iov_iter: first_{iovec,bvec}_segment() - simplify a bit

We return length + offset in page via *size.  Don't bother - the caller
can do that arithmetics just as well; just report the length to it.

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

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 1b5e96ddddf390144584ae6cde0192bb39f04d37..45dccecae9467e96daf061c24f75d2c5bd487633 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1308,7 +1308,7 @@ static unsigned long first_iovec_segment(const struct iov_iter *i,
                        continue;
                if (len > maxsize)
                        len = maxsize;
-               len += (*start = addr % PAGE_SIZE);
+               *start = addr % PAGE_SIZE;
                *size = len;
                return addr & PAGE_MASK;
        }
@@ -1328,7 +1328,7 @@ static struct page *first_bvec_segment(const struct iov_iter *i,
                len = maxsize;
        skip += i->bvec->bv_offset;
        page = i->bvec->bv_page + skip / PAGE_SIZE;
-       len += (*start = skip % PAGE_SIZE);
+       *start = skip % PAGE_SIZE;
        *size = len;
        return page;
 }
@@ -1357,24 +1357,24 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
                        gup_flags |= FOLL_NOFAULT;
 
                addr = first_iovec_segment(i, &len, start, maxsize);
-               if (len > maxpages * PAGE_SIZE)
-                       len = maxpages * PAGE_SIZE;
-               n = DIV_ROUND_UP(len, PAGE_SIZE);
+               n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
+               if (n > maxpages)
+                       n = maxpages;
                res = get_user_pages_fast(addr, n, gup_flags, pages);
                if (unlikely(res <= 0))
                        return res;
-               return (res == n ? len : res * PAGE_SIZE) - *start;
+               return min_t(size_t, len, res * PAGE_SIZE - *start);
        }
        if (iov_iter_is_bvec(i)) {
                struct page *page;
 
                page = first_bvec_segment(i, &len, start, maxsize);
-               if (len > maxpages * PAGE_SIZE)
-                       len = maxpages * PAGE_SIZE;
-               n = DIV_ROUND_UP(len, PAGE_SIZE);
-               while (n--)
+               n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
+               if (n > maxpages)
+                       n = maxpages;
+               for (int k = 0; k < n; k++)
                        get_page(*pages++ = page++);
-               return len - *start;
+               return min_t(size_t, len, n * PAGE_SIZE - *start);
        }
        if (iov_iter_is_pipe(i))
                return pipe_get_pages(i, pages, maxsize, maxpages, start);
@@ -1489,7 +1489,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
                        gup_flags |= FOLL_NOFAULT;
 
                addr = first_iovec_segment(i, &len, start, maxsize);
-               n = DIV_ROUND_UP(len, PAGE_SIZE);
+               n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
                p = get_pages_array(n);
                if (!p)
                        return -ENOMEM;
@@ -1500,19 +1500,19 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
                        return res;
                }
                *pages = p;
-               return (res == n ? len : res * PAGE_SIZE) - *start;
+               return min_t(size_t, len, res * PAGE_SIZE - *start);
        }
        if (iov_iter_is_bvec(i)) {
                struct page *page;
 
                page = first_bvec_segment(i, &len, start, maxsize);
-               n = DIV_ROUND_UP(len, PAGE_SIZE);
+               n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
                *pages = p = get_pages_array(n);
                if (!p)
                        return -ENOMEM;
-               while (n--)
+               for (int k = 0; k < n; k++)
                        get_page(*p++ = page++);
-               return len - *start;
+               return min_t(size_t, len, n * PAGE_SIZE - *start);
        }
        if (iov_iter_is_pipe(i))
                return pipe_get_pages_alloc(i, pages, maxsize, start);