linux-kernel - Re: [PATCH] staging: Disable lustre file system for MIPS, SH, and XTENSA

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Date:	Mon, 9 Sep 2013 07:01:47 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	Peng Tao <tao.peng@....com>, Peng Tao <bergwolf@...il.com>
Subject: Re: [PATCH] staging: Disable lustre file system for MIPS, SH, and
 XTENSA

On Sun, Sep 08, 2013 at 07:31:18PM -0700, Guenter Roeck wrote:
> On 09/08/2013 07:31 PM, Greg Kroah-Hartman wrote:
> >On Sun, Sep 08, 2013 at 07:24:19PM -0700, Guenter Roeck wrote:
> >>On 09/08/2013 06:59 PM, Greg Kroah-Hartman wrote:
> >>>On Sun, Sep 08, 2013 at 06:03:00PM -0700, Guenter Roeck wrote:
> >>>>mips allmodconfig fails with
> >>>>
> >>>>ERROR: "copy_from_user_page" [drivers/staging/lustre/lustre/libcfs/libcfs.ko]
> >>>>undefined!
> >>>>
> >>>>which is due to LUSTRE using copy_from_user_page which is not exported by any
> >>>>architecture.
> >>>
> >>>Any, or just these arches?
> >>>
> >>Other architectures implement it as define as far as I can see.
> >
> >Then why would it be a problem?
> >
> It isn't a problem for those other architectures. Mostly it is mapped to functions like memcpy().
> 
> Guenter
> 
> >>>>Unfortunately, LUSTRE can only be built as module, so there is no
> >>>>easy fix.
> >>>
> >>>Can't we just export the functions for those arches?  Surely lutre
> >>>isn't the first/only driver that needs this?
> >>>
> >>That would be another option.
> >>
> >>Actually, turns out Geert submitted a patch to do this for mips already, and Ralf applied it:
> >>
> >>https://lkml.org/lkml/2013/9/5/111
> >>
> >>So please forget this patch. If sh/xtensa actually need it, we can do the same there.
> >
> >Sounds good to me, consider it forgotten :)
> >
> >greg k-h

The proper "fix" seems to be to get rid of this new usage of 
copy_from_user_page() in lustre.
The code in question is nothing but a copy of __access_remote_vm()
from mm/memory.c...

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