[PATCH 6.7 115/713] md/raid1: record nonrot rdevs while adding/removing rdevs to conf

Sasha Levin
2024-03-24T22:49:14Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 2c27d09d3a76b33629d2e681bf8b774f776ade7f ]

For raid1, each read will iterate all the rdevs from conf and check if
any rdev is non-rotational, then choose rdev with minimal IO inflight
if so, or rdev with closest distance otherwise.

Disk nonrot info can be changed through sysfs entry:

/sys/block/[disk_name]/queue/rotational

However, consider that this should only be used for testing, and user
really shouldn't do this in real life. Record the number of non-rotational
disks in conf, to avoid checking each rdev in IO fast path and simplify
read_balance() a little bit.

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>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240229095714.926789-4-yukuai1@huaweicloud.com
Stable-dep-of: 257ac239ffcf ("md/raid1: fix choose next idle in read_balance()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/md.h | 1 +
drivers/md/raid1.c | 17 ++++++++++-------
drivers/md/raid1.h | 1 +
3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 8d881cc597992..27d187ca6258a 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -207,6 +207,7 @@ enum flag_bits {
* check if there is collision between raid1
* serial bios.
*/
+ Nonrot, /* non-rotational device (SSD) */
};

static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 57e2487a03507..27d15b640eff3 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -601,7 +601,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
int sectors;
int best_good_sectors;
int best_disk, best_dist_disk, best_pending_disk;
- int has_nonrot_disk;
int disk;
sector_t best_dist;
unsigned int min_pending;
@@ -622,7 +621,6 @@ 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;
- has_nonrot_disk = 0;
choose_next_idle = 0;
clear_bit(R1BIO_FailFast, &r1_bio->state);

@@ -639,7 +637,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
sector_t first_bad;
int bad_sectors;
unsigned int pending;
- bool nonrot;

rdev = conf->mirrors[disk].rdev;
if (r1_bio->bios[disk] == IO_BLOCKED
@@ -705,8 +702,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
/* At least two disks to choose from so failfast is OK */
set_bit(R1BIO_FailFast, &r1_bio->state);

- nonrot = bdev_nonrot(rdev->bdev);
- has_nonrot_disk |= nonrot;
pending = atomic_read(&rdev->nr_pending);
dist = abs(this_sector - conf->mirrors[disk].head_position);
if (choose_first) {
@@ -733,7 +728,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
* small, but not a big deal since when the second disk
* starts IO, the first disk is likely still busy.
*/
- if (nonrot && opt_iosize > 0 &&
+ 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 >=
@@ -765,7 +760,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
* mixed ratation/non-rotational disks depending on workload.
*/
if (best_disk == -1) {
- if (has_nonrot_disk || min_pending == 0)
+ if (READ_ONCE(conf->nonrot_disks) || min_pending == 0)
best_disk = best_pending_disk;
else
best_disk = best_dist_disk;
@@ -1772,6 +1767,11 @@ static bool raid1_add_conf(struct r1conf *conf, struct md_rdev *rdev, int disk,
if (info->rdev)
return false;

+ if (bdev_nonrot(rdev->bdev)) {
+ set_bit(Nonrot, &rdev->flags);
+ WRITE_ONCE(conf->nonrot_disks, conf->nonrot_disks + 1);
+ }
+
rdev->raid_disk = disk;
info->head_position = 0;
info->seq_start = MaxSector;
@@ -1795,6 +1795,9 @@ static bool raid1_remove_conf(struct r1conf *conf, int disk)
rdev->mddev->degraded < conf->raid_disks)
return false;

+ if (test_and_clear_bit(Nonrot, &rdev->flags))
+ WRITE_ONCE(conf->nonrot_disks, conf->nonrot_disks - 1);
+
WRITE_ONCE(info->rdev, NULL);
return true;
}
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index 14d4211a123a8..5300cbaa58a41 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -71,6 +71,7 @@ struct r1conf {
* allow for replacements.
*/
int raid_disks;
+ int nonrot_disks;

spinlock_t device_lock;

--
2.43.0