Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754210AbbDMO3O (ORCPT ); Mon, 13 Apr 2015 10:29:14 -0400 Received: from mta-out1.inet.fi ([62.71.2.227]:50513 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753974AbbDMO3L (ORCPT ); Mon, 13 Apr 2015 10:29:11 -0400 Date: Mon, 13 Apr 2015 17:26:55 +0300 From: "Kirill A. Shutemov" To: Laurent Dufour Cc: Pavel Emelyanov , Andrew Morton , "Kirill A. Shutemov" , Hugh Dickins , Rik van Riel , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Ingo Molnar , linuxppc-dev@lists.ozlabs.org, cov@codeaurora.org, criu@openvz.org Subject: Re: [RESEND PATCH v3 1/2] mm: Introducing arch_remap hook Message-ID: <20150413142655.GA14646@node.dhcp.inet.fi> References: <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> <552BCE87.8040103@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <552BCE87.8040103@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5449 Lines: 124 On Mon, Apr 13, 2015 at 04:11:19PM +0200, Laurent Dufour wrote: > On 13/04/2015 16:02, Kirill A. Shutemov wrote: > > On Mon, Apr 13, 2015 at 04:35:21PM +0300, Pavel Emelyanov wrote: > >> On 04/13/2015 04:21 PM, Laurent Dufour wrote: > >>> On 13/04/2015 15:13, Kirill A. Shutemov wrote: > >>>> On Mon, Apr 13, 2015 at 02:41:22PM +0200, Laurent Dufour wrote: > >>>>> On 13/04/2015 13:58, Kirill A. Shutemov wrote: > >>>>>> On Mon, Apr 13, 2015 at 11:56:27AM +0200, Laurent Dufour wrote: > >>>>>>> Some architecture would like to be triggered when a memory area is moved > >>>>>>> through the mremap system call. > >>>>>>> > >>>>>>> This patch is introducing a new arch_remap mm hook which is placed in the > >>>>>>> path of mremap, and is called before the old area is unmapped (and the > >>>>>>> arch_unmap hook is called). > >>>>>>> > >>>>>>> The architectures which need to call this hook should define > >>>>>>> __HAVE_ARCH_REMAP in their asm/mmu_context.h and provide the arch_remap > >>>>>>> service with the following prototype: > >>>>>>> void arch_remap(struct mm_struct *mm, > >>>>>>> unsigned long old_start, unsigned long old_end, > >>>>>>> unsigned long new_start, unsigned long new_end); > >>>>>>> > >>>>>>> Signed-off-by: Laurent Dufour > >>>>>>> Reviewed-by: Ingo Molnar > >>>>>>> --- > >>>>>>> mm/mremap.c | 19 +++++++++++++------ > >>>>>>> 1 file changed, 13 insertions(+), 6 deletions(-) > >>>>>>> > >>>>>>> diff --git a/mm/mremap.c b/mm/mremap.c > >>>>>>> index 2dc44b1cb1df..009db5565893 100644 > >>>>>>> --- a/mm/mremap.c > >>>>>>> +++ b/mm/mremap.c > >>>>>>> @@ -25,6 +25,7 @@ > >>>>>>> > >>>>>>> #include > >>>>>>> #include > >>>>>>> +#include > >>>>>>> > >>>>>>> #include "internal.h" > >>>>>>> > >>>>>>> @@ -286,13 +287,19 @@ static unsigned long move_vma(struct vm_area_struct *vma, > >>>>>>> old_len = new_len; > >>>>>>> old_addr = new_addr; > >>>>>>> new_addr = -ENOMEM; > >>>>>>> - } else if (vma->vm_file && vma->vm_file->f_op->mremap) { > >>>>>>> - err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma); > >>>>>>> - if (err < 0) { > >>>>>>> - move_page_tables(new_vma, new_addr, vma, old_addr, > >>>>>>> - moved_len, true); > >>>>>>> - return err; > >>>>>>> + } else { > >>>>>>> + if (vma->vm_file && vma->vm_file->f_op->mremap) { > >>>>>>> + err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma); > >>>>>>> + if (err < 0) { > >>>>>>> + move_page_tables(new_vma, new_addr, vma, > >>>>>>> + old_addr, moved_len, true); > >>>>>>> + return err; > >>>>>>> + } > >>>>>>> } > >>>>>>> +#ifdef __HAVE_ARCH_REMAP > >>>>>> > >>>>>> It would be cleaner to provide dummy arch_remap() for !__HAVE_ARCH_REMAP > >>>>>> in some generic header. > >>>>> > >>>>> The idea was to not impact all the architectures as arch_unmap(), > >>>>> arch_dup_mmap() or arch_exit_mmap() implies. > >>>>> > >>>>> I look at the headers where such a dummy arch_remap could be put but I > >>>>> can't figure out one which will not impact all the architecture. > >>>>> What about defining a dummy service earlier in mm/remap.c in the case > >>>>> __HAVE_ARCH_REMAP is not defined ? > >>>>> Something like : > >>>>> #ifndef __HAVE_ARCH_REMAP > >>>>> static inline void void arch_remap(struct mm_struct *mm, > >>>>> unsigned long old_start, > >>>>> unsigned long old_end, > >>>>> unsigned long new_start, > >>>>> unsigned long new_end) > >>>>> { > >>>>> } > >>>>> #endif > >>>> > >>>> Or just #define arch_remap(...) do { } while (0) > >>>> > >>> > >>> I guessed you wanted the arch_remap() prototype to be exposed somewhere > >>> in the code. > >>> > >>> To be honest, I can't find the benefit of defining a dummy arch_remap() > >>> in mm/remap.c if __HAVE_ARCH_REMAP is not defined instead of calling it > >>> in move_vma if __HAVE_ARCH_REMAP is defined. > >>> Is it really what you want ? > >> > >> I think Kirill meant something like e.g. the arch_enter_lazy_mmu_mode() > >> is implemented and called in mm/mremap.c -- the "generic" part is in the > >> include/asm-generic/pgtable.h and those architectures willing to have > >> their own implementation are in arch/$arch/... > >> > >> 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 > > , expecting it works as > > . But that's not the case. > > > > It probably worth at some point rework all to include > > at the end as we do for . > > But that's outside the scope of the patchset, I guess. > > > > I don't see any better candidate for such dummy header. :-/ > > Clearly, I'm not confortable with a rewrite of :( > > So what about this patch, is this v3 acceptable ? Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/