process_vm_access: take get_user_pages/put_pages one level up

... and trim the fuck out of process_vm_rw_pages() argument list.

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

diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 70ec315..c2a1916 100644 (file)
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -39,69 +39,39 @@
  * @bytes_copied: returns number of bytes successfully copied
  * Returns 0 on success, error code otherwise
  */
-static int process_vm_rw_pages(struct task_struct *task,
-                              struct mm_struct *mm,
-                              struct page **process_pages,
-                              unsigned long pa,
-                              unsigned long start_offset,
+static int process_vm_rw_pages(struct page **pages,
+                              unsigned offset,
                               unsigned long len,
                               struct iov_iter *iter,
                               int vm_write,
                               unsigned int nr_pages_to_copy,
                               ssize_t *bytes_copied)
 {
-       int pages_pinned;
-       int pgs_copied = 0;
-       int j;
-       int ret;
-       ssize_t bytes_to_copy;
-       ssize_t rc = 0;
-
        *bytes_copied = 0;
 
-       /* Get the pages we're interested in */
-       down_read(&mm->mmap_sem);
-       pages_pinned = get_user_pages(task, mm, pa,
-                                     nr_pages_to_copy,
-                                     vm_write, 0, process_pages, NULL);
-       up_read(&mm->mmap_sem);
-
-       if (pages_pinned != nr_pages_to_copy) {
-               rc = -EFAULT;
-               goto end;
-       }
-
        /* Do the copy for each page */
-       for (pgs_copied = 0;
-            (pgs_copied < nr_pages_to_copy) && iov_iter_count(iter);
-            pgs_copied++) {
-               struct page *page = process_pages[pgs_copied];
-               bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset, len);
+       while (iov_iter_count(iter) && nr_pages_to_copy--) {
+               struct page *page = *pages++;
+               size_t copy = min_t(ssize_t, PAGE_SIZE - offset, len);
+               size_t copied;
 
                if (vm_write) {
-                       if (bytes_to_copy > iov_iter_count(iter))
-                               bytes_to_copy = iov_iter_count(iter);
-                       ret = iov_iter_copy_from_user(page,
-                                       iter, start_offset, bytes_to_copy);
-                       iov_iter_advance(iter, ret);
+                       if (copy > iov_iter_count(iter))
+                               copy = iov_iter_count(iter);
+                       copied = iov_iter_copy_from_user(page, iter,
+                                       offset, copy);
+                       iov_iter_advance(iter, copied);
                        set_page_dirty_lock(page);
                } else {
-                       ret = copy_page_to_iter(page, start_offset,
-                                       bytes_to_copy, iter);
-               }
-               *bytes_copied += ret;
-               len -= ret;
-               if (ret < bytes_to_copy && iov_iter_count(iter)) {
-                       rc = -EFAULT;
-                       break;
+                       copied = copy_page_to_iter(page, offset, copy, iter);
                }
-               start_offset = 0;
+               *bytes_copied += copied;
+               len -= copied;
+               if (copied < copy && iov_iter_count(iter))
+                       return -EFAULT;
+               offset = 0;
        }
-
-end:
-       for (j = 0; j < pages_pinned; j++)
-               put_page(process_pages[j]);
-       return rc;
+       return 0;
 }
 
 /* Maximum number of pages kmalloc'd to hold struct page's during copy */
@@ -138,7 +108,6 @@ static int process_vm_rw_single_vec(unsigned long addr,
        ssize_t bytes_copied_loop;
        ssize_t rc = 0;
        unsigned long nr_pages_copied = 0;
-       unsigned long nr_pages_to_copy;
        unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
                / sizeof(struct pages *);
 
@@ -150,23 +119,35 @@ static int process_vm_rw_single_vec(unsigned long addr,
        nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
 
        while ((nr_pages_copied < nr_pages) && iov_iter_count(iter)) {
+               int nr_pages_to_copy;
+               int pages_pinned;
                nr_pages_to_copy = min(nr_pages - nr_pages_copied,
                                       max_pages_per_loop);
 
-               rc = process_vm_rw_pages(task, mm, process_pages, pa,
+               /* Get the pages we're interested in */
+               down_read(&mm->mmap_sem);
+               pages_pinned = get_user_pages(task, mm, pa,
+                                             nr_pages_to_copy,
+                                             vm_write, 0, process_pages, NULL);
+               up_read(&mm->mmap_sem);
+
+               if (pages_pinned <= 0)
+                       return -EFAULT;
+
+               rc = process_vm_rw_pages(process_pages,
                                         start_offset, len, iter,
-                                        vm_write, nr_pages_to_copy,
+                                        vm_write, pages_pinned,
                                         &bytes_copied_loop);
                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) {
-                       return rc;
-               } else {
-                       len -= bytes_copied_loop;
-                       nr_pages_copied += nr_pages_to_copy;
-                       pa += nr_pages_to_copy * PAGE_SIZE;
-               }
+               if (rc < 0)
+                       break;
        }
 
        return rc;