From 5693486bad2bc2ac585a2c24f7e2f3964b478df9 Mon Sep 17 00:00:00 2001 From: Joel Becker Date: Thu, 1 Jul 2010 15:13:31 -0700 Subject: 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 Cc: stable@kernel.org --- fs/ocfs2/quota_global.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/ocfs2/quota_global.c') diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c index 2bb35fe00511..4607923eb24c 100644 --- a/fs/ocfs2/quota_global.c +++ b/fs/ocfs2/quota_global.c @@ -775,7 +775,7 @@ static int ocfs2_acquire_dquot(struct dquot *dquot) * locking allocators ranks above a transaction start */ WARN_ON(journal_current_handle()); - status = ocfs2_extend_no_holes(gqinode, + status = ocfs2_extend_no_holes(gqinode, NULL, gqinode->i_size + (need_alloc << sb->s_blocksize_bits), gqinode->i_size); if (status < 0) -- cgit v1.2.3