From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Ming Lei To: Jens Axboe , linux-kernel@vger.kernel.org Cc: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig , "Kirill A . Shutemov" , Ming Lei , Jens Axboe , Kent Overstreet , Shaohua Li , Mike Christie , Guoqing Jiang , Hannes Reinecke , 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 22/60] block: comment on bio_alloc_pages() Date: Sat, 29 Oct 2016 16:08:21 +0800 Message-Id: <1477728600-12938-23-git-send-email-tom.leiming@gmail.com> In-Reply-To: <1477728600-12938-1-git-send-email-tom.leiming@gmail.com> References: <1477728600-12938-1-git-send-email-tom.leiming@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: This patch adds comment on usage of bio_alloc_pages(), also comments on one special case of bch_data_verify(). Signed-off-by: Ming Lei --- block/bio.c | 4 +++- drivers/md/bcache/debug.c | 6 ++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/block/bio.c b/block/bio.c index db85c5753a76..a49d1d89a85c 100644 --- a/block/bio.c +++ b/block/bio.c @@ -907,7 +907,9 @@ EXPORT_SYMBOL(bio_advance); * @bio: bio to allocate pages for * @gfp_mask: flags for allocation * - * Allocates pages up to @bio->bi_vcnt. + * Allocates pages up to @bio->bi_vcnt, and this function should only + * be called on a new initialized bio, which means no page isn't added + * to the bio via bio_add_page() yet. * * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are * freed. diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c index 430f3050663c..71a9f05918eb 100644 --- a/drivers/md/bcache/debug.c +++ b/drivers/md/bcache/debug.c @@ -110,6 +110,12 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio) struct bio_vec bv, cbv; struct bvec_iter iter, citer = { 0 }; + /* + * Once multipage bvec is supported, the bio_clone() + * has to make sure page count in this bio can be held + * in the new cloned bio because each single page need + * to assign to each bvec of the new bio. + */ check = bio_clone(bio, GFP_NOIO); if (!check) return; -- 2.7.4