iterate_bvec(): expand bvec.h macro forest, massage a bit

... incidentally, using pointer instead of index in an array
(the only change here) trims half-kilobyte of .text...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index fc071d7..58d53de 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -37,14 +37,23 @@
        n = wanted - n;                                         \
 }
 
-#define iterate_bvec(i, n, __v, __bi, skip, STEP) {    \
-       struct bvec_iter __start;                       \
-       __start.bi_size = n;                            \
-       __start.bi_bvec_done = skip;                    \
-       __start.bi_idx = 0;                             \
-       for_each_bvec(__v, i->bvec, __bi, __start) {    \
-               (void)(STEP);                           \
-       }                                               \
+#define iterate_bvec(i, n, __v, p, skip, STEP) {               \
+       size_t wanted = n;                                      \
+       while (n) {                                             \
+               unsigned offset = p->bv_offset + skip;          \
+               __v.bv_offset = offset % PAGE_SIZE;             \
+               __v.bv_page = p->bv_page + offset / PAGE_SIZE;  \
+               __v.bv_len = min(min(n, p->bv_len - skip),      \
+                    (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
+               (void)(STEP);                                   \
+               skip += __v.bv_len;                             \
+               if (skip == p->bv_len) {                        \
+                       skip = 0;                               \
+                       p++;                                    \
+               }                                               \
+               n -= __v.bv_len;                                \
+       }                                                       \
+       n = wanted - n;                                         \
 }
 
 #define iterate_xarray(i, n, __v, skip, STEP) {                \
@@ -98,11 +107,9 @@
                } else if (iov_iter_is_bvec(i)) {               \
                        const struct bio_vec *bvec = i->bvec;   \
                        struct bio_vec v;                       \
-                       struct bvec_iter __bi;                  \
-                       iterate_bvec(i, n, v, __bi, skip, (B))  \
-                       i->bvec = __bvec_iter_bvec(i->bvec, __bi);      \
-                       i->nr_segs -= i->bvec - bvec;           \
-                       skip = __bi.bi_bvec_done;               \
+                       iterate_bvec(i, n, v, bvec, skip, (B))  \
+                       i->nr_segs -= bvec - i->bvec;           \
+                       i->bvec = bvec;                         \
                } else if (iov_iter_is_kvec(i)) {               \
                        const struct kvec *kvec = i->kvec;      \
                        struct kvec v;                          \