Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752609AbdCFB7x (ORCPT ); Sun, 5 Mar 2017 20:59:53 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:54911 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752414AbdCFB7w (ORCPT ); Sun, 5 Mar 2017 20:59:52 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org Date: Mon, 6 Mar 2017 10:44:46 +0900 From: Minchan Kim To: "Kirill A. Shutemov" Cc: Hillf Danton , "Aneesh Kumar K.V" , "'Andrea Arcangeli'" , "'Andrew Morton'" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/4] thp: fix MADV_DONTNEED vs. MADV_FREE race Message-ID: <20170306014446.GB8779@bbox> References: <20170302151034.27829-1-kirill.shutemov@linux.intel.com> <20170302151034.27829-4-kirill.shutemov@linux.intel.com> <07b101d293df$ed8c9850$c8a5c8f0$@alibaba-inc.com> <20170303102636.bhd2zhtpds4mt62a@black.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170303102636.bhd2zhtpds4mt62a@black.fi.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3266 Lines: 91 Hello, Kirill, On Fri, Mar 03, 2017 at 01:26:36PM +0300, Kirill A. Shutemov wrote: > On Fri, Mar 03, 2017 at 01:35:11PM +0800, Hillf Danton wrote: > > > > On March 02, 2017 11:11 PM Kirill A. Shutemov wrote: > > > > > > Basically the same race as with numa balancing in change_huge_pmd(), but > > > a bit simpler to mitigate: we don't need to preserve dirty/young flags > > > here due to MADV_FREE functionality. > > > > > > Signed-off-by: Kirill A. Shutemov > > > Cc: Minchan Kim > > > --- > > > mm/huge_memory.c | 2 -- > > > 1 file changed, 2 deletions(-) > > > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > index bb2b3646bd78..324217c31ec9 100644 > > > --- a/mm/huge_memory.c > > > +++ b/mm/huge_memory.c > > > @@ -1566,8 +1566,6 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > > > deactivate_page(page); > > > > > > if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { > > > - orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, > > > - tlb->fullmm); > > > orig_pmd = pmd_mkold(orig_pmd); > > > orig_pmd = pmd_mkclean(orig_pmd); > > > > > $ grep -n set_pmd_at linux-4.10/arch/powerpc/mm/pgtable-book3s64.c > > > > /* > > * set a new huge pmd. We should not be called for updating > > * an existing pmd entry. That should go via pmd_hugepage_update. > > */ > > void set_pmd_at(struct mm_struct *mm, unsigned long addr, > > +Aneesh. > > Urgh... Power is special again. > > I think this should work fine. > > From 056914fa025992c0a2212aee057c26307ce60238 Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" > Date: Thu, 2 Mar 2017 16:47:45 +0300 > Subject: [PATCH] thp: fix MADV_DONTNEED vs. MADV_FREE race > > Basically the same race as with numa balancing in change_huge_pmd(), but > a bit simpler to mitigate: we don't need to preserve dirty/young flags > here due to MADV_FREE functionality. Could you elaborate a bit more here rather than relying on other patch's description? And could you say what happens to the userspace if that race happens? When I guess from title "MADV_DONTNEED vs MADV_FREE", a page cannot be zapped but marked lazyfree or vise versa? Right? Thanks. > > Signed-off-by: Kirill A. Shutemov > Cc: Minchan Kim > --- > mm/huge_memory.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index bb2b3646bd78..23c1b3d58cf4 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1566,8 +1566,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > deactivate_page(page); > > if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { > - orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, > - tlb->fullmm); > + pmdp_invalidate(vma, addr, pmd); > orig_pmd = pmd_mkold(orig_pmd); > orig_pmd = pmd_mkclean(orig_pmd); > > -- > Kirill A. Shutemov > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org