Treat writes as new when holes span across page boundaries
authorGoldwyn Rodrigues <rgoldwyn@gmail.com>
Thu, 17 Feb 2011 15:44:40 +0000 (09:44 -0600)
committerJoel Becker <jlbec@evilplan.org>
Mon, 28 Mar 2011 16:44:58 +0000 (09:44 -0700)
When a hole spans across page boundaries, the next write forces
a read of the block. This could end up reading existing garbage
data from the disk in ocfs2_map_page_blocks. This leads to
non-zero holes. In order to avoid this, mark the writes as new
when the holes span across page boundaries.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.de>
Signed-off-by: jlbec <jlbec@evilplan.org>
fs/ocfs2/aops.c

index 0d44b770184423f298b1983b732bca4af94bc205..b5d7fb9ab1f3eb615b8e6c9d1a1717037952dd2e 100644 (file)
@@ -1015,6 +1015,12 @@ static int ocfs2_prepare_page_for_write(struct inode *inode, u64 *p_blkno,
        ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), cpos,
                                        &cluster_start, &cluster_end);
 
+       /* treat the write as new if the a hole/lseek spanned across
+        * the page boundary.
+        */
+       new = new | ((i_size_read(inode) <= page_offset(page)) &&
+                       (page_offset(page) <= user_pos));
+
        if (page == wc->w_target_page) {
                map_from = user_pos & (PAGE_CACHE_SIZE - 1);
                map_to = map_from + user_len;