1 files changed, 18 insertions, 4 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 742893ea7390..356e976772bf 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1100,23 +1100,37 @@ out:
  */
 static int ocfs2_grab_pages_for_write(struct address_space *mapping,
                                       struct ocfs2_write_ctxt *wc,
-                                      u32 cpos, loff_t user_pos, int new,
+                                      u32 cpos, loff_t user_pos,
+                                      unsigned user_len, int new,
                                       struct page *mmap_page)
 {
         int ret = 0, i;
-        unsigned long start, target_index, index;
+        unsigned long start, target_index, end_index, index;
         struct inode *inode = mapping->host;
+        loff_t last_byte;
 
         target_index = user_pos >> PAGE_CACHE_SHIFT;
 
         /*
          * Figure out how many pages we'll be manipulating here. For
          * non allocating write, we just change the one
-         * page. Otherwise, we'll need a whole clusters worth.
+         * page. Otherwise, we'll need a whole clusters worth.  If we're
+         * writing past i_size, we only need enough pages to cover the
+         * last page of the write.
          */
         if (new) {
                 wc->w_num_pages = ocfs2_pages_per_cluster(inode->i_sb);
                 start = ocfs2_align_clusters_to_page_index(inode->i_sb, cpos);
+                /*
+                 * We need the index *past* the last page we could possibly
+                 * touch.  This is the page past the end of the write or
+                 * i_size, whichever is greater.
+                 */
+                last_byte = max(user_pos + user_len, i_size_read(inode));
+                BUG_ON(last_byte < 1);
+                end_index = ((last_byte - 1) >> PAGE_CACHE_SHIFT) + 1;
+                if ((start + wc->w_num_pages) > end_index)
+                        wc->w_num_pages = end_index - start;
         } else {
                 wc->w_num_pages = 1;
                 start = target_index;
@@ -1773,7 +1787,7 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
          * that we can zero and flush if we error after adding the
          * extent.
          */
-        ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos,
+        ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len,
                                          cluster_of_pages, mmap_page);
         if (ret) {
                 mlog_errno(ret);