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md/raid1: factor out the code to manage sequential IO

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There is no functional change for now, make read_balance() cleaner and
prepare to fix problems and refactor the handler of sequential IO.

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/20240229095714.926789-11-yukuai1@huaweicloud.com
This commit is contained in:
Yu Kuai 2024-02-29 17:57:13 +08:00 committed by Song Liu
parent 9f3ced7922
commit ba58f57fdf
1 changed files with 37 additions and 34 deletions
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71
drivers/md/raid1.c
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@ -705,6 +705,31 @@ static int choose_slow_rdev(struct r1conf *conf, struct r1bio *r1_bio,
return bb_disk;
}
static bool is_sequential(struct r1conf *conf, int disk, struct r1bio *r1_bio)
{
/* TODO: address issues with this check and concurrency. */
return conf->mirrors[disk].next_seq_sect == r1_bio->sector ||
conf->mirrors[disk].head_position == r1_bio->sector;
}
/*
* If buffered sequential IO size exceeds optimal iosize, check if there is idle
* disk. If yes, choose the idle disk.
*/
static bool should_choose_next(struct r1conf *conf, int disk)
{
struct raid1_info *mirror = &conf->mirrors[disk];
int opt_iosize;
if (!test_bit(Nonrot, &mirror->rdev->flags))
return false;
opt_iosize = bdev_io_opt(mirror->rdev->bdev) >> 9;
return opt_iosize > 0 && mirror->seq_start != MaxSector &&
mirror->next_seq_sect > opt_iosize &&
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
@ -768,43 +793,21 @@ 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);
/* Don't change to another disk for sequential reads */
if (conf->mirrors[disk].next_seq_sect == this_sector
|| dist == 0) {
int opt_iosize = bdev_io_opt(rdev->bdev) >> 9;
struct raid1_info *mirror = &conf->mirrors[disk];
/*
* If buffered sequential IO size exceeds optimal
* iosize, check if there is idle disk. If yes, choose
* the idle disk. read_balance could already choose an
* idle disk before noticing it's a sequential IO in
* this disk. This doesn't matter because this disk
* will idle, next time it will be utilized after the
* first disk has IO size exceeds optimal iosize. In
* this way, iosize of the first disk will be optimal
* iosize at least. iosize of the second disk might be
* small, but not a big deal since when the second disk
* starts IO, the first disk is likely still busy.
*/
if (test_bit(Nonrot, &rdev->flags) && opt_iosize > 0 &&
mirror->seq_start != MaxSector &&
mirror->next_seq_sect > opt_iosize &&
mirror->next_seq_sect - opt_iosize >=
mirror->seq_start) {
/*
* Add 'pending' to avoid choosing this disk if
* there is other idle disk.
*/
pending++;
/*
* If there is no other idle disk, this disk
* will be chosen.
*/
sequential_disk = disk;
} else {
if (is_sequential(conf, disk, r1_bio)) {
if (!should_choose_next(conf, disk)) {
best_disk = disk;
break;
}
/*
* Add 'pending' to avoid choosing this disk if
* there is other idle disk.
*/
pending++;
/*
* If there is no other idle disk, this disk
* will be chosen.
*/
sequential_disk = disk;
}
if (min_pending > pending) {