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@xxxxxxx>
---
drivers/md/raid10.c | 110 ++++++++++++++++++++-------------------------------
1 files changed, 44 insertions(+), 66 deletions(-)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 8e94626..8ea0aca 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -488,13 +488,19 @@ static int raid10_mergeable_bvec(struct request_queue *q,
static int read_balance(conf_t *conf, r10bio_t *r10_bio)
{
const sector_t this_sector = r10_bio->sector;
- int disk, slot, nslot;
+ int disk, slot;
const int sectors = r10_bio->sectors;
- sector_t new_distance, current_distance;
+ sector_t new_distance, best_dist;
mdk_rdev_t *rdev;
+ int do_balance;
+ int best_slot;
raid10_find_phys(conf, r10_bio);
rcu_read_lock();
+retry:
+ best_slot = -1;
+ best_dist = MaxSector;
+ do_balance = 1;
/*
* Check if we can balance. We can balance on the whole
* device if no resync is going on (recovery is ok), or below
@@ -502,86 +508,58 @@ static int read_balance(conf_t *conf, r10bio_t *r10_bio)
* above the resync window.
*/
if (conf->mddev->recovery_cp < MaxSector
- && (this_sector + sectors >= conf->next_resync)) {
- /* make sure that disk is operational */
- slot = 0;
- disk = r10_bio->devs[slot].devnum;
-
- while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
- r10_bio->devs[slot].bio == IO_BLOCKED ||
- !test_bit(In_sync, &rdev->flags)) {
- slot++;
- if (slot == conf->copies) {
- slot = 0;
- disk = -1;
- break;
- }
- disk = r10_bio->devs[slot].devnum;
- }
- goto rb_out;
- }
-
+ && (this_sector + sectors >= conf->next_resync))
+ do_balance = 0;
- /* make sure the disk is operational */
- slot = 0;
- disk = r10_bio->devs[slot].devnum;
- while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
- r10_bio->devs[slot].bio == IO_BLOCKED ||
- !test_bit(In_sync, &rdev->flags)) {
- slot ++;
- if (slot == conf->copies) {
- disk = -1;
- goto rb_out;
- }
+ for (slot = 0; slot < conf->copies ; slot++) {
+ if (r10_bio->devs[slot].bio == IO_BLOCKED)
+ continue;
disk = r10_bio->devs[slot].devnum;
- }
-
-
- current_distance = abs(r10_bio->devs[slot].addr -
- conf->mirrors[disk].head_position);
-
- /* Find the disk whose head is closest,
- * or - for far > 1 - find the closest to partition beginning */
-
- for (nslot = slot; nslot < conf->copies; nslot++) {
- int ndisk = r10_bio->devs[nslot].devnum;
-
-
- if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
- r10_bio->devs[nslot].bio == IO_BLOCKED ||
- !test_bit(In_sync, &rdev->flags))
+ rdev = rcu_dereference(conf->mirrors[disk].rdev);
+ if (rdev == NULL)
+ continue;
+ if (!test_bit(In_sync, &rdev->flags))
continue;
+ if (!do_balance)
+ break;
+
/* 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 (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending)) {
- disk = ndisk;
- slot = nslot;
+ if (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending))
break;
- }
/* for far > 1 always use the lowest address */
if (conf->far_copies > 1)
- new_distance = r10_bio->devs[nslot].addr;
+ new_distance = r10_bio->devs[slot].addr;
else
- new_distance = abs(r10_bio->devs[nslot].addr -
- conf->mirrors[ndisk].head_position);
- if (new_distance < current_distance) {
- current_distance = new_distance;
- disk = ndisk;
- slot = nslot;
+ new_distance = abs(r10_bio->devs[slot].addr -
+ conf->mirrors[disk].head_position);
+ if (new_distance < best_dist) {
+ best_dist = new_distance;
+ best_slot = slot;
}
}
+ if (slot == conf->copies)
+ slot = best_slot;
-rb_out:
- r10_bio->read_slot = slot;
-/* conf->next_seq_sect = this_sector + sectors;*/
-
- if (disk >= 0 && (rdev=rcu_dereference(conf->mirrors[disk].rdev))!= NULL)
- atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
- else
+ if (slot >= 0) {
+ disk = r10_bio->devs[slot].devnum;
+ rdev = rcu_dereference(conf->mirrors[disk].rdev);
+ if (!rdev)
+ goto retry;
+ atomic_inc(&rdev->nr_pending);
+ if (test_bit(Faulty, &rdev->flags)) {
+ /* Cannot risk returning a device that failed
+ * before we inc'ed nr_pending
+ */
+ rdev_dec_pending(rdev, conf->mddev);
+ goto retry;
+ }
+ r10_bio->read_slot = slot;
+ } else
disk = -1;
rcu_read_unlock();
--
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