[PATCH v9 72/96] block: Add bio_for_each_folio_all

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

Allow callers to iterate over each folio instead of each page.  The
bio need not have been constructed using folios originally.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/bio.h | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index f41f20ebc2c6..8af03cfcfbb6 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -194,7 +194,7 @@ static inline void bio_advance_iter_single(const struct bio *bio,
  */
 #define bio_for_each_bvec_all(bvl, bio, i)		\
 	for (i = 0, bvl = bio_first_bvec_all(bio);	\
-	     i < (bio)->bi_vcnt; i++, bvl++)		\
+	     i < (bio)->bi_vcnt; i++, bvl++)
 
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
@@ -320,6 +320,47 @@ static inline struct bio_vec *bio_last_bvec_all(struct bio *bio)
 	return &bio->bi_io_vec[bio->bi_vcnt - 1];
 }
 
+struct folio_iter {
+	struct folio *folio;
+	size_t offset;
+	size_t length;
+	size_t _seg_count;
+	int _i;
+};
+
+static inline
+void bio_first_folio(struct folio_iter *fi, struct bio *bio, int i)
+{
+	struct bio_vec *bvec = bio_first_bvec_all(bio) + i;
+
+	fi->folio = page_folio(bvec->bv_page);
+	fi->offset = bvec->bv_offset +
+			PAGE_SIZE * (bvec->bv_page - &fi->folio->page);
+	fi->_seg_count = bvec->bv_len;
+	fi->length = min(folio_size(fi->folio) - fi->offset, fi->_seg_count);
+	fi->_i = i;
+}
+
+static inline void bio_next_folio(struct folio_iter *fi, struct bio *bio)
+{
+	fi->_seg_count -= fi->length;
+	if (fi->_seg_count) {
+		fi->folio = folio_next(fi->folio);
+		fi->offset = 0;
+		fi->length = min(folio_size(fi->folio), fi->_seg_count);
+	} else if (fi->_i + 1 < bio->bi_vcnt) {
+		bio_first_folio(fi, bio, fi->_i + 1);
+	} else {
+		fi->folio = NULL;
+	}
+}
+
+/*
+ * Iterate over each folio in a bio.
+ */
+#define bio_for_each_folio_all(fi, bio)				\
+	for (bio_first_folio(&fi, bio, 0); fi.folio; bio_next_folio(&fi, bio))
+
 enum bip_flags {
 	BIP_BLOCK_INTEGRITY	= 1 << 0, /* block layer owns integrity data */
 	BIP_MAPPED_INTEGRITY	= 1 << 1, /* ref tag has been remapped */
-- 
2.30.2