Message-ID: <552CDD35.2030901@linux.vnet.ibm.com>
Date: Tue, 14 Apr 2015 11:26:13 +0200
From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
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To: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@kernel.org>
CC: "Kirill A. Shutemov" <kirill@shutemov.name>,
        Pavel Emelyanov <xemul@parallels.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
        Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, linuxppc-dev@lists.ozlabs.org,
        cov@codeaurora.org, criu@openvz.org
Subject: Re: [RESEND PATCH v3 1/2] mm: Introducing arch_remap hook
References: <cover.1428916945.git.ldufour@linux.vnet.ibm.com> <9d827fc618a718830b2c47aa87e8be546914c897.1428916945.git.ldufour@linux.vnet.ibm.com> <20150413115811.GA12354@node.dhcp.inet.fi> <552BB972.3010704@linux.vnet.ibm.com> <20150413131357.GC12354@node.dhcp.inet.fi> <552BC2CA.80309@linux.vnet.ibm.com>	<552BC619.9080603@parallels.com> <20150413140219.GA14480@node.dhcp.inet.fi> <20150413135951.b3d9f431892dbfa7156cc1b0@linux-foundation.org>
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On 13/04/2015 22:59, Andrew Morton wrote:
> On Mon, 13 Apr 2015 17:02:19 +0300 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> 
>>> Kirill, if I'm right with it, can you suggest the header where to put
>>> the "generic" mremap hook's (empty) body?
>>
>> I initially thought it would be enough to put it into
>> <asm-generic/mmu_context.h>, expecting it works as
>> <asm-generic/pgtable.h>. But that's not the case.
>>
>> It probably worth at some point rework all <asm/mmu_context.h> to include
>> <asm-generic/mmu_context.h> at the end as we do for <asm/pgtable.h>.
>> But that's outside the scope of the patchset, I guess.
>>
>> I don't see any better candidate for such dummy header. :-/
> 
> Do away with __HAVE_ARCH_REMAP and do it like this:
> 
> arch/x/include/asm/y.h:
> 
> 	extern void arch_remap(...);
> 	#define arch_remap arch_remap
> 
> include/linux/z.h:
> 
> 	#include <asm/y.h>
> 
> 	#ifndef arch_remap
> 	static inline void arch_remap(...) { }
> 	#define arch_remap arch_remap
> 	#endif

Hi Andrew,

I like your idea, but I can't find any good candidate for <asm/y.h> and
<linux/z.h>.

I tried with <linux/mm.h> and <asm/mmu_context.h> but
<asm/mmu_context.h> is already including <linux/mm.h>.

Do you have any suggestion ?

Another option could be to do it like the actual arch_unmap() in
<asm-generic/mm_hooks.h> but this is the opposite of your idea, and Ingo
was not comfortable with this idea due to the impact of the other
architectures.

Cheers,
Laurent.

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