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=-14.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 C3F53C2D0A3 for ; Fri, 6 Nov 2020 23:27:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2613321707 for ; Fri, 6 Nov 2020 23:27:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="QkxUgau6"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="aneQj9C2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728592AbgKFX1R (ORCPT ); Fri, 6 Nov 2020 18:27:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728096AbgKFX1P (ORCPT ); Fri, 6 Nov 2020 18:27:15 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EB3AC0613CF; Fri, 6 Nov 2020 15:27:15 -0800 (PST) Date: Fri, 06 Nov 2020 23:27:10 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1604705232; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/aUj8XDpWpqTfB8Bd812NLOF9FuF/6d72EGkdEECQVs=; b=QkxUgau6mAb91bH16bWTqFoJTW4tObRcS632Ay6Zr5GtZ7y2lDsWHD8NGx86iqXG3Eufxz OToqk+uRZ2b1iaHy2qK8J9s/u1uI1fQrP/ahgv3HuN3Xzcsdv1TcPdfolrr1jvdyIC7eUo OZYR23TkHfVnOEJk9GPGMXNLalZr03w/gr9vfox4I2MQCkx+p1yHq01LWtJKLAeQ4dVjH7 GeC26ZryjlQXH5VgYpPzJ+o0PCiwyytHlwCJT4V1ji0E2q+phVI+Eb+sE1a1fxA0mo74c0 5iRaV8hnk0aF//6zNJGRFSb2qkuaFkQDXo7m9RnQfWWJvyST4nTdhP1iXFmiCQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1604705232; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/aUj8XDpWpqTfB8Bd812NLOF9FuF/6d72EGkdEECQVs=; b=aneQj9C2XiHeu1zdi7gurUG22jSKVwK5EfDVKzv1/N8YyrfSDUZHMcXvMwOwmHu0n9WR5r 9fVMxngq368LyoAg== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/mm] highmem: High implementation details and document API Cc: Thomas Gleixner , Linus Torvalds , Christoph Hellwig , Andrew Morton , x86 , LKML In-Reply-To: <20201103095858.827582066@linutronix.de> References: <20201103095858.827582066@linutronix.de> MIME-Version: 1.0 Message-ID: <160470523060.397.4585912177423089262.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the core/mm branch of tip: Commit-ID: 13f876ba77ebd5125799bb042201f22cf73df154 Gitweb: https://git.kernel.org/tip/13f876ba77ebd5125799bb042201f22cf73df154 Author: Thomas Gleixner AuthorDate: Tue, 03 Nov 2020 10:27:34 +01:00 Committer: Thomas Gleixner CommitterDate: Fri, 06 Nov 2020 23:14:59 +01:00 highmem: High implementation details and document API Move the gory details of kmap & al into a private header and only document the interfaces which are usable by drivers. Signed-off-by: Thomas Gleixner Cc: Linus Torvalds Cc: Christoph Hellwig Cc: Andrew Morton Link: https://lore.kernel.org/r/20201103095858.827582066@linutronix.de --- include/linux/highmem-internal.h | 174 ++++++++++++++++++++- include/linux/highmem.h | 266 ++++++++++-------------------- mm/highmem.c | 11 +- 3 files changed, 274 insertions(+), 177 deletions(-) create mode 100644 include/linux/highmem-internal.h diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h new file mode 100644 index 0000000..6ceed90 --- /dev/null +++ b/include/linux/highmem-internal.h @@ -0,0 +1,174 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_HIGHMEM_INTERNAL_H +#define _LINUX_HIGHMEM_INTERNAL_H + +/* + * Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft. + */ +#ifdef CONFIG_KMAP_LOCAL +void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot); +void *__kmap_local_page_prot(struct page *page, pgprot_t prot); +void kunmap_local_indexed(void *vaddr); +#endif + +#ifdef CONFIG_HIGHMEM +#include + +#ifndef ARCH_HAS_KMAP_FLUSH_TLB +static inline void kmap_flush_tlb(unsigned long addr) { } +#endif + +#ifndef kmap_prot +#define kmap_prot PAGE_KERNEL +#endif + +void *kmap_high(struct page *page); +void kunmap_high(struct page *page); +void __kmap_flush_unused(void); +struct page *__kmap_to_page(void *addr); + +static inline void *kmap(struct page *page) +{ + void *addr; + + might_sleep(); + if (!PageHighMem(page)) + addr = page_address(page); + else + addr = kmap_high(page); + kmap_flush_tlb((unsigned long)addr); + return addr; +} + +static inline void kunmap(struct page *page) +{ + might_sleep(); + if (!PageHighMem(page)) + return; + kunmap_high(page); +} + +static inline struct page *kmap_to_page(void *addr) +{ + return __kmap_to_page(addr); +} + +static inline void kmap_flush_unused(void) +{ + __kmap_flush_unused(); +} + +static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) +{ + preempt_disable(); + pagefault_disable(); + return __kmap_local_page_prot(page, prot); +} + +static inline void *kmap_atomic(struct page *page) +{ + return kmap_atomic_prot(page, kmap_prot); +} + +static inline void *kmap_atomic_pfn(unsigned long pfn) +{ + preempt_disable(); + pagefault_disable(); + return __kmap_local_pfn_prot(pfn, kmap_prot); +} + +static inline void __kunmap_atomic(void *addr) +{ + kunmap_local_indexed(addr); + pagefault_enable(); + preempt_enable(); +} + +unsigned int __nr_free_highpages(void); +extern atomic_long_t _totalhigh_pages; + +static inline unsigned int nr_free_highpages(void) +{ + return __nr_free_highpages(); +} + +static inline unsigned long totalhigh_pages(void) +{ + return (unsigned long)atomic_long_read(&_totalhigh_pages); +} + +static inline void totalhigh_pages_inc(void) +{ + atomic_long_inc(&_totalhigh_pages); +} + +static inline void totalhigh_pages_add(long count) +{ + atomic_long_add(count, &_totalhigh_pages); +} + +#else /* CONFIG_HIGHMEM */ + +static inline struct page *kmap_to_page(void *addr) +{ + return virt_to_page(addr); +} + +static inline void *kmap(struct page *page) +{ + might_sleep(); + return page_address(page); +} + +static inline void kunmap_high(struct page *page) { } +static inline void kmap_flush_unused(void) { } + +static inline void kunmap(struct page *page) +{ +#ifdef ARCH_HAS_FLUSH_ON_KUNMAP + kunmap_flush_on_unmap(page_address(page)); +#endif +} + +static inline void *kmap_atomic(struct page *page) +{ + preempt_disable(); + pagefault_disable(); + return page_address(page); +} + +static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) +{ + return kmap_atomic(page); +} + +static inline void *kmap_atomic_pfn(unsigned long pfn) +{ + return kmap_atomic(pfn_to_page(pfn)); +} + +static inline void __kunmap_atomic(void *addr) +{ +#ifdef ARCH_HAS_FLUSH_ON_KUNMAP + kunmap_flush_on_unmap(addr); +#endif + pagefault_enable(); + preempt_enable(); +} + +static inline unsigned int nr_free_highpages(void) { return 0; } +static inline unsigned long totalhigh_pages(void) { return 0UL; } + +#endif /* CONFIG_HIGHMEM */ + +/* + * Prevent people trying to call kunmap_atomic() as if it were kunmap() + * kunmap_atomic() should get the return value of kmap_atomic, not the page. + */ +#define kunmap_atomic(__addr) \ +do { \ + BUILD_BUG_ON(__same_type((__addr), struct page *)); \ + __kunmap_atomic(__addr); \ +} while (0) + +#endif diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 3180a8f..7d098bd 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -11,199 +11,125 @@ #include -#ifndef ARCH_HAS_FLUSH_ANON_PAGE -static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr) -{ -} -#endif - -#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE -static inline void flush_kernel_dcache_page(struct page *page) -{ -} -static inline void flush_kernel_vmap_range(void *vaddr, int size) -{ -} -static inline void invalidate_kernel_vmap_range(void *vaddr, int size) -{ -} -#endif +#include "highmem-internal.h" -/* - * Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft. +/** + * kmap - Map a page for long term usage + * @page: Pointer to the page to be mapped + * + * Returns: The virtual address of the mapping + * + * Can only be invoked from preemptible task context because on 32bit + * systems with CONFIG_HIGHMEM enabled this function might sleep. + * + * For systems with CONFIG_HIGHMEM=n and for pages in the low memory area + * this returns the virtual address of the direct kernel mapping. + * + * The returned virtual address is globally visible and valid up to the + * point where it is unmapped via kunmap(). The pointer can be handed to + * other contexts. + * + * For highmem pages on 32bit systems this can be slow as the mapping space + * is limited and protected by a global lock. In case that there is no + * mapping slot available the function blocks until a slot is released via + * kunmap(). */ -#ifdef CONFIG_KMAP_LOCAL -void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot); -void *__kmap_local_page_prot(struct page *page, pgprot_t prot); -void kunmap_local_indexed(void *vaddr); -#endif - -#ifdef CONFIG_HIGHMEM -#include +static inline void *kmap(struct page *page); -#ifndef ARCH_HAS_KMAP_FLUSH_TLB -static inline void kmap_flush_tlb(unsigned long addr) { } -#endif - -#ifndef kmap_prot -#define kmap_prot PAGE_KERNEL -#endif - -void *kmap_high(struct page *page); -static inline void *kmap(struct page *page) -{ - void *addr; - - might_sleep(); - if (!PageHighMem(page)) - addr = page_address(page); - else - addr = kmap_high(page); - kmap_flush_tlb((unsigned long)addr); - return addr; -} +/** + * kunmap - Unmap the virtual address mapped by kmap() + * @addr: Virtual address to be unmapped + * + * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of + * pages in the low memory area. + */ +static inline void kunmap(struct page *page); -void kunmap_high(struct page *page); +/** + * kmap_to_page - Get the page for a kmap'ed address + * @addr: The address to look up + * + * Returns: The page which is mapped to @addr. + */ +static inline struct page *kmap_to_page(void *addr); -static inline void kunmap(struct page *page) -{ - might_sleep(); - if (!PageHighMem(page)) - return; - kunmap_high(page); -} +/** + * kmap_flush_unused - Flush all unused kmap mappings in order to + * remove stray mappings + */ +static inline void kmap_flush_unused(void); -/* - * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because - * no global lock is needed and because the kmap code must perform a global TLB - * invalidation when the kmap pool wraps. +/** + * kmap_atomic - Atomically map a page for temporary usage + * @page: Pointer to the page to be mapped + * + * Returns: The virtual address of the mapping + * + * Side effect: On return pagefaults and preemption are disabled. + * + * Can be invoked from any context. * - * However when holding an atomic kmap it is not legal to sleep, so atomic - * kmaps are appropriate for short, tight code paths only. + * 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: * - * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap - * gives a more generic (and caching) interface. But kmap_atomic can - * be used in IRQ contexts, so in some (very limited) cases we need - * it. + * addr1 = kmap_atomic(page1); + * addr2 = kmap_atomic(page2); + * ... + * kunmap_atomic(addr2); + * kunmap_atomic(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() it comes with restrictions + * about the pointer validity and the side effects of disabling page faults + * and preemption. Use it only when absolutely necessary, e.g. from non + * preemptible contexts. */ -static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) -{ - preempt_disable(); - pagefault_disable(); - return __kmap_local_page_prot(page, prot); -} +static inline void *kmap_atomic(struct page *page); -static inline void *kmap_atomic(struct page *page) -{ - return kmap_atomic_prot(page, kmap_prot); -} - -static inline void *kmap_atomic_pfn(unsigned long pfn) -{ - preempt_disable(); - pagefault_disable(); - return __kmap_local_pfn_prot(pfn, kmap_prot); -} - -static inline void __kunmap_atomic(void *addr) -{ - kunmap_local_indexed(addr); -} - -/* declarations for linux/mm/highmem.c */ -unsigned int nr_free_highpages(void); -extern atomic_long_t _totalhigh_pages; -static inline unsigned long totalhigh_pages(void) -{ - return (unsigned long)atomic_long_read(&_totalhigh_pages); -} - -static inline void totalhigh_pages_inc(void) -{ - atomic_long_inc(&_totalhigh_pages); -} - -static inline void totalhigh_pages_add(long count) -{ - atomic_long_add(count, &_totalhigh_pages); -} - -void kmap_flush_unused(void); - -struct page *kmap_to_page(void *addr); - -#else /* CONFIG_HIGHMEM */ - -static inline unsigned int nr_free_highpages(void) { return 0; } - -static inline struct page *kmap_to_page(void *addr) -{ - return virt_to_page(addr); -} - -static inline unsigned long totalhigh_pages(void) { return 0UL; } +/** + * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic() + * @addr: Virtual address to be unmapped + * + * Counterpart to kmap_atomic(). + * + * Undoes the side effects of kmap_atomic(), i.e. reenabling pagefaults and + * preemption. + * + * Other than that a NOOP for CONFIG_HIGHMEM=n and for mappings of pages + * in the low memory area. For real highmen pages the mapping which was + * established with kmap_atomic() is destroyed. + */ -static inline void *kmap(struct page *page) -{ - might_sleep(); - return page_address(page); -} +/* Highmem related interfaces for management code */ +static inline unsigned int nr_free_highpages(void); +static inline unsigned long totalhigh_pages(void); -static inline void kunmap_high(struct page *page) +#ifndef ARCH_HAS_FLUSH_ANON_PAGE +static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr) { } - -static inline void kunmap(struct page *page) -{ -#ifdef ARCH_HAS_FLUSH_ON_KUNMAP - kunmap_flush_on_unmap(page_address(page)); #endif -} -static inline void *kmap_atomic(struct page *page) +#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE +static inline void flush_kernel_dcache_page(struct page *page) { - preempt_disable(); - pagefault_disable(); - return page_address(page); } - -static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) +static inline void flush_kernel_vmap_range(void *vaddr, int size) { - return kmap_atomic(page); } - -static inline void *kmap_atomic_pfn(unsigned long pfn) +static inline void invalidate_kernel_vmap_range(void *vaddr, int size) { - return kmap_atomic(pfn_to_page(pfn)); } - -static inline void __kunmap_atomic(void *addr) -{ - /* - * Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic() - * handles re-enabling faults and preemption - */ -#ifdef ARCH_HAS_FLUSH_ON_KUNMAP - kunmap_flush_on_unmap(addr); #endif -} - -#define kmap_flush_unused() do {} while(0) - - -#endif /* CONFIG_HIGHMEM */ - -/* - * Prevent people trying to call kunmap_atomic() as if it were kunmap() - * kunmap_atomic() should get the return value of kmap_atomic, not the page. - */ -#define kunmap_atomic(__addr) \ -do { \ - BUILD_BUG_ON(__same_type((__addr), struct page *)); \ - __kunmap_atomic(__addr); \ - pagefault_enable(); \ - preempt_enable(); \ -} while (0) /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */ #ifndef clear_user_highpage diff --git a/mm/highmem.c b/mm/highmem.c index 499dfaf..54bd233 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -104,7 +104,7 @@ static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color) atomic_long_t _totalhigh_pages __read_mostly; EXPORT_SYMBOL(_totalhigh_pages); -unsigned int nr_free_highpages (void) +unsigned int __nr_free_highpages (void) { struct zone *zone; unsigned int pages = 0; @@ -141,7 +141,7 @@ pte_t * pkmap_page_table; do { spin_unlock(&kmap_lock); (void)(flags); } while (0) #endif -struct page *kmap_to_page(void *vaddr) +struct page *__kmap_to_page(void *vaddr) { unsigned long addr = (unsigned long)vaddr; @@ -152,7 +152,7 @@ struct page *kmap_to_page(void *vaddr) return virt_to_page(addr); } -EXPORT_SYMBOL(kmap_to_page); +EXPORT_SYMBOL(__kmap_to_page); static void flush_all_zero_pkmaps(void) { @@ -194,10 +194,7 @@ static void flush_all_zero_pkmaps(void) flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); } -/** - * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings - */ -void kmap_flush_unused(void) +void __kmap_flush_unused(void) { lock_kmap(); flush_all_zero_pkmaps();