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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 <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linuxfoundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/r/20201103095858.827582066@linutronix.de
This commit is contained in:
Thomas Gleixner
parent
9bf6f7bab3
commit
13f876ba77
174
include/linux/highmem-internal.h
Normal file
174
include/linux/highmem-internal.h
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@ -0,0 +1,174 @@
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_HIGHMEM_INTERNAL_H
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#define _LINUX_HIGHMEM_INTERNAL_H
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/*
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* Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft.
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*/
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#ifdef CONFIG_KMAP_LOCAL
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void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot);
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void *__kmap_local_page_prot(struct page *page, pgprot_t prot);
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void kunmap_local_indexed(void *vaddr);
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#endif
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#ifdef CONFIG_HIGHMEM
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#include <asm/highmem.h>
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#ifndef ARCH_HAS_KMAP_FLUSH_TLB
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static inline void kmap_flush_tlb(unsigned long addr) { }
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#endif
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#ifndef kmap_prot
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#define kmap_prot PAGE_KERNEL
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#endif
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void *kmap_high(struct page *page);
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void kunmap_high(struct page *page);
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void __kmap_flush_unused(void);
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struct page *__kmap_to_page(void *addr);
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static inline void *kmap(struct page *page)
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{
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void *addr;
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might_sleep();
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if (!PageHighMem(page))
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addr = page_address(page);
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else
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addr = kmap_high(page);
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kmap_flush_tlb((unsigned long)addr);
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return addr;
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}
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static inline void kunmap(struct page *page)
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{
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might_sleep();
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if (!PageHighMem(page))
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return;
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kunmap_high(page);
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}
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static inline struct page *kmap_to_page(void *addr)
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{
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return __kmap_to_page(addr);
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}
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static inline void kmap_flush_unused(void)
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{
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__kmap_flush_unused();
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}
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static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
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{
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preempt_disable();
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pagefault_disable();
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return __kmap_local_page_prot(page, prot);
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}
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static inline void *kmap_atomic(struct page *page)
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{
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return kmap_atomic_prot(page, kmap_prot);
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}
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static inline void *kmap_atomic_pfn(unsigned long pfn)
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{
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preempt_disable();
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pagefault_disable();
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return __kmap_local_pfn_prot(pfn, kmap_prot);
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}
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static inline void __kunmap_atomic(void *addr)
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{
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kunmap_local_indexed(addr);
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pagefault_enable();
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preempt_enable();
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}
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unsigned int __nr_free_highpages(void);
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extern atomic_long_t _totalhigh_pages;
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static inline unsigned int nr_free_highpages(void)
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{
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return __nr_free_highpages();
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}
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static inline unsigned long totalhigh_pages(void)
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{
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return (unsigned long)atomic_long_read(&_totalhigh_pages);
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}
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static inline void totalhigh_pages_inc(void)
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{
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atomic_long_inc(&_totalhigh_pages);
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}
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static inline void totalhigh_pages_add(long count)
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{
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atomic_long_add(count, &_totalhigh_pages);
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}
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#else /* CONFIG_HIGHMEM */
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static inline struct page *kmap_to_page(void *addr)
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{
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return virt_to_page(addr);
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}
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static inline void *kmap(struct page *page)
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{
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might_sleep();
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return page_address(page);
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}
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static inline void kunmap_high(struct page *page) { }
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static inline void kmap_flush_unused(void) { }
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static inline void kunmap(struct page *page)
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{
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#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
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kunmap_flush_on_unmap(page_address(page));
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#endif
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}
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static inline void *kmap_atomic(struct page *page)
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{
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preempt_disable();
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pagefault_disable();
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return page_address(page);
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}
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static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
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{
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return kmap_atomic(page);
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}
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static inline void *kmap_atomic_pfn(unsigned long pfn)
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{
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return kmap_atomic(pfn_to_page(pfn));
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}
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static inline void __kunmap_atomic(void *addr)
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{
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#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
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kunmap_flush_on_unmap(addr);
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#endif
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pagefault_enable();
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preempt_enable();
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}
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static inline unsigned int nr_free_highpages(void) { return 0; }
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static inline unsigned long totalhigh_pages(void) { return 0UL; }
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#endif /* CONFIG_HIGHMEM */
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/*
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* Prevent people trying to call kunmap_atomic() as if it were kunmap()
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* kunmap_atomic() should get the return value of kmap_atomic, not the page.
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*/
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#define kunmap_atomic(__addr) \
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do { \
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BUILD_BUG_ON(__same_type((__addr), struct page *)); \
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__kunmap_atomic(__addr); \
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} while (0)
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#endif
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@ -11,6 +11,108 @@
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#include <asm/cacheflush.h>
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#include "highmem-internal.h"
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/**
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* kmap - Map a page for long term usage
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* @page: Pointer to the page to be mapped
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*
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* Returns: The virtual address of the mapping
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*
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* Can only be invoked from preemptible task context because on 32bit
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* systems with CONFIG_HIGHMEM enabled this function might sleep.
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*
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* For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
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* this returns the virtual address of the direct kernel mapping.
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*
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* The returned virtual address is globally visible and valid up to the
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* point where it is unmapped via kunmap(). The pointer can be handed to
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* other contexts.
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*
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* For highmem pages on 32bit systems this can be slow as the mapping space
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* is limited and protected by a global lock. In case that there is no
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* mapping slot available the function blocks until a slot is released via
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* kunmap().
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*/
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static inline void *kmap(struct page *page);
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/**
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* kunmap - Unmap the virtual address mapped by kmap()
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* @addr: Virtual address to be unmapped
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*
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* Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
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* pages in the low memory area.
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*/
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static inline void kunmap(struct page *page);
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/**
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* kmap_to_page - Get the page for a kmap'ed address
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* @addr: The address to look up
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*
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* Returns: The page which is mapped to @addr.
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*/
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static inline struct page *kmap_to_page(void *addr);
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/**
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* kmap_flush_unused - Flush all unused kmap mappings in order to
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* remove stray mappings
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*/
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static inline void kmap_flush_unused(void);
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/**
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* kmap_atomic - Atomically map a page for temporary usage
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* @page: Pointer to the page to be mapped
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*
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* Returns: The virtual address of the mapping
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*
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* Side effect: On return pagefaults and preemption are disabled.
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*
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* Can be invoked from any context.
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*
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* Requires careful handling when nesting multiple mappings because the map
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* management is stack based. The unmap has to be in the reverse order of
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* the map operation:
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*
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* addr1 = kmap_atomic(page1);
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* addr2 = kmap_atomic(page2);
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* ...
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* kunmap_atomic(addr2);
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* kunmap_atomic(addr1);
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*
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* Unmapping addr1 before addr2 is invalid and causes malfunction.
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*
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* Contrary to kmap() mappings the mapping is only valid in the context of
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* the caller and cannot be handed to other contexts.
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*
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* On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
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* virtual address of the direct mapping. Only real highmem pages are
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* temporarily mapped.
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*
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* While it is significantly faster than kmap() it comes with restrictions
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* about the pointer validity and the side effects of disabling page faults
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* and preemption. Use it only when absolutely necessary, e.g. from non
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* preemptible contexts.
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*/
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static inline void *kmap_atomic(struct page *page);
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/**
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* kunmap_atomic - Unmap the virtual address mapped by kmap_atomic()
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* @addr: Virtual address to be unmapped
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*
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* Counterpart to kmap_atomic().
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*
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* Undoes the side effects of kmap_atomic(), i.e. reenabling pagefaults and
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* preemption.
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*
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* Other than that a NOOP for CONFIG_HIGHMEM=n and for mappings of pages
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* in the low memory area. For real highmen pages the mapping which was
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* established with kmap_atomic() is destroyed.
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*/
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/* Highmem related interfaces for management code */
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static inline unsigned int nr_free_highpages(void);
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static inline unsigned long totalhigh_pages(void);
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#ifndef ARCH_HAS_FLUSH_ANON_PAGE
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static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
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{
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@ -29,182 +131,6 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
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}
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#endif
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/*
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* Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft.
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*/
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#ifdef CONFIG_KMAP_LOCAL
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void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot);
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void *__kmap_local_page_prot(struct page *page, pgprot_t prot);
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void kunmap_local_indexed(void *vaddr);
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#endif
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#ifdef CONFIG_HIGHMEM
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#include <asm/highmem.h>
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#ifndef ARCH_HAS_KMAP_FLUSH_TLB
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static inline void kmap_flush_tlb(unsigned long addr) { }
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#endif
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#ifndef kmap_prot
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#define kmap_prot PAGE_KERNEL
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#endif
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void *kmap_high(struct page *page);
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static inline void *kmap(struct page *page)
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{
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void *addr;
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might_sleep();
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if (!PageHighMem(page))
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addr = page_address(page);
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else
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addr = kmap_high(page);
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kmap_flush_tlb((unsigned long)addr);
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return addr;
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}
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void kunmap_high(struct page *page);
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static inline void kunmap(struct page *page)
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{
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might_sleep();
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if (!PageHighMem(page))
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return;
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kunmap_high(page);
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}
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/*
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* kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
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* no global lock is needed and because the kmap code must perform a global TLB
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* invalidation when the kmap pool wraps.
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*
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* However when holding an atomic kmap it is not legal to sleep, so atomic
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* kmaps are appropriate for short, tight code paths only.
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*
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* The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
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* gives a more generic (and caching) interface. But kmap_atomic can
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* be used in IRQ contexts, so in some (very limited) cases we need
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* it.
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*/
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static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
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{
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preempt_disable();
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pagefault_disable();
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return __kmap_local_page_prot(page, prot);
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}
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static inline void *kmap_atomic(struct page *page)
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{
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return kmap_atomic_prot(page, kmap_prot);
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}
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static inline void *kmap_atomic_pfn(unsigned long pfn)
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{
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preempt_disable();
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pagefault_disable();
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return __kmap_local_pfn_prot(pfn, kmap_prot);
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}
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static inline void __kunmap_atomic(void *addr)
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{
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kunmap_local_indexed(addr);
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}
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/* declarations for linux/mm/highmem.c */
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unsigned int nr_free_highpages(void);
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extern atomic_long_t _totalhigh_pages;
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static inline unsigned long totalhigh_pages(void)
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{
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return (unsigned long)atomic_long_read(&_totalhigh_pages);
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}
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static inline void totalhigh_pages_inc(void)
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{
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atomic_long_inc(&_totalhigh_pages);
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}
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static inline void totalhigh_pages_add(long count)
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{
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atomic_long_add(count, &_totalhigh_pages);
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}
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void kmap_flush_unused(void);
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struct page *kmap_to_page(void *addr);
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#else /* CONFIG_HIGHMEM */
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static inline unsigned int nr_free_highpages(void) { return 0; }
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static inline struct page *kmap_to_page(void *addr)
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{
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return virt_to_page(addr);
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}
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static inline unsigned long totalhigh_pages(void) { return 0UL; }
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static inline void *kmap(struct page *page)
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{
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might_sleep();
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return page_address(page);
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}
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static inline void kunmap_high(struct page *page)
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{
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}
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static inline void kunmap(struct page *page)
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{
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#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
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kunmap_flush_on_unmap(page_address(page));
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#endif
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}
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static inline void *kmap_atomic(struct page *page)
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{
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preempt_disable();
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pagefault_disable();
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return page_address(page);
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}
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static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
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{
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return kmap_atomic(page);
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}
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static inline void *kmap_atomic_pfn(unsigned long pfn)
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{
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return kmap_atomic(pfn_to_page(pfn));
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}
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static inline void __kunmap_atomic(void *addr)
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{
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/*
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* Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic()
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* handles re-enabling faults and preemption
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*/
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#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
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kunmap_flush_on_unmap(addr);
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#endif
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}
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#define kmap_flush_unused() do {} while(0)
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#endif /* CONFIG_HIGHMEM */
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/*
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* Prevent people trying to call kunmap_atomic() as if it were kunmap()
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* kunmap_atomic() should get the return value of kmap_atomic, not the page.
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*/
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#define kunmap_atomic(__addr) \
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do { \
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BUILD_BUG_ON(__same_type((__addr), struct page *)); \
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__kunmap_atomic(__addr); \
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pagefault_enable(); \
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preempt_enable(); \
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} while (0)
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/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
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#ifndef clear_user_highpage
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static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
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11
mm/highmem.c
11
mm/highmem.c
@ -104,7 +104,7 @@ static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
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atomic_long_t _totalhigh_pages __read_mostly;
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EXPORT_SYMBOL(_totalhigh_pages);
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unsigned int nr_free_highpages (void)
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unsigned int __nr_free_highpages (void)
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{
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struct zone *zone;
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unsigned int pages = 0;
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@ -141,7 +141,7 @@ pte_t * pkmap_page_table;
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do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
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#endif
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struct page *kmap_to_page(void *vaddr)
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struct page *__kmap_to_page(void *vaddr)
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{
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unsigned long addr = (unsigned long)vaddr;
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@ -152,7 +152,7 @@ struct page *kmap_to_page(void *vaddr)
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return virt_to_page(addr);
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}
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EXPORT_SYMBOL(kmap_to_page);
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EXPORT_SYMBOL(__kmap_to_page);
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static void flush_all_zero_pkmaps(void)
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{
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@ -194,10 +194,7 @@ static void flush_all_zero_pkmaps(void)
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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();
|
||||
|
||||
Loading…
Reference in New Issue
Block a user