ocfs2: Zero the tail cluster when extending past i_size.
ocfs2's allocation unit is the cluster. This can be larger than a block
or even a memory page. This means that a file may have many blocks in
its last extent that are beyond the block containing i_size. There also
may be more unwritten extents after that.
When ocfs2 grows a file, it zeros the entire cluster in order to ensure
future i_size growth will see cleared blocks. Unfortunately,
block_write_full_page() drops the pages past i_size. This means that
ocfs2 is actually leaking garbage data into the tail end of that last
cluster. This is a bug.
We adjust ocfs2_write_begin_nolock() and ocfs2_extend_file() to detect
when a write or truncate is past i_size. They will use
ocfs2_zero_extend() to ensure the data is properly zeroed.
Older versions of ocfs2_zero_extend() simply zeroed every block between
i_size and the zeroing position. This presumes three things:
1) There is allocation for all of these blocks.
2) The extents are not unwritten.
3) The extents are not refcounted.
(1) and (2) hold true for non-sparse filesystems, which used to be the
only users of ocfs2_zero_extend(). (3) is another bug.
Since we're now using ocfs2_zero_extend() for sparse filesystems as
well, we teach ocfs2_zero_extend() to check every extent between
i_size and the zeroing position. If the extent is unwritten, it is
ignored. If it is refcounted, it is CoWed. Then it is zeroed.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Cc: stable@kernel.org
diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
index 8bd70d4..dc78764 100644
--- a/fs/ocfs2/quota_local.c
+++ b/fs/ocfs2/quota_local.c
@@ -971,7 +971,7 @@
u64 p_blkno;
/* We are protected by dqio_sem so no locking needed */
- status = ocfs2_extend_no_holes(lqinode,
+ status = ocfs2_extend_no_holes(lqinode, NULL,
lqinode->i_size + 2 * sb->s_blocksize,
lqinode->i_size);
if (status < 0) {
@@ -1114,7 +1114,7 @@
return ocfs2_local_quota_add_chunk(sb, type, offset);
/* We are protected by dqio_sem so no locking needed */
- status = ocfs2_extend_no_holes(lqinode,
+ status = ocfs2_extend_no_holes(lqinode, NULL,
lqinode->i_size + sb->s_blocksize,
lqinode->i_size);
if (status < 0) {