linux-ext4 - Re: fio test triggering bad data on ext4

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Date:	Fri, 18 Jun 2010 19:32:17 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	"tytso@....edu" <tytso@....edu>,
	"adilger@....com" <adilger@....com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: fio test triggering bad data on ext4

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@...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

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