Treat writes as new when holes span across page boundaries

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>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 0d44b770184..b5d7fb9ab1f 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -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;