Re: fiemap is broken for sparse file in ext4?

From: Eric Sandeen
Date: Fri Jun 11 2010 - 12:56:30 EST

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.


> Thanks
> Greg

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