[PATCH V6 05/30] block: introduce bio_for_each_chunk()

Ming Lei
2018-06-09T12:31:41Z

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.lei@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 397a38aca182..e9f74c73bbe6 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_chunk_iovec(bio, iter) \
+ bvec_iter_chunk_bvec((bio)->bi_io_vec, (iter))
+
/*
* Check whether this bio carries any data or not. A NULL bio is allowed.
*/
@@ -165,8 +168,8 @@ 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 chunk)
{
iter->bi_sector += bytes >> 9;

@@ -174,11 +177,26 @@ 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 (!chunk)
+ bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+ else
+ bvec_iter_chunk_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_chunk_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)
{
@@ -202,6 +220,16 @@ static inline bool bio_rewind_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_chunk(bvl, bio, iter, start) \
+ for (iter = (start); \
+ (iter).bi_size && \
+ ((bvl = bio_iter_chunk_iovec((bio), (iter))), 1); \
+ bio_advance_chunk_iter((bio), &(iter), (bvl).bv_len))
+
+/* returns one real segment(multipage bvec) each time */
+#define bio_for_each_chunk(bvl, bio, iter) \
+ __bio_for_each_chunk(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 52c90ea1a96a..9e082d023392 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_chunk_bvec(bvec, iter) \
+((struct bio_vec) { \
+ .bv_page = bvec_iter_chunk_page((bvec), (iter)), \
+ .bv_len = bvec_iter_chunk_len((bvec), (iter)), \
+ .bv_offset = bvec_iter_chunk_offset((bvec), (iter)), \
+})
+
+static inline bool __bvec_iter_advance(const struct bio_vec *bv,
+ struct bvec_iter *iter,
+ unsigned bytes, bool chunk)
{
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 (chunk)
+ len = bvec_iter_chunk_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_chunk_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