linux-ext4 - Re: [PATCH V14 00/18] block: support multi-page bvec

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Date:   Tue, 22 Jan 2019 10:01:30 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Theodore Ts'o <tytso@....edu>, Omar Sandoval <osandov@...com>,
        Dave Chinner <dchinner@...hat.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-raid@...r.kernel.org,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Gao Xiang <gaoxiang25@...wei.com>,
        Christoph Hellwig <hch@....de>, linux-ext4@...r.kernel.org,
        Coly Li <colyli@...e.de>, linux-bcache@...r.kernel.org,
        Boaz Harrosh <ooo@...ctrozaur.com>,
        Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com
Subject: Re: [PATCH V14 00/18] block: support multi-page bvec

On Mon, Jan 21, 2019 at 01:43:21AM -0800, Sagi Grimberg wrote:
> 
> > V14:
> > 	- drop patch(patch 4 in V13) for renaming bvec helpers, as suggested by Jens
> > 	- use mp_bvec_* as multi-page bvec helper name
> > 	- fix one build issue, which is caused by missing one converion of
> > 	bio_for_each_segment_all in fs/gfs2
> > 	- fix one 32bit ARCH specific issue caused by segment boundary mask
> > 	overflow
> 
> Hey Ming,
> 
> So is nvme-tcp also affected here? The only point where I see nvme-tcp
> can be affected is when initializing a bvec iter using bio_segments() as
> everywhere else we use iters which should transparently work..
> 
> I see that loop was converted, does it mean that nvme-tcp needs to
> call something like?
> --
> 	bio_for_each_mp_bvec(bv, bio, iter)
> 		nr_bvecs++;

bio_for_each_segment()/bio_segments() still works, just not as efficient
as bio_for_each_mp_bvec() given each multi-page bvec(very similar with scatterlist)
is returned in each loop.

I don't look at nvme-tcp code yet. But if nvme-tcp supports this way,
it can benefit from bio_for_each_mp_bvec().

Thanks,
Ming