iov_iter.c: iterate_and_advance

same as iterate_all_kinds, but iterator is moved to the position past
the last byte we'd handled.

iov_iter_advance() converted to it

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

diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 798fcb4..e91bf0a 100644 (file)
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -70,6 +70,33 @@
        }                                                       \
 }
 
+#define iterate_and_advance(i, n, v, I, B) {                   \
+       size_t skip = i->iov_offset;                            \
+       if (unlikely(i->type & ITER_BVEC)) {                    \
+               const struct bio_vec *bvec;                     \
+               struct bio_vec v;                               \
+               iterate_bvec(i, n, v, bvec, skip, (B))          \
+               if (skip == bvec->bv_len) {                     \
+                       bvec++;                                 \
+                       skip = 0;                               \
+               }                                               \
+               i->nr_segs -= bvec - i->bvec;                   \
+               i->bvec = bvec;                                 \
+       } else {                                                \
+               const struct iovec *iov;                        \
+               struct iovec v;                                 \
+               iterate_iovec(i, n, v, iov, skip, (I))          \
+               if (skip == iov->iov_len) {                     \
+                       iov++;                                  \
+                       skip = 0;                               \
+               }                                               \
+               i->nr_segs -= iov - i->iov;                     \
+               i->iov = iov;                                   \
+       }                                                       \
+       i->count -= n;                                          \
+       i->iov_offset = skip;                                   \
+}
+
 static size_t copy_to_iter_iovec(void *from, size_t bytes, struct iov_iter *i)
 {
        size_t skip, copy, left, wanted;
@@ -366,42 +393,6 @@ static size_t zero_iovec(size_t bytes, struct iov_iter *i)
        return wanted - bytes;
 }
 
-static void advance_iovec(struct iov_iter *i, size_t bytes)
-{
-       BUG_ON(i->count < bytes);
-
-       if (likely(i->nr_segs == 1)) {
-               i->iov_offset += bytes;
-               i->count -= bytes;
-       } else {
-               const struct iovec *iov = i->iov;
-               size_t base = i->iov_offset;
-               unsigned long nr_segs = i->nr_segs;
-
-               /*
-                * The !iov->iov_len check ensures we skip over unlikely
-                * zero-length segments (without overruning the iovec).
-                */
-               while (bytes || unlikely(i->count && !iov->iov_len)) {
-                       int copy;
-
-                       copy = min(bytes, iov->iov_len - base);
-                       BUG_ON(!i->count || i->count < copy);
-                       i->count -= copy;
-                       bytes -= copy;
-                       base += copy;
-                       if (iov->iov_len == base) {
-                               iov++;
-                               nr_segs--;
-                               base = 0;
-                       }
-               }
-               i->iov = iov;
-               i->iov_offset = base;
-               i->nr_segs = nr_segs;
-       }
-}
-
 /*
  * Fault in the first iovec of the given iov_iter, to a maximum length
  * of bytes. Returns 0 on success, or non-zero if the memory could not be
@@ -685,42 +676,6 @@ static size_t zero_bvec(size_t bytes, struct iov_iter *i)
        return wanted - bytes;
 }
 
-static void advance_bvec(struct iov_iter *i, size_t bytes)
-{
-       BUG_ON(i->count < bytes);
-
-       if (likely(i->nr_segs == 1)) {
-               i->iov_offset += bytes;
-               i->count -= bytes;
-       } else {
-               const struct bio_vec *bvec = i->bvec;
-               size_t base = i->iov_offset;
-               unsigned long nr_segs = i->nr_segs;
-
-               /*
-                * The !iov->iov_len check ensures we skip over unlikely
-                * zero-length segments (without overruning the iovec).
-                */
-               while (bytes || unlikely(i->count && !bvec->bv_len)) {
-                       int copy;
-
-                       copy = min(bytes, bvec->bv_len - base);
-                       BUG_ON(!i->count || i->count < copy);
-                       i->count -= copy;
-                       bytes -= copy;
-                       base += copy;
-                       if (bvec->bv_len == base) {
-                               bvec++;
-                               nr_segs--;
-                               base = 0;
-                       }
-               }
-               i->bvec = bvec;
-               i->iov_offset = base;
-               i->nr_segs = nr_segs;
-       }
-}
-
 static ssize_t get_pages_bvec(struct iov_iter *i,
                   struct page **pages, size_t maxsize, unsigned maxpages,
                   size_t *start)
@@ -849,10 +804,7 @@ EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 
 void iov_iter_advance(struct iov_iter *i, size_t size)
 {
-       if (i->type & ITER_BVEC)
-               advance_bvec(i, size);
-       else
-               advance_iovec(i, size);
+       iterate_and_advance(i, size, v, 0, 0)
 }
 EXPORT_SYMBOL(iov_iter_advance);