Re: [PATCH] md/raid1,raid10: don't pass down the REQ_RAHEAD flag

[Mikulas Patocka <mpatocka@redhat.com>]

On Mon, 19 May 2025, Yu Kuai wrote:

> Hi,
> 
> Please ignore the last reply, I misunderstand your commit message, I
> thought you said dm-raid, actually you said mdraid, and it's correct,
> if read_bio faild raid1/10 will set badblocks which is not expected.
> 
> Then for reada head IO, I still think don't kill REQ_RAHEAD for
> underlying disks is better, what do you think about skip handling IO
> error for ead ahead IO?
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 657d481525be..b8b4fead31f3 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -380,7 +380,10 @@ static void raid1_end_read_request(struct bio *bio)
>                 /* This was a fail-fast read so we definitely
>                  * want to retry */
>                 ;
> -       else {
> +       else if (bio->bi_opf & REQ_RAHEAD) {
> +               /* don't handle readahead error, which can fail at anytime. */
> +               uptodate = 1;
> +       } else {
>                 /* If all other devices have failed, we want to return
>                  * the error upwards rather than fail the last device.
>                  * Here we redefine "uptodate" to mean "Don't want to retry"
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index dce06bf65016..4d51aaf3b39b 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -399,6 +399,9 @@ static void raid10_end_read_request(struct bio *bio)
>                  * wait for the 'master' bio.
>                  */
>                 set_bit(R10BIO_Uptodate, &r10_bio->state);
> +       } else if (bio->bi_opf & REQ_RAHEAD) {
> +               /* don't handle readahead error, which can fail at anytime. */
> +               uptodate = 1;
>         } else {
>                 /* If all other devices that store this block have
>                  * failed, we want to return the error upwards rather
> 
> Thanks,
> Kuai

I confirm that this patch fixes the test.

Tested-by: Mikulas Patocka <mpatocka@redhat.com>

Mikulas