md/raid5: fix lockless max_nr_stripes reads

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:
	dfd2bf436709b2bccb78c2dda550dde93700efa7.

Fixes: 0009fad03337 ("raid5 improve too many read errors msg by adding limits")
Fixes: 3514da58be9c ("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>

0 files changed, 0 insertions, 0 deletions