Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758140AbZJMLe4 (ORCPT ); Tue, 13 Oct 2009 07:34:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755434AbZJMLez (ORCPT ); Tue, 13 Oct 2009 07:34:55 -0400 Received: from mk-filter-1-a-1.mail.uk.tiscali.com ([212.74.100.52]:26928 "EHLO mk-filter-1-a-1.mail.uk.tiscali.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754353AbZJMLey (ORCPT ); Tue, 13 Oct 2009 07:34:54 -0400 X-Trace: 273701757/mk-filter-1.mail.uk.tiscali.com/B2C/$b2c-THROTTLED-DYNAMIC/b2c-CUSTOMER-DYNAMIC-IP/80.41.95.113/None/hugh.dickins@tiscali.co.uk X-SBRS: None X-RemoteIP: 80.41.95.113 X-IP-MAIL-FROM: hugh.dickins@tiscali.co.uk X-SMTP-AUTH: X-MUA: X-IP-BHB: Once X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvQEAEsC1EpQKV9x/2dsb2JhbACBUdRIhC0E X-IronPort-AV: E=Sophos;i="4.44,550,1249254000"; d="scan'208";a="273701757" Date: Tue, 13 Oct 2009 12:33:58 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@sister.anvils To: Wu Fengguang cc: Andrew Morton , Linus Torvalds , stable@kernel.org, Rik van Riel , Christian Borntraeger , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Elladan , Nick Piggin , Andi Kleen , Christoph Lameter , Peter Zijlstra , KOSAKI Motohiro , Johannes Weiner , Minchan Kim , Andrea Arcangeli Subject: Re: [PATCH][BUGFIX] vmscan: limit VM_EXEC protection to file pages In-Reply-To: <20091013080054.GA20395@localhost> Message-ID: References: <200910122244.19666.borntraeger@de.ibm.com> <20091013022650.GB7345@localhost> <4AD3E6C4.805@redhat.com> <20091013080054.GA20395@localhost> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1978 Lines: 47 On Tue, 13 Oct 2009, Wu Fengguang wrote: > It is possible to have !Anon but SwapBacked pages, and some apps could > create huge number of such pages with MAP_SHARED|MAP_ANONYMOUS. These > pages go into the ANON lru list, and hence shall not be protected: we > only care mapped executable files. Failing to do so may trigger OOM. > > Tested-by: Christian Borntraeger > Reviewed-by: Rik van Riel > Signed-off-by: Wu Fengguang I'm not going to stand against this patch. But I would like to point out that it will "penalize" (well, no longer favour) executables being run from a tmpfs. Probably not a big deal. And I want to put on record that (like Andrea) I really loathe this (vm_flags & VM_EXEC) test: it's a heuristic unlike any other in page reclaim, and one that is open to any application writer to take unfair advantage of. I know that it's there to make some things work better, and that it has been successful (though now inevitably it's found to require a tweak - how long until its next tweak?). But I do hope that one day you will come up with something much more satisfactory here. Hugh > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- linux.orig/mm/vmscan.c 2009-10-13 09:49:05.000000000 +0800 > +++ linux/mm/vmscan.c 2009-10-13 09:49:37.000000000 +0800 > @@ -1356,7 +1356,7 @@ static void shrink_active_list(unsigned > * IO, plus JVM can create lots of anon VM_EXEC pages, > * so we ignore them here. > */ > - if ((vm_flags & VM_EXEC) && !PageAnon(page)) { > + if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { > list_add(&page->lru, &l_active); > continue; > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/