From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f197.google.com (mail-qk0-f197.google.com [209.85.220.197]) by kanga.kvack.org (Postfix) with ESMTP id C87E36B0390 for ; Wed, 29 Mar 2017 13:14:09 -0400 (EDT) Received: by mail-qk0-f197.google.com with SMTP id r140so7246170qke.11 for ; Wed, 29 Mar 2017 10:14:09 -0700 (PDT) Received: from mail-qk0-f170.google.com (mail-qk0-f170.google.com. [209.85.220.170]) by mx.google.com with ESMTPS id u8si6689915qtu.197.2017.03.29.10.14.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Mar 2017 10:14:08 -0700 (PDT) Received: by mail-qk0-f170.google.com with SMTP id p22so18799804qka.3 for ; Wed, 29 Mar 2017 10:14:08 -0700 (PDT) Subject: Re: [PATCH] mm: enable page poisoning early at boot References: <1490358246-11001-1-git-send-email-vinmenon@codeaurora.org> From: Laura Abbott Message-ID: <765ba1d2-d273-e4b1-7ec2-523fe2784ae2@redhat.com> Date: Wed, 29 Mar 2017 10:14:04 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Vinayak Menon , iamjoonsoo.kim@lge.com, mhocko@suse.com, akpm@linux-foundation.org Cc: shashim@codeaurora.org, linux-mm@kvack.org On 03/29/2017 10:04 AM, Laura Abbott wrote: > On 03/24/2017 05:24 AM, Vinayak Menon wrote: >> On SPARSEMEM systems page poisoning is enabled after buddy is up, because >> of the dependency on page extension init. This causes the pages released >> by free_all_bootmem not to be poisoned. This either delays or misses >> the identification of some issues because the pages have to undergo another >> cycle of alloc-free-alloc for any corruption to be detected. >> Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON >> flag. Since all the free pages will now be poisoned, the flag need not be >> verified before checking the poison during an alloc. >> >> Signed-off-by: Vinayak Menon >> --- >> >> An RFC was sent earlier (http://www.spinics.net/lists/linux-mm/msg123142.html) >> Not sure if there exists a code path that can free pages to buddy skipping >> kernel_poison_pages, making the flag PAGE_EXT_DEBUG_POISON a necessity. But >> the tests have not shown any issues. As per Laura's suggestion, the patch was >> tested with HIBERNATION enabled and no issues were seen. >> > > I gave this a spin on some of my machines and it appears to be working > okay. I wish we had a bit more context about why it was necessary to track > the poison in the page itself. > > This change means that we shouldn't need the "select PAGE_EXTENSION" > anymore so that can be dropped. If you do that, you can add > > Acked-by: Laura Abbott > Actually never mind on dropping the select. It's still needed for the guard page as well. Longer term it might be worth separating that out as well. You can still take my Ack. Thanks, Laura -- 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