Date: Wed, 8 Aug 2012 23:05:17 -0700
From: Tejun Heo <tj@kernel.org>
To: Kent Overstreet <koverstreet@google.com>
Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
        dm-devel@redhat.com, axboe@kernel.dk, agk@redhat.com, neilb@suse.de,
        drbd-dev@lists.linbit.com, vgoyal@redhat.com, mpatocka@redhat.com,
        sage@newdream.net, yehuda@hq.newdream.net
Subject: Re: [PATCH v5 05/12] block: Kill bi_destructor
Message-ID: <20120809060517.GB2845@dhcp-172-17-108-109.mtv.corp.google.com>
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Hello,

On Wed, Aug 08, 2012 at 05:21:54PM -0700, Kent Overstreet wrote:
> > What's wrong with good ol' NULL?
> 
> If it's NULL, we can't distinguish between bios where that field wasn't
> set (i.e. bios that were statically allocated somewhere) from bios that
> were allocated by bio_kmalloc().
> 
> It's just there to make debugging easier - if bi_cnt goes to 0 on a bio
> where it shouldn't we'll catch it at the BUG_ON() in bio_free() instead
> of kfreeing a bad pointer.

I fail to see how that improves anything.  slab will complain clearly
if it gets passed in a pointer to static area.  The benefit is
imaginery.  If there's no bioset, it's NULL.  Let's please keep things
usual.

Thanks.

-- 
tejun
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