linux-kernel - Re: fiemap is broken for sparse file in ext4?

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Message-ID: <4C123D94.7060003@redhat.com>
Date:	Fri, 11 Jun 2010 08:43:48 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Tao Ma <tao.ma@...cle.com>
CC:	linux-ext4@...r.kernel.org, Theodore Tso <tytso@....edu>,
	linux-kernel@...r.kernel.org
Subject: Re: fiemap is broken for sparse file in ext4?

Tao Ma wrote:
> Hi Eric,
>     Thanks for the quick response.
> 
> On 06/11/2010 12:08 PM, Eric Sandeen wrote:

...

>> What are you using to call fiemap?  Here it seems to be working:
> I just wrote a simple test program by calling ioctl. It is attached.
> btw, you need to call it immediately after dd so that we have a chance
> that ext4 don't have time to allocate extents. ;)
>>
>> # dd if=/dev/zero of=testfile1 bs=1M count=1 seek=1;
>>
>> # filefrag -v testfile1
>> Filesystem type is: ef53
>> Filesystem cylinder groups is approximately 119
>> File size of testfile1 is 2097152 (512 blocks, blocksize 4096)
>>   ext logical physical expected length flags
>>     0     256   151946               1 merged
>>     1     257   151951   151946      2 merged
>>     2     259   152434   151952    253 merged,eof
>> testfile1: 4 extents found
> I guess maybe filefrag use the diffrent ioctl flag, maybe
> FIEMAP_FLAG_SYNC to let ext4 sync first.

My tester isn't calling sync or using the sync flag, AFAIK.
I'll take a look at yours.

Thanks,
-Eric
 
> Regards,
> Tao
> 

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