[PATCH 22/60] block: comment on bio_alloc_pages()
From: Ming Lei <tom.leiming@gmail.com>
Date: 2016-10-29 08:08:21
Also in:
linux-bcache, linux-block, linux-fsdevel, lkml
Subsystem:
bcache (block layer cache), block layer, the rest · Maintainers:
Coly Li, Kent Overstreet, Jens Axboe, Linus Torvalds
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 <tom.leiming@gmail.com> --- 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