Re: [PATCH RFC v3 07/15] md/raid1: convert to use bio_submit_split_bioset()

[Yu Kuai]

Hi,

在 2025/09/01 14:43, Damien Le Moal 写道:
> On 9/1/25 12:32 PM, Yu Kuai wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > Unify bio split code, and prepare to fix disordered split IO.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> [...]
>
> > @@ -1586,18 +1577,13 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
> >   		max_sectors = min_t(int, max_sectors,
> >   				    BIO_MAX_VECS * (PAGE_SIZE >> 9));
> >   	if (max_sectors < bio_sectors(bio)) {
> > -		struct bio *split = bio_split(bio, max_sectors,
> > -					      GFP_NOIO, &conf->bio_split);
> > -
> > -		if (IS_ERR(split)) {
> > -			error = PTR_ERR(split);
> > +		bio = bio_submit_split_bioset(bio, max_sectors,
> > +					      &conf->bio_split);
> > +		if (!bio) {
> > +			set_bit(R1BIO_Returned, &r1_bio->state);
>
> Before it was "set_bit(R1BIO_Uptodate, &r1_bio->state);" that was done. Now it
> is R1BIO_Returned that is set. The commit message does not mention this change
> at all. Is this a bug fix ? If yes, that should be in a pre patch before the
> conversion to using bio_submit_split_bioset().

There should be no functional changes, before the change we:

1) set bio->bi_status to split error value;
2) set R1BIO_Uptodate;
3) raid_end_bio_io() check R1BIO_Returned is not set, and call
call_bio_endio();
4) call_bio_endio() check R1BIO_Uptodate is already set, keep the
bio->bi_status that is by split error;

With this change:
1) bio_submit_split_bioset() already fail the bio will split error;
2) set R1BIO_Returned;
3) raid_end_bio_io() check R1BIO_Returned is set and do nothing with the
bio;

And the same with raid10 in patch 8,9;

Perhaps I'll emphasize there is no function changes and explain a bit.

Thanks,
Kuai
> >   			goto err_handle;
> >   		}
> >   
> > -		bio_chain(split, bio);
> > -		trace_block_split(split, bio->bi_iter.bi_sector);
> > -		submit_bio_noacct(bio);
> > -		bio = split;
> >   		r1_bio->master_bio = bio;
> >   		r1_bio->sectors = max_sectors;
> >   	}
> > @@ -1687,8 +1673,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
> >   		}
> >   	}
> >   
> > -	bio->bi_status = errno_to_blk_status(error);
> > -	set_bit(R1BIO_Uptodate, &r1_bio->state);
> >   	raid_end_bio_io(r1_bio);
> >   }