From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id E09DE6B0266 for ; Mon, 6 Aug 2018 16:41:28 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id d5-v6so4624755edq.3 for ; Mon, 06 Aug 2018 13:41:28 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i2-v6si4663784edt.286.2018.08.06.13.41.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Aug 2018 13:41:27 -0700 (PDT) Date: Mon, 6 Aug 2018 22:41:19 +0200 From: Michal Hocko Subject: Re: [RFC v6 PATCH 2/2] mm: mmap: zap pages with read mmap_sem in munmap Message-ID: <20180806204119.GL10003@dhcp22.suse.cz> References: <1532628614-111702-1-git-send-email-yang.shi@linux.alibaba.com> <1532628614-111702-3-git-send-email-yang.shi@linux.alibaba.com> <20180803090759.GI27245@dhcp22.suse.cz> <20180806094005.GG19540@dhcp22.suse.cz> <76c0fc2b-fca7-9f22-214a-920ee2537898@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <76c0fc2b-fca7-9f22-214a-920ee2537898@linux.alibaba.com> Sender: owner-linux-mm@kvack.org List-ID: To: Yang Shi Cc: willy@infradead.org, ldufour@linux.vnet.ibm.com, kirill@shutemov.name, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon 06-08-18 09:46:30, Yang Shi wrote: > > > On 8/6/18 2:40 AM, Michal Hocko wrote: > > On Fri 03-08-18 14:01:58, Yang Shi wrote: > > > > > > On 8/3/18 2:07 AM, Michal Hocko wrote: > > > > On Fri 27-07-18 02:10:14, Yang Shi wrote: [...] > > > > > If the vma has VM_LOCKED | VM_HUGETLB | VM_PFNMAP or uprobe, they are > > > > > considered as special mappings. They will be dealt with before zapping > > > > > pages with write mmap_sem held. Basically, just update vm_flags. > > > > Well, I think it would be safer to simply fallback to the current > > > > implementation with these mappings and deal with them on top. This would > > > > make potential issues easier to bisect and partial reverts as well. > > > Do you mean just call do_munmap()? It sounds ok. Although we may waste some > > > cycles to repeat what has done, it sounds not too bad since those special > > > mappings should be not very common. > > VM_HUGETLB is quite spread. Especially for DB workloads. > > Wait a minute. In this way, it sounds we go back to my old implementation > with special handling for those mappings with write mmap_sem held, right? Yes, I would really start simple and add further enhacements on top. -- Michal Hocko SUSE Labs