block: rename __bio_add_pc_page to bio_add_hw_page

Rename __bio_add_pc_page() to bio_add_hw_page() and explicitly pass in a
max_sectors argument.

This max_sectors argument can be used to specify constraints from the
hardware.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[ jth: rebased and made public for blk-map.c ]
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 40 insertions, 25 deletions

diff --git a/block/bio.c b/block/bio.c
index 21cbaa6a1c20..aad0a6dad4f9 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -748,9 +748,14 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
 	return true;
 }
 
-static bool bio_try_merge_pc_page(struct request_queue *q, struct bio *bio,
-		struct page *page, unsigned len, unsigned offset,
-		bool *same_page)
+/*
+ * Try to merge a page into a segment, while obeying the hardware segment
+ * size limit.  This is not for normal read/write bios, but for passthrough
+ * or Zone Append operations that we can't split.
+ */
+static bool bio_try_merge_hw_seg(struct request_queue *q, struct bio *bio,
+				 struct page *page, unsigned len,
+				 unsigned offset, bool *same_page)
 {
 	struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
 	unsigned long mask = queue_segment_boundary(q);
@@ -765,38 +770,32 @@ static bool bio_try_merge_pc_page(struct request_queue *q, struct bio *bio,
 }
 
 /**
- *	__bio_add_pc_page	- attempt to add page to passthrough bio
- *	@q: the target queue
- *	@bio: destination bio
- *	@page: page to add
- *	@len: vec entry length
- *	@offset: vec entry offset
- *	@same_page: return if the merge happen inside the same page
- *
- *	Attempt to add a page to the bio_vec maplist. This can fail for a
- *	number of reasons, such as the bio being full or target block device
- *	limitations. The target block device must allow bio's up to PAGE_SIZE,
- *	so it is always possible to add a single page to an empty bio.
+ * bio_add_hw_page - attempt to add a page to a bio with hw constraints
+ * @q: the target queue
+ * @bio: destination bio
+ * @page: page to add
+ * @len: vec entry length
+ * @offset: vec entry offset
+ * @max_sectors: maximum number of sectors that can be added
+ * @same_page: return if the segment has been merged inside the same page
  *
- *	This should only be used by passthrough bios.
+ * Add a page to a bio while respecting the hardware max_sectors, max_segment
+ * and gap limitations.
  */
-int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
+int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset,
-		bool *same_page)
+		unsigned int max_sectors, bool *same_page)
 {
 	struct bio_vec *bvec;
 
-	/*
-	 * cloned bio must not modify vec list
-	 */
-	if (unlikely(bio_flagged(bio, BIO_CLONED)))
+	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 		return 0;
 
-	if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
+	if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
 		return 0;
 
 	if (bio->bi_vcnt > 0) {
-		if (bio_try_merge_pc_page(q, bio, page, len, offset, same_page))
+		if (bio_try_merge_hw_seg(q, bio, page, len, offset, same_page))
 			return len;
 
 		/*
@@ -823,11 +822,27 @@ int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 	return len;
 }
 
+/**
+ * bio_add_pc_page	- attempt to add page to passthrough bio
+ * @q: the target queue
+ * @bio: destination bio
+ * @page: page to add
+ * @len: vec entry length
+ * @offset: vec entry offset
+ *
+ * Attempt to add a page to the bio_vec maplist. This can fail for a
+ * number of reasons, such as the bio being full or target block device
+ * limitations. The target block device must allow bio's up to PAGE_SIZE,
+ * so it is always possible to add a single page to an empty bio.
+ *
+ * This should only be used by passthrough bios.
+ */
 int bio_add_pc_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset)
 {
 	bool same_page = false;
-	return __bio_add_pc_page(q, bio, page, len, offset, &same_page);
+	return bio_add_hw_page(q, bio, page, len, offset,
+			queue_max_hw_sectors(q), &same_page);
 }
 EXPORT_SYMBOL(bio_add_pc_page);