From patchwork Tue Jun 29 02:41:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12349183 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8FB2FC11F64 for ; Tue, 29 Jun 2021 02:41:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 49A11611AE for ; Tue, 29 Jun 2021 02:41:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49A11611AE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9F2828D010F; Mon, 28 Jun 2021 22:41:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9543F8D00F0; Mon, 28 Jun 2021 22:41:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7CEA88D010F; Mon, 28 Jun 2021 22:41:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id 4F6EF8D00F0 for ; Mon, 28 Jun 2021 22:41:21 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 4BB451B3EA for ; Tue, 29 Jun 2021 02:41:21 +0000 (UTC) X-FDA: 78305209962.30.595986D Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf27.hostedemail.com (Postfix) with ESMTP id F12898019361 for ; Tue, 29 Jun 2021 02:41:20 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2C804611AE; Tue, 29 Jun 2021 02:41:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624934480; bh=cmEO5iBmc5ITQEdAIhCVo7vS5Kn/MdhwbnzBA6MwwqI=; h=Date:From:To:Subject:In-Reply-To:From; b=rvhM5Crljtrs/0arq41xpTX1BmDct3lWCqS156ySdhy2WpB9iR/95dhAGD+60C97n 1GFKA0dNOQRanuzyeeN+wXS4+WcIxQDam1z8QW9XGGElDbp3Lx/6WpTOqvEmuaFoNm rtcuu343UpX0CjIijNFKiJ08WjtbOTFwXdBfsLA4= Date: Mon, 28 Jun 2021 19:41:19 -0700 From: Andrew Morton To: akpm@linux-foundation.org, anshuman.khandual@arm.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, william.kucharski@oracle.com, willy@infradead.org Subject: [patch 154/192] mm: make compound_head const-preserving Message-ID: <20210629024119.KP64mnhwd%akpm@linux-foundation.org> In-Reply-To: <20210628193256.008961950a714730751c1423@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: F12898019361 Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=rvhM5Crl; spf=pass (imf27.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: 4bt6ghyhnjdeqnejqejgn5gh7s3fszh6 X-HE-Tag: 1624934480-562478 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: From: "Matthew Wilcox (Oracle)" Subject: mm: make compound_head const-preserving 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. Link: https://lkml.kernel.org/r/20210416231531.2521383-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Vlastimil Babka Reviewed-by: Anshuman Khandual Reviewed-by: William Kucharski Signed-off-by: Andrew Morton --- include/linux/page-flags.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/include/linux/page-flags.h~mm-make-compound_head-const-preserving +++ a/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;