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/file.h b/fs/ocfs2/file.h
index d66cf4f..97bf761 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -54,8 +54,10 @@
int ocfs2_simple_size_update(struct inode *inode,
struct buffer_head *di_bh,
u64 new_i_size);
-int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size,
- u64 zero_to);
+int ocfs2_extend_no_holes(struct inode *inode, struct buffer_head *di_bh,
+ u64 new_i_size, u64 zero_to);
+int ocfs2_zero_extend(struct inode *inode, struct buffer_head *di_bh,
+ loff_t zero_to);
int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
int ocfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat);