From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zdenek Kabelac Subject: Re: [PATCH] Don't mlock guardpage if the stack is growing up Date: Thu, 12 May 2011 11:06:03 +0200 Message-ID: <4DCBA2FB.3040907@redhat.com> References: <4DC7D37F.9040308@redhat.com> <20110509224511.GC15227@parisc-linux.org> <20110510225659.GE9253@agk-dp.fab.redhat.com> <4DCA4C05.4030803@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Milan Broz , Alasdair G Kergon , Matthew Wilcox , Mikulas Patocka , linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, Hugh Dickins , Oleg Nesterov To: Linus Torvalds Return-path: In-Reply-To: List-ID: List-Id: linux-parisc.vger.kernel.org Dne 12.5.2011 04:12, Linus Torvalds napsal(a): > On Wed, May 11, 2011 at 1:42 AM, Milan Broz wrote: >> >> Another one is cryptsetup [..] > > Quite frankly, all security-related uses should always be happy about > a "MCL_SPARSE" model, since there is no point in ever bringing in > pages that haven't been used. The whole (and only) point of > mlock[all]() for them is the "avoid to push to disk" issue. > > I do wonder if we really should ever do the page-in at all. We might > simply be better off always just saying "we'll lock pages you've > touched, that's it". > For LVM we need to ensure the code which might ever be executed during disk suspend state must be paged and locked in - thus we would need MCL_SPARSE only on several selected 'unneeded' libraries - as we are obviously not really able to select which part of glibc might be needed during all code path (though I guess we may find some limits). But if we are sure that some libraries and locale files will never be used during suspend state - we do not care about those pages at all. So it's not like we would always need only MCL_SPARSE all the time - we would probably need to have some control to switch i.e. glibc into MCL_ALL. Zdenek