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md/raid1: protect sequential read hints for read balance

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The patch just suppress KCSAN noise. No functional change.

KCSAN reports a race, point to update_read_sectors() update next_seq_sect vs.
read next_seq_sect.

Protect next_seq_sect and seq_start with READ_ONCE/WRITE_ONCE, otherwise,
read balance see stale sequential-read hints.

KCSAN report:
==============
 BUG: KCSAN: data-race in raid1_read_request / raid1_read_request

 write to 0xffff8e3a2d6736d0 of 8 bytes by task 593784 on cpu 10:
  raid1_read_request+0xe5a/0x19f0
  raid1_make_request+0xdf/0x1990
  md_handle_request+0x4a2/0xa40
  [...]

 read to 0xffff8e3a2d6736d0 of 8 bytes by task 593776 on cpu 11:
  raid1_read_request+0xe3f/0x19f0
  raid1_make_request+0xdf/0x1990
  md_handle_request+0x4a2/0xa40
  [...]

 value changed: 0x0000000000356368 -> 0x0000000000356370

Signed-off-by: Chen Cheng <chencheng@fnnas.com>
Reviewed-by: Yu Kuai <yukuai@fygo.io>
Link: https://patch.msgid.link/20260623075940.2476255-1-chencheng@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
This commit is contained in:
Chen Cheng
2026-06-23 15:59:40 +08:00
committed by Yu Kuai
parent 371f7a1b39
commit e12e619c2e
1 changed files with 10 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/md/raid1.c
View File

@@ -604,9 +604,9 @@ static void update_read_sectors(struct r1conf *conf, int disk,
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;
if (READ_ONCE(info->next_seq_sect) != this_sector)
WRITE_ONCE(info->seq_start, this_sector);
WRITE_ONCE(info->next_seq_sect, this_sector + len);
}
static int choose_first_rdev(struct r1conf *conf, struct r1bio *r1_bio,
@@ -735,8 +735,7 @@ static int choose_slow_rdev(struct r1conf *conf, struct r1bio *r1_bio,
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 ||
return READ_ONCE(conf->mirrors[disk].next_seq_sect) == r1_bio->sector ||
READ_ONCE(conf->mirrors[disk].head_position) == r1_bio->sector;
}
@@ -747,15 +746,18 @@ static bool is_sequential(struct r1conf *conf, int disk, struct r1bio *r1_bio)
static bool should_choose_next(struct r1conf *conf, int disk)
{
struct raid1_info *mirror = &conf->mirrors[disk];
sector_t seq_start, next_seq_sect;
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;
seq_start = READ_ONCE(mirror->seq_start);
next_seq_sect = READ_ONCE(mirror->next_seq_sect);
return opt_iosize > 0 && seq_start != MaxSector &&
next_seq_sect > opt_iosize &&
next_seq_sect - opt_iosize >= seq_start;
}
static bool rdev_readable(struct md_rdev *rdev, struct r1bio *r1_bio)