[Linux-cluster] GFS2 + NFS crash BUG: Unable to handle kernelNULL pointer deference

[Colin Simpson]

I just ask this as I have a cluster where we wish to share a project
directories and home dirs and have them accessible by Linux clients via
NFS and PC's via Samba. As I say the locking cross OS doesn't matter. 

And using 2.6.32-71.24.1.el6.x86_64 kernel we are seeing the kernel
often panicing (every week or so) on one node. Could this be the cause?

It's hard to catch as the fencing has stopped me so far getting a good
core (and the change to crashkernel param which changed in 6.1 the new
param doesn't play with the old kernel) . Plus I guess I need to see if
it happens on the latest kernels, but they are worse for me due to
BZ#712139. I guess the first thing I'll get from support is try the
latest hotfix kernel (which I can only get once I've tested the test
kernel). Also plus long fence intervals aren't great to capture. 

So is it time for me to look at going back to ext4 for an HA file
server.

Can anyone from RH tell me if I'm wasting my time even trying this on
GFS2 (that I will get instability and kernel crashes)? 

Really unfortunate if so, as I really like the setup when it's
working.....

Also, after a node crashes some GFS mounts aren't too happy, they take a
long time to mount back on the original failed node. The filesystems are
dirty when we fsck them lots of 

Ondisk and fsck bitmaps differ at block 109405952 (0x6856700) 
Ondisk status is 1 (Data) but FSCK thinks it should be 0 (Free)
Metadata type is 0 (free)

Some differences in free space etc

Can anyone from RH tell me if I'm wasting my time even trying this on
GFS2 (that I will get GFS2 instability and kernel crashes)? 

Thanks

Colin

On Tue, 2011-07-12 at 02:29 +0100, Colin Simpson wrote:
> OK, so my question is, is there any other reason apart from the risk
> of
> individual file corruption from locking being incompatible between
> local/samba vs NFS that may lead to issues i.e. we aren't really
> interested in locking working between NFS and local/samba access just
> that it works consistently in NFS when accessing files that way (with
> a
> single node server) and locally/samba when accessing files that way.
> 
> I mean I'm thinking of, for example, I have a build that generates
> source code via NFS then some time later a PC comes in via Samba and
> accesses these files for building on that environment. The two systems
> aren't requiring locking to work cross platform/protocol, just need to
> be exported to the two systems. But locking on each one separately is
> useful.
> 
> If there are and we should be using all access via NFS on NFS exported
> filesystems, one issue that also springs to mind is commercial backup
> systems that support GFS2 but don't support backing up via NFS.
> 
> Is there anything else I should know about GFS2 limitations?
> Is there a book "GFS: The Missing Manual"? :)
> 
> Thanks
> 
> Colin
> 
> On Mon, 2011-07-11 at 13:05 +0100, J. Bruce Fields wrote:
> > On Mon, Jul 11, 2011 at 11:43:58AM +0100, Steven Whitehouse wrote:
> > > Hi,
> > >
> > > On Mon, 2011-07-11 at 09:30 +0100, Alan Brown wrote:
> > > > On 08/07/11 22:09, J. Bruce Fields wrote:
> > > >
> > > > > With default mount options, the linux NFS client (like most
> NFS
> > clients)
> > > > > assumes that a file has a most one writer at a time.
> > (Applications that
> > > > > need to do write-sharing over NFS need to use file locking.)
> > > >
> > > > The problem is that file locking on V3 isn't passed back down to
> > the
> > > > filesystem - hence the issues with nfs vs samba (or local disk
> > > > access(*)) on the same server.
> >
> > The NFS server *does* acquire locks on the exported filesystem (and
> > does
> > it the same way for v2, v3, and v4).
> >
> > For local filesystems (ext3, xfs, btrfs), this is sufficient.
> >
> > For exports of cluster filesystems like gfs2, there are more
> > complicated
> > problems that, as Steve says, will require some work to do to fix.
> >
> > Samba is a more complicated issue due to the imperfect match between
> > Windows and Linux locking semantics, but depending on how it's
> > configured Samba will also acquire locks on the exported filesystem.
> >
> > --b.
> >
> > --
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> > https://www.redhat.com/mailman/listinfo/linux-cluster
> >
> >
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