From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6AC8DC43381 for ; Wed, 27 Mar 2019 13:15:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BCA62146F for ; Wed, 27 Mar 2019 13:15:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553692510; bh=KjSD+aCYL/x5+QmPOrYaXOA/aVMJFLfLjNZCXLXNOAs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Wnr+o1x8QN7nY9GpD/GqpU0Ul1O6cJQ0jBDw6Kd/4OC6uxfqI7yGA87Fm75NJYRIc aVN1k7xzdxBRfMB2K3PLrsKqBr/fXgZcJFE7tBjmEqftfu26b8kmr5G/bqao6GH55T fxuk+dsHnk3JF69MJJk6SDlknueoYtxDn/je62S4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729224AbfC0NPJ (ORCPT ); Wed, 27 Mar 2019 09:15:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:35884 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728101AbfC0NPI (ORCPT ); Wed, 27 Mar 2019 09:15:08 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7D0A9AFD1; Wed, 27 Mar 2019 13:15:07 +0000 (UTC) Date: Wed, 27 Mar 2019 14:15:06 +0100 From: Michal Hocko To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, david@redhat.com, vbabka@suse.cz, willy@infradead.org, akpm@linux-foundation.org, Nicholas Piggin Subject: Re: [PATCH] mm/page-flags: Check enforce parameter in PF_ONLY_HEAD() Message-ID: <20190327131506.GI11927@dhcp22.suse.cz> References: <1553689672-28343-1-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1553689672-28343-1-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Cc Nick] On Wed 27-03-19 17:57:52, Anshuman Khandual wrote: > Just check for enforce parameter in PF_ONLY_HEAD() wrapper before calling > VM_BUG_ON_PGFLAGS() for tail pages. Why is this an actual fix? Only TESTPAGEFLAG doesn't enforce the check but I suspect that Nick just wanted the check to be _always_ performed as the name suggests. What kind of problem are you trying to solve? > Fixes: 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit") > Signed-off-by: Anshuman Khandual > --- > include/linux/page-flags.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 9f8712a4b1a5..82539e287bc6 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -229,7 +229,7 @@ static inline void page_init_poison(struct page *page, size_t size) > #define PF_ANY(page, enforce) PF_POISONED_CHECK(page) > #define PF_HEAD(page, enforce) PF_POISONED_CHECK(compound_head(page)) > #define PF_ONLY_HEAD(page, enforce) ({ \ > - VM_BUG_ON_PGFLAGS(PageTail(page), page); \ > + VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > PF_POISONED_CHECK(page); }) > #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > -- > 2.20.1 > -- Michal Hocko SUSE Labs