From: Ming Lei <ming.lei@redhat.com>
To: Coly Li <colyli@suse.de>
Cc: Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@infradead.org>,
Kent Overstreet <kent.overstreet@gmail.com>,
David Sterba <dsterba@suse.cz>, Huang Ying <ying.huang@intel.com>,
Mike Snitzer <snitzer@redhat.com>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Theodore Ts'o <tytso@mit.edu>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Filipe Manana <fdmanana@gmail.com>,
Randy Dunlap <rdunlap@infradead.org>,
linux-bcache@vger.kernel.org
Subject: Re: [PATCH V7 20/24] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()
Date: Thu, 28 Jun 2018 09:28:18 +0800 [thread overview]
Message-ID: <20180628012816.GH7583@ming.t460p> (raw)
In-Reply-To: <e1499d87-62b8-40a8-75a5-d9d1d81ce9c5@suse.de>
On Wed, Jun 27, 2018 at 11:55:33PM +0800, Coly Li wrote:
> On 2018/6/27 8:45 PM, Ming Lei wrote:
> > bch_bio_alloc_pages() is always called on one new bio, so it is safe
> > to access the bvec table directly. Given it is the only kind of this
> > case, open code the bvec table access since bio_for_each_segment_all()
> > will be changed to support for iterating over multipage bvec.
> >
> > Cc: Coly Li <colyli@suse.de>
> > Cc: linux-bcache@vger.kernel.org
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > drivers/md/bcache/util.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> > index fc479b026d6d..9f2a6fd5dfc9 100644
> > --- a/drivers/md/bcache/util.c
> > +++ b/drivers/md/bcache/util.c
> > @@ -268,7 +268,7 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
> > int i;
> > struct bio_vec *bv;
> >
>
> Hi Ming,
>
> > - bio_for_each_segment_all(bv, bio, i) {
> > + for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++) {
>
>
> Is it possible to treat this as a special condition of
> bio_for_each_segement_all() ? I mean only iterate one time in
> bvec_for_each_segment(). I hope the above change is not our last choice
> before I reply an Acked-by :-)
Now the bvec from bio_for_each_segement_all() can't be changed any more
since the referenced 'bvec' is generated in-flight given we store
real multipage bvec.
BTW, this way is actually suggested by Christoph for saving one new
helper of bio_for_each_bvec_all() as done in V6, and per previous discussion,
seems both Kent and Christoph agrees to convert bcache into bio_add_page()
finally.
So I guess this open code style should be fine.
Thanks,
Ming
next prev parent reply other threads:[~2018-06-28 1:28 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-27 12:45 [PATCH V7 00/24] block: support multipage bvec Ming Lei
2018-06-27 12:45 ` [PATCH V7 01/24] dm: use bio_split() when splitting out the already processed bio Ming Lei
2018-06-27 13:17 ` Mike Snitzer
2018-06-27 12:45 ` [PATCH V7 02/24] bcache: don't clone bio in bch_data_verify Ming Lei
2018-06-27 12:45 ` [PATCH V7 03/24] exofs: use bio_clone_fast in _write_mirror Ming Lei
2018-06-27 12:45 ` [PATCH V7 04/24] block: remove bio_clone_kmalloc Ming Lei
2018-06-27 12:45 ` [PATCH V7 05/24] md: remove a bogus comment Ming Lei
2018-06-27 12:45 ` [PATCH V7 06/24] block: unexport bio_clone_bioset Ming Lei
2018-06-27 12:45 ` [PATCH V7 07/24] block: simplify bio_check_pages_dirty Ming Lei
2018-06-27 12:45 ` [PATCH V7 08/24] block: bio_set_pages_dirty can't see NULL bv_page in a valid bio_vec Ming Lei
2018-06-27 12:45 ` [PATCH V7 09/24] block: use bio_add_page in bio_iov_iter_get_pages Ming Lei
2018-06-27 12:45 ` [PATCH V7 10/24] block: introduce multipage page bvec helpers Ming Lei
2018-06-27 15:59 ` kbuild test robot
2018-11-09 11:15 ` Ming Lei
2018-06-27 12:45 ` [PATCH V7 11/24] block: introduce bio_for_each_bvec() Ming Lei
2018-06-27 12:45 ` [PATCH V7 12/24] block: use bio_for_each_bvec() to compute multipage bvec count Ming Lei
2018-06-27 12:45 ` [PATCH V7 13/24] block: use bio_for_each_bvec() to map sg Ming Lei
2018-06-27 12:45 ` [PATCH V7 14/24] block: introduce bvec_last_segment() Ming Lei
2018-06-27 12:45 ` [PATCH V7 15/24] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-06-27 12:45 ` [PATCH V7 16/24] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2018-06-27 12:45 ` [PATCH V7 17/24] btrfs: move bio_pages_all() to btrfs Ming Lei
2018-06-27 12:45 ` [PATCH V7 18/24] block: introduce bio_bvecs() Ming Lei
2018-06-27 12:45 ` [PATCH V7 19/24] block: loop: pass multipage bvec to iov_iter Ming Lei
2018-06-27 12:45 ` [PATCH V7 20/24] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2018-06-27 15:55 ` Coly Li
2018-06-28 1:28 ` Ming Lei [this message]
2018-06-28 2:01 ` Coly Li
2018-06-27 12:45 ` [PATCH V7 21/24] block: allow bio_for_each_segment_all() to iterate over multipage bvec Ming Lei
2018-06-27 12:45 ` [PATCH V7 22/24] block: enable multipage bvecs Ming Lei
2018-06-27 12:45 ` [PATCH V7 23/24] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-06-27 12:45 ` [PATCH V7 24/24] block: document usage of bio iterator helpers Ming Lei
2018-06-27 18:13 ` Randy Dunlap
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180628012816.GH7583@ming.t460p \
--to=ming.lei@redhat.com \
--cc=axboe@fb.com \
--cc=colyli@suse.de \
--cc=darrick.wong@oracle.com \
--cc=dsterba@suse.cz \
--cc=fdmanana@gmail.com \
--cc=hch@infradead.org \
--cc=kent.overstreet@gmail.com \
--cc=linux-bcache@vger.kernel.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=rdunlap@infradead.org \
--cc=snitzer@redhat.com \
--cc=tytso@mit.edu \
--cc=ying.huang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).