linux-kernel - Re: [PATCH v2 08/14] block: Kill bi

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Message-ID: <20120524200012.GB18624@google.com>
Date:	Thu, 24 May 2012 13:00:12 -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 08/14] block: Kill bi_destructor

On Thu, May 24, 2012 at 03:52:02PM -0400, Vivek Goyal wrote:
> On Wed, May 23, 2012 at 05:02:45PM -0700, Kent Overstreet wrote:
> 
> [..]
> > @@ -234,6 +234,13 @@ void bio_free(struct bio *bio, struct bio_set *bs)
> >  {
> >  	void *p;
> >  
> > +	if (!bs) {
> > +		if (bio_integrity(bio))
> > +			bio_integrity_free(bio, fs_bio_set);
> > +		kfree(bio);
> > +		return;
> > +	}
> > +
> 
> Ok, this seems to be the code which will take care of freeing kmalloced
> bio. I think putting little comment about the explicit assumption is not
> a bad idea.

Yeah, it's changing the semantics of bio_free(). I'll document that.

> Somehow we need to integrate two patches so that we don't have memory leak
> in bisection and reading code becomes easier.

I don't think there's any memory leak issues with this patch... there
are various annoyances with the dm code, though.

> Also then what's the need of bio_reset() in previous patch. That seems to
> be independent from getting rid of pkt_bio_destructor(). I would think
> that keep we can split the patch and keep bio_reset() logic in a separate
> patch. In fact I am not even sure that for one driver we should introduce
> bio_reset() in generic block layer. So to me we should get rid of bio_reset()
> and let all the gory details remain in driver.

Well, it would be possible to kill bi_destructor without introducing
bio_reset() - but that'd mean the kill bi_destructor patch would have to
muck around in the pktcdvd code. IMO introducing bio_reset() makes the
rest of the patch series much cleaner.
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