linux-kernel - RE: mips: Re-introduce copy_user

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Message-ID: <100D68C7BA14664A8938383216E40DE04085641F@FMSMSX114.amr.corp.intel.com>
Date:	Wed, 4 Feb 2015 16:25:08 +0000
From:	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>
To:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Ralf Baechle <ralf@...ux-mips.org>
CC:	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Atsushi Nemoto <anemo@....ocn.ne.jp>
Subject: RE: mips: Re-introduce copy_user_page

There is no 'struct page' for the source of this data.  We have a kernel address for it; that's all.

-----Original Message-----
From: Leonid Yegoshin [mailto:Leonid.Yegoshin@...tec.com] 
Sent: Tuesday, February 03, 2015 10:40 AM
To: Guenter Roeck; Ralf Baechle
Cc: linux-mips@...ux-mips.org; linux-kernel@...r.kernel.org; Atsushi Nemoto; Wilcox, Matthew R
Subject: Re: mips: Re-introduce copy_user_page

On 01/30/2015 09:23 PM, Guenter Roeck wrote:
> Commit bcd022801ee5 ("MIPS: Fix COW D-cache aliasing on fork") replaced
> the inline function copy_user_page for mips with an external reference,
> but neglected to introduce the actual non-inline function. Restore it.
>
> Fixes: bcd022801ee5 ("MIPS: Fix COW D-cache aliasing on fork")
> Fixes: 4927b7d77c00 ("dax,ext2: replace the XIP page fault handler with the DAX page fault handler")
> Cc: Atsushi Nemoto <anemo@....ocn.ne.jp>
> Cc: Matthew Wilcox <matthew.r.wilcox@...el.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>

Why do you use copy_user_page?
It doesn't work properly in HIGHMEM environment and it is excluded from 
MIPS because of that, I believe.

You should use copy_user_highpage() for user pages.

- Leonid.

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