xlog_space_left: head behind tail ?

[Dave Chinner]

[ please leave the mailing list CC on responses. thanks. ]

[Fixed up the top posting mess, too]

On Mon, Sep 24, 2012 at 09:29:04PM +1200, Gregory Machin wrote:
> On Mon, Sep 24, 2012 at 7:26 PM, Dave Chinner <david at fromorbit.com> wrote:
> > On Mon, Sep 24, 2012 at 04:49:43PM +1200, Gregory Machin wrote:
> >> Hi.
> >>
> >> Since I started using Acronis backup software I have the following in my logs :
> >
> > What kernel?
>
> The Kernel : Linux nzhmlfpr04 2.6.32-279.5.2.el6.x86_64 #1 SMP Fri Aug
> 24 01:07:11 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
> OS CentOS : 6.3

So, it doesn't have the fix. You'll have to upgrade to 3.4 or
backport the patch yourself.

> >> Sep 22 20:17:54 nzhmlfpr04 kernel: XFS (dm-3): xlog_space_left: head behind tail
> >                                           ^^^^
> >> Sep 22 20:17:54 nzhmlfpr04 kernel:  tail_cycle = 125, tail_bytes = 489472
> >> Sep 22 20:17:54 nzhmlfpr04 kernel:  GH   cycle = 125, GH   bytes = 468080
> >> Sep 22 20:19:07 nzhmlfpr04 kernel: XFS (snumbd11d): Corruption
> >                                           ^^^^^^^^^
> >> detected. Unmount and run xfs_repair
> >
> > Note the different device names the errors are for? So the log space
> > warnings are from different filesystems to the one that corruption
> > has been found on. IOWs, unrelated.
>
> There are 4 xfs filesystems mounted on that machine.

According to the logs, there are at least 5: dm-{2,3,4,5} and
snumbd11d.

> >> and what else
> >> could have cause the 2nd ?
> >
> > Don't know. There's no stack trace in the error message, so I don't
> > even know where it came from. have you modified the xfs_error_level
> > sysctl to turn off verbose reporting?
>
> sysctl.conf is default for CentOS.

So there's an error that isn't reporting a stack by default. That
means it is probably a directory read that is triggering it -
knowing what errors xfs_repair reported would help narrow it down.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com