From patchwork Thu Jul 15 19:59:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12380881 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=-16.6 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,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 13C1AC636C9 for ; Thu, 15 Jul 2021 20:06:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B04A3613BB for ; Thu, 15 Jul 2021 20:06:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B04A3613BB 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 15DCE8D00F8; Thu, 15 Jul 2021 16:06:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0BFCD8D00EC; Thu, 15 Jul 2021 16:06:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EA2DC8D00F8; Thu, 15 Jul 2021 16:06:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0181.hostedemail.com [216.40.44.181]) by kanga.kvack.org (Postfix) with ESMTP id C76B48D00EC for ; Thu, 15 Jul 2021 16:06:46 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 9E56622869 for ; Thu, 15 Jul 2021 20:06:45 +0000 (UTC) X-FDA: 78365905170.36.66F631F Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf07.hostedemail.com (Postfix) with ESMTP id 590A31004E74 for ; Thu, 15 Jul 2021 20:06:45 +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=Q3P0tZNKkQBQCHQAnhrC3AbA7cH4qgibd4ubfHlUHLI=; b=mWY76eMUj8G00fQqpA8EPCLjmk f4rW8OKnZbU1NYSCjjR3zo1+oQJYVHv60+OWpspzSbf0/AmAlTkD0h7236LBgBlXh4A5h/OttBMJr DbGr21WckIYrJer/liWouLUdt7cfahXWvB+QxcyyI5xRKX+aG3tNPCvCcAwyRiYVH8IUVLyQ2Rtjq 8JVx6ysk1/UKp/eMeb+PP8kFfHJ9dcczJUvOVe5aqNmOe9/xDe5qtbCuHz9nQNvd/U8X4mS55CQX9 buZptiw7+MNwh9zE2k/mDlKoEGMsSnkAye9xN3WjrXhT4ezGvf/ja2A5+6V+JpRIkB1AqGRtthRaQ H2+R/HaQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m47ba-003mRJ-JM; Thu, 15 Jul 2021 20:05:29 +0000 From: "Matthew Wilcox (Oracle)" To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" , Christoph Hellwig Subject: [PATCH v14 04/39] mm: Add kmap_local_folio() Date: Thu, 15 Jul 2021 20:59:55 +0100 Message-Id: <20210715200030.899216-5-willy@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210715200030.899216-1-willy@infradead.org> References: <20210715200030.899216-1-willy@infradead.org> MIME-Version: 1.0 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 590A31004E74 X-Stat-Signature: qojww4mxoeccck7g8uy17atxt5adnpex Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=mWY76eMU; spf=none (imf07.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-HE-Tag: 1626379605-206279 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: 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