From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752110AbeBHBlw (ORCPT ); Wed, 7 Feb 2018 20:41:52 -0500 Received: from mga11.intel.com ([192.55.52.93]:58489 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153AbeBHBlu (ORCPT ); Wed, 7 Feb 2018 20:41:50 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,476,1511856000"; d="scan'208";a="28286809" Message-ID: <5A7BAB7D.7070805@intel.com> Date: Thu, 08 Feb 2018 09:44:29 +0800 From: Wei Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" 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 Subject: Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules 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> In-Reply-To: <20180207203004-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? 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