + /* Just give up on this device */ + md_error(rdev->mddev, rdev); + continue; } /* Ok, we need to write this bio, either to correct an * inconsistency or to correct an unreadable block. @@ -2034,7 +2048,6 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio) bio_copy_data(tbio, fbio); - d = r10_bio->devs[i].devnum; atomic_inc(&conf->mirrors[d].rdev->nr_pending); atomic_inc(&r10_bio->remaining); md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio)); @@ -2541,12 +2554,14 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio) bio_put(bio); r10_bio->devs[slot].bio = NULL; - if (mddev->ro == 0) { + if (mddev->ro) + r10_bio->devs[slot].bio = IO_BLOCKED; + else if (!test_bit(FailFast, &rdev->flags)) { freeze_array(conf, 1); fix_read_error(conf, mddev, r10_bio); unfreeze_array(conf); } else - r10_bio->devs[slot].bio = IO_BLOCKED; + md_error(mddev, rdev); rdev_dec_pending(rdev, mddev); @@ -2575,6 +2590,9 @@ read_more: + choose_data_offset(r10_bio, rdev); bio->bi_bdev = rdev->bdev; bio_set_op_attrs(bio, REQ_OP_READ, do_sync); + if (test_bit(FailFast, &rdev->flags) && + test_bit(R10BIO_FailFast, &r10_bio->state)) + bio->bi_opf |= MD_FAILFAST; bio->bi_private = r10_bio; bio->bi_end_io = raid10_end_read_request; trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), @@ -3096,6 +3114,8 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr, bio->bi_private = r10_bio; bio->bi_end_io = end_sync_read; bio_set_op_attrs(bio, REQ_OP_READ, 0); + if (test_bit(FailFast, &rdev->flags)) + bio->bi_opf |= MD_FAILFAST; from_addr = r10_bio->devs[j].addr; bio->bi_iter.bi_sector = from_addr + rdev->data_offset; @@ -3201,6 +3221,23 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr, rdev_dec_pending(mrdev, mddev); if (mreplace) rdev_dec_pending(mreplace, mddev); + if (r10_bio->devs[0].bio->bi_opf & MD_FAILFAST) { + /* Only want this if there is elsewhere to + * read from. 'j' is currently the first + * readable copy. + */ + int targets = 1; + for (; j < conf->copies; j++) { + int d = r10_bio->devs[j].devnum; + if (conf->mirrors[d].rdev && + test_bit(In_sync, + &conf->mirrors[d].rdev->flags)) + targets++; + } + if (targets == 1) + r10_bio->devs[0].bio->bi_opf + &= ~MD_FAILFAST; + } } if (biolist == NULL) { while (r10_bio) { @@ -3279,6 +3316,8 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr, bio->bi_private = r10_bio; bio->bi_end_io = end_sync_read; bio_set_op_attrs(bio, REQ_OP_READ, 0); + if (test_bit(FailFast, &conf->mirrors[d].rdev->flags)) + bio->bi_opf |= MD_FAILFAST; bio->bi_iter.bi_sector = sector + rdev->data_offset; bio->bi_bdev = rdev->bdev; count++; diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h index 18ec1f7a98bf..3162615e57bd 100644 --- a/drivers/md/raid10.h +++ b/drivers/md/raid10.h @@ -156,5 +156,7 @@ enum r10bio_state { * flag is set */ R10BIO_Previous, +/* failfast devices did receive failfast requests. */ + R10BIO_FailFast, }; #endif -- 2.20.1