block: ensure bio_iov_add_page can't fail

Adding the page could fail on the bio_full() condition, which checks for
either exceeding the bio's max segments or total size exceeding
UINT_MAX. We already ensure the max segments can't be exceeded, so just
ensure the total size won't reach the limit. This simplifies error
handling and removes unnecessary repeated bio_full() checks.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20220712153256.2202024-2-kbusch@fb.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bio.c

@@ -1165,8 +1165,6 @@ static int bio_iov_add_page(struct bio *bio, struct page *page,
 	bool same_page = false;
 
 	if (!__bio_try_merge_page(bio, page, len, offset, &same_page)) {
-		if (WARN_ON_ONCE(bio_full(bio, len)))
-			return -EINVAL;
 		__bio_add_page(bio, page, len, offset);
 		return 0;
 	}
@@ -1228,7 +1226,8 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	 * result to ensure the bio's total size is correct. The remainder of
 	 * the iov data will be picked up in the next bio iteration.
 	 */
-	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+	size = iov_iter_get_pages(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
+				  nr_pages, &offset);
 	if (size > 0)
 		size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
 	if (unlikely(size <= 0))
@@ -1238,16 +1237,16 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 		struct page *page = pages[i];
 
 		len = min_t(size_t, PAGE_SIZE - offset, left);
-		if (bio_op(bio) == REQ_OP_ZONE_APPEND)
+		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 			ret = bio_iov_add_zone_append_page(bio, page, len,
 					offset);
-		else
-			ret = bio_iov_add_page(bio, page, len, offset);
+			if (ret) {
+				bio_put_pages(pages + i, left, offset);
+				break;
+			}
+		} else
+			bio_iov_add_page(bio, page, len, offset);
 
-		if (ret) {
-			bio_put_pages(pages + i, left, offset);
-			break;
-		}
 		offset = 0;
 	}