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Re: vmsplice can't work well

To: Jens Axboe <axboe@xxxxxxxxx>
Subject: Re: vmsplice can't work well
From: David Chinner <dgc@xxxxxxx>
Date: Fri, 1 Sep 2006 09:17:02 +1000
Cc: "Jeffrey E. Hundstad" <jeffrey.hundstad@xxxxxxxx>, xfs@xxxxxxxxxxx, nathans@xxxxxxx
In-reply-to: <20060831092440.GC5528@xxxxxxxxx>
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On Thu, Aug 31, 2006 at 11:24:41AM +0200, Jens Axboe wrote:
> On Wed, Aug 30 2006, Jeffrey E. Hundstad wrote:
> > Jens Axboe wrote:
> > >On Wed, Aug 30 2006, Jeffrey E. Hundstad wrote:
> > >  
> > >>I tried your splie-git...tar.gz file and tried the splice-cp.  It
> > >>produced files that are the right length... but the files only contain
> > >>nulls.  Here's the straces:
> > >>    
> > >
> > >Works for me as well. Could be an fs issue, how large was the README and
> > >what filesystem did you use?
> > >
> > >  
> > The file was 1130 bytes (it was the README in that directory.)  The
> > filesystem is XFS.
> > 
> 
> I can reproduce this quite easily, doing:
> 
> nelson:~ # splice-cp sda.blktrace.0 foo
> 
> nelson:~ # md5sum sda.blktrace.0 foo 4754070ae77091468c830ea23b125d68
> sda.blktrace.0 efdc7b9d00692fdfe91a691277209267  foo

Not good.

> 'foo' contains only zeroes. Doing the same on ext3 yields the correct
> results, foo contains the right data. I'm testing on 2.16.18-rc5-current,
> Jeffrey used 2.6.17.x latest.

I had a quick look at the code and I can't see anything obviously wrong
in the XFS code. Where can I find the splice userspace application source,
Jens?

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group


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