Subject: Re: bug#6131: [PATCH]: fiemap support for efficient sparse file copy

From: Tao Ma <[email-masked]>
Date: Wed, 16 Jun 2010 13:45:41 +0800

Hi Paul,

On 06/16/2010 05:11 AM, Paul Eggert wrote:
> On 06/10/2010 05:35 PM, Tao Ma wrote:
>
>> there is a flag FIEMAP_EXTENT_DELALLOC in fiemap ...
>> with dd if=/dev/zero of=/mnt/ext4/a bs=1M count=1 seek=1
>> the ext4 can't return a valid fiemap extent.
>
> Hmm, this sounds like a fairly serious bug, in that it would prevent this
> part of cp from working.  What does the fiemap ioctl return in this buggy case?
> Is there some way that cp can detect the bug, and report it to the user,
> or work around it?  Or should we just assume that the bug will get fixed
> and that cp shouldn't worry about it?
I have prompted this to the linux ext4 
community(http://lkml.org/lkml/2010/6/10/412), they are working on it 
now I guess.

Regards,
Tao