linux-kernel - Re: [PATCH v2 12/26] raid1: use bio

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Message-ID: <20120912071736.715627f0@notabene.brown>
Date:	Wed, 12 Sep 2012 07:17:36 +1000
From:	NeilBrown <neilb@...e.de>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, axboe@...nel.dk, tj@...nel.org
Subject: Re: [PATCH v2 12/26] raid1: use bio_reset()

On Tue, 11 Sep 2012 11:28:25 -0700 Kent Overstreet <koverstreet@...gle.com>
wrote:

> On Tue, Sep 11, 2012 at 02:59:13PM +1000, NeilBrown wrote:
> > On Mon, 10 Sep 2012 17:22:23 -0700 Kent Overstreet <koverstreet@...gle.com>
> > wrote:
> > 
> > > I couldn't figure out what sbio->bi_end_io in process_checks() was
> > > supposed to be, so I took the easy way out.
> > 
> > Almost.
> > You save 'sbio->bi_end_io' to 'bi_end_io', then do nothing with it...
> 
> Whoops :) I think I must've gotten distracted and forgot to finish with
> that patch, I wasn't setting bi_private either.
> 
> > 
> > A little way above the 'fixup the bio for reuse' comment you'll find:
> > 
> > 		struct bio *sbio = r1_bio->bios[i];
> > ....
> > 		if (r1_bio->bios[i]->bi_end_io != end_sync_read)
> > 			continue;
> > 
> > which implies that if we don't 'continue', then sbio->bi_end_io ==
> > end_sync_read.
> 
> Ahh. I remember reading that, but I missed that that was sbio that was
> being checked.
> 
> > 
> > So I suspect you want to add
> >     sbio->bi_end_io = end_sync_read;
> > somewhere after the 'bio_reset()'.
> > 
> > If you happened to also fix that 'if' that I quoted so that it reads:
> > 
> >      if (sbio->bi_end_io != end_sync_read)
> >            continue;
> 
> Will do! How's this look?

Looks good.

Acked-by: NeilBrown <neilb@...e.de>

NeilBrown


> 
> 
> commit 40a4645a4346edd040066baedcf2184ac4211ba7
> Author: Kent Overstreet <koverstreet@...gle.com>
> Date:   Tue Sep 11 11:26:12 2012 -0700
> 
>     raid1: use bio_reset()
>     
>     Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
>     CC: Jens Axboe <axboe@...nel.dk>
>     CC: NeilBrown <neilb@...e.de>
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index ee85154..df68691 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1851,7 +1851,7 @@ static int process_checks(struct r1bio *r1_bio)
>  		struct bio *sbio = r1_bio->bios[i];
>  		int size;
>  
> -		if (r1_bio->bios[i]->bi_end_io != end_sync_read)
> +		if (sbio->bi_end_io != end_sync_read)
>  			continue;
>  
>  		if (test_bit(BIO_UPTODATE, &sbio->bi_flags)) {
> @@ -1876,16 +1876,15 @@ static int process_checks(struct r1bio *r1_bio)
>  			continue;
>  		}
>  		/* fixup the bio for reuse */
> +		bio_reset(sbio);
>  		sbio->bi_vcnt = vcnt;
>  		sbio->bi_size = r1_bio->sectors << 9;
> -		sbio->bi_idx = 0;
> -		sbio->bi_phys_segments = 0;
> -		sbio->bi_flags &= ~(BIO_POOL_MASK - 1);
> -		sbio->bi_flags |= 1 << BIO_UPTODATE;
> -		sbio->bi_next = NULL;
>  		sbio->bi_sector = r1_bio->sector +
>  			conf->mirrors[i].rdev->data_offset;
>  		sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
> +		sbio->bi_end_io = end_sync_read;
> +		sbio->bi_private = r1_bio;
> +
>  		size = sbio->bi_size;
>  		for (j = 0; j < vcnt ; j++) {
>  			struct bio_vec *bi;
> @@ -2426,18 +2425,7 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipp
>  	for (i = 0; i < conf->raid_disks * 2; i++) {
>  		struct md_rdev *rdev;
>  		bio = r1_bio->bios[i];
> -
> -		/* take from bio_init */
> -		bio->bi_next = NULL;
> -		bio->bi_flags &= ~(BIO_POOL_MASK-1);
> -		bio->bi_flags |= 1 << BIO_UPTODATE;
> -		bio->bi_rw = READ;
> -		bio->bi_vcnt = 0;
> -		bio->bi_idx = 0;
> -		bio->bi_phys_segments = 0;
> -		bio->bi_size = 0;
> -		bio->bi_end_io = NULL;
> -		bio->bi_private = NULL;
> +		bio_reset(bio);
>  
>  		rdev = rcu_dereference(conf->mirrors[i].rdev);
>  		if (rdev == NULL ||


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