Messages in this thread Patch in this message |  | | From | Ming Lei <> | Subject | [PATCH v1 07/54] bcache: comment on direct access to bvec table | Date | Tue, 27 Dec 2016 23:55:56 +0800 |
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Looks all are safe after multipage bvec is supported.
Signed-off-by: Ming Lei <tom.leiming@gmail.com> --- 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
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