Re: fio test triggering bad data on ext4

Jens Axboe
2010-06-18T17:32:18Z

On 2010-06-18 17:28, Eric Sandeen wrote:
> Jens Axboe wrote:
>> On 18/06/10 16.59, Eric Sandeen wrote:
>>
>>> Eric Sandeen wrote:
>>>
>>>> Jens Axboe wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I was writing a small fio job file to do writes and read verifies on a
>>>>> device. It forks 32 processes, each writing randomly to 4 files with a
>>>>> block size between 4k and 16k. When it has written 1024 of those blocks,
>>>>> it'll verify the oldest 512 of them. Each block is checksummed for every
>>>>> 512b. It uses libaio and O_DIRECT.
>>>>>
>>>>> It works on ext2 and btrfs. I haven't run it to completion yet, but they
>>>>> survive 15-20 minutes just fine. ext4 doesn't even go a full minutes
>>>>> before this triggers:
>>>>>
>>>> Jens, can you try XFS too? Since ext3 can't do direct IO to a hole,
>>>> (and I'm not sure about btrfs in that regard), ext4 may be most similar
>>>> to xfs's behavior on the test ... wondering how it fares.
>>>>
>>>> Thanks,
>>>> -Eric
>>>>
>>> Actually mingming had a patch for direct-io.c which may be related, I'll
>>> test that out.
>>>
>>
>> OK, I'll try XFS tonight as well.
>>
>>
>>
> I haven't been able to reproduce it on ext4 here, yet.
>
> FWIW here's the patch from mingming:
>
> When unaligned DIO writes, skip zero out the block if the buffer is marked
> unwritten. That means there is an asynconous direct IO (append or fill the hole)
> still pending.
>
> Signed-off-by: Mingming Cao <cmm@us.ibm.com>
> ---
> fs/direct-io.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> Index: linux-git/fs/direct-io.c
> ===================================================================
> --- linux-git.orig/fs/direct-io.c 2010-05-07 15:42:22.855033403 -0700
> +++ linux-git/fs/direct-io.c 2010-05-07 15:44:17.695007770 -0700
> @@ -740,7 +740,8 @@
> struct page *page;
>
> dio->start_zero_done = 1;
> - if (!dio->blkfactor || !buffer_new(&dio->map_bh))
> + if (!dio->blkfactor || !buffer_new(&dio->map_bh)
> + || buffer_unwritten(&dio->map_bh))
> return;
>
> dio_blocks_per_fs_block = 1 << dio->blkfactor;
>
>

What is this patch against?

--
Jens Axboe