From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-v6.9-rc1 commit 0091c5a269eca7ab0e057c3083804daed9997f08 category: bugfix bugzilla: 190197 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The way that best rdev is chosen: 1) If the read is sequential from one rdev: - if rdev is rotational, use this rdev; - if rdev is non-rotational, use this rdev until total read length exceed disk opt io size; 2) If the read is not sequential: - if there is idle disk, use it, otherwise: - if the array has non-rotational disk, choose the rdev with minimal inflight IO; - if all the underlaying disks are rotational disk, choose the rdev with closest IO; There are no functional changes, just to make code cleaner and prepare for following refactor. Co-developed-by: Paul Luse <paul.e.luse@linux.intel.com> Signed-off-by: Paul Luse <paul.e.luse@linux.intel.com> Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20240229095714.926789-12-yukuai1@huaweicloud.com Signed-off-by: Li Nan <linan122@huawei.com> --- drivers/md/raid1.c | 175 +++++++++++++++++++++++++-------------------- 1 file changed, 98 insertions(+), 77 deletions(-) diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index f89968d5d0d0..ba4fed333664 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -726,74 +726,71 @@ static bool should_choose_next(struct r1conf *conf, int disk) mirror->next_seq_sect - opt_iosize >= mirror->seq_start; } -/* - * This routine returns the disk from which the requested read should - * be done. There is a per-array 'next expected sequential IO' sector - * number - if this matches on the next IO then we use the last disk. - * There is also a per-disk 'last know head position' sector that is - * maintained from IRQ contexts, both the normal and the resync IO - * completion handlers update this position correctly. If there is no - * perfect sequential match then we pick the disk whose head is closest. - * - * If there are 2 mirrors in the same 2 devices, performance degrades - * because position is mirror, not device based. - * - * The rdev for the device selected will have nr_pending incremented. - */ -static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors) +static bool rdev_readable(struct md_rdev *rdev, struct r1bio *r1_bio) { - const sector_t this_sector = r1_bio->sector; - int sectors; - int best_good_sectors; - int best_disk, best_dist_disk, best_pending_disk, sequential_disk; - int disk; - sector_t best_dist; - unsigned int min_pending; - struct md_rdev *rdev; + if (!rdev || test_bit(Faulty, &rdev->flags)) + return false; - retry: - sectors = r1_bio->sectors; - best_disk = -1; - best_dist_disk = -1; - sequential_disk = -1; - best_dist = MaxSector; - best_pending_disk = -1; - min_pending = UINT_MAX; - best_good_sectors = 0; - clear_bit(R1BIO_FailFast, &r1_bio->state); + /* still in recovery */ + if (!test_bit(In_sync, &rdev->flags) && + rdev->recovery_offset < r1_bio->sector + r1_bio->sectors) + return false; - if (raid1_should_read_first(conf->mddev, this_sector, sectors)) - return choose_first_rdev(conf, r1_bio, max_sectors); + /* don't read from slow disk unless have to */ + if (test_bit(WriteMostly, &rdev->flags)) + return false; + + /* don't split IO for bad blocks unless have to */ + if (rdev_has_badblock(rdev, r1_bio->sector, r1_bio->sectors)) + return false; + + return true; +} + +struct read_balance_ctl { + sector_t closest_dist; + int closest_dist_disk; + int min_pending; + int min_pending_disk; + int sequential_disk; + int readable_disks; +}; + +static int choose_best_rdev(struct r1conf *conf, struct r1bio *r1_bio) +{ + int disk; + struct read_balance_ctl ctl = { + .closest_dist_disk = -1, + .closest_dist = MaxSector, + .min_pending_disk = -1, + .min_pending = UINT_MAX, + .sequential_disk = -1, + }; for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) { + struct md_rdev *rdev; sector_t dist; unsigned int pending; - rdev = conf->mirrors[disk].rdev; - if (r1_bio->bios[disk] == IO_BLOCKED - || rdev == NULL - || test_bit(Faulty, &rdev->flags)) - continue; - if (!test_bit(In_sync, &rdev->flags) && - rdev->recovery_offset < this_sector + sectors) - continue; - if (test_bit(WriteMostly, &rdev->flags)) + if (r1_bio->bios[disk] == IO_BLOCKED) continue; - if (rdev_has_badblock(rdev, this_sector, sectors)) + + rdev = conf->mirrors[disk].rdev; + if (!rdev_readable(rdev, r1_bio)) continue; - if (best_disk >= 0) - /* At least two disks to choose from so failfast is OK */ + /* At least two disks to choose from so failfast is OK */ + if (ctl.readable_disks++ == 1) set_bit(R1BIO_FailFast, &r1_bio->state); pending = atomic_read(&rdev->nr_pending); - dist = abs(this_sector - conf->mirrors[disk].head_position); + dist = abs(r1_bio->sector - conf->mirrors[disk].head_position); + /* Don't change to another disk for sequential reads */ if (is_sequential(conf, disk, r1_bio)) { - if (!should_choose_next(conf, disk)) { - best_disk = disk; - break; - } + if (!should_choose_next(conf, disk)) + return disk; + /* * Add 'pending' to avoid choosing this disk if * there is other idle disk. @@ -803,17 +800,17 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect * If there is no other idle disk, this disk * will be chosen. */ - sequential_disk = disk; + ctl.sequential_disk = disk; } - if (min_pending > pending) { - min_pending = pending; - best_pending_disk = disk; + if (ctl.min_pending > pending) { + ctl.min_pending = pending; + ctl.min_pending_disk = disk; } - if (dist < best_dist) { - best_dist = dist; - best_dist_disk = disk; + if (ctl.closest_dist > dist) { + ctl.closest_dist = dist; + ctl.closest_dist_disk = disk; } } @@ -821,8 +818,8 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect * sequential IO size exceeds optimal iosize, however, there is no other * idle disk, so choose the sequential disk. */ - if (best_disk == -1 && min_pending != 0) - best_disk = sequential_disk; + if (ctl.sequential_disk != -1 && ctl.min_pending != 0) + return ctl.sequential_disk; /* * If all disks are rotational, choose the closest disk. If any disk is @@ -830,25 +827,49 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect * disk is rotational, which might/might not be optimal for raids with * mixed ratation/non-rotational disks depending on workload. */ - if (best_disk == -1) { - if (READ_ONCE(conf->nonrot_disks) || min_pending == 0) - best_disk = best_pending_disk; - else - best_disk = best_dist_disk; - } + if (ctl.min_pending_disk != -1 && + (READ_ONCE(conf->nonrot_disks) || ctl.min_pending == 0)) + return ctl.min_pending_disk; + else + return ctl.closest_dist_disk; +} - if (best_disk >= 0) { - rdev = conf->mirrors[best_disk].rdev; - if (!rdev) - goto retry; +/* + * This routine returns the disk from which the requested read should be done. + * + * 1) If resync is in progress, find the first usable disk and use it even if it + * has some bad blocks. + * + * 2) Now that there is no resync, loop through all disks and skipping slow + * disks and disks with bad blocks for now. Only pay attention to key disk + * choice. + * + * 3) If we've made it this far, now look for disks with bad blocks and choose + * the one with most number of sectors. + * + * 4) If we are all the way at the end, we have no choice but to use a disk even + * if it is write mostly. + * + * The rdev for the device selected will have nr_pending incremented. + */ +static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, + int *max_sectors) +{ + int disk; - sectors = best_good_sectors; - update_read_sectors(conf, disk, this_sector, sectors); - } - *max_sectors = sectors; + clear_bit(R1BIO_FailFast, &r1_bio->state); + + if (raid1_should_read_first(conf->mddev, r1_bio->sector, + r1_bio->sectors)) + return choose_first_rdev(conf, r1_bio, max_sectors); - if (best_disk >= 0) - return best_disk; + disk = choose_best_rdev(conf, r1_bio); + if (disk >= 0) { + *max_sectors = r1_bio->sectors; + update_read_sectors(conf, disk, r1_bio->sector, + r1_bio->sectors); + return disk; + } /* * If we are here it means we didn't find a perfectly good disk so -- 2.39.2