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md: simplify raid10 read_balance
raid10 read balance has two different loop for looking through possible devices to chose the best. Collapse those into one loop and generally make the code more readable. Signed-off-by: NeilBrown <neilb@suse.de>
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parent
8258c53208
commit
56d9912106
1 changed files with 45 additions and 67 deletions
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@ -488,13 +488,19 @@ static int raid10_mergeable_bvec(struct request_queue *q,
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static int read_balance(conf_t *conf, r10bio_t *r10_bio)
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static int read_balance(conf_t *conf, r10bio_t *r10_bio)
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{
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{
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const sector_t this_sector = r10_bio->sector;
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const sector_t this_sector = r10_bio->sector;
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int disk, slot, nslot;
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int disk, slot;
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const int sectors = r10_bio->sectors;
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const int sectors = r10_bio->sectors;
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sector_t new_distance, current_distance;
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sector_t new_distance, best_dist;
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mdk_rdev_t *rdev;
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mdk_rdev_t *rdev;
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int do_balance;
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int best_slot;
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raid10_find_phys(conf, r10_bio);
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raid10_find_phys(conf, r10_bio);
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rcu_read_lock();
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rcu_read_lock();
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retry:
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best_slot = -1;
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best_dist = MaxSector;
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do_balance = 1;
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/*
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/*
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* Check if we can balance. We can balance on the whole
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* Check if we can balance. We can balance on the whole
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* device if no resync is going on (recovery is ok), or below
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* device if no resync is going on (recovery is ok), or below
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@ -502,86 +508,58 @@ static int read_balance(conf_t *conf, r10bio_t *r10_bio)
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* above the resync window.
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* above the resync window.
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*/
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*/
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if (conf->mddev->recovery_cp < MaxSector
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if (conf->mddev->recovery_cp < MaxSector
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&& (this_sector + sectors >= conf->next_resync)) {
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&& (this_sector + sectors >= conf->next_resync))
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/* make sure that disk is operational */
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do_balance = 0;
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slot = 0;
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disk = r10_bio->devs[slot].devnum;
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while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
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for (slot = 0; slot < conf->copies ; slot++) {
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r10_bio->devs[slot].bio == IO_BLOCKED ||
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if (r10_bio->devs[slot].bio == IO_BLOCKED)
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!test_bit(In_sync, &rdev->flags)) {
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slot++;
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if (slot == conf->copies) {
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slot = 0;
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disk = -1;
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break;
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}
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disk = r10_bio->devs[slot].devnum;
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}
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goto rb_out;
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}
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/* make sure the disk is operational */
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slot = 0;
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disk = r10_bio->devs[slot].devnum;
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while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
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r10_bio->devs[slot].bio == IO_BLOCKED ||
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!test_bit(In_sync, &rdev->flags)) {
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slot ++;
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if (slot == conf->copies) {
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disk = -1;
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goto rb_out;
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}
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disk = r10_bio->devs[slot].devnum;
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}
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current_distance = abs(r10_bio->devs[slot].addr -
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conf->mirrors[disk].head_position);
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/* Find the disk whose head is closest,
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* or - for far > 1 - find the closest to partition beginning */
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for (nslot = slot; nslot < conf->copies; nslot++) {
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int ndisk = r10_bio->devs[nslot].devnum;
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if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
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r10_bio->devs[nslot].bio == IO_BLOCKED ||
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!test_bit(In_sync, &rdev->flags))
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continue;
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continue;
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disk = r10_bio->devs[slot].devnum;
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rdev = rcu_dereference(conf->mirrors[disk].rdev);
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if (rdev == NULL)
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continue;
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if (!test_bit(In_sync, &rdev->flags))
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continue;
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if (!do_balance)
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break;
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/* This optimisation is debatable, and completely destroys
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/* This optimisation is debatable, and completely destroys
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* sequential read speed for 'far copies' arrays. So only
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* sequential read speed for 'far copies' arrays. So only
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* keep it for 'near' arrays, and review those later.
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* keep it for 'near' arrays, and review those later.
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*/
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*/
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if (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending)) {
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if (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending))
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disk = ndisk;
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slot = nslot;
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break;
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break;
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}
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/* for far > 1 always use the lowest address */
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/* for far > 1 always use the lowest address */
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if (conf->far_copies > 1)
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if (conf->far_copies > 1)
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new_distance = r10_bio->devs[nslot].addr;
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new_distance = r10_bio->devs[slot].addr;
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else
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else
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new_distance = abs(r10_bio->devs[nslot].addr -
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new_distance = abs(r10_bio->devs[slot].addr -
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conf->mirrors[ndisk].head_position);
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conf->mirrors[disk].head_position);
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if (new_distance < current_distance) {
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if (new_distance < best_dist) {
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current_distance = new_distance;
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best_dist = new_distance;
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disk = ndisk;
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best_slot = slot;
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slot = nslot;
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}
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}
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}
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}
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if (slot == conf->copies)
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slot = best_slot;
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rb_out:
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if (slot >= 0) {
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r10_bio->read_slot = slot;
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disk = r10_bio->devs[slot].devnum;
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/* conf->next_seq_sect = this_sector + sectors;*/
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rdev = rcu_dereference(conf->mirrors[disk].rdev);
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if (!rdev)
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if (disk >= 0 && (rdev=rcu_dereference(conf->mirrors[disk].rdev))!= NULL)
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goto retry;
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atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
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atomic_inc(&rdev->nr_pending);
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else
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if (test_bit(Faulty, &rdev->flags)) {
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/* Cannot risk returning a device that failed
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* before we inc'ed nr_pending
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*/
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rdev_dec_pending(rdev, conf->mddev);
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goto retry;
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}
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r10_bio->read_slot = slot;
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} else
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disk = -1;
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disk = -1;
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rcu_read_unlock();
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rcu_read_unlock();
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