This helper is used for iterating over multi-page bvec for bio
split & merge code.

Cc: Dave Chinner <dchin...@redhat.com>
Cc: Kent Overstreet <kent.overstr...@gmail.com>
Cc: Mike Snitzer <snit...@redhat.com>
Cc: dm-de...@redhat.com
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: linux-fsde...@vger.kernel.org
Cc: Shaohua Li <s...@kernel.org>
Cc: linux-r...@vger.kernel.org
Cc: linux-er...@lists.ozlabs.org
Cc: David Sterba <dste...@suse.com>
Cc: linux-bt...@vger.kernel.org
Cc: Darrick J. Wong <darrick.w...@oracle.com>
Cc: linux-...@vger.kernel.org
Cc: Gao Xiang <gaoxian...@huawei.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Theodore Ts'o <ty...@mit.edu>
Cc: linux-e...@vger.kernel.org
Cc: Coly Li <col...@suse.de>
Cc: linux-bca...@vger.kernel.org
Cc: Boaz Harrosh <o...@electrozaur.com>
Cc: Bob Peterson <rpete...@redhat.com>
Cc: cluster-devel@redhat.com
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 056fb627edb3..1f0dcf109841 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -76,6 +76,9 @@
 #define bio_data_dir(bio) \
        (op_is_write(bio_op(bio)) ? WRITE : READ)
 
+#define bio_iter_mp_iovec(bio, iter)                           \
+       mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))
+
 /*
  * Check whether this bio carries any data or not. A NULL bio is allowed.
  */
@@ -135,18 +138,33 @@ static inline bool bio_full(struct bio *bio)
 #define bio_for_each_segment_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 mp)
 {
        iter->bi_sector += bytes >> 9;
 
        if (bio_no_advance_iter(bio))
                iter->bi_size -= bytes;
        else
-               bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+               if (!mp)
+                       bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+               else
+                       mp_bvec_iter_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_mp_iter(struct bio *bio, struct bvec_iter *iter,
+                                      unsigned bytes)
+{
+       __bio_advance_iter(bio, iter, bytes, true);
+}
+
 #define __bio_for_each_segment(bvl, bio, iter, start)                  \
        for (iter = (start);                                            \
             (iter).bi_size &&                                          \
@@ -156,6 +174,16 @@ 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 = bio_iter_mp_iovec((bio), (iter))), 1);  \
+            bio_advance_mp_iter((bio), &(iter), (bvl).bv_len))
+
+/* returns one real segment(multipage bvec) each time */
+#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/bvec.h b/include/linux/bvec.h
index 8ef904a50577..3d61352cd8cf 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -124,8 +124,16 @@ 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 mp_bvec_iter_bvec(bvec, iter)                          \
+((struct bio_vec) {                                                    \
+       .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
+       .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
+       .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
+})
+
+static inline bool __bvec_iter_advance(const struct bio_vec *bv,
+                                      struct bvec_iter *iter,
+                                      unsigned bytes, bool mp)
 {
        if (WARN_ONCE(bytes > iter->bi_size,
                     "Attempted to advance past end of bvec iter\n")) {
@@ -134,8 +142,14 @@ 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 (mp)
+                       len = mp_bvec_iter_len(bv, *iter);
+               else
+                       len = bvec_iter_len(bv, *iter);
+
+               len = min(bytes, len);
 
                bytes -= len;
                iter->bi_size -= len;
@@ -173,6 +187,20 @@ 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 mp_bvec_iter_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

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