diff options
Diffstat (limited to 'include/linux/highmem.h')
| -rw-r--r-- | include/linux/highmem.h | 294 |
1 files changed, 107 insertions, 187 deletions
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 14e6202ce47f..f597830f26b4 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -11,217 +11,137 @@ #include <asm/cacheflush.h> -#ifndef ARCH_HAS_FLUSH_ANON_PAGE -static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr) -{ -} -#endif +#include "highmem-internal.h" -#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 <asm/kmap_types.h> - -#ifdef CONFIG_HIGHMEM -extern void *kmap_atomic_high_prot(struct page *page, pgprot_t prot); -extern void kunmap_atomic_high(void *kvaddr); -#include <asm/highmem.h> - -#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; -} - -void kunmap_high(struct page *page); - -static inline void kunmap(struct page *page) -{ - might_sleep(); - if (!PageHighMem(page)) - return; - kunmap_high(page); -} - -/* - * 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 - 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. * - * However when holding an atomic kmap it is not legal to sleep, so atomic - * kmaps are appropriate for short, tight code paths only. + * 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 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. + * 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(). */ -static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) -{ - preempt_disable(); - pagefault_disable(); - if (!PageHighMem(page)) - return page_address(page); - return kmap_atomic_high_prot(page, prot); -} -#define kmap_atomic(page) kmap_atomic_prot(page, kmap_prot) - -/* 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_dec(void) -{ - atomic_long_dec(&_totalhigh_pages); -} - -static inline void totalhigh_pages_add(long count) -{ - atomic_long_add(count, &_totalhigh_pages); -} - -static inline void totalhigh_pages_set(long val) -{ - atomic_long_set(&_totalhigh_pages, val); -} - -void kmap_flush_unused(void); +static inline void *kmap(struct page *page); -struct page *kmap_to_page(void *addr); - -#else /* CONFIG_HIGHMEM */ +/** + * 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); -static inline unsigned int nr_free_highpages(void) { return 0; } +/** + * 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 struct page *kmap_to_page(void *addr) -{ - return virt_to_page(addr); -} +/** + * kmap_flush_unused - Flush all unused kmap mappings in order to + * remove stray mappings + */ +static inline void kmap_flush_unused(void); -static inline unsigned long totalhigh_pages(void) { return 0UL; } +/** + * kmap_local_page - Map a page for temporary usage + * @page: Pointer to the page to be mapped + * + * 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_page(page1); + * addr2 = kmap_local_page(page2); + * ... + * 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_page() can rely on this side effect. + */ +static inline void *kmap_local_page(struct page *page); -static inline void *kmap(struct page *page) -{ - might_sleep(); - return page_address(page); -} +/** + * kmap_atomic - Atomically map a page for temporary usage - Deprecated! + * @page: Pointer to the page to be mapped + * + * Returns: The virtual address of the mapping + * + * Effectively a wrapper around kmap_local_page() which disables pagefaults + * and preemption. + * + * Do not use in new code. Use kmap_local_page() instead. + */ +static inline void *kmap_atomic(struct page *page); -static inline void kunmap_high(struct page *page) -{ -} +/** + * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic() + * @addr: Virtual address to be unmapped + * + * Counterpart to kmap_atomic(). + * + * Effectively a wrapper around kunmap_local() which additionally undoes + * the side effects of kmap_atomic(), i.e. reenabling pagefaults and + * preemption. + */ -static inline void kunmap(struct page *page) -{ -#ifdef ARCH_HAS_FLUSH_ON_KUNMAP - kunmap_flush_on_unmap(page_address(page)); -#endif -} +/* Highmem related interfaces for management code */ +static inline unsigned int nr_free_highpages(void); +static inline unsigned long totalhigh_pages(void); -static inline void *kmap_atomic(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) { - preempt_disable(); - pagefault_disable(); - return page_address(page); } -#define kmap_atomic_prot(page, prot) kmap_atomic(page) - -static inline void kunmap_atomic_high(void *addr) -{ - /* - * Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic() - * handles re-enabling faults + preemption - */ -#ifdef ARCH_HAS_FLUSH_ON_KUNMAP - kunmap_flush_on_unmap(addr); #endif -} - -#define kmap_atomic_pfn(pfn) kmap_atomic(pfn_to_page(pfn)) - -#define kmap_flush_unused() do {} while(0) - -#endif /* CONFIG_HIGHMEM */ - -#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32) - -DECLARE_PER_CPU(int, __kmap_atomic_idx); -static inline int kmap_atomic_idx_push(void) +#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE +static inline void flush_kernel_dcache_page(struct page *page) { - int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1; - -#ifdef CONFIG_DEBUG_HIGHMEM - WARN_ON_ONCE(in_irq() && !irqs_disabled()); - BUG_ON(idx >= KM_TYPE_NR); -#endif - return idx; } - -static inline int kmap_atomic_idx(void) +static inline void flush_kernel_vmap_range(void *vaddr, int size) { - return __this_cpu_read(__kmap_atomic_idx) - 1; } - -static inline void kmap_atomic_idx_pop(void) +static inline void invalidate_kernel_vmap_range(void *vaddr, int size) { -#ifdef CONFIG_DEBUG_HIGHMEM - int idx = __this_cpu_dec_return(__kmap_atomic_idx); - - BUG_ON(idx < 0); -#else - __this_cpu_dec(__kmap_atomic_idx); -#endif } - #endif -/* - * 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_high(addr); \ - pagefault_enable(); \ - preempt_enable(); \ -} while (0) - - /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */ #ifndef clear_user_highpage static inline void clear_user_highpage(struct page *page, unsigned long vaddr) |