commit: b71fc079b5d8f42b2a52743c8d2f1d35d655b1c5
From: Jan Kara <[email protected]>
Date: Wed, 26 Sep 2012 21:52:20 -0400
Subject: ext4: fix fdatasync() for files with only i_size changes

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.

CC: <[email protected]> # >= 2.6.32
Reported-by: Kristian Nielsen <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
---
 fs/ext4/inode.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0a31197..4df5e95 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4054,6 +4054,7 @@ static int ext4_do_update_inode(handle_t *handle,
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct buffer_head *bh = iloc->bh;
        int err = 0, rc, block;
+       int need_datasync = 0;
        uid_t i_uid;
        gid_t i_gid;
 
@@ -4104,7 +4105,10 @@ static int ext4_do_update_inode(handle_t *handle,
                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,
@@ -4157,7 +4161,7 @@ static int ext4_do_update_inode(handle_t *handle,
                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);
-- 
1.7.3.4
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