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Subject[PATCH V15 05/18] block: introduce bio_for_each_bvec() and rq_for_each_bvec()
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bio_for_each_bvec() is used for iterating over multi-page bvec for bio
split & merge code.

rq_for_each_bvec() can be used for drivers which may handle the
multi-page bvec directly, so far loop is one perfect use case.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/bio.h | 10 ++++++++++
include/linux/blkdev.h | 4 ++++
2 files changed, 14 insertions(+)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 72b4f7be2106..7ef8a7505c0a 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -156,6 +156,16 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
#define bio_for_each_segment(bvl, bio, iter) \
__bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)

+#define __bio_for_each_bvec(bvl, bio, iter, start) \
+ for (iter = (start); \
+ (iter).bi_size && \
+ ((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \
+ bio_advance_iter((bio), &(iter), (bvl).bv_len))
+
+/* iterate over multi-page bvec */
+#define bio_for_each_bvec(bvl, bio, iter) \
+ __bio_for_each_bvec(bvl, bio, iter, (bio)->bi_iter)
+
#define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)

static inline unsigned bio_segments(struct bio *bio)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3603270cb82d..b6292d469ea4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -792,6 +792,10 @@ struct req_iterator {
__rq_for_each_bio(_iter.bio, _rq) \
bio_for_each_segment(bvl, _iter.bio, _iter.iter)

+#define rq_for_each_bvec(bvl, _rq, _iter) \
+ __rq_for_each_bio(_iter.bio, _rq) \
+ bio_for_each_bvec(bvl, _iter.bio, _iter.iter)
+
#define rq_iter_last(bvec, _iter) \
(_iter.bio->bi_next == NULL && \
bio_iter_last(bvec, _iter.iter))
--
2.9.5
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