From patchwork Fri Apr 30 14:55:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12233625 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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 A9CC1C433B4 for ; Fri, 30 Apr 2021 15:04:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0E81961409 for ; Fri, 30 Apr 2021 15:04:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E81961409 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 89A936B006C; Fri, 30 Apr 2021 11:04:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 84A056B006E; Fri, 30 Apr 2021 11:04:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 713086B0070; Fri, 30 Apr 2021 11:04:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0009.hostedemail.com [216.40.44.9]) by kanga.kvack.org (Postfix) with ESMTP id 507396B006C for ; Fri, 30 Apr 2021 11:04:02 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0CECE485A for ; Fri, 30 Apr 2021 15:04:02 +0000 (UTC) X-FDA: 78089353524.02.7490C22 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf05.hostedemail.com (Postfix) with ESMTP id 7FC7AE005F11 for ; Fri, 30 Apr 2021 15:03:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=lOmqEPnS7Hw2fLegrIjeF+PaasHglD3GyP6d0HUc9GQ=; b=CsSgrvoY1Chojmg4apEUjTeFyV jcSU8yhuHSGNZQB8SlqPojoAg78sGXhlsa6UD2fxyb0rmtQBNeEm2Vg6Uv5DLevvjs7IxBjCMvBgz H02+A28vy6QIN9e93lrg1V9yTjJEhsmHsILCQhAIdJksaCYT8WQrklDc4DqMiu2l+XPcyoJe2+Kzu /ML1zjlk4MtAzJ8JXCloFc8sOmN45vhp8EGOuiuEjWuOtDd6CmzVcsvyFCJmclW8jHUDs/+i5G+VS NCItqz0H7s4Pv87DmYqOWBmBalraS9FflB3gyd2rYVJW2XS8M0WxcmD0lhktAnoHHoI+pJakXT3hu 33G87KJw==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lcUeR-00BB4J-7a; Fri, 30 Apr 2021 15:02:36 +0000 From: "Matthew Wilcox (Oracle)" To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org Cc: "Matthew Wilcox (Oracle)" , William Kucharski , Vlastimil Babka , Anshuman Khandual Subject: [PATCH 5/8] mm: Make compound_head const-preserving Date: Fri, 30 Apr 2021 15:55:46 +0100 Message-Id: <20210430145549.2662354-6-willy@infradead.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210430145549.2662354-1-willy@infradead.org> References: <20210430145549.2662354-1-willy@infradead.org> MIME-Version: 1.0 X-Stat-Signature: sxisnbiwgm4xazcnj1b9ipjrwhpeczo5 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7FC7AE005F11 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=CsSgrvoY; spf=none (imf05.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619795037-499338 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: If you pass a const pointer to compound_head(), you get a const pointer back; if you pass a mutable pointer, you get a mutable pointer back. Also remove an unnecessary forward definition of struct page; we're about to dereference page->compound_head, so it must already have been defined. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: William Kucharski Reviewed-by: Vlastimil Babka Reviewed-by: Anshuman Khandual --- include/linux/page-flags.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 04a34c08e0a6..d8e26243db25 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -177,17 +177,17 @@ enum pageflags { #ifndef __GENERATING_BOUNDS_H -struct page; /* forward declaration */ - -static inline struct page *compound_head(struct page *page) +static inline unsigned long _compound_head(const struct page *page) { unsigned long head = READ_ONCE(page->compound_head); if (unlikely(head & 1)) - return (struct page *) (head - 1); - return page; + return head - 1; + return (unsigned long)page; } +#define compound_head(page) ((typeof(page))_compound_head(page)) + static __always_inline int PageTail(struct page *page) { return READ_ONCE(page->compound_head) & 1;