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=-18.8 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,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 2B1DAC47E48 for ; Thu, 15 Jul 2021 04:21:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 146F861360 for ; Thu, 15 Jul 2021 04:21:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235551AbhGOEYk (ORCPT ); Thu, 15 Jul 2021 00:24:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230076AbhGOEYb (ORCPT ); Thu, 15 Jul 2021 00:24:31 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22341C06175F; Wed, 14 Jul 2021 21:21:38 -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=Q3P0tZNKkQBQCHQAnhrC3AbA7cH4qgibd4ubfHlUHLI=; b=H1WUkZDnuEVn52N3PeJ5KHdbnI ZQs7zReFPfjsUPm84hoc2OPUfZ19QDY6I49iYtb5+SJrH7e7Dc1mBrK97fDcZz+3/seAnmq57/DlW zfxG15tbdcsg/hUi133GL4aStb3wFjzrSv9rnpXtKJ4o4K5OEfKH2DqjoRl8NmOoiyTAsnaJ1W2+k Lv5p9RBANY6zM2ZfS7nhJB3ftKf78+RQoCqJAz+hc9zns6f5XdXHv3pXRDhhoCT+3ceOmGFH7hi4o FebvVsv9GutoCdncbnAdVUlungJiy9tLUtAfmtjbiZnesUoxauSHCN0KQad64tre21NSd6JgDNQ/U 55uZGxxg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m3sqz-002wvL-Nc; Thu, 15 Jul 2021 04:20:28 +0000 From: "Matthew Wilcox (Oracle)" To: linux-kernel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v14 054/138] mm: Add kmap_local_folio() Date: Thu, 15 Jul 2021 04:35:40 +0100 Message-Id: <20210715033704.692967-55-willy@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210715033704.692967-1-willy@infradead.org> References: <20210715033704.692967-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This allows us to map a portion of a folio. Callers can only expect to access up to the next page boundary. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig --- include/linux/highmem-internal.h | 11 +++++++++ include/linux/highmem.h | 38 ++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+) diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index 7902c7d8b55f..d5d6f930ae1d 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -73,6 +73,12 @@ static inline void *kmap_local_page(struct page *page) return __kmap_local_page_prot(page, kmap_prot); } +static inline void *kmap_local_folio(struct folio *folio, size_t offset) +{ + struct page *page = folio_page(folio, offset / PAGE_SIZE); + return __kmap_local_page_prot(page, kmap_prot) + offset % PAGE_SIZE; +} + static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot) { return __kmap_local_page_prot(page, prot); @@ -160,6 +166,11 @@ static inline void *kmap_local_page(struct page *page) return page_address(page); } +static inline void *kmap_local_folio(struct folio *folio, size_t offset) +{ + return page_address(&folio->page) + offset; +} + static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot) { return kmap_local_page(page); diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 8c6e8e996c87..85de3bd0b47d 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -96,6 +96,44 @@ static inline void kmap_flush_unused(void); */ static inline void *kmap_local_page(struct page *page); +/** + * kmap_local_folio - Map a page in this folio for temporary usage + * @folio: The folio to be mapped. + * @offset: The byte offset within the folio. + * + * Returns: The virtual address of the mapping + * + * Can be invoked from any context. + * + * Requires careful handling when nesting multiple mappings because the map + * management is stack based. The unmap has to be in the reverse order of + * the map operation: + * + * addr1 = kmap_local_folio(page1, offset1); + * addr2 = kmap_local_folio(page2, offset2); + * ... + * kunmap_local(addr2); + * kunmap_local(addr1); + * + * Unmapping addr1 before addr2 is invalid and causes malfunction. + * + * Contrary to kmap() mappings the mapping is only valid in the context of + * the caller and cannot be handed to other contexts. + * + * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the + * virtual address of the direct mapping. Only real highmem pages are + * temporarily mapped. + * + * While it is significantly faster than kmap() for the higmem case it + * comes with restrictions about the pointer validity. Only use when really + * necessary. + * + * On HIGHMEM enabled systems mapping a highmem page has the side effect of + * disabling migration in order to keep the virtual address stable across + * preemption. No caller of kmap_local_folio() can rely on this side effect. + */ +static inline void *kmap_local_folio(struct folio *folio, size_t offset); + /** * kmap_atomic - Atomically map a page for temporary usage - Deprecated! * @page: Pointer to the page to be mapped -- 2.30.2