Re: NFS client/sunrpc getting stuck on 2.6.36

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Fri, 2010-11-19 at 12:20 -0800, Simon Kirby wrote:
> On Thu, Nov 11, 2010 at 01:22:47PM +0800, Trond Myklebust wrote:
> 
> > On Wed, 2010-11-10 at 18:35 -0800, Simon Kirby wrote:
> > > Still seeing all sorts of boxes fall over with 2.6.35 and 2.6.36 NFS.
> > > Unfortunately, it doesn't happen all the time...only certain load
> > > patterns seem to start it off.  Once it starts, I can't find a way to
> > > make it recover without rebooting.
> > >...
> > > NFS: permission(0:4c/5284877), mask=0x1, res=0
> > > NFS: revalidating (0:4c/3247737045)
> > > 
> > > 900ms matches the probably-silly nfs mount settings we're currently using:
> > > 
> > > rw,hard,intr,tcp,timeo=9,retrans=3,rsize=8192,wsize=8192
> > > 
> > > Full kernel log here: http://0x.ca/sim/ref/2.6.36_stuck_nfs/
> > 
> > timeo=9 is a completely insane retransmit value for a tcp connection.
> > 
> > Please use the default timeo=600, and all will work correctly.
> 
> Ok, so, we were running with timeo=300 instead on a number of servers,
> and we were still seeing the problem on 2.6.36.  I've uploaded a new
> kernel log (lsh1051) here:
> 
> 	http://0x.ca/sim/ref/2.6.36_stuck_nfs/
> 
> The log starts out with the hung task warnings occurring after
> otherwise-normal operation.  Once I noticed, I set rpc/nfs_debug to 1,
> and then later set it to 255.

Were the NFS servers hung at this point? If so, then that probably
suffices to explain the hung task warnings (which would be false
positives) as being due to the page cache waiting to lock pages on which
I/O is being performed.

> Since several servers were stuck at the same time and we were losing
> quorum, I decided to try something more drastic and booted into
> 2.6.37-rc2-git3.  This kernel hasn't got stuck yet!  However, it's
> spitting out some new errors which may be worth looking into:
> 
> [ 1574.088812] NFS: server 10.10.52.222 error: fileid changed
> [ 1574.088814] fsid 0:18: expected fileid 0x4c081940, got 0x4c081950
> [11340.409447] NFS: server 10.10.52.228 error: fileid changed
> [11340.409450] fsid 0:45: expected fileid 0x696ff82, got 0x16a98bd7
> [20832.579912] NFS: server 10.10.52.225 error: fileid changed
> [20832.579914] fsid 0:2a: expected fileid 0x8c67ebab, got 0x8c6811e5
> [32775.957351] NFS: server 10.10.52.230 error: fileid changed
> [32775.957354] fsid 0:52: expected fileid 0x919041fd, got 0x93f1962d
> 
> These are also in the same kernel log.  The error code isn't new, so
> something else seems to have changed to cause it.

These indicate server bugs: your failover event appears to have caused
the inode numbers to have changed on a number of files. This is
something that shouldn't happen in a normal NFS environment, and so the
client prints out the above warnings...

Trond