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![Arun KS](/assets/img/avatar_default.png)
totalram_pages and totalhigh_pages are made static inline function. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes better to remove the lock and convert variables to atomic, with preventing poteintial store-to-read tearing as a bonus. [akpm@linux-foundation.org: coding style fixes] Link: http://lkml.kernel.org/r/1542090790-21750-4-git-send-email-arunks@codeaurora.org Signed-off-by: Arun KS <arunks@codeaurora.org> Suggested-by: Michal Hocko <mhocko@suse.com> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
484 lines
12 KiB
C
484 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* High memory handling common code and variables.
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*
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* (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
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* Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
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*
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*
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* Redesigned the x86 32-bit VM architecture to deal with
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* 64-bit physical space. With current x86 CPUs this
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* means up to 64 Gigabytes physical RAM.
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*
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* Rewrote high memory support to move the page cache into
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* high memory. Implemented permanent (schedulable) kmaps
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* based on Linus' idea.
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*
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* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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*/
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#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/swap.h>
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#include <linux/bio.h>
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#include <linux/pagemap.h>
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#include <linux/mempool.h>
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#include <linux/blkdev.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/highmem.h>
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#include <linux/kgdb.h>
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#include <asm/tlbflush.h>
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#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
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DEFINE_PER_CPU(int, __kmap_atomic_idx);
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#endif
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/*
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* Virtual_count is not a pure "count".
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* 0 means that it is not mapped, and has not been mapped
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* since a TLB flush - it is usable.
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* 1 means that there are no users, but it has been mapped
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* since the last TLB flush - so we can't use it.
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* n means that there are (n-1) current users of it.
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*/
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#ifdef CONFIG_HIGHMEM
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/*
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* Architecture with aliasing data cache may define the following family of
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* helper functions in its asm/highmem.h to control cache color of virtual
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* addresses where physical memory pages are mapped by kmap.
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*/
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#ifndef get_pkmap_color
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/*
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* Determine color of virtual address where the page should be mapped.
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*/
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static inline unsigned int get_pkmap_color(struct page *page)
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{
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return 0;
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}
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#define get_pkmap_color get_pkmap_color
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/*
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* Get next index for mapping inside PKMAP region for page with given color.
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*/
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static inline unsigned int get_next_pkmap_nr(unsigned int color)
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{
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static unsigned int last_pkmap_nr;
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last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
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return last_pkmap_nr;
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}
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/*
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* Determine if page index inside PKMAP region (pkmap_nr) of given color
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* has wrapped around PKMAP region end. When this happens an attempt to
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* flush all unused PKMAP slots is made.
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*/
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static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
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{
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return pkmap_nr == 0;
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}
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/*
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* Get the number of PKMAP entries of the given color. If no free slot is
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* found after checking that many entries, kmap will sleep waiting for
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* someone to call kunmap and free PKMAP slot.
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*/
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static inline int get_pkmap_entries_count(unsigned int color)
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{
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return LAST_PKMAP;
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}
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/*
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* Get head of a wait queue for PKMAP entries of the given color.
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* Wait queues for different mapping colors should be independent to avoid
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* unnecessary wakeups caused by freeing of slots of other colors.
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*/
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static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
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{
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static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
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return &pkmap_map_wait;
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}
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#endif
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atomic_long_t _totalhigh_pages __read_mostly;
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EXPORT_SYMBOL(_totalhigh_pages);
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EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
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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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for_each_populated_zone(zone) {
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if (is_highmem(zone))
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pages += zone_page_state(zone, NR_FREE_PAGES);
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}
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return pages;
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}
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static int pkmap_count[LAST_PKMAP];
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
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pte_t * pkmap_page_table;
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/*
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* Most architectures have no use for kmap_high_get(), so let's abstract
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* the disabling of IRQ out of the locking in that case to save on a
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* potential useless overhead.
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*/
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#ifdef ARCH_NEEDS_KMAP_HIGH_GET
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#define lock_kmap() spin_lock_irq(&kmap_lock)
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#define unlock_kmap() spin_unlock_irq(&kmap_lock)
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#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
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#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
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#else
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#define lock_kmap() spin_lock(&kmap_lock)
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#define unlock_kmap() spin_unlock(&kmap_lock)
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#define lock_kmap_any(flags) \
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do { spin_lock(&kmap_lock); (void)(flags); } while (0)
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#define unlock_kmap_any(flags) \
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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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{
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unsigned long addr = (unsigned long)vaddr;
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if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
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int i = PKMAP_NR(addr);
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return pte_page(pkmap_page_table[i]);
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}
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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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static void flush_all_zero_pkmaps(void)
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{
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int i;
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int need_flush = 0;
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flush_cache_kmaps();
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for (i = 0; i < LAST_PKMAP; i++) {
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struct page *page;
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/*
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* zero means we don't have anything to do,
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* >1 means that it is still in use. Only
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* a count of 1 means that it is free but
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* needs to be unmapped
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*/
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if (pkmap_count[i] != 1)
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continue;
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pkmap_count[i] = 0;
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/* sanity check */
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BUG_ON(pte_none(pkmap_page_table[i]));
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/*
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* Don't need an atomic fetch-and-clear op here;
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* no-one has the page mapped, and cannot get at
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* its virtual address (and hence PTE) without first
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* getting the kmap_lock (which is held here).
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* So no dangers, even with speculative execution.
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*/
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page = pte_page(pkmap_page_table[i]);
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pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
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set_page_address(page, NULL);
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need_flush = 1;
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}
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if (need_flush)
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flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
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}
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/**
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* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
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*/
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void kmap_flush_unused(void)
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{
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lock_kmap();
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flush_all_zero_pkmaps();
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unlock_kmap();
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}
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static inline unsigned long map_new_virtual(struct page *page)
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{
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unsigned long vaddr;
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int count;
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unsigned int last_pkmap_nr;
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unsigned int color = get_pkmap_color(page);
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start:
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count = get_pkmap_entries_count(color);
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/* Find an empty entry */
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for (;;) {
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last_pkmap_nr = get_next_pkmap_nr(color);
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if (no_more_pkmaps(last_pkmap_nr, color)) {
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flush_all_zero_pkmaps();
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count = get_pkmap_entries_count(color);
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}
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if (!pkmap_count[last_pkmap_nr])
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break; /* Found a usable entry */
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if (--count)
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continue;
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/*
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* Sleep for somebody else to unmap their entries
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*/
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{
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DECLARE_WAITQUEUE(wait, current);
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wait_queue_head_t *pkmap_map_wait =
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get_pkmap_wait_queue_head(color);
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__set_current_state(TASK_UNINTERRUPTIBLE);
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add_wait_queue(pkmap_map_wait, &wait);
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unlock_kmap();
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schedule();
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remove_wait_queue(pkmap_map_wait, &wait);
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lock_kmap();
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/* Somebody else might have mapped it while we slept */
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if (page_address(page))
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return (unsigned long)page_address(page);
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/* Re-start */
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goto start;
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}
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}
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vaddr = PKMAP_ADDR(last_pkmap_nr);
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set_pte_at(&init_mm, vaddr,
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&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
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pkmap_count[last_pkmap_nr] = 1;
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set_page_address(page, (void *)vaddr);
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return vaddr;
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}
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/**
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* kmap_high - map a highmem page into memory
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* @page: &struct page to map
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*
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* Returns the page's virtual memory address.
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*
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* We cannot call this from interrupts, as it may block.
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*/
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void *kmap_high(struct page *page)
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{
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unsigned long vaddr;
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/*
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* For highmem pages, we can't trust "virtual" until
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* after we have the lock.
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*/
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lock_kmap();
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vaddr = (unsigned long)page_address(page);
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if (!vaddr)
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vaddr = map_new_virtual(page);
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pkmap_count[PKMAP_NR(vaddr)]++;
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BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
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unlock_kmap();
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return (void*) vaddr;
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}
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EXPORT_SYMBOL(kmap_high);
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#ifdef ARCH_NEEDS_KMAP_HIGH_GET
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/**
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* kmap_high_get - pin a highmem page into memory
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* @page: &struct page to pin
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*
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* Returns the page's current virtual memory address, or NULL if no mapping
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* exists. If and only if a non null address is returned then a
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* matching call to kunmap_high() is necessary.
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*
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* This can be called from any context.
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*/
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void *kmap_high_get(struct page *page)
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{
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unsigned long vaddr, flags;
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lock_kmap_any(flags);
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vaddr = (unsigned long)page_address(page);
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if (vaddr) {
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BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
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pkmap_count[PKMAP_NR(vaddr)]++;
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}
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unlock_kmap_any(flags);
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return (void*) vaddr;
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}
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#endif
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/**
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* kunmap_high - unmap a highmem page into memory
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* @page: &struct page to unmap
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*
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* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
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* only from user context.
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*/
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void kunmap_high(struct page *page)
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{
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unsigned long vaddr;
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unsigned long nr;
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unsigned long flags;
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int need_wakeup;
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unsigned int color = get_pkmap_color(page);
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wait_queue_head_t *pkmap_map_wait;
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lock_kmap_any(flags);
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vaddr = (unsigned long)page_address(page);
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BUG_ON(!vaddr);
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nr = PKMAP_NR(vaddr);
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/*
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* A count must never go down to zero
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* without a TLB flush!
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*/
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need_wakeup = 0;
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switch (--pkmap_count[nr]) {
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case 0:
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BUG();
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case 1:
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/*
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* Avoid an unnecessary wake_up() function call.
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* The common case is pkmap_count[] == 1, but
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* no waiters.
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* The tasks queued in the wait-queue are guarded
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* by both the lock in the wait-queue-head and by
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* the kmap_lock. As the kmap_lock is held here,
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* no need for the wait-queue-head's lock. Simply
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* test if the queue is empty.
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*/
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pkmap_map_wait = get_pkmap_wait_queue_head(color);
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need_wakeup = waitqueue_active(pkmap_map_wait);
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}
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unlock_kmap_any(flags);
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/* do wake-up, if needed, race-free outside of the spin lock */
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if (need_wakeup)
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wake_up(pkmap_map_wait);
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}
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EXPORT_SYMBOL(kunmap_high);
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#endif
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#if defined(HASHED_PAGE_VIRTUAL)
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#define PA_HASH_ORDER 7
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/*
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* Describes one page->virtual association
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*/
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struct page_address_map {
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struct page *page;
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void *virtual;
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struct list_head list;
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};
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static struct page_address_map page_address_maps[LAST_PKMAP];
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/*
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* Hash table bucket
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*/
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static struct page_address_slot {
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struct list_head lh; /* List of page_address_maps */
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spinlock_t lock; /* Protect this bucket's list */
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} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
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static struct page_address_slot *page_slot(const struct page *page)
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{
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return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
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}
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/**
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* page_address - get the mapped virtual address of a page
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* @page: &struct page to get the virtual address of
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*
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* Returns the page's virtual address.
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*/
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void *page_address(const struct page *page)
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{
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unsigned long flags;
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void *ret;
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struct page_address_slot *pas;
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if (!PageHighMem(page))
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return lowmem_page_address(page);
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pas = page_slot(page);
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ret = NULL;
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spin_lock_irqsave(&pas->lock, flags);
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if (!list_empty(&pas->lh)) {
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struct page_address_map *pam;
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list_for_each_entry(pam, &pas->lh, list) {
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if (pam->page == page) {
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ret = pam->virtual;
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goto done;
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}
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}
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}
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done:
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spin_unlock_irqrestore(&pas->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(page_address);
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/**
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* set_page_address - set a page's virtual address
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* @page: &struct page to set
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* @virtual: virtual address to use
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*/
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void set_page_address(struct page *page, void *virtual)
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{
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unsigned long flags;
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struct page_address_slot *pas;
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struct page_address_map *pam;
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BUG_ON(!PageHighMem(page));
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pas = page_slot(page);
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if (virtual) { /* Add */
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pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
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pam->page = page;
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pam->virtual = virtual;
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spin_lock_irqsave(&pas->lock, flags);
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list_add_tail(&pam->list, &pas->lh);
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spin_unlock_irqrestore(&pas->lock, flags);
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} else { /* Remove */
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spin_lock_irqsave(&pas->lock, flags);
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list_for_each_entry(pam, &pas->lh, list) {
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if (pam->page == page) {
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list_del(&pam->list);
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spin_unlock_irqrestore(&pas->lock, flags);
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goto done;
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}
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}
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spin_unlock_irqrestore(&pas->lock, flags);
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}
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done:
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return;
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}
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void __init page_address_init(void)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
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INIT_LIST_HEAD(&page_address_htable[i].lh);
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spin_lock_init(&page_address_htable[i].lock);
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}
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}
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#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
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