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=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 D934DC433ED for ; Fri, 30 Apr 2021 18:09:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD05461468 for ; Fri, 30 Apr 2021 18:09:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230363AbhD3SKU (ORCPT ); Fri, 30 Apr 2021 14:10:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229750AbhD3SKT (ORCPT ); Fri, 30 Apr 2021 14:10:19 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D7FCC06174A for ; Fri, 30 Apr 2021 11:09:31 -0700 (PDT) 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=A802DAakCNgP6KnNXKekfbSJdxZYtwtXlAPimCEZ7Y4=; b=O+qVOhwu7R8pbqSsrVD7MmpeuY S+fcDuiW8Qa3Kfvg5MxwVSsqsAEDqJ3yKdW2RELeFdhCgj210vafpDsfNjkMi4HFr/k2RCxF11zl9 AWZTbir4hxcyY0Rxtc146ON22zCcuh9E8AzSksHSyRcGKnhrW/PYsIb9/szbFEleIQxbPJ2/LObOF 8mfJdeYlZPTHkoL8NfkRJJgeRNVvBAaKRQNkZ6CJgOZpCyEeF1OLxrr0IRvkwq58rhKrDAkP3zOP0 Z1Nds8eR292na3cypoG4NYG8Qam+/ho1/MzL0vqZsEC/QZWbjF5vEi5+oGHIq80x4aQR6cwdjYlch +9A735Vg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lcXZ2-00BMJ7-Ho; Fri, 30 Apr 2021 18:08:48 +0000 From: "Matthew Wilcox (Oracle)" To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org Cc: "Matthew Wilcox (Oracle)" , Jeff Layton Subject: [PATCH v8 01/31] mm: Introduce struct folio Date: Fri, 30 Apr 2021 19:07:10 +0100 Message-Id: <20210430180740.2707166-2-willy@infradead.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210430180740.2707166-1-willy@infradead.org> References: <20210430180740.2707166-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org A struct folio is a new abstraction to replace the venerable struct page. A function which takes a struct folio argument declares that it will operate on the entire (possibly compound) page, not just PAGE_SIZE bytes. In return, the caller guarantees that the pointer it is passing does not point to a tail page. Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Jeff Layton --- Documentation/core-api/mm-api.rst | 1 + include/linux/mm.h | 74 +++++++++++++++++++++++++++++++ include/linux/mm_types.h | 60 +++++++++++++++++++++++++ include/linux/page-flags.h | 27 +++++++++++ 4 files changed, 162 insertions(+) diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst index 34f46df91a8b..cbf5858dadac 100644 --- a/Documentation/core-api/mm-api.rst +++ b/Documentation/core-api/mm-api.rst @@ -95,5 +95,6 @@ More Memory Management Functions .. kernel-doc:: mm/mempolicy.c .. kernel-doc:: include/linux/mm_types.h :internal: +.. kernel-doc:: include/linux/page-flags.h .. kernel-doc:: include/linux/mm.h :internal: diff --git a/include/linux/mm.h b/include/linux/mm.h index 2327f99b121f..b29c86824e6b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -950,6 +950,20 @@ static inline unsigned int compound_order(struct page *page) return page[1].compound_order; } +/** + * folio_order - The allocation order of a folio. + * @folio: The folio. + * + * A folio is composed of 2^order pages. See get_order() for the definition + * of order. + * + * Return: The order of the folio. + */ +static inline unsigned int folio_order(struct folio *folio) +{ + return compound_order(&folio->page); +} + static inline bool hpage_pincount_available(struct page *page) { /* @@ -1595,6 +1609,65 @@ static inline void set_page_links(struct page *page, enum zone_type zone, #endif } +/** + * folio_nr_pages - The number of pages in the folio. + * @folio: The folio. + * + * Return: A number which is a power of two. + */ +static inline unsigned long folio_nr_pages(struct folio *folio) +{ + return compound_nr(&folio->page); +} + +/** + * folio_next - Move to the next physical folio. + * @folio: The folio we're currently operating on. + * + * If you have physically contiguous memory which may span more than + * one folio (eg a &struct bio_vec), use this function to move from one + * folio to the next. Do not use it if the memory is only virtually + * contiguous as the folios are almost certainly not adjacent to each + * other. This is the folio equivalent to writing ``page++``. + * + * Context: We assume that the folios are refcounted and/or locked at a + * higher level and do not adjust the reference counts. + * Return: The next struct folio. + */ +static inline struct folio *folio_next(struct folio *folio) +{ + return (struct folio *)folio_page(folio, folio_nr_pages(folio)); +} + +/** + * folio_shift - The number of bits covered by this folio. + * @folio: The folio. + * + * A folio contains a number of bytes which is a power-of-two in size. + * This function tells you which power-of-two the folio is. + * + * Context: The caller should have a reference on the folio to prevent + * it from being split. It is not necessary for the folio to be locked. + * Return: The base-2 logarithm of the size of this folio. + */ +static inline unsigned int folio_shift(struct folio *folio) +{ + return PAGE_SHIFT + folio_order(folio); +} + +/** + * folio_size - The number of bytes in a folio. + * @folio: The folio. + * + * Context: The caller should have a reference on the folio to prevent + * it from being split. It is not necessary for the folio to be locked. + * Return: The number of bytes in this folio. + */ +static inline size_t folio_size(struct folio *folio) +{ + return PAGE_SIZE << folio_order(folio); +} + /* * Some inline functions in vmstat.h depend on page_zone() */ @@ -1699,6 +1772,7 @@ extern void pagefault_out_of_memory(void); #define offset_in_page(p) ((unsigned long)(p) & ~PAGE_MASK) #define offset_in_thp(page, p) ((unsigned long)(p) & (thp_size(page) - 1)) +#define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 1)) /* * Flags passed to show_mem() and show_free_areas() to suppress output in diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5aacc1c10a45..276e358c75d3 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -224,6 +224,66 @@ struct page { #endif } _struct_page_alignment; +/** + * struct folio - Represents a contiguous set of bytes. + * @flags: Identical to the page flags. + * @lru: Least Recently Used list; tracks how recently this folio was used. + * @mapping: The file this page belongs to, or refers to the anon_vma for + * anonymous pages. + * @index: Offset within the file, in units of pages. For anonymous pages, + * this is the index from the beginning of the mmap. + * @private: Filesystem per-folio data (see folio_attach_private()). + * Used for swp_entry_t if folio_swapcache(). + * @_mapcount: Do not access this member directly. Use folio_mapcount() to + * find out how many times this folio is mapped by userspace. + * @_refcount: Do not access this member directly. Use folio_ref_count() + * to find how many references there are to this folio. + * @memcg_data: Memory Control Group data. + * + * A folio is a physically, virtually and logically contiguous set + * of bytes. It is a power-of-two in size, and it is aligned to that + * same power-of-two. It is at least as large as %PAGE_SIZE. If it is + * in the page cache, it is at a file offset which is a multiple of that + * power-of-two. It may be mapped into userspace at an address which is + * at an arbitrary page offset, but its kernel virtual address is aligned + * to its size. + */ +struct folio { + /* private: don't document the anon union */ + union { + struct { + /* public: */ + unsigned long flags; + struct list_head lru; + struct address_space *mapping; + pgoff_t index; + unsigned long private; + atomic_t _mapcount; + atomic_t _refcount; +#ifdef CONFIG_MEMCG + unsigned long memcg_data; +#endif + /* private: the union with struct page is transitional */ + }; + struct page page; + }; +}; + +static_assert(sizeof(struct page) == sizeof(struct folio)); +#define FOLIO_MATCH(pg, fl) \ + static_assert(offsetof(struct page, pg) == offsetof(struct folio, fl)) +FOLIO_MATCH(flags, flags); +FOLIO_MATCH(lru, lru); +FOLIO_MATCH(compound_head, lru); +FOLIO_MATCH(index, index); +FOLIO_MATCH(private, private); +FOLIO_MATCH(_mapcount, _mapcount); +FOLIO_MATCH(_refcount, _refcount); +#ifdef CONFIG_MEMCG +FOLIO_MATCH(memcg_data, memcg_data); +#endif +#undef FOLIO_MATCH + static inline atomic_t *compound_mapcount_ptr(struct page *page) { return &page[1].compound_mapcount; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index d8e26243db25..e069aa8b11b7 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -188,6 +188,33 @@ static inline unsigned long _compound_head(const struct page *page) #define compound_head(page) ((typeof(page))_compound_head(page)) +/** + * page_folio - Converts from page to folio. + * @p: The page. + * + * Every page is part of a folio. This function cannot be called on a + * NULL pointer. + * + * Context: No reference, nor lock is required on @page. If the caller + * does not hold a reference, this call may race with a folio split, so + * it should re-check the folio still contains this page after gaining + * a reference on the folio. + * Return: The folio which contains this page. + */ +#define page_folio(p) (_Generic((p), \ + const struct page *: (const struct folio *)_compound_head(p), \ + struct page *: (struct folio *)_compound_head(p))) + +/** + * folio_page - Return a page from a folio. + * @folio: The folio. + * @n: The page number to return. + * + * @n is relative to the start of the folio. It should be between + * 0 and folio_nr_pages(@folio) - 1, but this is not checked for. + */ +#define folio_page(folio, n) nth_page(&(folio)->page, n) + static __always_inline int PageTail(struct page *page) { return READ_ONCE(page->compound_head) & 1; -- 2.30.2