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authorMing Lei <ming.lei@redhat.com>2019-04-23 02:51:04 (GMT)
committerJens Axboe <axboe@kernel.dk>2019-04-23 13:57:07 (GMT)
commit551879a48f01826fd86568d7bd1e774cb0de3295 (patch)
tree5278aedd731a02b77f5dbc3fc23553e34f8728a0 /block
parent6c88d73515c444323c57fba9069456b819700e79 (diff)
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block: clarify that bio_add_page() and related helpers can add multi pages
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@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/bio.c26
1 files changed, 15 insertions, 11 deletions
diff --git a/block/bio.c b/block/bio.c
index 5959141..c81ed2d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -667,6 +667,8 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
return false;
}
+ WARN_ON_ONCE(same_page && (len + off) > PAGE_SIZE);
+
return true;
}
@@ -786,9 +788,9 @@ 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.
*
@@ -796,6 +798,8 @@ 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,
@@ -818,11 +822,11 @@ 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.
@@ -845,13 +849,13 @@ 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,