Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755397AbcL0QAo (ORCPT ); Tue, 27 Dec 2016 11:00:44 -0500 Received: from mail-pg0-f66.google.com ([74.125.83.66]:33216 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752551AbcL0P7v (ORCPT ); Tue, 27 Dec 2016 10:59:51 -0500 From: Ming Lei To: Jens Axboe , linux-kernel@vger.kernel.org Cc: linux-block@vger.kernel.org, Christoph Hellwig , Ming Lei , Kent Overstreet , Shaohua Li , Guoqing Jiang , Zheng Liu , Mike Christie , Jiri Kosina , Eric Wheeler , Yijing Wang , Al Viro , linux-bcache@vger.kernel.org (open list:BCACHE (BLOCK LAYER CACHE)), linux-raid@vger.kernel.org (open list:SOFTWARE RAID (Multiple Disks) SUPPORT) Subject: [PATCH v1 07/54] bcache: comment on direct access to bvec table Date: Tue, 27 Dec 2016 23:55:56 +0800 Message-Id: <1482854250-13481-8-git-send-email-tom.leiming@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1482854250-13481-1-git-send-email-tom.leiming@gmail.com> References: <1482854250-13481-1-git-send-email-tom.leiming@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2647 Lines: 79 Looks all are safe after multipage bvec is supported. Signed-off-by: Ming Lei --- drivers/md/bcache/btree.c | 1 + drivers/md/bcache/super.c | 6 ++++++ drivers/md/bcache/util.c | 7 +++++++ 3 files changed, 14 insertions(+) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index a43eedd5804d..fc35cfb4d0f1 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -428,6 +428,7 @@ static void do_btree_node_write(struct btree *b) continue_at(cl, btree_node_write_done, NULL); } else { + /* No harm for multipage bvec since the new is just allocated */ b->bio->bi_vcnt = 0; bch_bio_map(b->bio, i); diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 3a19cbc8b230..607b022259dc 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -208,6 +208,7 @@ static void write_bdev_super_endio(struct bio *bio) static void __write_super(struct cache_sb *sb, struct bio *bio) { + /* single page bio, safe for multipage bvec */ struct cache_sb *out = page_address(bio->bi_io_vec[0].bv_page); unsigned i; @@ -1156,6 +1157,8 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page, dc->bdev->bd_holder = dc; bio_init(&dc->sb_bio, dc->sb_bio.bi_inline_vecs, 1); + + /* single page bio, safe for multipage bvec */ dc->sb_bio.bi_io_vec[0].bv_page = sb_page; get_page(sb_page); @@ -1799,6 +1802,7 @@ void bch_cache_release(struct kobject *kobj) for (i = 0; i < RESERVE_NR; i++) free_fifo(&ca->free[i]); + /* single page bio, safe for multipage bvec */ if (ca->sb_bio.bi_inline_vecs[0].bv_page) put_page(ca->sb_bio.bi_io_vec[0].bv_page); @@ -1854,6 +1858,8 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page, ca->bdev->bd_holder = ca; bio_init(&ca->sb_bio, ca->sb_bio.bi_inline_vecs, 1); + + /* single page bio, safe for multipage bvec */ ca->sb_bio.bi_io_vec[0].bv_page = sb_page; get_page(sb_page); diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c index dde6172f3f10..5cc0b49a65fb 100644 --- a/drivers/md/bcache/util.c +++ b/drivers/md/bcache/util.c @@ -222,6 +222,13 @@ 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; -- 2.7.4