bio_add_page() and __bio_add_page() are capable of adding pages into
bio, and now we have at least two such usages alreay:
- __bio_iov_bvec_add_pages()
- nvmet_bdev_execute_rw().
So update comments on these two helpers.
The thing is a bit special for __bio_try_merge_page(), given the caller
needs to know if the new added page is same with the last added page,
then it isn't safe to pass multi-page in case that 'same_page' is true,
so adds warning on potential misuse, and updates comment on
__bio_try_merge_page().
Cc: [email protected]
Cc: [email protected]
Cc: Christoph Hellwig <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
---
block/bio.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 8d516d508ae3..07315056c2f6 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -662,6 +662,8 @@ static inline bool page_is_mergeable(const struct bio_vec
*bv,
if (same_page && (vec_end_addr & PAGE_MASK) != page_addr)
return false;
+ WARN_ON_ONCE(same_page && (len + off) > PAGE_SIZE);
+
return true;
}
@@ -781,9 +783,9 @@ EXPORT_SYMBOL(bio_add_pc_page);
/**
* __bio_try_merge_page - try appending data to an existing bvec.
* @bio: destination bio
- * @page: page to add
+ * @page: start page to add
* @len: length of the data to add
- * @off: offset of the data in @page
+ * @off: offset of the data relative to @page
* @same_page: if %true only merge if the new data is in the same physical
* page as the last segment of the bio.
*
@@ -791,6 +793,8 @@ EXPORT_SYMBOL(bio_add_pc_page);
* a useful optimisation for file systems with a block size smaller than the
* page size.
*
+ * Warn if (@len, @off) crosses pages in case that @same_page is true.
+ *
* Return %true on success or %false on failure.
*/
bool __bio_try_merge_page(struct bio *bio, struct page *page,
@@ -813,11 +817,11 @@ bool __bio_try_merge_page(struct bio *bio, struct page
*page,
EXPORT_SYMBOL_GPL(__bio_try_merge_page);
/**
- * __bio_add_page - add page to a bio in a new segment
+ * __bio_add_page - add page(s) to a bio in a new segment
* @bio: destination bio
- * @page: page to add
- * @len: length of the data to add
- * @off: offset of the data in @page
+ * @page: start page to add
+ * @len: length of the data to add, may cross pages
+ * @off: offset of the data relative to @page, may cross pages
*
* Add the data at @page + @off to @bio as a new bvec. The caller must ensure
* that @bio has space for another bvec.
@@ -840,13 +844,13 @@ void __bio_add_page(struct bio *bio, struct page *page,
EXPORT_SYMBOL_GPL(__bio_add_page);
/**
- * bio_add_page - attempt to add page to bio
+ * bio_add_page - attempt to add page(s) to bio
* @bio: destination bio
- * @page: page to add
- * @len: vec entry length
- * @offset: vec entry offset
+ * @page: start page to add
+ * @len: vec entry length, may cross pages
+ * @offset: vec entry offset relative to @page, may cross pages
*
- * Attempt to add a page to the bio_vec maplist. This will only fail
+ * Attempt to add page(s) to the bio_vec maplist. This will only fail
* if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.
*/
int bio_add_page(struct bio *bio, struct page *page,
--
2.9.5
