From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 190BC6B0003 for ; Wed, 25 Apr 2018 05:50:44 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id x134-v6so12435024oif.19 for ; Wed, 25 Apr 2018 02:50:44 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id f15-v6si4899883otj.28.2018.04.25.02.50.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 25 Apr 2018 02:50:42 -0700 (PDT) Date: Wed, 25 Apr 2018 05:50:41 -0400 (EDT) From: Chunyu Hu Reply-To: Chunyu Hu Message-ID: <482146467.19754107.1524649841393.JavaMail.zimbra@redhat.com> In-Reply-To: <20180424134148.qkvqqa4c37l6irvg@armageddon.cambridge.arm.com> References: <1524243513-29118-1-git-send-email-chuhu@redhat.com> <20180420175023.3c4okuayrcul2bom@armageddon.cambridge.arm.com> <20180422125141.GF17484@dhcp22.suse.cz> <20180424132057.GE17484@dhcp22.suse.cz> <20180424134148.qkvqqa4c37l6irvg@armageddon.cambridge.arm.com> Subject: Re: [RFC] mm: kmemleak: replace __GFP_NOFAIL to GFP_NOWAIT in gfp_kmemleak_mask MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas Cc: Michal Hocko , Chunyu Hu , Dmitry Vyukov , LKML , Linux-MM ----- Original Message ----- > From: "Catalin Marinas" > To: "Michal Hocko" > Cc: "Chunyu Hu" , "Dmitry Vyukov" , "Chunyu Hu" , "LKML" > , "Linux-MM" > Sent: Tuesday, April 24, 2018 9:41:48 PM > Subject: Re: [RFC] mm: kmemleak: replace __GFP_NOFAIL to GFP_NOWAIT in gfp_kmemleak_mask > > On Tue, Apr 24, 2018 at 07:20:57AM -0600, Michal Hocko wrote: > > On Mon 23-04-18 12:17:32, Chunyu Hu wrote: > > [...] > > > So if there is a new flag, it would be the 25th bits. > > > > No new flags please. Can you simply store a simple bool into > > fail_page_alloc > > and have save/restore api for that? > > For kmemleak, we probably first hit failslab. Something like below may > do the trick: > > diff --git a/mm/failslab.c b/mm/failslab.c > index 1f2f248e3601..63f13da5cb47 100644 > --- a/mm/failslab.c > +++ b/mm/failslab.c > @@ -29,6 +29,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t > gfpflags) > if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB)) > return false; > > + if (s->flags & SLAB_NOLEAKTRACE) > + return false; > + > return should_fail(&failslab.attr, s->object_size); > } This maybe is the easy enough way for skipping fault injection for kmemleak slab object. > > > Can we get a second should_fail() via should_fail_alloc_page() if a new > slab page is allocated? looking at code path blow, what do you mean by getting a second should_fail() via fail_alloc_page? Seems we need to insert the flag between alloc_slab_page and alloc_pages()? Without GFP flag, it's difficult to pass info to should_fail_alloc_page and keep simple at same time. Or as Michal suggested, completely disabling page alloc fail injection when kmemleak enabled. And enable it again when kmemleak off. alloc_slab_page <========= flag to change the behavior of should_fail_alloc_page alloc_pages alloc_pages_current __alloc_pages_nodemask prepare_alloc_pages should_fail_alloc_page > > -- > Catalin > -- Regards, Chunyu Hu