From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f198.google.com (mail-qt0-f198.google.com [209.85.216.198]) by kanga.kvack.org (Postfix) with ESMTP id BDE2D6B0003 for ; Wed, 7 Feb 2018 22:04:50 -0500 (EST) Received: by mail-qt0-f198.google.com with SMTP id z15so2685148qti.16 for ; Wed, 07 Feb 2018 19:04:50 -0800 (PST) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id f57si931143qtf.153.2018.02.07.19.04.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Feb 2018 19:04:49 -0800 (PST) Date: Thu, 8 Feb 2018 05:04:43 +0200 From: "Michael S. Tsirkin" Subject: Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules Message-ID: <20180208050337-mutt-send-email-mst@kernel.org> References: <1517986471-15185-1-git-send-email-wei.w.wang@intel.com> <1517986471-15185-4-git-send-email-wei.w.wang@intel.com> <20180207203004-mutt-send-email-mst@kernel.org> <5A7BAB7D.7070805@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5A7BAB7D.7070805@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wei Wang Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com, huangzhichao@huawei.com On Thu, Feb 08, 2018 at 09:44:29AM +0800, Wei Wang wrote: > On 02/08/2018 02:34 AM, Michael S. Tsirkin wrote: > > On Wed, Feb 07, 2018 at 02:54:30PM +0800, Wei Wang wrote: > > > In some usages, e.g. virtio-balloon, a kernel module needs to know if > > > page poisoning is in use. This patch exposes the page_poisoning_enabled > > > function to kernel modules. > > > > > > Signed-off-by: Wei Wang > > > Cc: Andrew Morton > > > Cc: Michal Hocko > > > Cc: Michael S. Tsirkin > > > --- > > > mm/page_poison.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/mm/page_poison.c b/mm/page_poison.c > > > index e83fd44..c08d02a 100644 > > > --- a/mm/page_poison.c > > > +++ b/mm/page_poison.c > > > @@ -30,6 +30,11 @@ bool page_poisoning_enabled(void) > > > debug_pagealloc_enabled())); > > > } > > > +/** > > > + * page_poisoning_enabled - check if page poisoning is enabled > > > + * > > > + * Return true if page poisoning is enabled, or false if not. > > > + */ > > > static void poison_page(struct page *page) > > > { > > > void *addr = kmap_atomic(page); > > > @@ -37,6 +42,7 @@ static void poison_page(struct page *page) > > > memset(addr, PAGE_POISON, PAGE_SIZE); > > > kunmap_atomic(addr); > > > } > > > +EXPORT_SYMBOL_GPL(page_poisoning_enabled); > > > static void poison_pages(struct page *page, int n) > > > { > > Looks like both the comment and the export are in the wrong place. > > Thanks. Will be more careful. > > > I'm a bit concerned that callers also in fact poke at the > > PAGE_POISON - exporting that seems to be more of an accident > > as it's only used without page_poisoning.c - it might be > > better to have page_poisoning_enabled get u8 * and set it. > > > > PAGE_POISON is a macro defined in the header, why would callers using it be > a concern? It might be a good idea to move it out of there though. > Do you suggest to have: > > bool page_poisoning_get(u8 *val) > { > if (page_poisoning_enabled()) { > *val = PAGE_POISON; > return true; > } > > return false; > } > EXPORT_SYMBOL_GPL(page_poisoning_get); > > > Best, > Wei Something like this, yes. -- MST -- 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