Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752495AbdHJPbp (ORCPT ); Thu, 10 Aug 2017 11:31:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:57174 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751492AbdHJPbo (ORCPT ); Thu, 10 Aug 2017 11:31:44 -0400 Date: Thu, 10 Aug 2017 17:31:41 +0200 From: Michal Hocko To: Rik van Riel Cc: Matthew Wilcox , Mike Kravetz , Florian Weimer , linux-kernel@vger.kernel.org, linux-mm@kvack.org, colm@allcosts.net, akpm@linux-foundation.org, keescook@chromium.org, luto@amacapital.net, wad@chromium.org, mingo@kernel.org, kirill@shutemov.name, dave.hansen@intel.com Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Message-ID: <20170810153140.GB24628@dhcp22.suse.cz> References: <20170806140425.20937-1-riel@redhat.com> <1502198148.6577.18.camel@redhat.com> <0324df31-717d-32c1-95ef-351c5b23105f@oracle.com> <1502207168.6577.25.camel@redhat.com> <20170808165211.GE31390@bombadil.infradead.org> <1502217914.6577.32.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1502217914.6577.32.camel@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1606 Lines: 44 On Tue 08-08-17 14:45:14, Rik van Riel wrote: > On Tue, 2017-08-08 at 09:52 -0700, Matthew Wilcox wrote: > > On Tue, Aug 08, 2017 at 11:46:08AM -0400, Rik van Riel wrote: > > > On Tue, 2017-08-08 at 08:19 -0700, Mike Kravetz wrote: > > > > If the use case is fairly specific, then perhaps it makes sense > > > > to > > > > make MADV_WIPEONFORK not applicable (EINVAL) for mappings where > > > > the > > > > result is 'questionable'. > > > > > > That would be a question for Florian and Colm. > > > > > > If they are OK with MADV_WIPEONFORK only working on > > > anonymous VMAs (no file mapping), that certainly could > > > be implemented. > > > > > > On the other hand, I am not sure that introducing cases > > > where MADV_WIPEONFORK does not implement wipe-on-fork > > > semantics would reduce user confusion... > > > > It'll simply do exactly what it does today, so it won't introduce any > > new fallback code. > > Sure, but actually implementing MADV_WIPEONFORK in a > way that turns file mapped VMAs into zero page backed > anonymous VMAs after fork takes no more code than > implementing it in a way that refuses to work on VMAs > that have a file backing. > > There is no complexity argument for or against either > approach. > > The big question is, what is the best for users? > > Should we return -EINVAL when MADV_WIPEONFORK is called > on a VMA that has a file backing, and only succeed on > anonymous VMAs? I would rather be conservative and implement the bare minimum until there is a reasonable usecase to demand the feature for shared mappings as well. -- Michal Hocko SUSE Labs