Re: fiemap is broken for sparse file in ext4?

From: Eric Sandeen
Date: Fri Jun 11 2010 - 19:55:22 EST

Tao Ma wrote:
> Hi Eric,
> Eric Sandeen wrote:
>> Greg Freemyer wrote:
>>> On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen@xxxxxxxxxx>
>>> wrote:
>>>> Tao Ma 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. ;)
>>>> OK I take it back, I do see it. *cough* too many different filesystems
>>>> on this box ... ;)
>>>> Yes, it does look like a bug.
>>>> -Eric
>>> I'm not clear how this is supposed to work.
>>> Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the
>>> fiemap call, or is there a kernel bug as well?
>> The flag is optional, though maybe filefrag should use it.
>> Without it, we should get the proper logical offset and a
>> delalloc-flagged
>> extent returned
>>> If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently
>>> a problem?
>> yep, we should get one delalloc extent in the results and we don't.
> With FIEMAP_FLAG_SYNC set, my test shows that we get one extent without
> dealloc flags. So no problem with it.
> We have another different test result? ;)

No, I misread. :( Calling with FIEMAP_FLAG_SYNC works as expected.


> Regards,
> Tao

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