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

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Date:   Wed, 21 Jun 2023 11:22:29 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Yu Kuai <yukuai1@...weicloud.com>
Cc:     xni@...hat.com, song@...nel.org, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next 3/8] raid5: fix missing io accounting in
 raid5_align_endio()

Hi,

在 2023/06/20 17:57, Paul Menzel 写道:
> 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*?

I'll up date this.

> 
>> 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?

You mean that I initialize 'rdev' and 'mdev' while declaration?
I think code is cleaner this way, and this is too tiny to make a patch
for this... I will keep this for now.  😉

Thanks,
Kuai

> 
>>       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
> 
> .
>