linux-kernel - Re: [GIT] Sparc

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Message-Id: <20141027140938.142f83a4c3bc6512dd73b54c@linux-foundation.org>
Date:	Mon, 27 Oct 2014 14:09:38 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>, sparclinux@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steve Capper <steve.capper@...aro.org>
Subject: Re: [GIT] Sparc

On Fri, 24 Oct 2014 12:47:48 -0700 Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Fri, Oct 24, 2014 at 10:32 AM, David Miller <davem@...emloft.net> wrote:
> >
> >    It's really idiotic to have a weak symbolled fallback that just
> >    returns zero, and causes this kind of bug.  There should be no
> >    backup implementation and the link should fail if the architecture
> >    fails to provide __get_user_pages_fast() and supports transparent
> >    hugepages.
> 
> Agreed. I think the weak fallback is for the "no hugepages support"
> case, but that does sound very annoying and fragile.
> 

Yup.  I'm thinking the get_user_pages_fast() and
__get_user_pages_fast() in mm/util.c should be made non-weak and moved
to mm/nommu.c.

With that change, MMU architctures will need to either define
CONFIG_HAVE_GENERIC_RCU_GUP or implement their own versions.

Perhaps sparc should be defining CONFIG_HAVE_GENERIC_RCU_GUP.

We really should switch x86 to the generic version - from a quick read
it looks like it will work without needing any changes.

Steve, thoughts?
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