Re: kNFS troubles (2.2.14pre15, Mandrake 7.0)

[Neil Brown]

On Thursday January 20, [e-mail] wrote:
> Hi,
> 
> since I updated my NFS server to the new Mandrake 7.0 distro I cannot run a
> single KDE application any more. Strangely, only KDE apps are affected (so
> far). I'll just forward the details I posted to the KDE mailing list.
> 
> The problem occurs whenever a KDE app tries to access its configuration or
> starts a file open dialog. It hangs with CPU stuck at about 40% on both
> server and client. strace and tcpdump logs are below.
> 
> Whose fault is it? knfsd, or KDE/Qt?
> 
> I'll happily give anyone a login to debug the problem.
> 
> 
> Thanks for any help!
> 

...

> 
> I chose to strace krdb because it's the first app that is started by the
> startkde script (and it hangs).
> 
> krdb STRACE:
> read(6, 0x40508000, 4096)               = -1 EPERM (Operation not permitted)
> fstat(6, {st_mode=S_IFREG|S_ISGID|0640, st_size=76, ...}) = 0
> read(6, 0x40508000, 4096)               = -1 EIO (Input/output error)
> fstat(6, {st_mode=S_IFREG|S_ISGID|0640, st_size=76, ...}) = 0
> 
> Is it trying to open/read a suid file (which one) and getting IO errors? I can
> do that with the shell perfectly...

st_mode=S_IFREG|S_ISGID|0640 implies a "mandatory locking" file. 
knfsd currently refuses to touch mandatory locking files as NFS (v2
and v3 at least) cannot support mandatory locking.  It would probably
be as safe, and less intrusive, to allow access but simply deny all
lock requests to a mandatory locking file, but I haven't looked into
the issues very deeply.

Do you know which file is being accessed?  used "tcpdump -s 300"
should help you find out.
Does it "need" to have mandatory locking set?

NeilBrown