Re: 2.6.24: RPC: bad TCP reclen 0x00020090 (large)

[Andrew Morton <akpm@linux-foundation.org>]

(suitable cc added)

(regression)

On Wed, 13 Feb 2008 17:02:53 +0300 Michael Tokarev <mjt@tls.msk.ru> wrote:

> Hello!
> 
> After upgrading to 2.6.24 (from .23), we're seeing ALOT
> of messages like in $subj in dmesg:
> 
> Feb 13 13:21:39 paltus kernel: RPC: bad TCP reclen 0x00020090 (large)
> Feb 13 13:21:46 paltus kernel: printk: 3586 messages suppressed.
> Feb 13 13:21:46 paltus kernel: RPC: bad TCP reclen 0x00020090 (large)
> Feb 13 13:21:49 paltus kernel: printk: 371 messages suppressed.
> Feb 13 13:21:49 paltus kernel: RPC: bad TCP reclen 0x00020090 (large)
> Feb 13 13:21:55 paltus kernel: printk: 2979 messages suppressed.
> ...
> 
> with linux NFS server.  The clients are all linux too, mostly 2.6.23
> and some 2.6.22.
> 
> I found the "offending" piece of code in net/sunrpc/svcsock.c,
> in routine svc_tcp_recvfrom() with condition being:
> 
>    if (svsk->sk_reclen > serv->sv_max_mesg) ...
> 
> This happens after a server reboot.  At this point, client(s) are trying
> to perform some NFS transaction and fail, and server starts generating
> the above messages - till I do a umount followed by mount on all clients.
> Before, such situation (nfs server reboot) were handled transparently,
> ie, there was nothing to do, the mount continued working just fine when
> the server comes back online.
> 
> Now, I'm not sure if it's really 2.6.24-specific problem or a userspace
> problem.  Some time ago we also upgraded nfs-kernel-server (Debian)
> package, and the remount-after-nfs-server-reboot problem started to
> occur at THAT time (and it is something to worry about as well, I just
> had no time to deal with it); but the dmesg spamming only appeared
> with 2.6.24.
> 
> How to debug the issue further on from this point?
>