linux-kernel - Re: [PATCH -next 3/8] raid5: fix missing io accounting in raid5_align

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Date:   Tue, 20 Jun 2023 11:57:52 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     xni@...hat.com, song@...nel.org, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next 3/8] raid5: fix missing io accounting in
 raid5_align_endio()

Dear Yu,


Thank you for your patch.

Am 19.06.23 um 22:48 schrieb Yu Kuai:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Io will only be accounted as done from raid5_align_endio() if the io
> succeed, and io inflight counter will be leaked if such io failed.

succeed*s* or succeed*ed*?

> Fix this problem by switching to use md_account_bio() for io accounting.

How can this be tested?

> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   drivers/md/raid5.c | 29 ++++++++---------------------
>   1 file changed, 8 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index cef0b400b2ee..4cdb35e54251 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -5468,26 +5468,17 @@ static struct bio *remove_bio_from_retry(struct r5conf *conf,
>    */
>   static void raid5_align_endio(struct bio *bi)
>   {
> -	struct md_io_clone *md_io_clone = bi->bi_private;
> -	struct bio *raid_bi = md_io_clone->orig_bio;
> -	struct mddev *mddev;
> -	struct r5conf *conf;
> -	struct md_rdev *rdev;
> +	struct bio *raid_bi = bi->bi_private;
> +	struct md_rdev *rdev = (void *)raid_bi->bi_next;
> +	struct mddev *mddev = rdev->mddev;
> +	struct r5conf *conf = mddev->private;
>   	blk_status_t error = bi->bi_status;
> -	unsigned long start_time = md_io_clone->start_time;
>   
>   	bio_put(bi);
> -
> -	rdev = (void*)raid_bi->bi_next;
>   	raid_bi->bi_next = NULL;
> -	mddev = rdev->mddev;
> -	conf = mddev->private;
> -

This looks like unnecessary refactoring. No idea what the preferred 
style for the subsystem is though. If it is wanted, maybe make it a 
separate commit?

>   	rdev_dec_pending(rdev, conf->mddev);
>   
>   	if (!error) {
> -		if (blk_queue_io_stat(raid_bi->bi_bdev->bd_disk->queue))
> -			bio_end_io_acct(raid_bi, start_time);
>   		bio_endio(raid_bi);
>   		if (atomic_dec_and_test(&conf->active_aligned_reads))
>   			wake_up(&conf->wait_for_quiescent);
> @@ -5506,7 +5497,6 @@ static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
>   	struct md_rdev *rdev;
>   	sector_t sector, end_sector, first_bad;
>   	int bad_sectors, dd_idx;
> -	struct md_io_clone *md_io_clone;
>   	bool did_inc;
>   
>   	if (!in_chunk_boundary(mddev, raid_bio)) {
> @@ -5543,16 +5533,13 @@ static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
>   		return 0;
>   	}
>   
> -	align_bio = bio_alloc_clone(rdev->bdev, raid_bio, GFP_NOIO,
> -				    &mddev->io_clone_set);
> -	md_io_clone = container_of(align_bio, struct md_io_clone, bio_clone);
> +	md_account_bio(mddev, &raid_bio);
>   	raid_bio->bi_next = (void *)rdev;
> -	if (blk_queue_io_stat(raid_bio->bi_bdev->bd_disk->queue))
> -		md_io_clone->start_time = bio_start_io_acct(raid_bio);
> -	md_io_clone->orig_bio = raid_bio;
>   
> +	align_bio = bio_alloc_clone(rdev->bdev, raid_bio, GFP_NOIO,
> +				    &mddev->bio_set);
>   	align_bio->bi_end_io = raid5_align_endio;
> -	align_bio->bi_private = md_io_clone;
> +	align_bio->bi_private = raid_bio;
>   	align_bio->bi_iter.bi_sector = sector;
>   
>   	/* No reshape active, so we can trust rdev->data_offset */


Kind regards,

Paul