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md/raid1: factor out read_first_rdev() from read_balance()

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read_balance() is hard to understand because there are too many status
and branches, and it's overlong.

This patch factor out the case to read the first rdev from
read_balance(), there are no functional changes.

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/20240229095714.926789-8-yukuai1@huaweicloud.com
This commit is contained in:
Yu Kuai 2024-02-29 17:57:10 +08:00 committed by Song Liu
parent f109207629
commit 31a7333175
1 changed files with 46 additions and 17 deletions
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63
drivers/md/raid1.c
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@ -579,6 +579,47 @@ static sector_t align_to_barrier_unit_end(sector_t start_sector,
return len;
}
static void update_read_sectors(struct r1conf *conf, int disk,
sector_t this_sector, int len)
{
struct raid1_info *info = &conf->mirrors[disk];
atomic_inc(&info->rdev->nr_pending);
if (info->next_seq_sect != this_sector)
info->seq_start = this_sector;
info->next_seq_sect = this_sector + len;
}
static int choose_first_rdev(struct r1conf *conf, struct r1bio *r1_bio,
int *max_sectors)
{
sector_t this_sector = r1_bio->sector;
int len = r1_bio->sectors;
int disk;
for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
struct md_rdev *rdev;
int read_len;
if (r1_bio->bios[disk] == IO_BLOCKED)
continue;
rdev = conf->mirrors[disk].rdev;
if (!rdev || test_bit(Faulty, &rdev->flags))
continue;
/* choose the first disk even if it has some bad blocks. */
read_len = raid1_check_read_range(rdev, this_sector, &len);
if (read_len > 0) {
update_read_sectors(conf, disk, this_sector, read_len);
*max_sectors = read_len;
return disk;
}
}
return -1;
}
/*
* This routine returns the disk from which the requested read should
* be done. There is a per-array 'next expected sequential IO' sector
@ -603,7 +644,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
sector_t best_dist;
unsigned int min_pending;
struct md_rdev *rdev;
int choose_first;
retry:
sectors = r1_bio->sectors;
@ -614,10 +654,11 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
best_pending_disk = -1;
min_pending = UINT_MAX;
best_good_sectors = 0;
choose_first = raid1_should_read_first(conf->mddev, this_sector,
sectors);
clear_bit(R1BIO_FailFast, &r1_bio->state);
if (raid1_should_read_first(conf->mddev, this_sector, sectors))
return choose_first_rdev(conf, r1_bio, max_sectors);
for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
sector_t dist;
sector_t first_bad;
@ -663,8 +704,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
* bad_sectors from another device..
*/
bad_sectors -= (this_sector - first_bad);
if (choose_first && sectors > bad_sectors)
sectors = bad_sectors;
if (best_good_sectors > sectors)
best_good_sectors = sectors;
@ -674,8 +713,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
best_good_sectors = good_sectors;
best_disk = disk;
}
if (choose_first)
break;
}
continue;
} else {
@ -690,10 +727,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
pending = atomic_read(&rdev->nr_pending);
dist = abs(this_sector - conf->mirrors[disk].head_position);
if (choose_first) {
best_disk = disk;
break;
}
/* Don't change to another disk for sequential reads */
if (conf->mirrors[disk].next_seq_sect == this_sector
|| dist == 0) {
@ -769,13 +802,9 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
rdev = conf->mirrors[best_disk].rdev;
if (!rdev)
goto retry;
atomic_inc(&rdev->nr_pending);
sectors = best_good_sectors;
if (conf->mirrors[best_disk].next_seq_sect != this_sector)
conf->mirrors[best_disk].seq_start = this_sector;
conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;
update_read_sectors(conf, disk, this_sector, sectors);
}
*max_sectors = sectors;