Re: [PATCH] md/raid1: protect head_position for read balance

[yu kuai]

在 2026/6/19 12:41, Chen Cheng 写道:

> From: Chen Cheng<chencheng@xxxxxxxxx>
>
> KCSAN reports a data race between raid1_end_read_request() and
> raid1_read_request().
>
> The completion path updates conf->mirrors[disk].head_position in
> update_head_pos() without a lock, while the read-balance heuristic reads
> the same field locklessly in is_sequential() and choose_best_rdev().
>
> KCSAN report:
> =========================
>    BUG: KCSAN: data-race in raid1_end_read_request / raid1_read_request
>
>    write to 0xffff8f0306ba7868 of 8 bytes by interrupt on cpu 9:
>      raid1_end_read_request+0xb5/0x440
>      bio_endio+0x3c9/0x3e0
>      blk_update_request+0x257/0x770
>      scsi_end_request+0x4d/0x520
>      scsi_io_completion+0x6f/0x990
>      scsi_finish_command+0x188/0x280
>      scsi_complete+0xac/0x160
>      blk_complete_reqs+0x8e/0xb0
>      blk_done_softirq+0x1d/0x30
>     [...]
>
>    read to 0xffff8f0306ba7868 of 8 bytes by task 667002 on cpu 11:
>      raid1_read_request+0x497/0x1a10
>      raid1_make_request+0xdf/0x1950
>      md_handle_request+0x2c5/0x700
>      md_submit_bio+0x126/0x320
>      __submit_bio+0x2ec/0x3a0
>      submit_bio_noacct_nocheck+0x572/0x890
>     [...]
>
>    value changed: 0x0000000000000078 -> 0x00000000005fe448
>
> Signed-off-by: Chen Cheng<chencheng@xxxxxxxxx>
> ---
>   drivers/md/raid1.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
Applied to md-7.2

-- 
Thanks,
Kuai