Re: Wrong free space reported for XFS filesystem

Re: Wrong free space reported for XFS filesystem

[David Chinner]

On Wed, Sep 06, 2006 at 10:54:34AM +0200, Jesper Juhl wrote:
> For your information;
> 
> I've been running a bunch of benchmarks on a 250GB XFS filesystem.
> After the benchmarks had run for a few hours and almost filled up the
> fs, I removed all the files and did a "df -h" with interresting
> results :
> 
> /dev/mapper/Data1-test
>                     250G  -64Z  251G 101% /mnt/test
> 
> "df -k"  reported this :
> 
> /dev/mapper/Data1-test
>                     262144000 -73786976294838202960 262147504 101% /mnt/test
....
> The filesystem is mounted like this :
> 
> /dev/mapper/Data1-test on /mnt/test type xfs
> (rw,noatime,ihashsize=64433,logdev=/dev/Log1/test_log,usrquota)

So the in-core accounting has underflowed by a small amount but the
on disk accounting is correct.

We've had a few reports of this that I know of over the past couple of years,
but we've never managed to find a reproducable test case for it.

Can you describe what benchmark you were runnin, wht kernel you were
using and whether any of the tests hit  an ENOSPC condition?

Also, in future can you cc xfs@oss.sgi.com on XFS bug reports?

Cheers,

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

Re: Wrong free space reported for XFS filesystem

[David Chinner]

On Thu, Sep 07, 2006 at 04:17:53PM +0200, Jesper Juhl wrote:
> On 07/09/06, David Chinner <dgc@sgi.com> wrote:
> >On Wed, Sep 06, 2006 at 10:54:34AM +0200, Jesper Juhl wrote:
> >> For your information;
> >>
> >> I've been running a bunch of benchmarks on a 250GB XFS filesystem.
> >> After the benchmarks had run for a few hours and almost filled up the
> >> fs, I removed all the files and did a "df -h" with interresting
> >> results :
.....
> >So the in-core accounting has underflowed by a small amount but the
> >on disk accounting is correct.
> >
> >We've had a few reports of this that I know of over the past
> >couple of years, but we've never managed to find a reproducable
> >test case for it.
> >Can you describe what benchmark you were runnin, wht kernel you were
> >using
> 
> The kernel is 2.6.18-rc6 SMP

Ok, so it's a current problem....

> >and whether any of the tests hit  an ENOSPC condition?
> >
> That I don't know.
> 
> The script I was running is this one :

<snip>

That doesn't really narrow down the scope at all. All that script
tells me is that problem is <waves hands> somewhere inside XFS....  :/
Can you try to isolate which of the loads is causing the problem?

That being said, this looks like a good stress load - I'll pass it
onto our QA folks...

Cheers,

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