[RESEND PATCH V5 05/33] block: introduce bio_for_each_segment()

[Ming Lei]

This helper is used to iterate multipage bvec for bio spliting/merge,
and it is required in bio_clone_bioset() too, so introduce it.

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 include/linux/bio.h  | 34 +++++++++++++++++++++++++++++++---
 include/linux/bvec.h | 36 ++++++++++++++++++++++++++++++++----
 2 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7f92af1299ad..3d3795b9a353 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -80,6 +80,9 @@
 #define bio_data_dir(bio) \
        (op_is_write(bio_op(bio)) ? WRITE : READ)
 
+#define bio_iter_seg_iovec(bio, iter)                          \
+       bvec_iter_segment_bvec((bio)->bi_io_vec, (iter))
+
 /*
  * Check whether this bio carries any data or not. A NULL bio is allowed.
  */
@@ -160,8 +163,8 @@ static inline void *bio_data(struct bio *bio)
 #define bio_for_each_page_all(bvl, bio, i)                             \
        for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++)
 
-static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
-                                   unsigned bytes)
+static inline void __bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
+                                     unsigned bytes, bool seg)
 {
        iter->bi_sector += bytes >> 9;
 
@@ -169,11 +172,26 @@ static inline void bio_advance_iter(struct bio *bio, 
struct bvec_iter *iter,
                iter->bi_size -= bytes;
                iter->bi_done += bytes;
        } else {
-               bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+               if (!seg)
+                       bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+               else
+                       bvec_iter_seg_advance(bio->bi_io_vec, iter, bytes);
                /* TODO: It is reasonable to complete bio with error here. */
        }
 }
 
+static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
+                                   unsigned bytes)
+{
+       __bio_advance_iter(bio, iter, bytes, false);
+}
+
+static inline void bio_advance_seg_iter(struct bio *bio, struct bvec_iter 
*iter,
+                                      unsigned bytes)
+{
+       __bio_advance_iter(bio, iter, bytes, true);
+}
+
 static inline bool bio_rewind_iter(struct bio *bio, struct bvec_iter *iter,
                unsigned int bytes)
 {
@@ -197,6 +215,16 @@ static inline bool bio_rewind_iter(struct bio *bio, struct 
bvec_iter *iter,
 #define bio_for_each_page(bvl, bio, iter)                              \
        __bio_for_each_page(bvl, bio, iter, (bio)->bi_iter)
 
+#define __bio_for_each_segment(bvl, bio, iter, start)          \
+       for (iter = (start);                                            \
+            (iter).bi_size &&                                          \
+               ((bvl = bio_iter_seg_iovec((bio), (iter))), 1);         \
+            bio_advance_seg_iter((bio), &(iter), (bvl).bv_len))
+
+/* returns one real segment(multipage bvec) each time */
+#define bio_for_each_segment(bvl, bio, iter)                   \
+       __bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)
+
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
 static inline unsigned bio_pages(struct bio *bio)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 2433c73fa5ea..84c395feed49 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -126,8 +126,16 @@ struct bvec_iter {
        .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
 })
 
-static inline bool bvec_iter_advance(const struct bio_vec *bv,
-               struct bvec_iter *iter, unsigned bytes)
+#define bvec_iter_segment_bvec(bvec, iter)                             \
+((struct bio_vec) {                                                    \
+       .bv_page        = bvec_iter_segment_page((bvec), (iter)),       \
+       .bv_len         = bvec_iter_segment_len((bvec), (iter)),        \
+       .bv_offset      = bvec_iter_segment_offset((bvec), (iter)),     \
+})
+
+static inline bool __bvec_iter_advance(const struct bio_vec *bv,
+                                      struct bvec_iter *iter,
+                                      unsigned bytes, bool segment)
 {
        if (WARN_ONCE(bytes > iter->bi_size,
                     "Attempted to advance past end of bvec iter\n")) {
@@ -136,8 +144,14 @@ static inline bool bvec_iter_advance(const struct bio_vec 
*bv,
        }
 
        while (bytes) {
-               unsigned iter_len = bvec_iter_len(bv, *iter);
-               unsigned len = min(bytes, iter_len);
+               unsigned len;
+
+               if (segment)
+                       len = bvec_iter_segment_len(bv, *iter);
+               else
+                       len = bvec_iter_len(bv, *iter);
+
+               len = min(bytes, len);
 
                bytes -= len;
                iter->bi_size -= len;
@@ -176,6 +190,20 @@ static inline bool bvec_iter_rewind(const struct bio_vec 
*bv,
        return true;
 }
 
+static inline bool bvec_iter_advance(const struct bio_vec *bv,
+                                    struct bvec_iter *iter,
+                                    unsigned bytes)
+{
+       return __bvec_iter_advance(bv, iter, bytes, false);
+}
+
+static inline bool bvec_iter_seg_advance(const struct bio_vec *bv,
+                                        struct bvec_iter *iter,
+                                        unsigned bytes)
+{
+       return __bvec_iter_advance(bv, iter, bytes, true);
+}
+
 #define for_each_bvec(bvl, bio_vec, iter, start)                       \
        for (iter = (start);                                            \
             (iter).bi_size &&                                          \
-- 
2.9.5