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-rw-r--r--mm/highmem.c484
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diff --git a/mm/highmem.c b/mm/highmem.c
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+// SPDX-License-Identifier: GPL-2.0
+/*
+ * High memory handling common code and variables.
+ *
+ * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
+ * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
+ *
+ *
+ * Redesigned the x86 32-bit VM architecture to deal with
+ * 64-bit physical space. With current x86 CPUs this
+ * means up to 64 Gigabytes physical RAM.
+ *
+ * Rewrote high memory support to move the page cache into
+ * high memory. Implemented permanent (schedulable) kmaps
+ * based on Linus' idea.
+ *
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/export.h>
+#include <linux/swap.h>
+#include <linux/bio.h>
+#include <linux/pagemap.h>
+#include <linux/mempool.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/highmem.h>
+#include <linux/kgdb.h>
+#include <asm/tlbflush.h>
+#include <linux/vmalloc.h>
+
+#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
+DEFINE_PER_CPU(int, __kmap_atomic_idx);
+#endif
+
+/*
+ * Virtual_count is not a pure "count".
+ * 0 means that it is not mapped, and has not been mapped
+ * since a TLB flush - it is usable.
+ * 1 means that there are no users, but it has been mapped
+ * since the last TLB flush - so we can't use it.
+ * n means that there are (n-1) current users of it.
+ */
+#ifdef CONFIG_HIGHMEM
+
+/*
+ * Architecture with aliasing data cache may define the following family of
+ * helper functions in its asm/highmem.h to control cache color of virtual
+ * addresses where physical memory pages are mapped by kmap.
+ */
+#ifndef get_pkmap_color
+
+/*
+ * Determine color of virtual address where the page should be mapped.
+ */
+static inline unsigned int get_pkmap_color(struct page *page)
+{
+ return 0;
+}
+#define get_pkmap_color get_pkmap_color
+
+/*
+ * Get next index for mapping inside PKMAP region for page with given color.
+ */
+static inline unsigned int get_next_pkmap_nr(unsigned int color)
+{
+ static unsigned int last_pkmap_nr;
+
+ last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
+ return last_pkmap_nr;
+}
+
+/*
+ * Determine if page index inside PKMAP region (pkmap_nr) of given color
+ * has wrapped around PKMAP region end. When this happens an attempt to
+ * flush all unused PKMAP slots is made.
+ */
+static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
+{
+ return pkmap_nr == 0;
+}
+
+/*
+ * Get the number of PKMAP entries of the given color. If no free slot is
+ * found after checking that many entries, kmap will sleep waiting for
+ * someone to call kunmap and free PKMAP slot.
+ */
+static inline int get_pkmap_entries_count(unsigned int color)
+{
+ return LAST_PKMAP;
+}
+
+/*
+ * Get head of a wait queue for PKMAP entries of the given color.
+ * Wait queues for different mapping colors should be independent to avoid
+ * unnecessary wakeups caused by freeing of slots of other colors.
+ */
+static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
+{
+ static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
+
+ return &pkmap_map_wait;
+}
+#endif
+
+atomic_long_t _totalhigh_pages __read_mostly;
+EXPORT_SYMBOL(_totalhigh_pages);
+
+EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
+
+unsigned int nr_free_highpages (void)
+{
+ struct zone *zone;
+ unsigned int pages = 0;
+
+ for_each_populated_zone(zone) {
+ if (is_highmem(zone))
+ pages += zone_page_state(zone, NR_FREE_PAGES);
+ }
+
+ return pages;
+}
+
+static int pkmap_count[LAST_PKMAP];
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
+
+pte_t * pkmap_page_table;
+
+/*
+ * Most architectures have no use for kmap_high_get(), so let's abstract
+ * the disabling of IRQ out of the locking in that case to save on a
+ * potential useless overhead.
+ */
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
+#define lock_kmap() spin_lock_irq(&kmap_lock)
+#define unlock_kmap() spin_unlock_irq(&kmap_lock)
+#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
+#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
+#else
+#define lock_kmap() spin_lock(&kmap_lock)
+#define unlock_kmap() spin_unlock(&kmap_lock)
+#define lock_kmap_any(flags) \
+ do { spin_lock(&kmap_lock); (void)(flags); } while (0)
+#define unlock_kmap_any(flags) \
+ do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
+#endif
+
+struct page *kmap_to_page(void *vaddr)
+{
+ unsigned long addr = (unsigned long)vaddr;
+
+ if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
+ int i = PKMAP_NR(addr);
+ return pte_page(pkmap_page_table[i]);
+ }
+
+ return virt_to_page(addr);
+}
+EXPORT_SYMBOL(kmap_to_page);
+
+static void flush_all_zero_pkmaps(void)
+{
+ int i;
+ int need_flush = 0;
+
+ flush_cache_kmaps();
+
+ for (i = 0; i < LAST_PKMAP; i++) {
+ struct page *page;
+
+ /*
+ * zero means we don't have anything to do,
+ * >1 means that it is still in use. Only
+ * a count of 1 means that it is free but
+ * needs to be unmapped
+ */
+ if (pkmap_count[i] != 1)
+ continue;
+ pkmap_count[i] = 0;
+
+ /* sanity check */
+ BUG_ON(pte_none(pkmap_page_table[i]));
+
+ /*
+ * Don't need an atomic fetch-and-clear op here;
+ * no-one has the page mapped, and cannot get at
+ * its virtual address (and hence PTE) without first
+ * getting the kmap_lock (which is held here).
+ * So no dangers, even with speculative execution.
+ */
+ page = pte_page(pkmap_page_table[i]);
+ pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
+
+ set_page_address(page, NULL);
+ need_flush = 1;
+ }
+ if (need_flush)
+ 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)
+{
+ lock_kmap();
+ flush_all_zero_pkmaps();
+ unlock_kmap();
+}
+
+static inline unsigned long map_new_virtual(struct page *page)
+{
+ unsigned long vaddr;
+ int count;
+ unsigned int last_pkmap_nr;
+ unsigned int color = get_pkmap_color(page);
+
+start:
+ count = get_pkmap_entries_count(color);
+ /* Find an empty entry */
+ for (;;) {
+ last_pkmap_nr = get_next_pkmap_nr(color);
+ if (no_more_pkmaps(last_pkmap_nr, color)) {
+ flush_all_zero_pkmaps();
+ count = get_pkmap_entries_count(color);
+ }
+ if (!pkmap_count[last_pkmap_nr])
+ break; /* Found a usable entry */
+ if (--count)
+ continue;
+
+ /*
+ * Sleep for somebody else to unmap their entries
+ */
+ {
+ DECLARE_WAITQUEUE(wait, current);
+ wait_queue_head_t *pkmap_map_wait =
+ get_pkmap_wait_queue_head(color);
+
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ add_wait_queue(pkmap_map_wait, &wait);
+ unlock_kmap();
+ schedule();
+ remove_wait_queue(pkmap_map_wait, &wait);
+ lock_kmap();
+
+ /* Somebody else might have mapped it while we slept */
+ if (page_address(page))
+ return (unsigned long)page_address(page);
+
+ /* Re-start */
+ goto start;
+ }
+ }
+ vaddr = PKMAP_ADDR(last_pkmap_nr);
+ set_pte_at(&init_mm, vaddr,
+ &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
+
+ pkmap_count[last_pkmap_nr] = 1;
+ set_page_address(page, (void *)vaddr);
+
+ return vaddr;
+}
+
+/**
+ * kmap_high - map a highmem page into memory
+ * @page: &struct page to map
+ *
+ * Returns the page's virtual memory address.
+ *
+ * We cannot call this from interrupts, as it may block.
+ */
+void *kmap_high(struct page *page)
+{
+ unsigned long vaddr;
+
+ /*
+ * For highmem pages, we can't trust "virtual" until
+ * after we have the lock.
+ */
+ lock_kmap();
+ vaddr = (unsigned long)page_address(page);
+ if (!vaddr)
+ vaddr = map_new_virtual(page);
+ pkmap_count[PKMAP_NR(vaddr)]++;
+ BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
+ unlock_kmap();
+ return (void*) vaddr;
+}
+
+EXPORT_SYMBOL(kmap_high);
+
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
+/**
+ * kmap_high_get - pin a highmem page into memory
+ * @page: &struct page to pin
+ *
+ * Returns the page's current virtual memory address, or NULL if no mapping
+ * exists. If and only if a non null address is returned then a
+ * matching call to kunmap_high() is necessary.
+ *
+ * This can be called from any context.
+ */
+void *kmap_high_get(struct page *page)
+{
+ unsigned long vaddr, flags;
+
+ lock_kmap_any(flags);
+ vaddr = (unsigned long)page_address(page);
+ if (vaddr) {
+ BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
+ pkmap_count[PKMAP_NR(vaddr)]++;
+ }
+ unlock_kmap_any(flags);
+ return (void*) vaddr;
+}
+#endif
+
+/**
+ * kunmap_high - unmap a highmem page into memory
+ * @page: &struct page to unmap
+ *
+ * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
+ * only from user context.
+ */
+void kunmap_high(struct page *page)
+{
+ unsigned long vaddr;
+ unsigned long nr;
+ unsigned long flags;
+ int need_wakeup;
+ unsigned int color = get_pkmap_color(page);
+ wait_queue_head_t *pkmap_map_wait;
+
+ lock_kmap_any(flags);
+ vaddr = (unsigned long)page_address(page);
+ BUG_ON(!vaddr);
+ nr = PKMAP_NR(vaddr);
+
+ /*
+ * A count must never go down to zero
+ * without a TLB flush!
+ */
+ need_wakeup = 0;
+ switch (--pkmap_count[nr]) {
+ case 0:
+ BUG();
+ case 1:
+ /*
+ * Avoid an unnecessary wake_up() function call.
+ * The common case is pkmap_count[] == 1, but
+ * no waiters.
+ * The tasks queued in the wait-queue are guarded
+ * by both the lock in the wait-queue-head and by
+ * the kmap_lock. As the kmap_lock is held here,
+ * no need for the wait-queue-head's lock. Simply
+ * test if the queue is empty.
+ */
+ pkmap_map_wait = get_pkmap_wait_queue_head(color);
+ need_wakeup = waitqueue_active(pkmap_map_wait);
+ }
+ unlock_kmap_any(flags);
+
+ /* do wake-up, if needed, race-free outside of the spin lock */
+ if (need_wakeup)
+ wake_up(pkmap_map_wait);
+}
+
+EXPORT_SYMBOL(kunmap_high);
+#endif /* CONFIG_HIGHMEM */
+
+#if defined(HASHED_PAGE_VIRTUAL)
+
+#define PA_HASH_ORDER 7
+
+/*
+ * Describes one page->virtual association
+ */
+struct page_address_map {
+ struct page *page;
+ void *virtual;
+ struct list_head list;
+};
+
+static struct page_address_map page_address_maps[LAST_PKMAP];
+
+/*
+ * Hash table bucket
+ */
+static struct page_address_slot {
+ struct list_head lh; /* List of page_address_maps */
+ spinlock_t lock; /* Protect this bucket's list */
+} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
+
+static struct page_address_slot *page_slot(const struct page *page)
+{
+ return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
+}
+
+/**
+ * page_address - get the mapped virtual address of a page
+ * @page: &struct page to get the virtual address of
+ *
+ * Returns the page's virtual address.
+ */
+void *page_address(const struct page *page)
+{
+ unsigned long flags;
+ void *ret;
+ struct page_address_slot *pas;
+
+ if (!PageHighMem(page))
+ return lowmem_page_address(page);
+
+ pas = page_slot(page);
+ ret = NULL;
+ spin_lock_irqsave(&pas->lock, flags);
+ if (!list_empty(&pas->lh)) {
+ struct page_address_map *pam;
+
+ list_for_each_entry(pam, &pas->lh, list) {
+ if (pam->page == page) {
+ ret = pam->virtual;
+ goto done;
+ }
+ }
+ }
+done:
+ spin_unlock_irqrestore(&pas->lock, flags);
+ return ret;
+}
+
+EXPORT_SYMBOL(page_address);
+
+/**
+ * set_page_address - set a page's virtual address
+ * @page: &struct page to set
+ * @virtual: virtual address to use
+ */
+void set_page_address(struct page *page, void *virtual)
+{
+ unsigned long flags;
+ struct page_address_slot *pas;
+ struct page_address_map *pam;
+
+ BUG_ON(!PageHighMem(page));
+
+ pas = page_slot(page);
+ if (virtual) { /* Add */
+ pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
+ pam->page = page;
+ pam->virtual = virtual;
+
+ spin_lock_irqsave(&pas->lock, flags);
+ list_add_tail(&pam->list, &pas->lh);
+ spin_unlock_irqrestore(&pas->lock, flags);
+ } else { /* Remove */
+ spin_lock_irqsave(&pas->lock, flags);
+ list_for_each_entry(pam, &pas->lh, list) {
+ if (pam->page == page) {
+ list_del(&pam->list);
+ spin_unlock_irqrestore(&pas->lock, flags);
+ goto done;
+ }
+ }
+ spin_unlock_irqrestore(&pas->lock, flags);
+ }
+done:
+ return;
+}
+
+void __init page_address_init(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
+ INIT_LIST_HEAD(&page_address_htable[i].lh);
+ spin_lock_init(&page_address_htable[i].lock);
+ }
+}
+
+#endif /* defined(HASHED_PAGE_VIRTUAL) */
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