From patchwork Fri Apr 16 23:15:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12209291 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=-16.5 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,URIBL_BLOCKED,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 14987C433ED for ; Fri, 16 Apr 2021 23:17:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9FA686109F for ; Fri, 16 Apr 2021 23:17:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FA686109F 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 3D0B46B006C; Fri, 16 Apr 2021 19:17:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3802A6B006E; Fri, 16 Apr 2021 19:17:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2960A6B0072; Fri, 16 Apr 2021 19:17:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0095.hostedemail.com [216.40.44.95]) by kanga.kvack.org (Postfix) with ESMTP id 115666B006C for ; Fri, 16 Apr 2021 19:17:09 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id CD0431803044B for ; Fri, 16 Apr 2021 23:17:08 +0000 (UTC) X-FDA: 78039792936.10.2EA1A73 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf03.hostedemail.com (Postfix) with ESMTP id C3CDEC0001EE for ; Fri, 16 Apr 2021 23:17:04 +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=/qqs9tp+kiyQL1m0mXkIuqlBljhf16wBFlxJh1VptKw=; b=Z8EtYV1GqOIkMgD7iPf3L8u+Nw JnuFNauyEgqd9NsaDMbyVbkUcfMwd169BGAgIWsNBncjVuVFdBd8uEnj/JR/MwksytXhO5PPVtaTw mAFs/j2EulB4QzhHB/NcdcsJp6OqPoqgB5YlsOuW2zF0fyXYGUQ/Yx1tEvvZeYkda5iVghGSR3jBj y5sLZ6jLU4SRx9p/TMjXnfahlQD4k/eoQsgDSgEqfjjbUsasLCXppuIhViW6sVFaQfBW9x5hi3Qve TnUM3Y5lrYpyWZby6QeTr4boNPxI9Nb5HrKPyBtuJymhnfxQrIkSX1Y9UVmgaVZgPhqGoGkU7Hd5o Wt4kEXHA==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lXXhL-00AZzb-4N; Fri, 16 Apr 2021 23:16:32 +0000 From: "Matthew Wilcox (Oracle)" To: linux-mm@kvack.org Cc: "Matthew Wilcox (Oracle)" , Andrew Morton , linux-kernel@vger.kernel.org Subject: [PATCH 4/6] mm: Make compound_head const-preserving Date: Sat, 17 Apr 2021 00:15:29 +0100 Message-Id: <20210416231531.2521383-5-willy@infradead.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210416231531.2521383-1-willy@infradead.org> References: <20210416231531.2521383-1-willy@infradead.org> MIME-Version: 1.0 X-Stat-Signature: jx9tzhprj1bnfp4up19awa93h3p6gyta X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C3CDEC0001EE Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf03; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618615024-534375 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: 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;