md/raid1: make sequential read detection per disk based
Currently the sequential read detection is global wide. It's natural to make it
per disk based, which can improve the detection for concurrent multiple
sequential reads. And next patch will make SSD read balance not use distance
based algorithm, where this change help detect truly sequential read for SSD.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index d3d3568..fb96c0c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -497,9 +497,8 @@
const sector_t this_sector = r1_bio->sector;
int sectors;
int best_good_sectors;
- int start_disk;
int best_disk;
- int i;
+ int disk;
sector_t best_dist;
struct md_rdev *rdev;
int choose_first;
@@ -517,23 +516,16 @@
best_good_sectors = 0;
if (conf->mddev->recovery_cp < MaxSector &&
- (this_sector + sectors >= conf->next_resync)) {
+ (this_sector + sectors >= conf->next_resync))
choose_first = 1;
- start_disk = 0;
- } else {
+ else
choose_first = 0;
- start_disk = conf->last_used;
- }
- for (i = 0 ; i < conf->raid_disks * 2 ; i++) {
+ for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
sector_t dist;
sector_t first_bad;
int bad_sectors;
- int disk = start_disk + i;
- if (disk >= conf->raid_disks * 2)
- disk -= conf->raid_disks * 2;
-
rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (r1_bio->bios[disk] == IO_BLOCKED
|| rdev == NULL
@@ -594,7 +586,7 @@
dist = abs(this_sector - conf->mirrors[disk].head_position);
if (choose_first
/* Don't change to another disk for sequential reads */
- || conf->next_seq_sect == this_sector
+ || conf->mirrors[disk].next_seq_sect == this_sector
|| dist == 0
/* If device is idle, use it */
|| atomic_read(&rdev->nr_pending) == 0) {
@@ -620,8 +612,7 @@
goto retry;
}
sectors = best_good_sectors;
- conf->next_seq_sect = this_sector + sectors;
- conf->last_used = best_disk;
+ conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;
}
rcu_read_unlock();
*max_sectors = sectors;
@@ -2599,7 +2590,6 @@
conf->recovery_disabled = mddev->recovery_disabled - 1;
err = -EIO;
- conf->last_used = -1;
for (i = 0; i < conf->raid_disks * 2; i++) {
disk = conf->mirrors + i;
@@ -2625,19 +2615,9 @@
if (disk->rdev &&
(disk->rdev->saved_raid_disk < 0))
conf->fullsync = 1;
- } else if (conf->last_used < 0)
- /*
- * The first working device is used as a
- * starting point to read balancing.
- */
- conf->last_used = i;
+ }
}
- if (conf->last_used < 0) {
- printk(KERN_ERR "md/raid1:%s: no operational mirrors\n",
- mdname(mddev));
- goto abort;
- }
err = -ENOMEM;
conf->thread = md_register_thread(raid1d, mddev, "raid1");
if (!conf->thread) {
@@ -2894,7 +2874,6 @@
conf->raid_disks = mddev->raid_disks = raid_disks;
mddev->delta_disks = 0;
- conf->last_used = 0; /* just make sure it is in-range */
lower_barrier(conf);
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);