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From:   Ming Lei <ming.lei@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>,
        Omar Sandoval <osandov@fb.com>,
        Sagi Grimberg <sagi@grimberg.me>,
        Dave Chinner <dchinner@redhat.com>,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Mike Snitzer <snitzer@redhat.com>, dm-devel@redhat.com,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, Shaohua Li <shli@kernel.org>,
        linux-raid@vger.kernel.org, David Sterba <dsterba@suse.com>,
        linux-btrfs@vger.kernel.org,
        "Darrick J . Wong" <darrick.wong@oracle.com>,
        linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>,
        Christoph Hellwig <hch@lst.de>, linux-ext4@vger.kernel.org,
        Coly Li <colyli@suse.de>, linux-bcache@vger.kernel.org,
        Boaz Harrosh <ooo@electrozaur.com>,
        Bob Peterson <rpeterso@redhat.com>, cluster-devel@redhat.com,
        Ming Lei <ming.lei@redhat.com>
Subject: [PATCH V11 11/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()
Date:   Wed, 21 Nov 2018 11:23:19 +0800
Message-Id: <20181121032327.8434-12-ming.lei@redhat.com>
In-Reply-To: <20181121032327.8434-1-ming.lei@redhat.com>
References: <20181121032327.8434-1-ming.lei@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/md/bcache/util.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index 20eddeac1531..62fb917f7a4f 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c
@@ -270,7 +270,11 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
 	int i;
 	struct bio_vec *bv;
 
-	bio_for_each_segment_all(bv, bio, i) {
+	/*
+	 * This is called on freshly new bio, so it is safe to access the
+	 * bvec table directly.
+	 */
+	for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++, i++) {
 		bv->bv_page = alloc_page(gfp_mask);
 		if (!bv->bv_page) {
 			while (--bv >= bio->bi_io_vec)
-- 
2.9.5