[PATCH v4 5/6] block: enable zone-append for iov_iter of bvec type

[Kanchan Joshi <joshi.k@xxxxxxxxxxx>]

zone-append with bvec iov_iter gives WARN_ON, and returns -EINVAL.
Add new helper to process such iov_iter and add pages in bio honoring
zone-append specific constraints.
This is used to enable zone-append with io-uring fixed-buffer.

Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
Signed-off-by: Selvakumar S <selvakuma.s1@xxxxxxxxxxx>
Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
Signed-off-by: Javier Gonzalez <javier.gonz@xxxxxxxxxxx>
---
 block/bio.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 0cecdbc..ade9da7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -975,6 +975,30 @@ static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter)
 	iov_iter_advance(iter, size);
 	return 0;
 }
+static int __bio_iov_bvec_append_add_pages(struct bio *bio, struct iov_iter *iter)
+{
+	const struct bio_vec *bv = iter->bvec;
+	unsigned int len;
+	size_t size;
+	struct request_queue *q = bio->bi_disk->queue;
+	unsigned int max_append_sectors = queue_max_zone_append_sectors(q);
+	bool same_page = false;
+
+	if (WARN_ON_ONCE(!max_append_sectors))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(iter->iov_offset > bv->bv_len))
+		return -EINVAL;
+
+	len = min_t(size_t, bv->bv_len - iter->iov_offset, iter->count);
+	size = bio_add_hw_page(q, bio, bv->bv_page, len,
+				bv->bv_offset + iter->iov_offset,
+				max_append_sectors, &same_page);
+	if (unlikely(size != len))
+		return -EINVAL;
+	iov_iter_advance(iter, size);
+	return 0;
+}
 
 #define PAGE_PTRS_PER_BVEC     (sizeof(struct bio_vec) / sizeof(struct page *))
 
@@ -1105,9 +1129,10 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 
 	do {
 		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
-			if (WARN_ON_ONCE(is_bvec))
-				return -EINVAL;
-			ret = __bio_iov_append_get_pages(bio, iter);
+			if (is_bvec)
+				ret = __bio_iov_bvec_append_add_pages(bio, iter);
+			else
+				ret = __bio_iov_append_get_pages(bio, iter);
 		} else {
 			if (is_bvec)
 				ret = __bio_iov_bvec_add_pages(bio, iter);
-- 
2.7.4