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Re: [PATCH] xfs: return FIEMAP_EXTENT_UNKNOWN for delayed allocation ext

To: Jeff Liu <jeff.liu@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: return FIEMAP_EXTENT_UNKNOWN for delayed allocation extent
From: Ben Myers <bpm@xxxxxxx>
Date: Wed, 19 Jun 2013 14:31:39 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51BFC536.6030909@xxxxxxxxxx>
References: <51B08D71.7090404@xxxxxxxxxx> <20130617215353.GF20932@xxxxxxx> <51BFC536.6030909@xxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
Hey Jeff,

On Tue, Jun 18, 2013 at 10:25:58AM +0800, Jeff Liu wrote:
> On 06/18/2013 05:53 AM, Ben Myers wrote:
> > On Thu, Jun 06, 2013 at 06:24:01AM -0700, Jeff Liu wrote:
> >> From: Jie Liu <jeff.liu@xxxxxxxxxx>
> >>
> >> For FIEMAP ioctl(2), if an extent is in delayed allocation
> >> state, we need to return the FIEMAP_EXTENT_UNKNOWN flag except
> >> the FIEMAP_EXTENT_DELALLOC because its data location is unknown.
> >>
> >> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> > 
> > Looks fine.  Is there an email thread I can reference?
> 
> I can't found an email thread to verify that, but according to
> the specification of fiemap interface in kernel doc:
> Documentation/filesystems/fiemap.txt
> 
> * FIEMAP_EXTENT_UNKNOWN
> The location of this extent is currently unknown. This may indicate
> the data is stored on an inaccessible volume or that no storage has
> been allocated for the file yet.
> 
> * FIEMAP_EXTENT_DELALLOC
>   - This will also set FIEMAP_EXTENT_UNKNOWN. 
>     ^^^^^ <-- so the unknown flags should be set as well.
> 
> Delayed allocation - while there is data for this extent, its
> physical location has not been allocated yet.

Thanks.  That's just what I needed.  Applied.

> Also, Btrfs did it.

Heh.  Must be right then!  ;)

Regards,
        Ben

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