[PATCH v1 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

[Ming Lei <ming.lei@xxxxxxxxxxxxx>]

bvec has provided one iterator already, so not necessary
to invent a new wheel for this job.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
---
 lib/iov_iter.c | 31 +++++++++++--------------------
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc..5e1b224 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -3,6 +3,7 @@
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/bvec_iter.h>
 #include <net/checksum.h>
 
 #define iterate_iovec(i, n, __v, __p, skip, STEP) {    \
@@ -57,35 +58,25 @@
 }
 
 #define iterate_bvec(i, n, __v, __p, skip, STEP) {     \
-       size_t wanted = n;                              \
+       struct bvec_iter __bi, __start;                 \
+       __start.bi_size = n;                            \
+       __start.bi_bvec_done = skip;                    \
+       __start.bi_idx = 0;                             \
        __p = i->bvec;                                  \
-       __v.bv_len = min_t(size_t, n, __p->bv_len - skip);      \
-       if (likely(__v.bv_len)) {                       \
-               __v.bv_page = __p->bv_page;             \
-               __v.bv_offset = __p->bv_offset + skip;  \
+       for_each_bvec(__v, __p, __bi, __start) {        \
                (void)(STEP);                           \
-               skip += __v.bv_len;                     \
-               n -= __v.bv_len;                        \
        }                                               \
-       while (unlikely(n)) {                           \
-               __p++;                                  \
-               __v.bv_len = min_t(size_t, n, __p->bv_len);     \
-               if (unlikely(!__v.bv_len))              \
-                       continue;                       \
-               __v.bv_page = __p->bv_page;             \
-               __v.bv_offset = __p->bv_offset;         \
-               (void)(STEP);                           \
+       if (!__bi.bi_idx)                               \
+               skip += __v.bv_len;                     \
+       else                                            \
                skip = __v.bv_len;                      \
-               n -= __v.bv_len;                        \
-       }                                               \
-       n = wanted;                                     \
 }
 
 #define iterate_all_kinds(i, n, v, I, B, K) {                  \
        size_t skip = i->iov_offset;                            \
        if (unlikely(i->type & ITER_BVEC)) {                    \
                const struct bio_vec *bvec;                     \
-               struct bio_vec v;                               \
+               struct bio_vec v = { 0 };                       \
                iterate_bvec(i, n, v, bvec, skip, (B))          \
        } else if (unlikely(i->type & ITER_KVEC)) {             \
                const struct kvec *kvec;                        \
@@ -102,7 +93,7 @@
        size_t skip = i->iov_offset;                            \
        if (unlikely(i->type & ITER_BVEC)) {                    \
                const struct bio_vec *bvec;                     \
-               struct bio_vec v;                               \
+               struct bio_vec v = { 0 };                       \
                iterate_bvec(i, n, v, bvec, skip, (B))          \
                if (skip == bvec->bv_len) {                     \
                        bvec++;                                 \
-- 
1.9.1