linux-kernel - Re: [PATCH 09/60] dm: dm.c: replace 'bio->bi_vcnt == 1' with !bio_multiple

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Date:   Tue, 1 Nov 2016 19:09:06 -0800
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Ming Lei <tom.leiming@...il.com>, Jens Axboe <axboe@...com>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        "maintainer:DEVICE-MAPPER (LVM)" <dm-devel@...hat.com>,
        Shaohua Li <shli@...nel.org>,
        "open list:SOFTWARE RAID (Multiple Disks) SUPPORT" 
        <linux-raid@...r.kernel.org>
Subject: Re: [PATCH 09/60] dm: dm.c: replace 'bio->bi_vcnt == 1' with
 !bio_multiple_segments

On Mon, Oct 31, 2016 at 08:29:01AM -0700, Christoph Hellwig wrote:
> On Sat, Oct 29, 2016 at 04:08:08PM +0800, Ming Lei wrote:
> > Avoid to access .bi_vcnt directly, because it may be not what
> > the driver expected any more after supporting multipage bvec.
> > 
> > Signed-off-by: Ming Lei <tom.leiming@...il.com>
> 
> It would be really nice to have a comment in the code why it's
> even checking for multiple segments.

Or ideally refactor the code to not care about multiple segments at all.