linux-kernel - Re: BUG in __key_instantiate_and_link(): unable to handle kernel paging request at 0000632e6472616f

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Message-ID: <4FDEEF38.8030101@tomt.net>
Date:	Mon, 18 Jun 2012 11:04:56 +0200
From:	Andre Tomt <andre@...t.net>
To:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
CC:	"Schumaker, Bryan" <Bryan.Schumaker@...app.com>,
	Linux-NFS <linux-nfs@...r.kernel.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	David Howells <dhowells@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG in __key_instantiate_and_link(): unable to handle kernel
 paging request at 0000632e6472616f

On 16. juni 2012 21:59, Myklebust, Trond wrote:
> It looks to me as if the legacy upcall code is assuming that there can
> be no more than 1 upcall at a time: there is only a single
> idmap->idmap_key_cons, which gets assigned in nfs_idmap_legacy_upcall
> and then read in idmap_pipe_downcall.
>
> Bryan, can you look into this? I suspect that we need a mutex or
> something like that (for the legacy upcall case only) to ensure that
> nobody overwrites the idmap->idmap_key_cons while an upcall is in
> progress.
>
> Andre, if you want idmapper scalability, then you should rather use the
> new idmapper upcall. You need a recent version of the nfs-utils package,
> the keyutils package, and they you should add an 'id_resolver' line
> to /etc/request-keys.conf as per the nfsidmap manpage.

Indeed, using keyutils did avoid the crashes here, 40 hours and counting.

Are there any downsides of having keyutils w/ id_resolver on by default 
in a distribution? Would it break older kernels or nfs-utils (just not 
getting used is fine, obviously)?
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