Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933356AbdLRMYp (ORCPT ); Mon, 18 Dec 2017 07:24:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35124 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932873AbdLRMYl (ORCPT ); Mon, 18 Dec 2017 07:24:41 -0500 From: Ming Lei To: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet Cc: Huang Ying , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, "Theodore Ts'o" , "Darrick J . Wong" , Coly Li , Filipe Manana , Ming Lei , linux-bcache@vger.kernel.org Subject: [PATCH V4 07/45] bcache: comment on direct access to bvec table Date: Mon, 18 Dec 2017 20:22:09 +0800 Message-Id: <20171218122247.3488-8-ming.lei@redhat.com> In-Reply-To: <20171218122247.3488-1-ming.lei@redhat.com> References: <20171218122247.3488-1-ming.lei@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 18 Dec 2017 12:24:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1397 Lines: 42 All direct access to bvec table are safe even after multipage bvec is supported. Cc: linux-bcache@vger.kernel.org Acked-by: Coly Li Signed-off-by: Ming Lei --- drivers/md/bcache/btree.c | 1 + drivers/md/bcache/util.c | 7 +++++++ 2 files changed, 8 insertions(+) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 81e8dc3dbe5e..02a4cf646fdc 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -432,6 +432,7 @@ static void do_btree_node_write(struct btree *b) continue_at(cl, btree_node_write_done, NULL); } else { + /* No problem for multipage bvec since the bio is just allocated */ b->bio->bi_vcnt = 0; bch_bio_map(b->bio, i); diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c index e548b8b51322..61813d230015 100644 --- a/drivers/md/bcache/util.c +++ b/drivers/md/bcache/util.c @@ -249,6 +249,13 @@ uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done) : 0; } +/* + * Generally it isn't good to access .bi_io_vec and .bi_vcnt directly, + * the preferred way is bio_add_page, but in this case, bch_bio_map() + * supposes that the bvec table is empty, so it is safe to access + * .bi_vcnt & .bi_io_vec in this way even after multipage bvec is + * supported. + */ void bch_bio_map(struct bio *bio, void *base) { size_t size = bio->bi_iter.bi_size; -- 2.9.5