From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 2275428025E for ; Thu, 22 Dec 2016 13:35:38 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id i131so37486068wmf.3 for ; Thu, 22 Dec 2016 10:35:38 -0800 (PST) Received: from mail-wm0-x241.google.com (mail-wm0-x241.google.com. [2a00:1450:400c:c09::241]) by mx.google.com with ESMTPS id a1si32750673wjw.115.2016.12.22.10.35.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Dec 2016 10:35:36 -0800 (PST) Received: by mail-wm0-x241.google.com with SMTP id u144so37664996wmu.0 for ; Thu, 22 Dec 2016 10:35:36 -0800 (PST) Date: Thu, 22 Dec 2016 21:35:33 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] mm: pmd dirty emulation in page fault handler Message-ID: <20161222183533.GA29876@node.shutemov.name> References: <1482364101-16204-1-git-send-email-minchan@kernel.org> <20161222081713.GA32480@node.shutemov.name> <20161222145203.GA18970@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161222145203.GA18970@bbox> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, Jason Evans , "Kirill A . Shutemov" , Will Deacon , Catalin Marinas , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "[4.5+]" , Andreas Schwab On Thu, Dec 22, 2016 at 11:52:03PM +0900, Minchan Kim wrote: > Hello, > > On Thu, Dec 22, 2016 at 11:17:13AM +0300, Kirill A. Shutemov wrote: > > < snip > > > > diff --git a/mm/memory.c b/mm/memory.c > > > index 36c774f..7408ddc 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -3637,18 +3637,20 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > > > if (pmd_protnone(orig_pmd) && vma_is_accessible(vma)) > > > return do_huge_pmd_numa_page(&vmf, orig_pmd); > > > > > > - if ((vmf.flags & FAULT_FLAG_WRITE) && > > > - !pmd_write(orig_pmd)) { > > > - ret = wp_huge_pmd(&vmf, orig_pmd); > > > - if (!(ret & VM_FAULT_FALLBACK)) > > > + if (vmf.flags & FAULT_FLAG_WRITE) { > > > + if (!pmd_write(orig_pmd)) { > > > + ret = wp_huge_pmd(&vmf, orig_pmd); > > > + if (ret == VM_FAULT_FALLBACK) > > > > In theory, more than one flag can be set and it would lead to > > false-negative. Bit check was the right thing. > > > > And I don't understand why do you need to change code in > > __handle_mm_fault() at all. > > From what I see change to huge_pmd_set_accessed() should be enough. > > Yeb. Thanks for the review. Here v2 goes. > > From b3ec95c0df91ad113525968a4a6b53030fd0b48d Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Thu, 22 Dec 2016 23:43:49 +0900 > Subject: [PATCH v2] mm: pmd dirty emulation in page fault handler > > Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. > http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de > > The problem is page fault handler supports only accessed flag emulation > for THP page of SW-dirty/accessed architecture. > > This patch enables dirty-bit emulation for those architectures. > Without it, MADV_FREE makes application hang by repeated fault forever. > > [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called > > Cc: Jason Evans > Cc: Kirill A. Shutemov > Cc: Will Deacon > Cc: Catalin Marinas > Cc: linux-arch@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: [4.5+] > Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") > Reported-by: Andreas Schwab > Signed-off-by: Minchan Kim Acked-by: Kirill A. Shutemov -- 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