[PATCH 03/11] block: introduce bio_add_append_page

[Johannes Thumshirn <johannes.thumshirn@xxxxxxx>]

For REQ_OP_ZONE_APPEND we cannot add unlimited amounts of pages to a bio,
as the bio cannot be split later on.

This is similar to what we have to do for passthrough pages as well, just
with a different limit.

Introduce bio_add_append_page() which can used by file-systems add pages for
a REQ_OP_ZONE_APPEND bio.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
---
 block/bio.c         | 37 ++++++++++++++++++++++++++++++-------
 block/blk-map.c     |  2 +-
 include/linux/bio.h |  2 +-
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 5bff80fc2ad9..3bd648671a28 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -732,7 +732,7 @@ static bool bio_try_merge_pc_page(struct request_queue *q, struct bio *bio,
  */
 static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset,
-		bool *same_page)
+		bool *same_page, unsigned int max_sectors)
 {
 	struct bio_vec *bvec;
 
@@ -742,7 +742,7 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 	if (unlikely(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) {
@@ -777,10 +777,20 @@ 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_pc_page(q, bio, page, len, offset, &same_page,
+				 queue_max_hw_sectors(q));
 }
 EXPORT_SYMBOL(bio_add_pc_page);
 
+int bio_add_append_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,
+				 queue_max_zone_append_sectors(q));
+}
+EXPORT_SYMBOL(bio_add_append_page);
+
 /**
  * __bio_try_merge_page - try appending data to an existing bvec.
  * @bio: destination bio
@@ -945,8 +955,15 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 
 		len = min_t(size_t, PAGE_SIZE - offset, left);
 
-		if (__bio_try_merge_page(bio, page, len, offset, &same_page)) {
-			if (same_page)
+		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
+			size = bio_add_append_page(bio->bi_disk->queue, bio,
+						   page, len, offset);
+
+			if (size != len)
+				return -E2BIG;
+		} else if (__bio_try_merge_page(bio, page, len, offset,
+						&same_page)) {
+				if (same_page)
 				put_page(page);
 		} else {
 			if (WARN_ON_ONCE(bio_full(bio, len)))
@@ -1389,11 +1406,12 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
  */
 struct bio *bio_map_user_iov(struct request_queue *q,
 			     struct iov_iter *iter,
-			     gfp_t gfp_mask)
+			     gfp_t gfp_mask, unsigned int op)
 {
 	int j;
 	struct bio *bio;
 	int ret;
+	unsigned int max_sectors;
 
 	if (!iov_iter_count(iter))
 		return ERR_PTR(-EINVAL);
@@ -1402,6 +1420,11 @@ struct bio *bio_map_user_iov(struct request_queue *q,
 	if (!bio)
 		return ERR_PTR(-ENOMEM);
 
+	if (op == REQ_OP_ZONE_APPEND)
+		max_sectors = queue_max_zone_append_sectors(q);
+	else
+		max_sectors = queue_max_hw_sectors(q);
+
 	while (iov_iter_count(iter)) {
 		struct page **pages;
 		ssize_t bytes;
@@ -1429,7 +1452,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
 					n = bytes;
 
 				if (!__bio_add_pc_page(q, bio, page, n, offs,
-						&same_page)) {
+						&same_page, max_sectors)) {
 					if (same_page)
 						put_page(page);
 					break;
diff --git a/block/blk-map.c b/block/blk-map.c
index b0790268ed9d..a83ba39251a9 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -72,7 +72,7 @@ static int __blk_rq_map_user_iov(struct request *rq,
 	if (copy)
 		bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
 	else
-		bio = bio_map_user_iov(q, iter, gfp_mask);
+		bio = bio_map_user_iov(q, iter, gfp_mask, req_op(rq));
 
 	if (IS_ERR(bio))
 		return PTR_ERR(bio);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index ef640fd76c23..ef69e52cc8d9 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -444,7 +444,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
 void bio_release_pages(struct bio *bio, bool mark_dirty);
 struct rq_map_data;
 extern struct bio *bio_map_user_iov(struct request_queue *,
-				    struct iov_iter *, gfp_t);
+				    struct iov_iter *, gfp_t, unsigned int);
 extern void bio_unmap_user(struct bio *);
 extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
 				gfp_t);
-- 
2.24.1