From 6b740b8d79252f13bcb7e5d3c1d43157e78a81e7 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 19 Mar 2012 12:46:39 +1100 Subject: [PATCH] md/raid1: handle merge_bvec_fn in member devices. Currently we don't honour merge_bvec_fn in member devices so if there is one, we force all requests to be single-page at most. This is not ideal. So create a raid1 merge_bvec_fn to check that function in children as well. This introduces a small problem. There is no locking around calls the ->merge_bvec_fn and subsequent calls to ->make_request. So a device added between these could end up getting a request which violates its merge_bvec_fn. Currently the best we can do is synchronize_sched(). This will work providing no preemption happens. If there is is preemption, we just have to hope that new devices are largely consistent with old devices. Signed-off-by: NeilBrown --- drivers/md/raid1.c | 77 +++++++++++++++++++++++++++++++++------------- 1 file changed, 56 insertions(+), 21 deletions(-) diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index a933bd4065a5..4a40a200d769 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -523,6 +523,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect rdev = rcu_dereference(conf->mirrors[disk].rdev); if (r1_bio->bios[disk] == IO_BLOCKED || rdev == NULL + || test_bit(Unmerged, &rdev->flags) || test_bit(Faulty, &rdev->flags)) continue; if (!test_bit(In_sync, &rdev->flags) && @@ -614,6 +615,39 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect return best_disk; } +static int raid1_mergeable_bvec(struct request_queue *q, + struct bvec_merge_data *bvm, + struct bio_vec *biovec) +{ + struct mddev *mddev = q->queuedata; + struct r1conf *conf = mddev->private; + sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev); + int max = biovec->bv_len; + + if (mddev->merge_check_needed) { + int disk; + rcu_read_lock(); + for (disk = 0; disk < conf->raid_disks * 2; disk++) { + struct md_rdev *rdev = rcu_dereference( + conf->mirrors[disk].rdev); + if (rdev && !test_bit(Faulty, &rdev->flags)) { + struct request_queue *q = + bdev_get_queue(rdev->bdev); + if (q->merge_bvec_fn) { + bvm->bi_sector = sector + + rdev->data_offset; + bvm->bi_bdev = rdev->bdev; + max = min(max, q->merge_bvec_fn( + q, bvm, biovec)); + } + } + } + rcu_read_unlock(); + } + return max; + +} + int md_raid1_congested(struct mddev *mddev, int bits) { struct r1conf *conf = mddev->private; @@ -1015,7 +1049,8 @@ read_again: break; } r1_bio->bios[i] = NULL; - if (!rdev || test_bit(Faulty, &rdev->flags)) { + if (!rdev || test_bit(Faulty, &rdev->flags) + || test_bit(Unmerged, &rdev->flags)) { if (i < conf->raid_disks) set_bit(R1BIO_Degraded, &r1_bio->state); continue; @@ -1335,6 +1370,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) struct mirror_info *p; int first = 0; int last = conf->raid_disks - 1; + struct request_queue *q = bdev_get_queue(rdev->bdev); if (mddev->recovery_disabled == conf->recovery_disabled) return -EBUSY; @@ -1342,23 +1378,17 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) if (rdev->raid_disk >= 0) first = last = rdev->raid_disk; + if (q->merge_bvec_fn) { + set_bit(Unmerged, &rdev->flags); + mddev->merge_check_needed = 1; + } + for (mirror = first; mirror <= last; mirror++) { p = conf->mirrors+mirror; if (!p->rdev) { disk_stack_limits(mddev->gendisk, rdev->bdev, rdev->data_offset << 9); - /* as we don't honour merge_bvec_fn, we must - * never risk violating it, so limit - * ->max_segments to one lying with a single - * page, as a one page request is never in - * violation. - */ - if (rdev->bdev->bd_disk->queue->merge_bvec_fn) { - blk_queue_max_segments(mddev->queue, 1); - blk_queue_segment_boundary(mddev->queue, - PAGE_CACHE_SIZE - 1); - } p->head_position = 0; rdev->raid_disk = mirror; @@ -1383,6 +1413,19 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) break; } } + if (err == 0 && test_bit(Unmerged, &rdev->flags)) { + /* Some requests might not have seen this new + * merge_bvec_fn. We must wait for them to complete + * before merging the device fully. + * First we make sure any code which has tested + * our function has submitted the request, then + * we wait for all outstanding requests to complete. + */ + synchronize_sched(); + raise_barrier(conf); + lower_barrier(conf); + clear_bit(Unmerged, &rdev->flags); + } md_integrity_add_rdev(rdev, mddev); print_conf(conf); return err; @@ -2627,15 +2670,6 @@ static int run(struct mddev *mddev) continue; disk_stack_limits(mddev->gendisk, rdev->bdev, rdev->data_offset << 9); - /* as we don't honour merge_bvec_fn, we must never risk - * violating it, so limit ->max_segments to 1 lying within - * a single page, as a one page request is never in violation. - */ - if (rdev->bdev->bd_disk->queue->merge_bvec_fn) { - blk_queue_max_segments(mddev->queue, 1); - blk_queue_segment_boundary(mddev->queue, - PAGE_CACHE_SIZE - 1); - } } mddev->degraded = 0; @@ -2669,6 +2703,7 @@ static int run(struct mddev *mddev) if (mddev->queue) { mddev->queue->backing_dev_info.congested_fn = raid1_congested; mddev->queue->backing_dev_info.congested_data = mddev; + blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec); } return md_integrity_register(mddev); }