[ 068/147] ext4: fix fdatasync() for files with only i_size changes

Ben Hutchings
2012-10-14T14:58:54Z

From: Jan Kara <jack@suse.cz>

commit b71fc079b5d8f42b2a52743c8d2f1d35d655b1c5 upstream.

Code tracking when transaction needs to be committed on fdatasync(2) forgets
to handle a situation when only inode's i_size is changed. Thus in such
situations fdatasync(2) doesn't force transaction with new i_size to disk
and that can result in wrong i_size after a crash.

Fix the issue by updating inode's i_datasync_tid whenever its size is
updated.

Reported-by: Kristian Nielsen <knielsen@knielsen-hq.org>
Signed-off-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext4/inode.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4007,6 +4007,7 @@ static int ext4_do_update_inode(handle_t
struct ext4_inode_info *ei = EXT4_I(inode);
struct buffer_head *bh = iloc->bh;
int err = 0, rc, block;
+ int need_datasync = 0;

/* For fields not not tracking in the in-memory inode,
* initialise them to zero for new inodes. */
@@ -4055,7 +4056,10 @@ static int ext4_do_update_inode(handle_t
raw_inode->i_file_acl_high =
cpu_to_le16(ei->i_file_acl >> 32);
raw_inode->i_file_acl_lo = cpu_to_le32(ei->i_file_acl);
- ext4_isize_set(raw_inode, ei->i_disksize);
+ if (ei->i_disksize != ext4_isize(raw_inode)) {
+ ext4_isize_set(raw_inode, ei->i_disksize);
+ need_datasync = 1;
+ }
if (ei->i_disksize > 0x7fffffffULL) {
struct super_block *sb = inode->i_sb;
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
@@ -4108,7 +4112,7 @@ static int ext4_do_update_inode(handle_t
err = rc;
ext4_clear_inode_state(inode, EXT4_STATE_NEW);

- ext4_update_inode_fsync_trans(handle, inode, 0);
+ ext4_update_inode_fsync_trans(handle, inode, need_datasync);
out_brelse:
brelse(bh);
ext4_std_error(inode->i_sb, err);