Re: [PATCH v2 3/3] md/raid1,raid10: fix bio accounting for split md cloned bios

[Yu Kuai]

Hi,

在 2026/5/1 19:46, Abd-Alrhman Masalkhi 写道:
> Use md_cloned_bio() to control bio accounting instead of relying
> on r1bio_existed in raid1 or the io_accounting flag in raid10.
>
> The previous logic does not reliably reflect whether a bio is an
> md cloned bio. When a failed bio is split and resubmitted via
> bio_submit_split_bioset() on the error path, this can lead to either
> double accounting for md cloned bios, or missing accounting for bios
> returned from bio_submit_split_bioset()
>
> Fix this by using md_cloned_bio() to detect md cloned bios and
> skip accounting accordingly.
>
> Fixes: bb2a9acefaf9 ("md/raid1: switch to use md_account_bio() for io accounting")
> Fixes: 820455238366 ("md/raid10: switch to use md_account_bio() for io accounting")

The same as patch 2, I don't think this patch fix any problem. And I
think current IO accounting is correct.

> Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@xxxxxxxxx>
> ---
> This patch depends on patch 1.
>
> Changes in v2:
>   - New patch.
> ---
>   drivers/md/raid1.c  | 2 +-
>   drivers/md/raid10.c | 8 ++++----
>   2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index c52ecd38c163..dfaf34141325 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1396,7 +1396,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
>   	}
>   
>   	r1_bio->read_disk = rdisk;
> -	if (!r1bio_existed) {
> +	if (likely(!md_cloned_bio(mddev, bio))) {
>   		md_account_bio(mddev, &bio);
>   		r1_bio->master_bio = bio;
>   	}
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 8c6fc398260e..93af7bbc9005 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -1146,7 +1146,7 @@ static bool regular_request_wait(struct mddev *mddev, struct r10conf *conf,
>   }
>   
>   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
> -				struct r10bio *r10_bio, bool io_accounting)
> +				struct r10bio *r10_bio)
>   {
>   	struct r10conf *conf = mddev->private;
>   	struct bio *read_bio;
> @@ -1226,7 +1226,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>   	}
>   	slot = r10_bio->read_slot;
>   
> -	if (io_accounting) {
> +	if (likely(!md_cloned_bio(mddev, bio))) {
>   		md_account_bio(mddev, &bio);
>   		r10_bio->master_bio = bio;
>   	}
> @@ -1552,7 +1552,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
>   			conf->geo.raid_disks);
>   
>   	if (bio_data_dir(bio) == READ)
> -		raid10_read_request(mddev, bio, r10_bio, true);
> +		raid10_read_request(mddev, bio, r10_bio);
>   	else
>   		raid10_write_request(mddev, bio, r10_bio);
>   }
> @@ -2872,7 +2872,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
>   
>   	rdev_dec_pending(rdev, mddev);
>   	r10_bio->state = 0;
> -	raid10_read_request(mddev, r10_bio->master_bio, r10_bio, false);
> +	raid10_read_request(mddev, r10_bio->master_bio, r10_bio);
>   	/*
>   	 * allow_barrier after re-submit to ensure no sync io
>   	 * can be issued while regular io pending.

-- 
Thansk,
Kuai