Treat writes as new when holes span across page boundaries

commit 272b62c1f0f6f742046e45b50b6fec98860208a0 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 5fc918ca25722038e19ebaa1c9880cbd72ef5cb1..35d256b5add2a065debbe686175f155e9e3a5731 100644 (file)
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1091,6 +1091,12 @@ 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;