block: move the bi_size update out of __bio_try_merge_page

The update of bi_size is the only thing in __bio_try_merge_page that
needs a bio.  Move it to the callers, and merge __bio_try_merge_page
and page_is_mergeable into a single bvec_try_merge_page that only takes
the current bvec instead of a full bio.  This will allow reusing this
function for supporting multi-page integrity payload bvecs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jinyoung Choi <j-young.choi@samsung.com>
Link: https://lore.kernel.org/r/20230724165433.117645-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bio.c

@@ -903,9 +903,8 @@ static inline bool bio_full(struct bio *bio, unsigned len)
 	return false;
 }
 
-static inline bool page_is_mergeable(const struct bio_vec *bv,
-		struct page *page, unsigned int len, unsigned int off,
-		bool *same_page)
+static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
+		unsigned int len, unsigned int off, bool *same_page)
 {
 	size_t bv_end = bv->bv_offset + bv->bv_len;
 	phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) + bv_end - 1;
@@ -919,38 +918,14 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
 		return false;
 
 	*same_page = ((vec_end_addr & PAGE_MASK) == page_addr);
-	if (*same_page)
-		return true;
-	else if (IS_ENABLED(CONFIG_KMSAN))
-		return false;
-	return (bv->bv_page + bv_end / PAGE_SIZE) == (page + off / PAGE_SIZE);
-}
-
-/**
- * __bio_try_merge_page - try appending data to an existing bvec.
- * @bio: destination bio
- * @page: start page to add
- * @len: length of the data to add
- * @off: offset of the data relative to @page
- * @same_page: return if the segment has been merged inside the same page
- *
- * Try to add the data at @page + @off to the last bvec of @bio.  This is 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.
- */
-static bool __bio_try_merge_page(struct bio *bio, struct page *page,
-		unsigned int len, unsigned int off, bool *same_page)
-{
-	struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
+	if (!*same_page) {
+		if (IS_ENABLED(CONFIG_KMSAN))
+			return false;
+		if (bv->bv_page + bv_end / PAGE_SIZE != page + off / PAGE_SIZE)
+			return false;
+	}
 
-	if (!page_is_mergeable(bv, page, len, off, same_page))
-		return false;
 	bv->bv_len += len;
-	bio->bi_iter.bi_size += len;
 	return true;
 }
 
@@ -972,7 +947,7 @@ static bool bio_try_merge_hw_seg(struct request_queue *q, struct bio *bio,
 		return false;
 	if (bv->bv_len + len > queue_max_segment_size(q))
 		return false;
-	return __bio_try_merge_page(bio, page, len, offset, same_page);
+	return bvec_try_merge_page(bv, page, len, offset, same_page);
 }
 
 /**
@@ -1001,8 +976,11 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 		return 0;
 
 	if (bio->bi_vcnt > 0) {
-		if (bio_try_merge_hw_seg(q, bio, page, len, offset, same_page))
+		if (bio_try_merge_hw_seg(q, bio, page, len, offset,
+				same_page)) {
+			bio->bi_iter.bi_size += len;
 			return len;
+		}
 
 		if (bio->bi_vcnt >=
 		    min(bio->bi_max_vecs, queue_max_segments(q)))
@@ -1123,8 +1101,11 @@ int bio_add_page(struct bio *bio, struct page *page,
 		return 0;
 
 	if (bio->bi_vcnt > 0 &&
-	    __bio_try_merge_page(bio, page, len, offset, &same_page))
+	    bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
+				page, len, offset, &same_page)) {
+		bio->bi_iter.bi_size += len;
 		return len;
+	}
 
 	if (bio->bi_vcnt >= bio->bi_max_vecs)
 		return 0;
@@ -1206,7 +1187,9 @@ static int bio_iov_add_page(struct bio *bio, struct page *page,
 		return -EIO;
 
 	if (bio->bi_vcnt > 0 &&
-	    __bio_try_merge_page(bio, page, len, offset, &same_page)) {
+	    bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
+				page, len, offset, &same_page)) {
+		bio->bi_iter.bi_size += len;
 		if (same_page)
 			bio_release_page(bio, page);
 		return 0;