Re: [PATCH] md/raid5: use stripe state snapshot in break_stripe_batch_list()

[yu kuai]

在 2026/6/18 21:47, Chen Cheng 写道:

> From: Chen Cheng<chencheng@xxxxxxxxx>
>
> The patch just suppress KCSAN noise. No functional change.
>
> RAID-5 can group multi full-stripe-write aka stripe_head into a
> batch aka batch_list, with one head_sh leading them. Call
> break_stripe_batch_list() when the batch is finished, or,
> a stripe has to be dropped out of the batch.
>
> break_stripe_batch_list() reads stripe state several times while
> request paths can update thost state words concurrently with
> lockless bitops, which reported by KCSAN.
>
> Use a snapshot to guarantees that the value used for
> warning, copying, and handle checks is internally consistent
> at current read moment.
>
> KCSAN report:
> ==============================================
> BUG: KCSAN: data-race in __add_stripe_bio / break_stripe_batch_list
>
> write (marked) to 0xffff8e89d4f0b988 of 8 bytes by task 4323 on cpu 3:
>    __add_stripe_bio+0x35e/0x400
>    raid5_make_request+0x6ac/0x2930
>    md_handle_request+0x4a2/0xa40
>    md_submit_bio+0x109/0x1a0
>    __submit_bio+0x2ec/0x390
>    submit_bio_noacct_nocheck+0x457/0x710
>    submit_bio_noacct+0x2a7/0xc20
>    submit_bio+0x56/0x250
>    blkdev_direct_IO+0x54c/0xda0
>    blkdev_write_iter+0x38f/0x570
>    aio_write+0x22b/0x490
>    io_submit_one+0xa51/0xf70
>
> read to 0xffff8e89d4f0b988 of 8 bytes by task 4290 on cpu 4:
>    break_stripe_batch_list+0x3ce/0x480
>    handle_stripe_clean_event+0x720/0x9b0
>    handle_stripe+0x32fb/0x4500
>    handle_active_stripes.isra.0+0x6e0/0xa50
>    raid5d+0x7e0/0xba0
>
> Signed-off-by: Chen Cheng<chencheng@xxxxxxxxx>
> ---
>   drivers/md/raid5.c | 45 ++++++++++++++++++++++++++-------------------
>   1 file changed, 26 insertions(+), 19 deletions(-)
Applied to md-7.2

-- 
Thanks,
Kuai