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: linux-xfs@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/bio.c | 40 ++++++++++++++++++++++------------------
include/linux/bio.h | 4 ++--
2 files changed, 24 insertions(+), 20 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index b64cedc7f87c..0cfb2fd981c3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -750,9 +750,9 @@ EXPORT_SYMBOL(bio_add_pc_page);
/**
* __bio_try_merge_page - try appending data to an existing bvec.
* @bio: destination bio
- * @page: page to add
+ * @start_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 @start_page
* @same_page: if %true only merge if the new data is in the same physical
* page as the last segment of the bio.
*
@@ -760,9 +760,11 @@ EXPORT_SYMBOL(bio_add_pc_page);
* a useful optimisation for file systems with a block size smaller than the
* page size.
*
+ * Warn if @same_page is true and (@len, @off) crosses pages.
+ *
* Return %true on success or %false on failure.
*/
-bool __bio_try_merge_page(struct bio *bio, struct page *page,
+bool __bio_try_merge_page(struct bio *bio, struct page *start_page,
unsigned int len, unsigned int off, bool same_page)
{
if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
@@ -772,10 +774,12 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) +
bv->bv_offset + bv->bv_len - 1;
- phys_addr_t page_addr = page_to_phys(page);
+ phys_addr_t page_addr = page_to_phys(start_page);
if (vec_end_addr + 1 != page_addr + off)
return false;
+
+ WARN_ON_ONCE(same_page && (len + off) > PAGE_SIZE);
if (same_page && (vec_end_addr & PAGE_MASK) != page_addr)
return false;
@@ -788,16 +792,16 @@ 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
+ * @start_page: start page to add
+ * @len: length of the data to add, may cross pages
+ * @off: offset of the data relative to @start_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.
*/
-void __bio_add_page(struct bio *bio, struct page *page,
+void __bio_add_page(struct bio *bio, struct page *start_page,
unsigned int len, unsigned int off)
{
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt];
@@ -805,7 +809,7 @@ void __bio_add_page(struct bio *bio, struct page *page,
WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
WARN_ON_ONCE(bio_full(bio));
- bv->bv_page = page;
+ bv->bv_page = start_page;
bv->bv_offset = off;
bv->bv_len = len;
@@ -815,22 +819,22 @@ 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
+ * @start_page: start page to add
+ * @len: vec entry length, may cross pages
+ * @offset: vec entry offset relative to @start_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,
+int bio_add_page(struct bio *bio, struct page *start_page,
unsigned int len, unsigned int offset)
{
- if (!__bio_try_merge_page(bio, page, len, offset, false)) {
+ if (!__bio_try_merge_page(bio, start_page, len, offset, false)) {
if (bio_full(bio))
return 0;
- __bio_add_page(bio, page, len, offset);
+ __bio_add_page(bio, start_page, len, offset);
}
return len;
}
diff --git a/include/linux/bio.h b/include/linux/bio.h
index bb6090aa165d..40acfe5dc99f 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -432,9 +432,9 @@ void bio_chain(struct bio *, struct bio *);
extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
unsigned int, unsigned int);
-bool __bio_try_merge_page(struct bio *bio, struct page *page,
+bool __bio_try_merge_page(struct bio *bio, struct page *start_page,
unsigned int len, unsigned int off, bool same_page);
-void __bio_add_page(struct bio *bio, struct page *page,
+void __bio_add_page(struct bio *bio, struct page *start_page,
unsigned int len, unsigned int off);
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
struct rq_map_data;
--
2.9.5
