process_vm_rw_pages(): pass accurate amount of bytes

... makes passing the amount of pages unnecessary

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

1 files changed, 14 insertions, 8 deletions

diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index c2a1916bacbf..83252d783482 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -41,20 +41,22 @@
  */
 static int process_vm_rw_pages(struct page **pages,
                                unsigned offset,
-                               unsigned long len,
+                               size_t len,
                                struct iov_iter *iter,
                                int vm_write,
-                               unsigned int nr_pages_to_copy,
                                ssize_t *bytes_copied)
 {
         *bytes_copied = 0;
 
         /* Do the copy for each page */
-        while (iov_iter_count(iter) && nr_pages_to_copy--) {
+        while (iov_iter_count(iter) && len) {
                 struct page *page = *pages++;
-                size_t copy = min_t(ssize_t, PAGE_SIZE - offset, len);
+                size_t copy = PAGE_SIZE - offset;
                 size_t copied;
 
+                if (copy > len)
+                        copy = len;
+
                 if (vm_write) {
                         if (copy > iov_iter_count(iter))
                                 copy = iov_iter_count(iter);
@@ -121,6 +123,7 @@ static int process_vm_rw_single_vec(unsigned long addr,
         while ((nr_pages_copied < nr_pages) && iov_iter_count(iter)) {
                 int nr_pages_to_copy;
                 int pages_pinned;
+                size_t n;
                 nr_pages_to_copy = min(nr_pages - nr_pages_copied,
                                        max_pages_per_loop);
 
@@ -134,18 +137,21 @@ static int process_vm_rw_single_vec(unsigned long addr,
                 if (pages_pinned <= 0)
                         return -EFAULT;
 
+                n = pages_pinned * PAGE_SIZE - start_offset;
+                if (n > len)
+                        n = len;
+
                 rc = process_vm_rw_pages(process_pages,
-                                         start_offset, len, iter,
-                                         vm_write, pages_pinned,
+                                         start_offset, n, iter,
+                                         vm_write,
                                          &bytes_copied_loop);
+                len -= n;
                 start_offset = 0;
                 *bytes_copied += bytes_copied_loop;
-                len -= bytes_copied_loop;
                 nr_pages_copied += pages_pinned;
                 pa += pages_pinned * PAGE_SIZE;
                 while (pages_pinned)
                         put_page(process_pages[--pages_pinned]);
-
                 if (rc < 0)
                         break;
         }