An update to my previous posts:
The problem re-occurred today - from /var/log/messages on a client:
Mar 20 10:35:20 client automount[465]: attempting to mount entry
/net/server1
Mar 20 10:35:37 client kernel: nfs: server server1 not responding, still
trying
Mar 20 10:38:57 client kernel: nfs: task 62879 can't get a request slot
Mar 20 10:39:23 client kernel: nfs: server server1 OK
Mar 20 10:39:23 client kernel: nfs: server server1 OK
...
Mar 20 10:44:23 client1 automount[21355]: expired /net/server1
Accessing /net/server1 after this time gives "Permission denied" - until
manually umount'ing.
The machine server1 crashed or was rebooted between 10:35 and 10:39.
The client is running a RedHat 2.4.7-10 based kernel - with the
linux-2.4.7-seekdir.dif NFS client patch and a patch to ignore server
fsid changes across reboots.
This _seems_ to a problem with the server crashing - as other clients
had exactly the same problem at the same time.
Would other NFS client patches improve matters?
Thanks
James Pearson
James Pearson wrote:
>
> Since sending my original message, I've found something on the kernel
> list about a similar situation - see:
>
> http://www.geocrawler.com/archives/3/35/2001/12/2700/7351178/
>
> I asked the original sender if he had any more info:
>
> > maybe the symptom is different, but the cause is the same, i don't know.
> > If you write a script, that tries to unmount, you duplicate the functionality
> > of the automounter daemon to a certain degree, what might lead to the same
> > problems. I think the code path in fs/autofs4/root.c line 300+ is problematic:
> >
> >
> > /*
> > * If this dentry is unhashed, then we shouldn't honour this
> > * lookup even if the dentry is positive. Returning ENOENT here
> > * doesn't do the right thing for all system calls, but it should
> > * be OK for the operations we permit from an autofs.
> > */
> > if ( dentry->d_inode && d_unhashed(dentry) )
> > return ERR_PTR(-ENOENT);
> >
> > In my opinion it can happen that between the revalidate in 286 and this
> > check for 'hashedness' another thread invalidates the entry and thus
> > the syscall fails. When i find the time, i'll try to find out and fix. Possible,
> > that it fixes also your problem, but currently i can't imagine a
> > scenario including unavailable NFS-servers, that leads to this permission
> > denied error.
>
> Could what is described be the problem?
>
> Is there a "fix"?
>
> Thanks
>
> James Pearson
>
> James Pearson wrote:
> >
> > I'm using autofs4 (autofs-4.0.0pre10) to mount a number of NFS mounts
> > using a NIS map on machines running a RedHat based 2.4.7-10 kernel.
> >
> > Occasionally trying to access a mount point (that has been working fine)
> > gives e.g:
> >
> > # cd /net/server1
> > cd: /net/server1: Permission denied
> >
> > This mount point never unmounts - even with sending SIGUSR1 to automount
> >
> > The only way I can unmount the file system is by explicitly using umount
> >
> > i.e. umount /net/server1
> >
> > works OK and subsequent access to /net/server1 mounts the remote file
> > system OK
> >
> > The remote "servers' in question tend to be other Linux workstations,
> > that I _think_ have crashed (or been rebooted) while being mounted by
> > the clients ...
> >
> > Is there anything I can do to fix this?
> >
> > In the meantime, I'm thinking of having a simple script that attempts to
> > umount everything under the automount mount point every few minutes or
> > so (by looking for these mounts in mtab) - is this likely to cause
> > problems/confusion with automount?
> >
> > Thanks
> >
> > James Pearson
> >
> > _______________________________________________
> > NFS maillist - [email protected]
> > https://lists.sourceforge.net/lists/listinfo/nfs
_______________________________________________
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