[PATCH V11 03/19] block: introduce bio_for_each_bvec()

Ming Lei
2018-11-21T03:25:40Z

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

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/bio.h | 25 ++++++++++++++++++++++---
include/linux/bvec.h | 36 +++++++++++++++++++++++++++++-------
2 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 056fb627edb3..7560209d6a8a 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) \
+ segment_iter_bvec((bio)->bi_io_vec, (iter))
+
/*
* Check whether this bio carries any data or not. A NULL bio is allowed.
*/
@@ -135,18 +138,24 @@ 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, unsigned max_seg_len)
{
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);
+ __bvec_iter_advance(bio->bi_io_vec, iter, bytes, max_seg_len);
/* 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, PAGE_SIZE);
+}
+
#define __bio_for_each_segment(bvl, bio, iter, start) \
for (iter = (start); \
(iter).bi_size && \
@@ -156,6 +165,16 @@ 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_iter((bio), &(iter), (bvl).bv_len, BVEC_MAX_LEN))
+
+/* returns one real segment(multi-page 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 ed90bbf4c9c9..b279218c5c4d 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -25,6 +25,8 @@
#include <linux/errno.h>
#include <linux/mm.h>

+#define BVEC_MAX_LEN ((unsigned int)-1)
+
/*
* was unsigned short, but we might as well be ready for > 64kB I/O pages
*/
@@ -87,8 +89,15 @@ 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 segment_iter_bvec(bvec, iter) \
+((struct bio_vec) { \
+ .bv_page = segment_iter_page((bvec), (iter)), \
+ .bv_len = segment_iter_len((bvec), (iter)), \
+ .bv_offset = segment_iter_offset((bvec), (iter)), \
+})
+
+static inline bool __bvec_iter_advance(const struct bio_vec *bv,
+ struct bvec_iter *iter, unsigned bytes, unsigned max_seg_len)
{
if (WARN_ONCE(bytes > iter->bi_size,
"Attempted to advance past end of bvec iter\n")) {
@@ -97,12 +106,18 @@ 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 segment_len = segment_iter_len(bv, *iter);

- bytes -= len;
- iter->bi_size -= len;
- iter->bi_bvec_done += len;
+ if (max_seg_len < BVEC_MAX_LEN)
+ segment_len = min_t(unsigned, segment_len,
+ max_seg_len -
+ bvec_iter_offset(bv, *iter));
+
+ segment_len = min(bytes, segment_len);
+
+ bytes -= segment_len;
+ iter->bi_size -= segment_len;
+ iter->bi_bvec_done += segment_len;

if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
iter->bi_bvec_done = 0;
@@ -136,6 +151,13 @@ 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, PAGE_SIZE);
+}
+
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
--
2.9.5