block: Add bio_for_each_folio_all()

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@infradead.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/Documentation/core-api/kernel-api.rst b/Documentation/core-api/kernel-api.rst
index 2e718680514802ac4843303ec0be634f9a8970ce..7f0cb604b6ab3217319ea50a75e31db596eb454c 100644 (file)
--- a/Documentation/core-api/kernel-api.rst
+++ b/Documentation/core-api/kernel-api.rst
@@ -279,6 +279,7 @@ Accounting Framework
 Block Devices
 =============
 
+.. kernel-doc:: include/linux/bio.h
 .. kernel-doc:: block/blk-core.c
    :export:
 

diff --git a/include/linux/bio.h b/include/linux/bio.h
index a783cac49978e9944f4d235ee6e0d3dc274fd9ed..e3c9e8207f126d203a461adc634efd6722a37ed9 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -166,7 +166,7 @@ static inline void bio_advance(struct bio *bio, unsigned int nbytes)
  */
 #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)
 
@@ -260,6 +260,57 @@ static inline struct bio_vec *bio_last_bvec_all(struct bio *bio)
        return &bio->bi_io_vec[bio->bi_vcnt - 1];
 }
 
+/**
+ * struct folio_iter - State for iterating all folios in a bio.
+ * @folio: The current folio we're iterating.  NULL after the last folio.
+ * @offset: The byte offset within the current folio.
+ * @length: The number of bytes in this iteration (will not cross folio
+ *     boundary).
+ */
+struct folio_iter {
+       struct folio *folio;
+       size_t offset;
+       size_t length;
+       /* private: for use by the iterator */
+       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;
+       }
+}
+
+/**
+ * bio_for_each_folio_all - Iterate over each folio in a bio.
+ * @fi: struct folio_iter which is updated for each folio.
+ * @bio: struct bio to iterate over.
+ */
+#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 */