Commit 31a73331 authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

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



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: default avatarPaul Luse <paul.e.luse@linux.intel.com>
Signed-off-by: default avatarPaul Luse <paul.e.luse@linux.intel.com>
Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarXiao Ni <xni@redhat.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240229095714.926789-8-yukuai1@huaweicloud.com
parent f1092076

drivers/md/raid1.c

+46 −17
Original line number Diff line number Diff line
@@ -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;

		sectors = best_good_sectors;

		update_read_sectors(conf, disk, this_sector, sectors);

	}

	*max_sectors = sectors;