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@xxxxxxxxx>
---
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
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