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=-18.7 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,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 BAC0DC47435 for ; Tue, 8 Dec 2020 20:23:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A347723A7B for ; Tue, 8 Dec 2020 20:23:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729179AbgLHUWt (ORCPT ); Tue, 8 Dec 2020 15:22:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728379AbgLHUWs (ORCPT ); Tue, 8 Dec 2020 15:22:48 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 487E2C0611CF; Tue, 8 Dec 2020 12:22:05 -0800 (PST) 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=GXe88oFVuW5E50eWvehgyMPXo+ZSI7ysxpRbYPxEyKw=; b=L1OAotuFTl9MqvWQhrRpWjeJg7 +NIHpnE87lRzWc6LFtgOO507tVsQcSG8RjCTgQb1Y+pwZEjOfkRrNZAkeN+6Tf00VPF7V6wHDYXsc z0DaFe7sTFsHdOSAuqm5IXnFATDBFn+NTCo7w7V/8mbGo8/zkecQr78Vns995egjAMN2UFVwj0WtO LBv0s1Jinda1fnTss8fp25rI+mjD0vvoHj4DsPc2aE/0PDlS/gRWtNqOJ51JN7E457oqgBG5h9V2n PGfXHzIi+0Q1uca8c1BAjYhlG68a16ShaOeZG2+gOUnoTc7l6o6q1SwXfLvQALum4+a/nRTBBvOfK flYx11kw==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kmiwr-00050B-Lk; Tue, 08 Dec 2020 19:46:57 +0000 From: "Matthew Wilcox (Oracle)" To: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: "Matthew Wilcox (Oracle)" , linux-kernel@vger.kernel.org Subject: [RFC PATCH 01/11] mm: Introduce struct folio Date: Tue, 8 Dec 2020 19:46:43 +0000 Message-Id: <20201208194653.19180-2-willy@infradead.org> X-Mailer: git-send-email 2.21.3 In-Reply-To: <20201208194653.19180-1-willy@infradead.org> References: <20201208194653.19180-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org We have trouble keeping track of whether we've already called compound_head() to ensure we're not operating on a tail page. Further, it's never clear whether we intend a struct page to refer to PAGE_SIZE bytes or page_size(compound_head(page)). Introduce a new type 'struct folio' that always refers to an entire (possibly compound) page, and points to the head page (or base page). Signed-off-by: Matthew Wilcox (Oracle) --- include/linux/mm.h | 5 +++++ include/linux/mm_types.h | 17 +++++++++++++++++ 2 files changed, 22 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index d1f64744ace2..7db9a10f084b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -916,6 +916,11 @@ static inline unsigned int compound_order(struct page *page) return page[1].compound_order; } +static inline unsigned int folio_order(struct folio *folio) +{ + return compound_order(&folio->page); +} + static inline bool hpage_pincount_available(struct page *page) { /* diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 65df8abd90bd..d7e487d9998f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -223,6 +223,23 @@ struct page { #endif } _struct_page_alignment; +/* + * A struct folio is either a base (order-0) page or the head page of + * a compound page. + */ +struct folio { + struct page page; +}; + +static inline struct folio *page_folio(struct page *page) +{ + unsigned long head = READ_ONCE(page->compound_head); + + if (unlikely(head & 1)) + return (struct folio *)(head - 1); + return (struct folio *)page; +} + static inline atomic_t *compound_mapcount_ptr(struct page *page) { return &page[1].compound_mapcount; -- 2.29.2