Date: Thu, 24 May 2012 14:31:58 -0700
From: Kent Overstreet <koverstreet@google.com>
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org,
        dm-devel@redhat.com, linux-fsdevel@vger.kernel.org, tj@kernel.org,
        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 v2 09/14] block: Add an explicit bio flag for bios that
 own their bvec
Message-ID: <20120524213158.GB22664@google.com>
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On Thu, May 24, 2012 at 07:57:34PM +0300, Boaz Harrosh wrote:
> How do you insure that the original bio which owns the
> bvec is not freed before the split-out bio.
> 
> Perhaps calling code needs to make sure by taking an extra
> ref on the original bio, or something. If so a big fat comment
> at bio_split is do.

Yeah, just added that.

> 
> And I understand you did not like my suggestion of negating
> the meaning of the flag, so the default is zero?
> Please say why?

I liked it at first, but I think I prefer having the flag be set
if bio_free() must take some action; i.e. you set the flag when you
allocate bi_io_vec. Also, I think bio_alloc_bioset() getting
reimplemented is less likely than people open coding bio splitting or
something that shares bi_io_vec in the future, so it's slightlry less
likely to be used wrong this way.
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