linux-kernel - Re: [PATCH v2 04/14] block: Add bio_clone

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Date:	Thu, 24 May 2012 17:31:14 -0700
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org,
	dm-devel@...hat.com, linux-fsdevel@...r.kernel.org, tj@...nel.org,
	axboe@...nel.dk, agk@...hat.com, neilb@...e.de,
	drbd-dev@...ts.linbit.com, bharrosh@...asas.com,
	mpatocka@...hat.com, sage@...dream.net, yehuda@...newdream.net
Subject: Re: [PATCH v2 04/14] block: Add bio_clone_kmalloc()

On Thu, May 24, 2012 at 02:59:19PM -0400, Vivek Goyal wrote:
> On Wed, May 23, 2012 at 05:02:41PM -0700, Kent Overstreet wrote:
> 
> [..]
> > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> > index 013c7a5..5a953c6 100644
> > --- a/drivers/block/rbd.c
> > +++ b/drivers/block/rbd.c
> > @@ -729,7 +729,7 @@ static struct bio *bio_chain_clone(struct bio **old, struct bio **next,
> >  	}
> >  
> >  	while (old_chain && (total < len)) {
> > -		tmp = bio_kmalloc(gfpmask, old_chain->bi_max_vecs);
> > +		tmp = bio_clone_kmalloc(old_chain, gfpmask);
> >  		if (!tmp)
> >  			goto err_out;
> >  
> > @@ -751,13 +751,9 @@ static struct bio *bio_chain_clone(struct bio **old, struct bio **next,
> >  			if (!bp)
> >  				goto err_out;
> >  
> > -			__bio_clone(tmp, &bp->bio1);
> > -
> >  			*next = &bp->bio2;
> 
> Is this code correct. Now original code might clone bio after split and
> new code will clone the original bio itself and not the split one?

Argh, you're right, I screwed that up.

I'd like to get rid of all the open coded bio_clone()s out there (to
reduce the amount of code that "Only clone bio vecs that are in use" has
to change, but this code is too tricky - I'm just going to drop this
bit.
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