block: add bio_for_each_bvec_all()

An upcoming Btrfs fix needs to know the original size of a non-cloned
bios. Rather than accessing the bvec table directly, let's add a
bio_for_each_bvec_all() accessor.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

.clang-format

@@ -80,6 +80,7 @@ ForEachMacros:
   - 'ax25_uid_for_each'
   - '__bio_for_each_bvec'
   - 'bio_for_each_bvec'
+  - 'bio_for_each_bvec_all'
   - 'bio_for_each_integrity_vec'
   - '__bio_for_each_segment'
   - 'bio_for_each_segment'

Documentation/block/biovecs.rst

@@ -129,6 +129,7 @@ Usage of helpers:
 ::
 
 	bio_for_each_segment_all()
+	bio_for_each_bvec_all()
 	bio_first_bvec_all()
 	bio_first_page_all()
 	bio_last_bvec_all()
@@ -143,4 +144,5 @@ Usage of helpers:
   bio_vec' will contain a multi-page IO vector during the iteration::
 
 	bio_for_each_bvec()
+	bio_for_each_bvec_all()
 	rq_for_each_bvec()

include/linux/bio.h

@@ -169,6 +169,14 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 #define bio_for_each_bvec(bvl, bio, iter)			\
 	__bio_for_each_bvec(bvl, bio, iter, (bio)->bi_iter)
 
+/*
+ * Iterate over all multi-page bvecs. Drivers shouldn't use this version for the
+ * same reasons as bio_for_each_segment_all().
+ */
+#define bio_for_each_bvec_all(bvl, bio, i)		\
+	for (i = 0, bvl = bio_first_bvec_all(bio);	\
+	     i < (bio)->bi_vcnt; i++, bvl++)		\
+
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
 static inline unsigned bio_segments(struct bio *bio)