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md/raid5: fix lockless max_nr_stripes reads

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max_nr_stripes is updated under cache_size_mutex in the stripe cache
grow/shrink paths, while is_inactive_blocked() and
raid5_end_read_request() read it without that lock.

Use READ_ONCE() for those reads in lockless path to match the WRITE_ONCE()
updates and avoid KCSAN data race reports.

A similar issue was previously fixed in commit-id:
	dfd2bf4367.

Fixes: 0009fad033 ("raid5 improve too many read errors msg by adding limits")
Fixes: 3514da58be ("md/raid5: Make is_inactive_blocked() helper")

KCSAN report:
=================

BUG: KCSAN: data-race in grow_one_stripe / is_inactive_blocked

write (marked) to 0xffff8f01f0b5a268 of 4 bytes by task 12616 on cpu 9:
 grow_one_stripe+0x2d8/0x320
 raid5d+0xb57/0xba0
 md_thread+0x15a/0x2d0
 [..........]

read to 0xffff8f01f0b5a268 of 4 bytes by task 12670 on cpu 11:
 is_inactive_blocked+0x97/0xc0
 raid5_get_active_stripe+0x2fd/0xa70
 raid5_make_request+0x4aa/0x2940
 [..........]

value changed: 0x000003b9 -> 0x000003ba

Signed-off-by: Chen Cheng <chencheng@fnnas.com>
Reviewed-by: Yu Kuai <yukuai@fygo.io>
Link: https://patch.msgid.link/20260624024042.2561803-1-chencheng@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
This commit is contained in:
Chen Cheng
2026-06-24 10:40:42 +08:00
committed by Yu Kuai
parent e12e619c2e
commit 6cb6ab75bd
1 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/md/raid5.c
View File

@@ -801,7 +801,7 @@ static bool is_inactive_blocked(struct r5conf *conf, int hash)
return true;
return (atomic_read(&conf->active_stripes) <
(conf->max_nr_stripes * 3 / 4));
(READ_ONCE(conf->max_nr_stripes) * 3 / 4));
}
struct stripe_head *raid5_get_active_stripe(struct r5conf *conf,
@@ -2785,6 +2785,7 @@ static void raid5_end_read_request(struct bio * bi)
} else {
int retry = 0;
int set_bad = 0;
int max_nr_stripes = READ_ONCE(conf->max_nr_stripes);
clear_bit(R5_UPTODATE, &sh->dev[i].flags);
if (!(bi->bi_status == BLK_STS_PROTECTION))
@@ -2810,13 +2811,12 @@ static void raid5_end_read_request(struct bio * bi)
mdname(conf->mddev),
(unsigned long long)s,
rdev->bdev);
} else if (atomic_read(&rdev->read_errors)
> conf->max_nr_stripes) {
} else if (atomic_read(&rdev->read_errors) > max_nr_stripes) {
if (!test_bit(Faulty, &rdev->flags)) {
pr_warn("md/raid:%s: %d read_errors > %d stripes\n",
mdname(conf->mddev),
atomic_read(&rdev->read_errors),
conf->max_nr_stripes);
max_nr_stripes);
pr_warn("md/raid:%s: Too many read errors, failing device %pg.\n",
mdname(conf->mddev), rdev->bdev);
}