Re: [PATCH] ext4: sync the directory inode in ext4_sync_parent()

[Curt Wohlgemuth <curtw@google.com>]

Hi Eric:

On Tue, Apr 5, 2011 at 12:35 PM, Eric Sandeen <sandeen@redhat.com> wrote:
> On 4/5/11 12:27 PM, Curt Wohlgemuth wrote:
>> ext4 has taken the stance that, in the absence of a journal,
>> when an fsync/fdatasync of an inode is done, the parent
>> directory should be sync'ed if this inode entry is new.
>> ext4_sync_parent(), which implements this, does indeed sync
>> the dirent pages for parent directories, but it does not
>> sync the directory *inode*.  This patch fixes this.
>>
>> I tested this using a power fail test, which panics a
>> machine running a file server getting requests from a
>> client.  Without this patch, on about every other test run,
>> the server is missing many, many files that had been synced.
>> With this patch, on > 6 runs, I see zero files being lost.
>>
>> Signed-off-by: Curt Wohlgemuth <curtw@google.com>
>> ---
>>  fs/ext4/fsync.c |   11 ++++++++++-
>>  1 files changed, 10 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
>> index 7f74019..a276348 100644
>> --- a/fs/ext4/fsync.c
>> +++ b/fs/ext4/fsync.c
>> @@ -128,6 +128,7 @@ extern int ext4_flush_completed_IO(struct inode *inode)
>>  static void ext4_sync_parent(struct inode *inode)
>>  {
>>       struct dentry *dentry = NULL;
>> +     int ret;
>>
>>       while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
>>               ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
>> @@ -136,7 +137,15 @@ static void ext4_sync_parent(struct inode *inode)
>>               if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
>>                       break;
>>               inode = dentry->d_parent->d_inode;
>> -             sync_mapping_buffers(inode->i_mapping);
>> +             ret = sync_mapping_buffers(inode->i_mapping);
>> +             if (! ret) {
>> +                     struct writeback_control wbc = {
>> +                             .sync_mode = WB_SYNC_ALL,
>> +                             .nr_to_write = 0, /* metadata-only; caller
>> +                                                  takes care of data */
>> +                     };
>> +                     (void)sync_inode(inode, &wbc);
>
> I know ext4_sync_parent was a void already, but why don't we send errors back up through ext4_sync_file?

Well, you could argue that a failure to sync the parent shouldn't
cause the inode's fsync() to fail, but I probably wouldn't :-) .  I'll
resend a patch that implements this.

Thanks,
Curt

>
> -Eric
>
>> +             }
>>       }
>>  }
>>
>
>
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