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 , Kent Overstreet , Shaohua Li , Mike Christie , Hannes Reinecke , Guoqing Jiang , Jiri Kosina , Zheng Liu , Eric Wheeler , Yijing Wang , Coly Li , 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 21/60] bcache: comment on direct access to bvec table Date: Sat, 29 Oct 2016 16:08:20 +0800 Message-Id: <1477728600-12938-22-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: 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 81d3db40cd7b..b419bc91ba32 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 d8a6d807b498..52876fcf2b36 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -207,6 +207,7 @@ 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; @@ -1153,6 +1154,8 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page, dc->bdev->bd_holder = dc; bio_init_with_vec_table(&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); @@ -1794,6 +1797,7 @@ 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); @@ -1850,6 +1854,8 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page, ca->bdev->bd_holder = ca; bio_init_with_vec_table(&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