iov_iter: clean csum_and_copy_...() primitives up a bit

1) kmap_atomic() is not needed here, kmap_local_page() is enough.
2) No need to make sum = csum_block_add(sum, next, off); conditional
upon next != 0 - adding 0 is a no-op as far as csum_block_add()
is concerned.

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

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index ba7eb65..3b442d2 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -600,9 +600,9 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
                return 0;
        do {
                size_t chunk = min_t(size_t, n, PAGE_SIZE - r);
-               char *p = kmap_atomic(pipe->bufs[i_head & p_mask].page);
+               char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
                sum = csum_and_memcpy(p + r, addr, chunk, sum, off);
-               kunmap_atomic(p);
+               kunmap_local(p);
                i->head = i_head;
                i->iov_offset = r + chunk;
                n -= chunk;
@@ -1665,8 +1665,7 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
        }
        iterate_and_advance(i, bytes, base, len, off, ({
                next = csum_and_copy_from_user(base, addr + off, len);
-               if (next)
-                       sum = csum_block_add(sum, next, off);
+               sum = csum_block_add(sum, next, off);
                next ? 0 : len;
        }), ({
                sum = csum_and_memcpy(addr + off, base, len, sum, off);
@@ -1693,8 +1692,7 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
        }
        iterate_and_advance(i, bytes, base, len, off, ({
                next = csum_and_copy_to_user(addr + off, base, len);
-               if (next)
-                       sum = csum_block_add(sum, next, off);
+               sum = csum_block_add(sum, next, off);
                next ? 0 : len;
        }), ({
                sum = csum_and_memcpy(base, addr + off, len, sum, off);