initial_commit

1 files changed, 3993 insertions, 0 deletions

diff --git a/mm/memory.c b/mm/memory.c
new file mode 100644
index 00000000..d49b58ab
--- /dev/null
+++ b/mm/memory.c
@@ -0,0 +1,3993 @@
+/*
+ *  linux/mm/memory.c
+ *
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ */
+
+/*
+ * demand-loading started 01.12.91 - seems it is high on the list of
+ * things wanted, and it should be easy to implement. - Linus
+ */
+
+/*
+ * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
+ * pages started 02.12.91, seems to work. - Linus.
+ *
+ * Tested sharing by executing about 30 /bin/sh: under the old kernel it
+ * would have taken more than the 6M I have free, but it worked well as
+ * far as I could see.
+ *
+ * Also corrected some "invalidate()"s - I wasn't doing enough of them.
+ */
+
+/*
+ * Real VM (paging to/from disk) started 18.12.91. Much more work and
+ * thought has to go into this. Oh, well..
+ * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
+ *		Found it. Everything seems to work now.
+ * 20.12.91  -  Ok, making the swap-device changeable like the root.
+ */
+
+/*
+ * 05.04.94  -  Multi-page memory management added for v1.1.
+ * 		Idea by Alex Bligh (alex@cconcepts.co.uk)
+ *
+ * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
+ *		(Gerhard.Wichert@pdb.siemens.de)
+ *
+ * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
+ */
+
+#include <linux/kernel_stat.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/mman.h>
+#include <linux/swap.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/ksm.h>
+#include <linux/rmap.h>
+#include <linux/module.h>
+#include <linux/delayacct.h>
+#include <linux/init.h>
+#include <linux/writeback.h>
+#include <linux/memcontrol.h>
+#include <linux/mmu_notifier.h>
+#include <linux/kallsyms.h>
+#include <linux/swapops.h>
+#include <linux/elf.h>
+#include <linux/gfp.h>
+
+#include <asm/io.h>
+#include <asm/pgalloc.h>
+#include <asm/uaccess.h>
+#include <asm/tlb.h>
+#include <asm/tlbflush.h>
+#include <asm/pgtable.h>
+
+#include "internal.h"
+
+#ifndef CONFIG_NEED_MULTIPLE_NODES
+/* use the per-pgdat data instead for discontigmem - mbligh */
+unsigned long max_mapnr;
+struct page *mem_map;
+
+EXPORT_SYMBOL(max_mapnr);
+EXPORT_SYMBOL(mem_map);
+#endif
+
+unsigned long num_physpages;
+/*
+ * A number of key systems in x86 including ioremap() rely on the assumption
+ * that high_memory defines the upper bound on direct map memory, then end
+ * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
+ * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
+ * and ZONE_HIGHMEM.
+ */
+void * high_memory;
+
+EXPORT_SYMBOL(num_physpages);
+EXPORT_SYMBOL(high_memory);
+
+/*
+ * Randomize the address space (stacks, mmaps, brk, etc.).
+ *
+ * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
+ *   as ancient (libc5 based) binaries can segfault. )
+ */
+int randomize_va_space __read_mostly =
+#ifdef CONFIG_COMPAT_BRK
+					1;
+#else
+					2;
+#endif
+
+static int __init disable_randmaps(char *s)
+{
+	randomize_va_space = 0;
+	return 1;
+}
+__setup("norandmaps", disable_randmaps);
+
+unsigned long zero_pfn __read_mostly;
+unsigned long highest_memmap_pfn __read_mostly;
+
+/*
+ * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
+ */
+static int __init init_zero_pfn(void)
+{
+	zero_pfn = page_to_pfn(ZERO_PAGE(0));
+	return 0;
+}
+core_initcall(init_zero_pfn);
+
+
+#if defined(SPLIT_RSS_COUNTING)
+
+static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
+{
+	int i;
+
+	for (i = 0; i < NR_MM_COUNTERS; i++) {
+		if (task->rss_stat.count[i]) {
+			add_mm_counter(mm, i, task->rss_stat.count[i]);
+			task->rss_stat.count[i] = 0;
+		}
+	}
+	task->rss_stat.events = 0;
+}
+
+static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
+{
+	struct task_struct *task = current;
+
+	if (likely(task->mm == mm))
+		task->rss_stat.count[member] += val;
+	else
+		add_mm_counter(mm, member, val);
+}
+#define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
+#define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
+
+/* sync counter once per 64 page faults */
+#define TASK_RSS_EVENTS_THRESH	(64)
+static void check_sync_rss_stat(struct task_struct *task)
+{
+	if (unlikely(task != current))
+		return;
+	if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
+		__sync_task_rss_stat(task, task->mm);
+}
+
+unsigned long get_mm_counter(struct mm_struct *mm, int member)
+{
+	long val = 0;
+
+	/*
+	 * Don't use task->mm here...for avoiding to use task_get_mm()..
+	 * The caller must guarantee task->mm is not invalid.
+	 */
+	val = atomic_long_read(&mm->rss_stat.count[member]);
+	/*
+	 * counter is updated in asynchronous manner and may go to minus.
+	 * But it's never be expected number for users.
+	 */
+	if (val < 0)
+		return 0;
+	return (unsigned long)val;
+}
+
+void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
+{
+	__sync_task_rss_stat(task, mm);
+}
+#else /* SPLIT_RSS_COUNTING */
+
+#define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
+#define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
+
+static void check_sync_rss_stat(struct task_struct *task)
+{
+}
+
+#endif /* SPLIT_RSS_COUNTING */
+
+#ifdef HAVE_GENERIC_MMU_GATHER
+
+static int tlb_next_batch(struct mmu_gather *tlb)
+{
+	struct mmu_gather_batch *batch;
+
+	batch = tlb->active;
+	if (batch->next) {
+		tlb->active = batch->next;
+		return 1;
+	}
+
+	batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
+	if (!batch)
+		return 0;
+
+	batch->next = NULL;
+	batch->nr   = 0;
+	batch->max  = MAX_GATHER_BATCH;
+
+	tlb->active->next = batch;
+	tlb->active = batch;
+
+	return 1;
+}
+
+/* tlb_gather_mmu
+ *	Called to initialize an (on-stack) mmu_gather structure for page-table
+ *	tear-down from @mm. The @fullmm argument is used when @mm is without
+ *	users and we're going to destroy the full address space (exit/execve).
+ */
+void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
+{
+	tlb->mm = mm;
+
+	tlb->fullmm     = fullmm;
+	tlb->need_flush = 0;
+	tlb->fast_mode  = (num_possible_cpus() == 1);
+	tlb->local.next = NULL;
+	tlb->local.nr   = 0;
+	tlb->local.max  = ARRAY_SIZE(tlb->__pages);
+	tlb->active     = &tlb->local;
+
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+	tlb->batch = NULL;
+#endif
+}
+
+void tlb_flush_mmu(struct mmu_gather *tlb)
+{
+	struct mmu_gather_batch *batch;
+
+	if (!tlb->need_flush)
+		return;
+	tlb->need_flush = 0;
+	tlb_flush(tlb);
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+	tlb_table_flush(tlb);
+#endif
+
+	if (tlb_fast_mode(tlb))
+		return;
+
+	for (batch = &tlb->local; batch; batch = batch->next) {
+		free_pages_and_swap_cache(batch->pages, batch->nr);
+		batch->nr = 0;
+	}
+	tlb->active = &tlb->local;
+}
+
+/* tlb_finish_mmu
+ *	Called at the end of the shootdown operation to free up any resources
+ *	that were required.
+ */
+void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+	struct mmu_gather_batch *batch, *next;
+
+	tlb_flush_mmu(tlb);
+
+	/* keep the page table cache within bounds */
+	check_pgt_cache();
+
+	for (batch = tlb->local.next; batch; batch = next) {
+		next = batch->next;
+		free_pages((unsigned long)batch, 0);
+	}
+	tlb->local.next = NULL;
+}
+
+/* __tlb_remove_page
+ *	Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
+ *	handling the additional races in SMP caused by other CPUs caching valid
+ *	mappings in their TLBs. Returns the number of free page slots left.
+ *	When out of page slots we must call tlb_flush_mmu().
+ */
+int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
+{
+	struct mmu_gather_batch *batch;
+
+	tlb->need_flush = 1;
+
+	if (tlb_fast_mode(tlb)) {
+		free_page_and_swap_cache(page);
+		return 1; /* avoid calling tlb_flush_mmu() */
+	}
+
+	batch = tlb->active;
+	batch->pages[batch->nr++] = page;
+	if (batch->nr == batch->max) {
+		if (!tlb_next_batch(tlb))
+			return 0;
+		batch = tlb->active;
+	}
+	VM_BUG_ON(batch->nr > batch->max);
+
+	return batch->max - batch->nr;
+}
+
+#endif /* HAVE_GENERIC_MMU_GATHER */
+
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+
+/*
+ * See the comment near struct mmu_table_batch.
+ */
+
+static void tlb_remove_table_smp_sync(void *arg)
+{
+	/* Simply deliver the interrupt */
+}
+
+static void tlb_remove_table_one(void *table)
+{
+	/*
+	 * This isn't an RCU grace period and hence the page-tables cannot be
+	 * assumed to be actually RCU-freed.
+	 *
+	 * It is however sufficient for software page-table walkers that rely on
+	 * IRQ disabling. See the comment near struct mmu_table_batch.
+	 */
+	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
+	__tlb_remove_table(table);
+}
+
+static void tlb_remove_table_rcu(struct rcu_head *head)
+{
+	struct mmu_table_batch *batch;
+	int i;
+
+	batch = container_of(head, struct mmu_table_batch, rcu);
+
+	for (i = 0; i < batch->nr; i++)
+		__tlb_remove_table(batch->tables[i]);
+
+	free_page((unsigned long)batch);
+}
+
+void tlb_table_flush(struct mmu_gather *tlb)
+{
+	struct mmu_table_batch **batch = &tlb->batch;
+
+	if (*batch) {
+		call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
+		*batch = NULL;
+	}
+}
+
+void tlb_remove_table(struct mmu_gather *tlb, void *table)
+{
+	struct mmu_table_batch **batch = &tlb->batch;
+
+	tlb->need_flush = 1;
+
+	/*
+	 * When there's less then two users of this mm there cannot be a
+	 * concurrent page-table walk.
+	 */
+	if (atomic_read(&tlb->mm->mm_users) < 2) {
+		__tlb_remove_table(table);
+		return;
+	}
+
+	if (*batch == NULL) {
+		*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
+		if (*batch == NULL) {
+			tlb_remove_table_one(table);
+			return;
+		}
+		(*batch)->nr = 0;
+	}
+	(*batch)->tables[(*batch)->nr++] = table;
+	if ((*batch)->nr == MAX_TABLE_BATCH)
+		tlb_table_flush(tlb);
+}
+
+#endif /* CONFIG_HAVE_RCU_TABLE_FREE */
+
+/*
+ * If a p?d_bad entry is found while walking page tables, report
+ * the error, before resetting entry to p?d_none.  Usually (but
+ * very seldom) called out from the p?d_none_or_clear_bad macros.
+ */
+
+void pgd_clear_bad(pgd_t *pgd)
+{
+	pgd_ERROR(*pgd);
+	pgd_clear(pgd);
+}
+
+void pud_clear_bad(pud_t *pud)
+{
+	pud_ERROR(*pud);
+	pud_clear(pud);
+}
+
+void pmd_clear_bad(pmd_t *pmd)
+{
+	pmd_ERROR(*pmd);
+	pmd_clear(pmd);
+}
+
+/*
+ * Note: this doesn't free the actual pages themselves. That
+ * has been handled earlier when unmapping all the memory regions.
+ */
+static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
+			   unsigned long addr)
+{
+	pgtable_t token = pmd_pgtable(*pmd);
+	pmd_clear(pmd);
+	pte_free_tlb(tlb, token, addr);
+	tlb->mm->nr_ptes--;
+}
+
+static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
+				unsigned long addr, unsigned long end,
+				unsigned long floor, unsigned long ceiling)
+{
+	pmd_t *pmd;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none_or_clear_bad(pmd))
+			continue;
+		free_pte_range(tlb, pmd, addr);
+	} while (pmd++, addr = next, addr != end);
+
+	start &= PUD_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PUD_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pmd = pmd_offset(pud, start);
+	pud_clear(pud);
+	pmd_free_tlb(tlb, pmd, start);
+}
+
+static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
+				unsigned long addr, unsigned long end,
+				unsigned long floor, unsigned long ceiling)
+{
+	pud_t *pud;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
+	} while (pud++, addr = next, addr != end);
+
+	start &= PGDIR_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PGDIR_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pud = pud_offset(pgd, start);
+	pgd_clear(pgd);
+	pud_free_tlb(tlb, pud, start);
+}
+
+/*
+ * This function frees user-level page tables of a process.
+ *
+ * Must be called with pagetable lock held.
+ */
+void free_pgd_range(struct mmu_gather *tlb,
+			unsigned long addr, unsigned long end,
+			unsigned long floor, unsigned long ceiling)
+{
+	pgd_t *pgd;
+	unsigned long next;
+
+	/*
+	 * The next few lines have given us lots of grief...
+	 *
+	 * Why are we testing PMD* at this top level?  Because often
+	 * there will be no work to do at all, and we'd prefer not to
+	 * go all the way down to the bottom just to discover that.
+	 *
+	 * Why all these "- 1"s?  Because 0 represents both the bottom
+	 * of the address space and the top of it (using -1 for the
+	 * top wouldn't help much: the masks would do the wrong thing).
+	 * The rule is that addr 0 and floor 0 refer to the bottom of
+	 * the address space, but end 0 and ceiling 0 refer to the top
+	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
+	 * that end 0 case should be mythical).
+	 *
+	 * Wherever addr is brought up or ceiling brought down, we must
+	 * be careful to reject "the opposite 0" before it confuses the
+	 * subsequent tests.  But what about where end is brought down
+	 * by PMD_SIZE below? no, end can't go down to 0 there.
+	 *
+	 * Whereas we round start (addr) and ceiling down, by different
+	 * masks at different levels, in order to test whether a table
+	 * now has no other vmas using it, so can be freed, we don't
+	 * bother to round floor or end up - the tests don't need that.
+	 */
+
+	addr &= PMD_MASK;
+	if (addr < floor) {
+		addr += PMD_SIZE;
+		if (!addr)
+			return;
+	}
+	if (ceiling) {
+		ceiling &= PMD_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		end -= PMD_SIZE;
+	if (addr > end - 1)
+		return;
+
+	pgd = pgd_offset(tlb->mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		free_pud_range(tlb, pgd, addr, next, floor, ceiling);
+	} while (pgd++, addr = next, addr != end);
+}
+
+void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
+		unsigned long floor, unsigned long ceiling)
+{
+	while (vma) {
+		struct vm_area_struct *next = vma->vm_next;
+		unsigned long addr = vma->vm_start;
+
+		/*
+		 * Hide vma from rmap and truncate_pagecache before freeing
+		 * pgtables
+		 */
+		unlink_anon_vmas(vma);
+		unlink_file_vma(vma);
+
+		if (is_vm_hugetlb_page(vma)) {
+			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
+				floor, next? next->vm_start: ceiling);
+		} else {
+			/*
+			 * Optimization: gather nearby vmas into one call down
+			 */
+			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
+			       && !is_vm_hugetlb_page(next)) {
+				vma = next;
+				next = vma->vm_next;
+				unlink_anon_vmas(vma);
+				unlink_file_vma(vma);
+			}
+			free_pgd_range(tlb, addr, vma->vm_end,
+				floor, next? next->vm_start: ceiling);
+		}
+		vma = next;
+	}
+}
+
+int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
+		pmd_t *pmd, unsigned long address)
+{
+	pgtable_t new = pte_alloc_one(mm, address);
+	int wait_split_huge_page;
+	if (!new)
+		return -ENOMEM;
+
+	/*
+	 * Ensure all pte setup (eg. pte page lock and page clearing) are
+	 * visible before the pte is made visible to other CPUs by being
+	 * put into page tables.
+	 *
+	 * The other side of the story is the pointer chasing in the page
+	 * table walking code (when walking the page table without locking;
+	 * ie. most of the time). Fortunately, these data accesses consist
+	 * of a chain of data-dependent loads, meaning most CPUs (alpha
+	 * being the notable exception) will already guarantee loads are
+	 * seen in-order. See the alpha page table accessors for the
+	 * smp_read_barrier_depends() barriers in page table walking code.
+	 */
+	smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
+
+	spin_lock(&mm->page_table_lock);
+	wait_split_huge_page = 0;
+	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
+		mm->nr_ptes++;
+		pmd_populate(mm, pmd, new);
+		new = NULL;
+	} else if (unlikely(pmd_trans_splitting(*pmd)))
+		wait_split_huge_page = 1;
+	spin_unlock(&mm->page_table_lock);
+	if (new)
+		pte_free(mm, new);
+	if (wait_split_huge_page)
+		wait_split_huge_page(vma->anon_vma, pmd);
+	return 0;
+}
+
+int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
+{
+	pte_t *new = pte_alloc_one_kernel(&init_mm, address);
+	if (!new)
+		return -ENOMEM;
+
+	smp_wmb(); /* See comment in __pte_alloc */
+
+	spin_lock(&init_mm.page_table_lock);
+	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
+		pmd_populate_kernel(&init_mm, pmd, new);
+		new = NULL;
+	} else
+		VM_BUG_ON(pmd_trans_splitting(*pmd));
+	spin_unlock(&init_mm.page_table_lock);
+	if (new)
+		pte_free_kernel(&init_mm, new);
+	return 0;
+}
+
+static inline void init_rss_vec(int *rss)
+{
+	memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
+}
+
+static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
+{
+	int i;
+
+	if (current->mm == mm)
+		sync_mm_rss(current, mm);
+	for (i = 0; i < NR_MM_COUNTERS; i++)
+		if (rss[i])
+			add_mm_counter(mm, i, rss[i]);
+}
+
+/*
+ * This function is called to print an error when a bad pte
+ * is found. For example, we might have a PFN-mapped pte in
+ * a region that doesn't allow it.
+ *
+ * The calling function must still handle the error.
+ */
+static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
+			  pte_t pte, struct page *page)
+{
+	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
+	pud_t *pud = pud_offset(pgd, addr);
+	pmd_t *pmd = pmd_offset(pud, addr);
+	struct address_space *mapping;
+	pgoff_t index;
+	static unsigned long resume;
+	static unsigned long nr_shown;
+	static unsigned long nr_unshown;
+
+	/*
+	 * Allow a burst of 60 reports, then keep quiet for that minute;
+	 * or allow a steady drip of one report per second.
+	 */
+	if (nr_shown == 60) {
+		if (time_before(jiffies, resume)) {
+			nr_unshown++;
+			return;
+		}
+		if (nr_unshown) {
+			printk(KERN_ALERT
+				"BUG: Bad page map: %lu messages suppressed\n",
+				nr_unshown);
+			nr_unshown = 0;
+		}
+		nr_shown = 0;
+	}
+	if (nr_shown++ == 0)
+		resume = jiffies + 60 * HZ;
+
+	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
+	index = linear_page_index(vma, addr);
+
+	printk(KERN_ALERT
+		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
+		current->comm,
+		(long long)pte_val(pte), (long long)pmd_val(*pmd));
+	if (page)
+		dump_page(page);
+	printk(KERN_ALERT
+		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
+		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
+	/*
+	 * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
+	 */
+	if (vma->vm_ops)
+		print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
+				(unsigned long)vma->vm_ops->fault);
+	if (vma->vm_file && vma->vm_file->f_op)
+		print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
+				(unsigned long)vma->vm_file->f_op->mmap);
+	dump_stack();
+	add_taint(TAINT_BAD_PAGE);
+}
+
+static inline int is_cow_mapping(vm_flags_t flags)
+{
+	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+}
+
+#ifndef is_zero_pfn
+static inline int is_zero_pfn(unsigned long pfn)
+{
+	return pfn == zero_pfn;
+}
+#endif
+
+#ifndef my_zero_pfn
+static inline unsigned long my_zero_pfn(unsigned long addr)
+{
+	return zero_pfn;
+}
+#endif
+
+/*
+ * vm_normal_page -- This function gets the "struct page" associated with a pte.
+ *
+ * "Special" mappings do not wish to be associated with a "struct page" (either
+ * it doesn't exist, or it exists but they don't want to touch it). In this
+ * case, NULL is returned here. "Normal" mappings do have a struct page.
+ *
+ * There are 2 broad cases. Firstly, an architecture may define a pte_special()
+ * pte bit, in which case this function is trivial. Secondly, an architecture
+ * may not have a spare pte bit, which requires a more complicated scheme,
+ * described below.
+ *
+ * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
+ * special mapping (even if there are underlying and valid "struct pages").
+ * COWed pages of a VM_PFNMAP are always normal.
+ *
+ * The way we recognize COWed pages within VM_PFNMAP mappings is through the
+ * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
+ * set, and the vm_pgoff will point to the first PFN mapped: thus every special
+ * mapping will always honor the rule
+ *
+ *	pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
+ *
+ * And for normal mappings this is false.
+ *
+ * This restricts such mappings to be a linear translation from virtual address
+ * to pfn. To get around this restriction, we allow arbitrary mappings so long
+ * as the vma is not a COW mapping; in that case, we know that all ptes are
+ * special (because none can have been COWed).
+ *
+ *
+ * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
+ *
+ * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
+ * page" backing, however the difference is that _all_ pages with a struct
+ * page (that is, those where pfn_valid is true) are refcounted and considered
+ * normal pages by the VM. The disadvantage is that pages are refcounted
+ * (which can be slower and simply not an option for some PFNMAP users). The
+ * advantage is that we don't have to follow the strict linearity rule of
+ * PFNMAP mappings in order to support COWable mappings.
+ *
+ */
+#ifdef __HAVE_ARCH_PTE_SPECIAL
+# define HAVE_PTE_SPECIAL 1
+#else
+# define HAVE_PTE_SPECIAL 0
+#endif
+struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+				pte_t pte)
+{
+	unsigned long pfn = pte_pfn(pte);
+
+	if (HAVE_PTE_SPECIAL) {
+		if (likely(!pte_special(pte)))
+			goto check_pfn;
+		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
+			return NULL;
+		if (!is_zero_pfn(pfn))
+			print_bad_pte(vma, addr, pte, NULL);
+		return NULL;
+	}
+
+	/* !HAVE_PTE_SPECIAL case follows: */
+
+	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
+		if (vma->vm_flags & VM_MIXEDMAP) {
+			if (!pfn_valid(pfn))
+				return NULL;
+			goto out;
+		} else {
+			unsigned long off;
+			off = (addr - vma->vm_start) >> PAGE_SHIFT;
+			if (pfn == vma->vm_pgoff + off)
+				return NULL;
+			if (!is_cow_mapping(vma->vm_flags))
+				return NULL;
+		}
+	}
+
+	if (is_zero_pfn(pfn))
+		return NULL;
+check_pfn:
+	if (unlikely(pfn > highest_memmap_pfn)) {
+		print_bad_pte(vma, addr, pte, NULL);
+		return NULL;
+	}
+
+	/*
+	 * NOTE! We still have PageReserved() pages in the page tables.
+	 * eg. VDSO mappings can cause them to exist.
+	 */
+out:
+	return pfn_to_page(pfn);
+}
+
+/*
+ * copy one vm_area from one task to the other. Assumes the page tables
+ * already present in the new task to be cleared in the whole range
+ * covered by this vma.
+ */
+
+static inline unsigned long
+copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
+		unsigned long addr, int *rss)
+{
+	unsigned long vm_flags = vma->vm_flags;
+	pte_t pte = *src_pte;
+	struct page *page;
+
+	/* pte contains position in swap or file, so copy. */
+	if (unlikely(!pte_present(pte))) {
+		if (!pte_file(pte)) {
+			swp_entry_t entry = pte_to_swp_entry(pte);
+
+			if (swap_duplicate(entry) < 0)
+				return entry.val;
+
+			/* make sure dst_mm is on swapoff's mmlist. */
+			if (unlikely(list_empty(&dst_mm->mmlist))) {
+				spin_lock(&mmlist_lock);
+				if (list_empty(&dst_mm->mmlist))
+					list_add(&dst_mm->mmlist,
+						 &src_mm->mmlist);
+				spin_unlock(&mmlist_lock);
+			}
+			if (likely(!non_swap_entry(entry)))
+				rss[MM_SWAPENTS]++;
+			else if (is_write_migration_entry(entry) &&
+					is_cow_mapping(vm_flags)) {
+				/*
+				 * COW mappings require pages in both parent
+				 * and child to be set to read.
+				 */
+				make_migration_entry_read(&entry);
+				pte = swp_entry_to_pte(entry);
+				set_pte_at(src_mm, addr, src_pte, pte);
+			}
+		}
+		goto out_set_pte;
+	}
+
+	/*
+	 * If it's a COW mapping, write protect it both
+	 * in the parent and the child
+	 */
+	if (is_cow_mapping(vm_flags)) {
+		ptep_set_wrprotect(src_mm, addr, src_pte);
+		pte = pte_wrprotect(pte);
+	}
+
+	/*
+	 * If it's a shared mapping, mark it clean in
+	 * the child
+	 */
+	if (vm_flags & VM_SHARED)
+		pte = pte_mkclean(pte);
+	pte = pte_mkold(pte);
+
+	page = vm_normal_page(vma, addr, pte);
+	if (page) {
+		get_page(page);
+		page_dup_rmap(page);
+		if (PageAnon(page))
+			rss[MM_ANONPAGES]++;
+		else
+			rss[MM_FILEPAGES]++;
+	}
+
+out_set_pte:
+	set_pte_at(dst_mm, addr, dst_pte, pte);
+	return 0;
+}
+
+int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+		   pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
+		   unsigned long addr, unsigned long end)
+{
+	pte_t *orig_src_pte, *orig_dst_pte;
+	pte_t *src_pte, *dst_pte;
+	spinlock_t *src_ptl, *dst_ptl;
+	int progress = 0;
+	int rss[NR_MM_COUNTERS];
+	swp_entry_t entry = (swp_entry_t){0};
+
+again:
+	init_rss_vec(rss);
+
+	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
+	if (!dst_pte)
+		return -ENOMEM;
+	src_pte = pte_offset_map(src_pmd, addr);
+	src_ptl = pte_lockptr(src_mm, src_pmd);
+	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+	orig_src_pte = src_pte;
+	orig_dst_pte = dst_pte;
+	arch_enter_lazy_mmu_mode();
+
+	do {
+		/*
+		 * We are holding two locks at this point - either of them
+		 * could generate latencies in another task on another CPU.
+		 */
+		if (progress >= 32) {
+			progress = 0;
+			if (need_resched() ||
+			    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
+				break;
+		}
+		if (pte_none(*src_pte)) {
+			progress++;
+			continue;
+		}
+		entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
+							vma, addr, rss);
+		if (entry.val)
+			break;
+		progress += 8;
+	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
+
+	arch_leave_lazy_mmu_mode();
+	spin_unlock(src_ptl);
+	pte_unmap(orig_src_pte);
+	add_mm_rss_vec(dst_mm, rss);
+	pte_unmap_unlock(orig_dst_pte, dst_ptl);
+	cond_resched();
+
+	if (entry.val) {
+		if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
+			return -ENOMEM;
+		progress = 0;
+	}
+	if (addr != end)
+		goto again;
+	return 0;
+}
+
+static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
+		unsigned long addr, unsigned long end)
+{
+	pmd_t *src_pmd, *dst_pmd;
+	unsigned long next;
+
+	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
+	if (!dst_pmd)
+		return -ENOMEM;
+	src_pmd = pmd_offset(src_pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_trans_huge(*src_pmd)) {
+			int err;
+			VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
+			err = copy_huge_pmd(dst_mm, src_mm,
+					    dst_pmd, src_pmd, addr, vma);
+			if (err == -ENOMEM)
+				return -ENOMEM;
+			if (!err)
+				continue;
+			/* fall through */
+		}
+		if (pmd_none_or_clear_bad(src_pmd))
+			continue;
+		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
+						vma, addr, next))
+			return -ENOMEM;
+	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
+	return 0;
+}
+
+static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
+		unsigned long addr, unsigned long end)
+{
+	pud_t *src_pud, *dst_pud;
+	unsigned long next;
+
+	dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
+	if (!dst_pud)
+		return -ENOMEM;
+	src_pud = pud_offset(src_pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(src_pud))
+			continue;
+		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
+						vma, addr, next))
+			return -ENOMEM;
+	} while (dst_pud++, src_pud++, addr = next, addr != end);
+	return 0;
+}
+
+int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+		struct vm_area_struct *vma)
+{
+	pgd_t *src_pgd, *dst_pgd;
+	unsigned long next;
+	unsigned long addr = vma->vm_start;
+	unsigned long end = vma->vm_end;
+	int ret;
+
+	/*
+	 * Don't copy ptes where a page fault will fill them correctly.
+	 * Fork becomes much lighter when there are big shared or private
+	 * readonly mappings. The tradeoff is that copy_page_range is more
+	 * efficient than faulting.
+	 */
+	if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
+		if (!vma->anon_vma)
+			return 0;
+	}
+
+	if (is_vm_hugetlb_page(vma))
+		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
+
+	if (unlikely(is_pfn_mapping(vma))) {
+		/*
+		 * We do not free on error cases below as remove_vma
+		 * gets called on error from higher level routine
+		 */
+		ret = track_pfn_vma_copy(vma);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * We need to invalidate the secondary MMU mappings only when
+	 * there could be a permission downgrade on the ptes of the
+	 * parent mm. And a permission downgrade will only happen if
+	 * is_cow_mapping() returns true.
+	 */
+	if (is_cow_mapping(vma->vm_flags))
+		mmu_notifier_invalidate_range_start(src_mm, addr, end);
+
+	ret = 0;
+	dst_pgd = pgd_offset(dst_mm, addr);
+	src_pgd = pgd_offset(src_mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(src_pgd))
+			continue;
+		if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
+					    vma, addr, next))) {
+			ret = -ENOMEM;
+			break;
+		}
+	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
+
+	if (is_cow_mapping(vma->vm_flags))
+		mmu_notifier_invalidate_range_end(src_mm,
+						  vma->vm_start, end);
+	return ret;
+}
+
+static unsigned long zap_pte_range(struct mmu_gather *tlb,
+				struct vm_area_struct *vma, pmd_t *pmd,
+				unsigned long addr, unsigned long end,
+				struct zap_details *details)
+{
+	struct mm_struct *mm = tlb->mm;
+	int force_flush = 0;
+	int rss[NR_MM_COUNTERS];
+	spinlock_t *ptl;
+	pte_t *start_pte;
+	pte_t *pte;
+
+again:
+	init_rss_vec(rss);
+	start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+	pte = start_pte;
+	arch_enter_lazy_mmu_mode();
+	do {
+		pte_t ptent = *pte;
+		if (pte_none(ptent)) {
+			continue;
+		}
+
+		if (pte_present(ptent)) {
+			struct page *page;
+
+			page = vm_normal_page(vma, addr, ptent);
+			if (unlikely(details) && page) {
+				/*
+				 * unmap_shared_mapping_pages() wants to
+				 * invalidate cache without truncating:
+				 * unmap shared but keep private pages.
+				 */
+				if (details->check_mapping &&
+				    details->check_mapping != page->mapping)
+					continue;
+				/*
+				 * Each page->index must be checked when
+				 * invalidating or truncating nonlinear.
+				 */
+				if (details->nonlinear_vma &&
+				    (page->index < details->first_index ||
+				     page->index > details->last_index))
+					continue;
+			}
+			ptent = ptep_get_and_clear_full(mm, addr, pte,
+							tlb->fullmm);
+			tlb_remove_tlb_entry(tlb, pte, addr);
+			if (unlikely(!page))
+				continue;
+			if (unlikely(details) && details->nonlinear_vma
+			    && linear_page_index(details->nonlinear_vma,
+						addr) != page->index)
+				set_pte_at(mm, addr, pte,
+					   pgoff_to_pte(page->index));
+			if (PageAnon(page))
+				rss[MM_ANONPAGES]--;
+			else {
+				if (pte_dirty(ptent))
+					set_page_dirty(page);
+				if (pte_young(ptent) &&
+				    likely(!VM_SequentialReadHint(vma)))
+					mark_page_accessed(page);
+				rss[MM_FILEPAGES]--;
+			}
+			page_remove_rmap(page);
+			if (unlikely(page_mapcount(page) < 0))
+				print_bad_pte(vma, addr, ptent, page);
+			force_flush = !__tlb_remove_page(tlb, page);
+			if (force_flush)
+				break;
+			continue;
+		}
+		/*
+		 * If details->check_mapping, we leave swap entries;
+		 * if details->nonlinear_vma, we leave file entries.
+		 */
+		if (unlikely(details))
+			continue;
+		if (pte_file(ptent)) {
+			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
+				print_bad_pte(vma, addr, ptent, NULL);
+		} else {
+			swp_entry_t entry = pte_to_swp_entry(ptent);
+
+			if (!non_swap_entry(entry))
+				rss[MM_SWAPENTS]--;
+			if (unlikely(!free_swap_and_cache(entry)))
+				print_bad_pte(vma, addr, ptent, NULL);
+		}
+		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
+	} while (pte++, addr += PAGE_SIZE, addr != end);
+
+	add_mm_rss_vec(mm, rss);
+	arch_leave_lazy_mmu_mode();
+	pte_unmap_unlock(start_pte, ptl);
+
+	/*
+	 * mmu_gather ran out of room to batch pages, we break out of
+	 * the PTE lock to avoid doing the potential expensive TLB invalidate
+	 * and page-free while holding it.
+	 */
+	if (force_flush) {
+		force_flush = 0;
+		tlb_flush_mmu(tlb);
+		if (addr != end)
+			goto again;
+	}
+
+	return addr;
+}
+
+static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
+				struct vm_area_struct *vma, pud_t *pud,
+				unsigned long addr, unsigned long end,
+				struct zap_details *details)
+{
+	pmd_t *pmd;
+	unsigned long next;
+
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_trans_huge(*pmd)) {
+			if (next - addr != HPAGE_PMD_SIZE) {
+				VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
+				split_huge_page_pmd(vma->vm_mm, pmd);
+			} else if (zap_huge_pmd(tlb, vma, pmd))
+				goto next;
+			/* fall through */
+		}
+		/*
+		 * Here there can be other concurrent MADV_DONTNEED or
+		 * trans huge page faults running, and if the pmd is
+		 * none or trans huge it can change under us. This is
+		 * because MADV_DONTNEED holds the mmap_sem in read
+		 * mode.
+		 */
+		if (pmd_none_or_trans_huge_or_clear_bad(pmd))
+			goto next;
+		next = zap_pte_range(tlb, vma, pmd, addr, next, details);
+next:
+		cond_resched();
+	} while (pmd++, addr = next, addr != end);
+
+	return addr;
+}
+
+static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
+				struct vm_area_struct *vma, pgd_t *pgd,
+				unsigned long addr, unsigned long end,
+				struct zap_details *details)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		next = zap_pmd_range(tlb, vma, pud, addr, next, details);
+	} while (pud++, addr = next, addr != end);
+
+	return addr;
+}
+
+static unsigned long unmap_page_range(struct mmu_gather *tlb,
+				struct vm_area_struct *vma,
+				unsigned long addr, unsigned long end,
+				struct zap_details *details)
+{
+	pgd_t *pgd;
+	unsigned long next;
+
+	if (details && !details->check_mapping && !details->nonlinear_vma)
+		details = NULL;
+
+	BUG_ON(addr >= end);
+	mem_cgroup_uncharge_start();
+	tlb_start_vma(tlb, vma);
+	pgd = pgd_offset(vma->vm_mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		next = zap_pud_range(tlb, vma, pgd, addr, next, details);
+	} while (pgd++, addr = next, addr != end);
+	tlb_end_vma(tlb, vma);
+	mem_cgroup_uncharge_end();
+
+	return addr;
+}
+
+#ifdef CONFIG_PREEMPT
+# define ZAP_BLOCK_SIZE	(8 * PAGE_SIZE)
+#else
+/* No preempt: go for improved straight-line efficiency */
+# define ZAP_BLOCK_SIZE	(1024 * PAGE_SIZE)
+#endif
+
+/**
+ * unmap_vmas - unmap a range of memory covered by a list of vma's
+ * @tlb: address of the caller's struct mmu_gather
+ * @vma: the starting vma
+ * @start_addr: virtual address at which to start unmapping
+ * @end_addr: virtual address at which to end unmapping
+ * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
+ * @details: details of nonlinear truncation or shared cache invalidation
+ *
+ * Returns the end address of the unmapping (restart addr if interrupted).
+ *
+ * Unmap all pages in the vma list.
+ *
+ * We aim to not hold locks for too long (for scheduling latency reasons).
+ * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
+ * return the ending mmu_gather to the caller.
+ *
+ * Only addresses between `start' and `end' will be unmapped.
+ *
+ * The VMA list must be sorted in ascending virtual address order.
+ *
+ * unmap_vmas() assumes that the caller will flush the whole unmapped address
+ * range after unmap_vmas() returns.  So the only responsibility here is to
+ * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
+ * drops the lock and schedules.
+ */
+unsigned long unmap_vmas(struct mmu_gather *tlb,
+		struct vm_area_struct *vma, unsigned long start_addr,
+		unsigned long end_addr, unsigned long *nr_accounted,
+		struct zap_details *details)
+{
+	unsigned long start = start_addr;
+	struct mm_struct *mm = vma->vm_mm;
+
+	mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
+	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
+		unsigned long end;
+
+		start = max(vma->vm_start, start_addr);
+		if (start >= vma->vm_end)
+			continue;
+		end = min(vma->vm_end, end_addr);
+		if (end <= vma->vm_start)
+			continue;
+
+		if (vma->vm_flags & VM_ACCOUNT)
+			*nr_accounted += (end - start) >> PAGE_SHIFT;
+
+		if (unlikely(is_pfn_mapping(vma)))
+			untrack_pfn_vma(vma, 0, 0);
+
+		while (start != end) {
+			if (unlikely(is_vm_hugetlb_page(vma))) {
+				/*
+				 * It is undesirable to test vma->vm_file as it
+				 * should be non-null for valid hugetlb area.
+				 * However, vm_file will be NULL in the error
+				 * cleanup path of do_mmap_pgoff. When
+				 * hugetlbfs ->mmap method fails,
+				 * do_mmap_pgoff() nullifies vma->vm_file
+				 * before calling this function to clean up.
+				 * Since no pte has actually been setup, it is
+				 * safe to do nothing in this case.
+				 */
+				if (vma->vm_file)
+					unmap_hugepage_range(vma, start, end, NULL);
+
+				start = end;
+			} else
+				start = unmap_page_range(tlb, vma, start, end, details);
+		}
+	}
+
+	mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
+	return start;	/* which is now the end (or restart) address */
+}
+
+/**
+ * zap_page_range - remove user pages in a given range
+ * @vma: vm_area_struct holding the applicable pages
+ * @address: starting address of pages to zap
+ * @size: number of bytes to zap
+ * @details: details of nonlinear truncation or shared cache invalidation
+ */
+unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
+		unsigned long size, struct zap_details *details)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct mmu_gather tlb;
+	unsigned long end = address + size;
+	unsigned long nr_accounted = 0;
+
+	lru_add_drain();
+	tlb_gather_mmu(&tlb, mm, 0);
+	update_hiwater_rss(mm);
+	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
+	tlb_finish_mmu(&tlb, address, end);
+	return end;
+}
+
+/**
+ * zap_vma_ptes - remove ptes mapping the vma
+ * @vma: vm_area_struct holding ptes to be zapped
+ * @address: starting address of pages to zap
+ * @size: number of bytes to zap
+ *
+ * This function only unmaps ptes assigned to VM_PFNMAP vmas.
+ *
+ * The entire address range must be fully contained within the vma.
+ *
+ * Returns 0 if successful.
+ */
+int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
+		unsigned long size)
+{
+	if (address < vma->vm_start || address + size > vma->vm_end ||
+	    		!(vma->vm_flags & VM_PFNMAP))
+		return -1;
+	zap_page_range(vma, address, size, NULL);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(zap_vma_ptes);
+
+/**
+ * follow_page - look up a page descriptor from a user-virtual address
+ * @vma: vm_area_struct mapping @address
+ * @address: virtual address to look up
+ * @flags: flags modifying lookup behaviour
+ *
+ * @flags can have FOLL_ flags set, defined in <linux/mm.h>
+ *
+ * Returns the mapped (struct page *), %NULL if no mapping exists, or
+ * an error pointer if there is a mapping to something not represented
+ * by a page descriptor (see also vm_normal_page()).
+ */
+struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
+			unsigned int flags)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *ptep, pte;
+	spinlock_t *ptl;
+	struct page *page;
+	struct mm_struct *mm = vma->vm_mm;
+
+	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
+	if (!IS_ERR(page)) {
+		BUG_ON(flags & FOLL_GET);
+		goto out;
+	}
+
+	page = NULL;
+	pgd = pgd_offset(mm, address);
+	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+		goto no_page_table;
+
+	pud = pud_offset(pgd, address);
+	if (pud_none(*pud))
+		goto no_page_table;
+	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
+		BUG_ON(flags & FOLL_GET);
+		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
+		goto out;
+	}
+	if (unlikely(pud_bad(*pud)))
+		goto no_page_table;
+
+	pmd = pmd_offset(pud, address);
+	if (pmd_none(*pmd))
+		goto no_page_table;
+	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
+		BUG_ON(flags & FOLL_GET);
+		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
+		goto out;
+	}
+	if (pmd_trans_huge(*pmd)) {
+		if (flags & FOLL_SPLIT) {
+			split_huge_page_pmd(mm, pmd);
+			goto split_fallthrough;
+		}
+		spin_lock(&mm->page_table_lock);
+		if (likely(pmd_trans_huge(*pmd))) {
+			if (unlikely(pmd_trans_splitting(*pmd))) {
+				spin_unlock(&mm->page_table_lock);
+				wait_split_huge_page(vma->anon_vma, pmd);
+			} else {
+				page = follow_trans_huge_pmd(mm, address,
+							     pmd, flags);
+				spin_unlock(&mm->page_table_lock);
+				goto out;
+			}
+		} else
+			spin_unlock(&mm->page_table_lock);
+		/* fall through */
+	}
+split_fallthrough:
+	if (unlikely(pmd_bad(*pmd)))
+		goto no_page_table;
+
+	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+
+	pte = *ptep;
+	if (!pte_present(pte))
+		goto no_page;
+	if ((flags & FOLL_WRITE) && !pte_write(pte))
+		goto unlock;
+
+	page = vm_normal_page(vma, address, pte);
+	if (unlikely(!page)) {
+		if ((flags & FOLL_DUMP) ||
+		    !is_zero_pfn(pte_pfn(pte)))
+			goto bad_page;
+		page = pte_page(pte);
+	}
+
+	if (flags & FOLL_GET)
+		get_page_foll(page);
+	if (flags & FOLL_TOUCH) {
+		if ((flags & FOLL_WRITE) &&
+		    !pte_dirty(pte) && !PageDirty(page))
+			set_page_dirty(page);
+		/*
+		 * pte_mkyoung() would be more correct here, but atomic care
+		 * is needed to avoid losing the dirty bit: it is easier to use
+		 * mark_page_accessed().
+		 */
+		mark_page_accessed(page);
+	}
+	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
+		/*
+		 * The preliminary mapping check is mainly to avoid the
+		 * pointless overhead of lock_page on the ZERO_PAGE
+		 * which might bounce very badly if there is contention.
+		 *
+		 * If the page is already locked, we don't need to
+		 * handle it now - vmscan will handle it later if and
+		 * when it attempts to reclaim the page.
+		 */
+		if (page->mapping && trylock_page(page)) {
+			lru_add_drain();  /* push cached pages to LRU */
+			/*
+			 * Because we lock page here and migration is
+			 * blocked by the pte's page reference, we need
+			 * only check for file-cache page truncation.
+			 */
+			if (page->mapping)
+				mlock_vma_page(page);
+			unlock_page(page);
+		}
+	}
+unlock:
+	pte_unmap_unlock(ptep, ptl);
+out:
+	return page;
+
+bad_page:
+	pte_unmap_unlock(ptep, ptl);
+	return ERR_PTR(-EFAULT);
+
+no_page:
+	pte_unmap_unlock(ptep, ptl);
+	if (!pte_none(pte))
+		return page;
+
+no_page_table:
+	/*
+	 * When core dumping an enormous anonymous area that nobody
+	 * has touched so far, we don't want to allocate unnecessary pages or
+	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
+	 * then get_dump_page() will return NULL to leave a hole in the dump.
+	 * But we can only make this optimization where a hole would surely
+	 * be zero-filled if handle_mm_fault() actually did handle it.
+	 */
+	if ((flags & FOLL_DUMP) &&
+	    (!vma->vm_ops || !vma->vm_ops->fault))
+		return ERR_PTR(-EFAULT);
+	return page;
+}
+
+static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
+{
+	return stack_guard_page_start(vma, addr) ||
+	       stack_guard_page_end(vma, addr+PAGE_SIZE);
+}
+
+/**
+ * __get_user_pages() - pin user pages in memory
+ * @tsk:	task_struct of target task
+ * @mm:		mm_struct of target mm
+ * @start:	starting user address
+ * @nr_pages:	number of pages from start to pin
+ * @gup_flags:	flags modifying pin behaviour
+ * @pages:	array that receives pointers to the pages pinned.
+ *		Should be at least nr_pages long. Or NULL, if caller
+ *		only intends to ensure the pages are faulted in.
+ * @vmas:	array of pointers to vmas corresponding to each page.
+ *		Or NULL if the caller does not require them.
+ * @nonblocking: whether waiting for disk IO or mmap_sem contention
+ *
+ * Returns number of pages pinned. This may be fewer than the number
+ * requested. If nr_pages is 0 or negative, returns 0. If no pages
+ * were pinned, returns -errno. Each page returned must be released
+ * with a put_page() call when it is finished with. vmas will only
+ * remain valid while mmap_sem is held.
+ *
+ * Must be called with mmap_sem held for read or write.
+ *
+ * __get_user_pages walks a process's page tables and takes a reference to
+ * each struct page that each user address corresponds to at a given
+ * instant. That is, it takes the page that would be accessed if a user
+ * thread accesses the given user virtual address at that instant.
+ *
+ * This does not guarantee that the page exists in the user mappings when
+ * __get_user_pages returns, and there may even be a completely different
+ * page there in some cases (eg. if mmapped pagecache has been invalidated
+ * and subsequently re faulted). However it does guarantee that the page
+ * won't be freed completely. And mostly callers simply care that the page
+ * contains data that was valid *at some point in time*. Typically, an IO
+ * or similar operation cannot guarantee anything stronger anyway because
+ * locks can't be held over the syscall boundary.
+ *
+ * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
+ * the page is written to, set_page_dirty (or set_page_dirty_lock, as
+ * appropriate) must be called after the page is finished with, and
+ * before put_page is called.
+ *
+ * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
+ * or mmap_sem contention, and if waiting is needed to pin all pages,
+ * *@nonblocking will be set to 0.
+ *
+ * In most cases, get_user_pages or get_user_pages_fast should be used
+ * instead of __get_user_pages. __get_user_pages should be used only if
+ * you need some special @gup_flags.
+ */
+int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long start, int nr_pages, unsigned int gup_flags,
+		     struct page **pages, struct vm_area_struct **vmas,
+		     int *nonblocking)
+{
+	int i;
+	unsigned long vm_flags;
+
+	if (nr_pages <= 0)
+		return 0;
+
+	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
+
+	/* 
+	 * Require read or write permissions.
+	 * If FOLL_FORCE is set, we only require the "MAY" flags.
+	 */
+	vm_flags  = (gup_flags & FOLL_WRITE) ?
+			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
+	vm_flags &= (gup_flags & FOLL_FORCE) ?
+			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
+	i = 0;
+
+	do {
+		struct vm_area_struct *vma;
+
+		vma = find_extend_vma(mm, start);
+		if (!vma && in_gate_area(mm, start)) {
+			unsigned long pg = start & PAGE_MASK;
+			pgd_t *pgd;
+			pud_t *pud;
+			pmd_t *pmd;
+			pte_t *pte;
+
+			/* user gate pages are read-only */
+			if (gup_flags & FOLL_WRITE)
+				return i ? : -EFAULT;
+			if (pg > TASK_SIZE)
+				pgd = pgd_offset_k(pg);
+			else
+				pgd = pgd_offset_gate(mm, pg);
+			BUG_ON(pgd_none(*pgd));
+			pud = pud_offset(pgd, pg);
+			BUG_ON(pud_none(*pud));
+			pmd = pmd_offset(pud, pg);
+			if (pmd_none(*pmd))
+				return i ? : -EFAULT;
+			VM_BUG_ON(pmd_trans_huge(*pmd));
+			pte = pte_offset_map(pmd, pg);
+			if (pte_none(*pte)) {
+				pte_unmap(pte);
+				return i ? : -EFAULT;
+			}
+			vma = get_gate_vma(mm);
+			if (pages) {
+				struct page *page;
+
+				page = vm_normal_page(vma, start, *pte);
+				if (!page) {
+					if (!(gup_flags & FOLL_DUMP) &&
+					     is_zero_pfn(pte_pfn(*pte)))
+						page = pte_page(*pte);
+					else {
+						pte_unmap(pte);
+						return i ? : -EFAULT;
+					}
+				}
+				pages[i] = page;
+				get_page(page);
+			}
+			pte_unmap(pte);
+			goto next_page;
+		}
+
+		if (!vma ||
+		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
+		    !(vm_flags & vma->vm_flags))
+			return i ? : -EFAULT;
+
+		if (is_vm_hugetlb_page(vma)) {
+			i = follow_hugetlb_page(mm, vma, pages, vmas,
+					&start, &nr_pages, i, gup_flags);
+			continue;
+		}
+
+		do {
+			struct page *page;
+			unsigned int foll_flags = gup_flags;
+
+			/*
+			 * If we have a pending SIGKILL, don't keep faulting
+			 * pages and potentially allocating memory.
+			 */
+			if (unlikely(fatal_signal_pending(current)))
+				return i ? i : -ERESTARTSYS;
+
+			cond_resched();
+			while (!(page = follow_page(vma, start, foll_flags))) {
+				int ret;
+				unsigned int fault_flags = 0;
+
+				/* For mlock, just skip the stack guard page. */
+				if (foll_flags & FOLL_MLOCK) {
+					if (stack_guard_page(vma, start))
+						goto next_page;
+				}
+				if (foll_flags & FOLL_WRITE)
+					fault_flags |= FAULT_FLAG_WRITE;
+				if (nonblocking)
+					fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+				if (foll_flags & FOLL_NOWAIT)
+					fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
+
+				ret = handle_mm_fault(mm, vma, start,
+							fault_flags);
+
+				if (ret & VM_FAULT_ERROR) {
+					if (ret & VM_FAULT_OOM)
+						return i ? i : -ENOMEM;
+					if (ret & (VM_FAULT_HWPOISON |
+						   VM_FAULT_HWPOISON_LARGE)) {
+						if (i)
+							return i;
+						else if (gup_flags & FOLL_HWPOISON)
+							return -EHWPOISON;
+						else
+							return -EFAULT;
+					}
+					if (ret & VM_FAULT_SIGBUS)
+						return i ? i : -EFAULT;
+					BUG();
+				}
+
+				if (tsk) {
+					if (ret & VM_FAULT_MAJOR)
+						tsk->maj_flt++;
+					else
+						tsk->min_flt++;
+				}
+
+				if (ret & VM_FAULT_RETRY) {
+					if (nonblocking)
+						*nonblocking = 0;
+					return i;
+				}
+
+				/*
+				 * The VM_FAULT_WRITE bit tells us that
+				 * do_wp_page has broken COW when necessary,
+				 * even if maybe_mkwrite decided not to set
+				 * pte_write. We can thus safely do subsequent
+				 * page lookups as if they were reads. But only
+				 * do so when looping for pte_write is futile:
+				 * in some cases userspace may also be wanting
+				 * to write to the gotten user page, which a
+				 * read fault here might prevent (a readonly
+				 * page might get reCOWed by userspace write).
+				 */
+				if ((ret & VM_FAULT_WRITE) &&
+				    !(vma->vm_flags & VM_WRITE))
+					foll_flags &= ~FOLL_WRITE;
+
+				cond_resched();
+			}
+			if (IS_ERR(page))
+				return i ? i : PTR_ERR(page);
+			if (pages) {
+				pages[i] = page;
+
+				flush_anon_page(vma, page, start);
+				flush_dcache_page(page);
+			}
+next_page:
+			if (vmas)
+				vmas[i] = vma;
+			i++;
+			start += PAGE_SIZE;
+			nr_pages--;
+		} while (nr_pages && start < vma->vm_end);
+	} while (nr_pages);
+	return i;
+}
+EXPORT_SYMBOL(__get_user_pages);
+
+/*
+ * fixup_user_fault() - manually resolve a user page fault
+ * @tsk:	the task_struct to use for page fault accounting, or
+ *		NULL if faults are not to be recorded.
+ * @mm:		mm_struct of target mm
+ * @address:	user address
+ * @fault_flags:flags to pass down to handle_mm_fault()
+ *
+ * This is meant to be called in the specific scenario where for locking reasons
+ * we try to access user memory in atomic context (within a pagefault_disable()
+ * section), this returns -EFAULT, and we want to resolve the user fault before
+ * trying again.
+ *
+ * Typically this is meant to be used by the futex code.
+ *
+ * The main difference with get_user_pages() is that this function will
+ * unconditionally call handle_mm_fault() which will in turn perform all the
+ * necessary SW fixup of the dirty and young bits in the PTE, while
+ * handle_mm_fault() only guarantees to update these in the struct page.
+ *
+ * This is important for some architectures where those bits also gate the
+ * access permission to the page because they are maintained in software.  On
+ * such architectures, gup() will not be enough to make a subsequent access
+ * succeed.
+ *
+ * This should be called with the mm_sem held for read.
+ */
+int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
+		     unsigned long address, unsigned int fault_flags)
+{
+	struct vm_area_struct *vma;
+	int ret;
+
+	vma = find_extend_vma(mm, address);
+	if (!vma || address < vma->vm_start)
+		return -EFAULT;
+
+	ret = handle_mm_fault(mm, vma, address, fault_flags);
+	if (ret & VM_FAULT_ERROR) {
+		if (ret & VM_FAULT_OOM)
+			return -ENOMEM;
+		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
+			return -EHWPOISON;
+		if (ret & VM_FAULT_SIGBUS)
+			return -EFAULT;
+		BUG();
+	}
+	if (tsk) {
+		if (ret & VM_FAULT_MAJOR)
+			tsk->maj_flt++;
+		else
+			tsk->min_flt++;
+	}
+	return 0;
+}
+
+/*
+ * get_user_pages() - pin user pages in memory
+ * @tsk:	the task_struct to use for page fault accounting, or
+ *		NULL if faults are not to be recorded.
+ * @mm:		mm_struct of target mm
+ * @start:	starting user address
+ * @nr_pages:	number of pages from start to pin
+ * @write:	whether pages will be written to by the caller
+ * @force:	whether to force write access even if user mapping is
+ *		readonly. This will result in the page being COWed even
+ *		in MAP_SHARED mappings. You do not want this.
+ * @pages:	array that receives pointers to the pages pinned.
+ *		Should be at least nr_pages long. Or NULL, if caller
+ *		only intends to ensure the pages are faulted in.
+ * @vmas:	array of pointers to vmas corresponding to each page.
+ *		Or NULL if the caller does not require them.
+ *
+ * Returns number of pages pinned. This may be fewer than the number
+ * requested. If nr_pages is 0 or negative, returns 0. If no pages
+ * were pinned, returns -errno. Each page returned must be released
+ * with a put_page() call when it is finished with. vmas will only
+ * remain valid while mmap_sem is held.
+ *
+ * Must be called with mmap_sem held for read or write.
+ *
+ * get_user_pages walks a process's page tables and takes a reference to
+ * each struct page that each user address corresponds to at a given
+ * instant. That is, it takes the page that would be accessed if a user
+ * thread accesses the given user virtual address at that instant.
+ *
+ * This does not guarantee that the page exists in the user mappings when
+ * get_user_pages returns, and there may even be a completely different
+ * page there in some cases (eg. if mmapped pagecache has been invalidated
+ * and subsequently re faulted). However it does guarantee that the page
+ * won't be freed completely. And mostly callers simply care that the page
+ * contains data that was valid *at some point in time*. Typically, an IO
+ * or similar operation cannot guarantee anything stronger anyway because
+ * locks can't be held over the syscall boundary.
+ *
+ * If write=0, the page must not be written to. If the page is written to,
+ * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
+ * after the page is finished with, and before put_page is called.
+ *
+ * get_user_pages is typically used for fewer-copy IO operations, to get a
+ * handle on the memory by some means other than accesses via the user virtual
+ * addresses. The pages may be submitted for DMA to devices or accessed via
+ * their kernel linear mapping (via the kmap APIs). Care should be taken to
+ * use the correct cache flushing APIs.
+ *
+ * See also get_user_pages_fast, for performance critical applications.
+ */
+int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long start, int nr_pages, int write, int force,
+		struct page **pages, struct vm_area_struct **vmas)
+{
+	int flags = FOLL_TOUCH;
+
+	if (pages)
+		flags |= FOLL_GET;
+	if (write)
+		flags |= FOLL_WRITE;
+	if (force)
+		flags |= FOLL_FORCE;
+
+	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
+				NULL);
+}
+EXPORT_SYMBOL(get_user_pages);
+
+/**
+ * get_dump_page() - pin user page in memory while writing it to core dump
+ * @addr: user address
+ *
+ * Returns struct page pointer of user page pinned for dump,
+ * to be freed afterwards by page_cache_release() or put_page().
+ *
+ * Returns NULL on any kind of failure - a hole must then be inserted into
+ * the corefile, to preserve alignment with its headers; and also returns
+ * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
+ * allowing a hole to be left in the corefile to save diskspace.
+ *
+ * Called without mmap_sem, but after all other threads have been killed.
+ */
+#ifdef CONFIG_ELF_CORE
+struct page *get_dump_page(unsigned long addr)
+{
+	struct vm_area_struct *vma;
+	struct page *page;
+
+	if (__get_user_pages(current, current->mm, addr, 1,
+			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
+			     NULL) < 1)
+		return NULL;
+	flush_cache_page(vma, addr, page_to_pfn(page));
+	return page;
+}
+#endif /* CONFIG_ELF_CORE */
+
+pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
+			spinlock_t **ptl)
+{
+	pgd_t * pgd = pgd_offset(mm, addr);
+	pud_t * pud = pud_alloc(mm, pgd, addr);
+	if (pud) {
+		pmd_t * pmd = pmd_alloc(mm, pud, addr);
+		if (pmd) {
+			VM_BUG_ON(pmd_trans_huge(*pmd));
+			return pte_alloc_map_lock(mm, pmd, addr, ptl);
+		}
+	}
+	return NULL;
+}
+
+/*
+ * This is the old fallback for page remapping.
+ *
+ * For historical reasons, it only allows reserved pages. Only
+ * old drivers should use this, and they needed to mark their
+ * pages reserved for the old functions anyway.
+ */
+static int insert_page(struct vm_area_struct *vma, unsigned long addr,
+			struct page *page, pgprot_t prot)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	int retval;
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	retval = -EINVAL;
+	if (PageAnon(page))
+		goto out;
+	retval = -ENOMEM;
+	flush_dcache_page(page);
+	pte = get_locked_pte(mm, addr, &ptl);
+	if (!pte)
+		goto out;
+	retval = -EBUSY;
+	if (!pte_none(*pte))
+		goto out_unlock;
+
+	/* Ok, finally just insert the thing.. */
+	get_page(page);
+	inc_mm_counter_fast(mm, MM_FILEPAGES);
+	page_add_file_rmap(page);
+	set_pte_at(mm, addr, pte, mk_pte(page, prot));
+
+	retval = 0;
+	pte_unmap_unlock(pte, ptl);
+	return retval;
+out_unlock:
+	pte_unmap_unlock(pte, ptl);
+out:
+	return retval;
+}
+
+/**
+ * vm_insert_page - insert single page into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @page: source kernel page
+ *
+ * This allows drivers to insert individual pages they've allocated
+ * into a user vma.
+ *
+ * The page has to be a nice clean _individual_ kernel allocation.
+ * If you allocate a compound page, you need to have marked it as
+ * such (__GFP_COMP), or manually just split the page up yourself
+ * (see split_page()).
+ *
+ * NOTE! Traditionally this was done with "remap_pfn_range()" which
+ * took an arbitrary page protection parameter. This doesn't allow
+ * that. Your vma protection will have to be set up correctly, which
+ * means that if you want a shared writable mapping, you'd better
+ * ask for a shared writable mapping!
+ *
+ * The page does not need to be reserved.
+ */
+int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
+			struct page *page)
+{
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return -EFAULT;
+	if (!page_count(page))
+		return -EINVAL;
+	vma->vm_flags |= VM_INSERTPAGE;
+	return insert_page(vma, addr, page, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_insert_page);
+
+static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn, pgprot_t prot)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	int retval;
+	pte_t *pte, entry;
+	spinlock_t *ptl;
+
+	retval = -ENOMEM;
+	pte = get_locked_pte(mm, addr, &ptl);
+	if (!pte)
+		goto out;
+	retval = -EBUSY;
+	if (!pte_none(*pte))
+		goto out_unlock;
+
+	/* Ok, finally just insert the thing.. */
+	entry = pte_mkspecial(pfn_pte(pfn, prot));
+	set_pte_at(mm, addr, pte, entry);
+	update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
+
+	retval = 0;
+out_unlock:
+	pte_unmap_unlock(pte, ptl);
+out:
+	return retval;
+}
+
+/**
+ * vm_insert_pfn - insert single pfn into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn
+ *
+ * Similar to vm_inert_page, this allows drivers to insert individual pages
+ * they've allocated into a user vma. Same comments apply.
+ *
+ * This function should only be called from a vm_ops->fault handler, and
+ * in that case the handler should return NULL.
+ *
+ * vma cannot be a COW mapping.
+ *
+ * As this is called only for pages that do not currently exist, we
+ * do not need to flush old virtual caches or the TLB.
+ */
+int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn)
+{
+	int ret;
+	pgprot_t pgprot = vma->vm_page_prot;
+	/*
+	 * Technically, architectures with pte_special can avoid all these
+	 * restrictions (same for remap_pfn_range).  However we would like
+	 * consistency in testing and feature parity among all, so we should
+	 * try to keep these invariants in place for everybody.
+	 */
+	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
+	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
+						(VM_PFNMAP|VM_MIXEDMAP));
+	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
+	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
+
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return -EFAULT;
+	if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
+		return -EINVAL;
+
+	ret = insert_pfn(vma, addr, pfn, pgprot);
+
+	if (ret)
+		untrack_pfn_vma(vma, pfn, PAGE_SIZE);
+
+	return ret;
+}
+EXPORT_SYMBOL(vm_insert_pfn);
+
+int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn)
+{
+	BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
+
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return -EFAULT;
+
+	/*
+	 * If we don't have pte special, then we have to use the pfn_valid()
+	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
+	 * refcount the page if pfn_valid is true (hence insert_page rather
+	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
+	 * without pte special, it would there be refcounted as a normal page.
+	 */
+	if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
+		struct page *page;
+
+		page = pfn_to_page(pfn);
+		return insert_page(vma, addr, page, vma->vm_page_prot);
+	}
+	return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_insert_mixed);
+
+/*
+ * maps a range of physical memory into the requested pages. the old
+ * mappings are removed. any references to nonexistent pages results
+ * in null mappings (currently treated as "copy-on-access")
+ */
+static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
+			unsigned long addr, unsigned long end,
+			unsigned long pfn, pgprot_t prot)
+{
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
+	if (!pte)
+		return -ENOMEM;
+	arch_enter_lazy_mmu_mode();
+	do {
+		BUG_ON(!pte_none(*pte));
+		set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
+		pfn++;
+	} while (pte++, addr += PAGE_SIZE, addr != end);
+	arch_leave_lazy_mmu_mode();
+	pte_unmap_unlock(pte - 1, ptl);
+	return 0;
+}
+
+static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
+			unsigned long addr, unsigned long end,
+			unsigned long pfn, pgprot_t prot)
+{
+	pmd_t *pmd;
+	unsigned long next;
+
+	pfn -= addr >> PAGE_SHIFT;
+	pmd = pmd_alloc(mm, pud, addr);
+	if (!pmd)
+		return -ENOMEM;
+	VM_BUG_ON(pmd_trans_huge(*pmd));
+	do {
+		next = pmd_addr_end(addr, end);
+		if (remap_pte_range(mm, pmd, addr, next,
+				pfn + (addr >> PAGE_SHIFT), prot))
+			return -ENOMEM;
+	} while (pmd++, addr = next, addr != end);
+	return 0;
+}
+
+static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
+			unsigned long addr, unsigned long end,
+			unsigned long pfn, pgprot_t prot)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	pfn -= addr >> PAGE_SHIFT;
+	pud = pud_alloc(mm, pgd, addr);
+	if (!pud)
+		return -ENOMEM;
+	do {
+		next = pud_addr_end(addr, end);
+		if (remap_pmd_range(mm, pud, addr, next,
+				pfn + (addr >> PAGE_SHIFT), prot))
+			return -ENOMEM;
+	} while (pud++, addr = next, addr != end);
+	return 0;
+}
+
+/**
+ * remap_pfn_range - remap kernel memory to userspace
+ * @vma: user vma to map to
+ * @addr: target user address to start at
+ * @pfn: physical address of kernel memory
+ * @size: size of map area
+ * @prot: page protection flags for this mapping
+ *
+ *  Note: this is only safe if the mm semaphore is held when called.
+ */
+int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
+		    unsigned long pfn, unsigned long size, pgprot_t prot)
+{
+	pgd_t *pgd;
+	unsigned long next;
+	unsigned long end = addr + PAGE_ALIGN(size);
+	struct mm_struct *mm = vma->vm_mm;
+	int err;
+
+	/*
+	 * Physically remapped pages are special. Tell the
+	 * rest of the world about it:
+	 *   VM_IO tells people not to look at these pages
+	 *	(accesses can have side effects).
+	 *   VM_RESERVED is specified all over the place, because
+	 *	in 2.4 it kept swapout's vma scan off this vma; but
+	 *	in 2.6 the LRU scan won't even find its pages, so this
+	 *	flag means no more than count its pages in reserved_vm,
+	 * 	and omit it from core dump, even when VM_IO turned off.
+	 *   VM_PFNMAP tells the core MM that the base pages are just
+	 *	raw PFN mappings, and do not have a "struct page" associated
+	 *	with them.
+	 *
+	 * There's a horrible special case to handle copy-on-write
+	 * behaviour that some programs depend on. We mark the "original"
+	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
+	 */
+	if (addr == vma->vm_start && end == vma->vm_end) {
+		vma->vm_pgoff = pfn;
+		vma->vm_flags |= VM_PFN_AT_MMAP;
+	} else if (is_cow_mapping(vma->vm_flags))
+		return -EINVAL;
+
+	vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
+
+	err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
+	if (err) {
+		/*
+		 * To indicate that track_pfn related cleanup is not
+		 * needed from higher level routine calling unmap_vmas
+		 */
+		vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
+		vma->vm_flags &= ~VM_PFN_AT_MMAP;
+		return -EINVAL;
+	}
+
+	BUG_ON(addr >= end);
+	pfn -= addr >> PAGE_SHIFT;
+	pgd = pgd_offset(mm, addr);
+	flush_cache_range(vma, addr, end);
+	do {
+		next = pgd_addr_end(addr, end);
+		err = remap_pud_range(mm, pgd, addr, next,
+				pfn + (addr >> PAGE_SHIFT), prot);
+		if (err)
+			break;
+	} while (pgd++, addr = next, addr != end);
+
+	if (err)
+		untrack_pfn_vma(vma, pfn, PAGE_ALIGN(size));
+
+	return err;
+}
+EXPORT_SYMBOL(remap_pfn_range);
+
+static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
+				     unsigned long addr, unsigned long end,
+				     pte_fn_t fn, void *data)
+{
+	pte_t *pte;
+	int err;
+	pgtable_t token;
+	spinlock_t *uninitialized_var(ptl);
+
+	pte = (mm == &init_mm) ?
+		pte_alloc_kernel(pmd, addr) :
+		pte_alloc_map_lock(mm, pmd, addr, &ptl);
+	if (!pte)
+		return -ENOMEM;
+
+	BUG_ON(pmd_huge(*pmd));
+
+	arch_enter_lazy_mmu_mode();
+
+	token = pmd_pgtable(*pmd);
+
+	do {
+		err = fn(pte++, token, addr, data);
+		if (err)
+			break;
+	} while (addr += PAGE_SIZE, addr != end);
+
+	arch_leave_lazy_mmu_mode();
+
+	if (mm != &init_mm)
+		pte_unmap_unlock(pte-1, ptl);
+	return err;
+}
+
+static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
+				     unsigned long addr, unsigned long end,
+				     pte_fn_t fn, void *data)
+{
+	pmd_t *pmd;
+	unsigned long next;
+	int err;
+
+	BUG_ON(pud_huge(*pud));
+
+	pmd = pmd_alloc(mm, pud, addr);
+	if (!pmd)
+		return -ENOMEM;
+	do {
+		next = pmd_addr_end(addr, end);
+		err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
+		if (err)
+			break;
+	} while (pmd++, addr = next, addr != end);
+	return err;
+}
+
+static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
+				     unsigned long addr, unsigned long end,
+				     pte_fn_t fn, void *data)
+{
+	pud_t *pud;
+	unsigned long next;
+	int err;
+
+	pud = pud_alloc(mm, pgd, addr);
+	if (!pud)
+		return -ENOMEM;
+	do {
+		next = pud_addr_end(addr, end);
+		err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
+		if (err)
+			break;
+	} while (pud++, addr = next, addr != end);
+	return err;
+}
+
+/*
+ * Scan a region of virtual memory, filling in page tables as necessary
+ * and calling a provided function on each leaf page table.
+ */
+int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
+			unsigned long size, pte_fn_t fn, void *data)
+{
+	pgd_t *pgd;
+	unsigned long next;
+	unsigned long end = addr + size;
+	int err;
+
+	BUG_ON(addr >= end);
+	pgd = pgd_offset(mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
+		if (err)
+			break;
+	} while (pgd++, addr = next, addr != end);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(apply_to_page_range);
+
+/*
+ * handle_pte_fault chooses page fault handler according to an entry
+ * which was read non-atomically.  Before making any commitment, on
+ * those architectures or configurations (e.g. i386 with PAE) which
+ * might give a mix of unmatched parts, do_swap_page and do_nonlinear_fault
+ * must check under lock before unmapping the pte and proceeding
+ * (but do_wp_page is only called after already making such a check;
+ * and do_anonymous_page can safely check later on).
+ */
+static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
+				pte_t *page_table, pte_t orig_pte)
+{
+	int same = 1;
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
+	if (sizeof(pte_t) > sizeof(unsigned long)) {
+		spinlock_t *ptl = pte_lockptr(mm, pmd);
+		spin_lock(ptl);
+		same = pte_same(*page_table, orig_pte);
+		spin_unlock(ptl);
+	}
+#endif
+	pte_unmap(page_table);
+	return same;
+}
+
+static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
+{
+	/*
+	 * If the source page was a PFN mapping, we don't have
+	 * a "struct page" for it. We do a best-effort copy by
+	 * just copying from the original user address. If that
+	 * fails, we just zero-fill it. Live with it.
+	 */
+	if (unlikely(!src)) {
+		void *kaddr = kmap_atomic(dst, KM_USER0);
+		void __user *uaddr = (void __user *)(va & PAGE_MASK);
+
+		/*
+		 * This really shouldn't fail, because the page is there
+		 * in the page tables. But it might just be unreadable,
+		 * in which case we just give up and fill the result with
+		 * zeroes.
+		 */
+		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
+			clear_page(kaddr);
+		kunmap_atomic(kaddr, KM_USER0);
+		flush_dcache_page(dst);
+	} else
+		copy_user_highpage(dst, src, va, vma);
+}
+
+/*
+ * This routine handles present pages, when users try to write
+ * to a shared page. It is done by copying the page to a new address
+ * and decrementing the shared-page counter for the old page.
+ *
+ * Note that this routine assumes that the protection checks have been
+ * done by the caller (the low-level page fault routine in most cases).
+ * Thus we can safely just mark it writable once we've done any necessary
+ * COW.
+ *
+ * We also mark the page dirty at this point even though the page will
+ * change only once the write actually happens. This avoids a few races,
+ * and potentially makes it more efficient.
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), with pte both mapped and locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *page_table, pmd_t *pmd,
+		spinlock_t *ptl, pte_t orig_pte)
+	__releases(ptl)
+{
+	struct page *old_page, *new_page;
+	pte_t entry;
+	int ret = 0;
+	int page_mkwrite = 0;
+	struct page *dirty_page = NULL;
+
+	old_page = vm_normal_page(vma, address, orig_pte);
+	if (!old_page) {
+		/*
+		 * VM_MIXEDMAP !pfn_valid() case
+		 *
+		 * We should not cow pages in a shared writeable mapping.
+		 * Just mark the pages writable as we can't do any dirty
+		 * accounting on raw pfn maps.
+		 */
+		if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
+				     (VM_WRITE|VM_SHARED))
+			goto reuse;
+		goto gotten;
+	}
+
+	/*
+	 * Take out anonymous pages first, anonymous shared vmas are
+	 * not dirty accountable.
+	 */
+	if (PageAnon(old_page) && !PageKsm(old_page)) {
+		if (!trylock_page(old_page)) {
+			page_cache_get(old_page);
+			pte_unmap_unlock(page_table, ptl);
+			lock_page(old_page);
+			page_table = pte_offset_map_lock(mm, pmd, address,
+							 &ptl);
+			if (!pte_same(*page_table, orig_pte)) {
+				unlock_page(old_page);
+				goto unlock;
+			}
+			page_cache_release(old_page);
+		}
+		if (reuse_swap_page(old_page)) {
+			/*
+			 * The page is all ours.  Move it to our anon_vma so
+			 * the rmap code will not search our parent or siblings.
+			 * Protected against the rmap code by the page lock.
+			 */
+			page_move_anon_rmap(old_page, vma, address);
+			unlock_page(old_page);
+			goto reuse;
+		}
+		unlock_page(old_page);
+	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
+					(VM_WRITE|VM_SHARED))) {
+		/*
+		 * Only catch write-faults on shared writable pages,
+		 * read-only shared pages can get COWed by
+		 * get_user_pages(.write=1, .force=1).
+		 */
+		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
+			struct vm_fault vmf;
+			int tmp;
+
+			vmf.virtual_address = (void __user *)(address &
+								PAGE_MASK);
+			vmf.pgoff = old_page->index;
+			vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
+			vmf.page = old_page;
+
+			/*
+			 * Notify the address space that the page is about to
+			 * become writable so that it can prohibit this or wait
+			 * for the page to get into an appropriate state.
+			 *
+			 * We do this without the lock held, so that it can
+			 * sleep if it needs to.
+			 */
+			page_cache_get(old_page);
+			pte_unmap_unlock(page_table, ptl);
+
+			tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
+			if (unlikely(tmp &
+					(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
+				ret = tmp;
+				goto unwritable_page;
+			}
+			if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
+				lock_page(old_page);
+				if (!old_page->mapping) {
+					ret = 0; /* retry the fault */
+					unlock_page(old_page);
+					goto unwritable_page;
+				}
+			} else
+				VM_BUG_ON(!PageLocked(old_page));
+
+			/*
+			 * Since we dropped the lock we need to revalidate
+			 * the PTE as someone else may have changed it.  If
+			 * they did, we just return, as we can count on the
+			 * MMU to tell us if they didn't also make it writable.
+			 */
+			page_table = pte_offset_map_lock(mm, pmd, address,
+							 &ptl);
+			if (!pte_same(*page_table, orig_pte)) {
+				unlock_page(old_page);
+				goto unlock;
+			}
+
+			page_mkwrite = 1;
+		}
+		dirty_page = old_page;
+		get_page(dirty_page);
+
+reuse:
+		flush_cache_page(vma, address, pte_pfn(orig_pte));
+		entry = pte_mkyoung(orig_pte);
+		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+		if (ptep_set_access_flags(vma, address, page_table, entry,1))
+			update_mmu_cache(vma, address, page_table);
+		pte_unmap_unlock(page_table, ptl);
+		ret |= VM_FAULT_WRITE;
+
+		if (!dirty_page)
+			return ret;
+
+		/*
+		 * Yes, Virginia, this is actually required to prevent a race
+		 * with clear_page_dirty_for_io() from clearing the page dirty
+		 * bit after it clear all dirty ptes, but before a racing
+		 * do_wp_page installs a dirty pte.
+		 *
+		 * __do_fault is protected similarly.
+		 */
+		if (!page_mkwrite) {
+			wait_on_page_locked(dirty_page);
+			set_page_dirty_balance(dirty_page, page_mkwrite);
+		}
+		put_page(dirty_page);
+		if (page_mkwrite) {
+			struct address_space *mapping = dirty_page->mapping;
+
+			set_page_dirty(dirty_page);
+			unlock_page(dirty_page);
+			page_cache_release(dirty_page);
+			if (mapping)	{
+				/*
+				 * Some device drivers do not set page.mapping
+				 * but still dirty their pages
+				 */
+				balance_dirty_pages_ratelimited(mapping);
+			}
+		}
+
+		/* file_update_time outside page_lock */
+		if (vma->vm_file)
+			file_update_time(vma->vm_file);
+
+		return ret;
+	}
+
+	/*
+	 * Ok, we need to copy. Oh, well..
+	 */
+	page_cache_get(old_page);
+gotten:
+	pte_unmap_unlock(page_table, ptl);
+
+	if (unlikely(anon_vma_prepare(vma)))
+		goto oom;
+
+	if (is_zero_pfn(pte_pfn(orig_pte))) {
+		new_page = alloc_zeroed_user_highpage_movable(vma, address);
+		if (!new_page)
+			goto oom;
+	} else {
+		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+		if (!new_page)
+			goto oom;
+		cow_user_page(new_page, old_page, address, vma);
+	}
+	__SetPageUptodate(new_page);
+
+	if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
+		goto oom_free_new;
+
+	/*
+	 * Re-check the pte - we dropped the lock
+	 */
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+	if (likely(pte_same(*page_table, orig_pte))) {
+		if (old_page) {
+			if (!PageAnon(old_page)) {
+				dec_mm_counter_fast(mm, MM_FILEPAGES);
+				inc_mm_counter_fast(mm, MM_ANONPAGES);
+			}
+		} else
+			inc_mm_counter_fast(mm, MM_ANONPAGES);
+		flush_cache_page(vma, address, pte_pfn(orig_pte));
+		entry = mk_pte(new_page, vma->vm_page_prot);
+		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+		/*
+		 * Clear the pte entry and flush it first, before updating the
+		 * pte with the new entry. This will avoid a race condition
+		 * seen in the presence of one thread doing SMC and another
+		 * thread doing COW.
+		 */
+		ptep_clear_flush(vma, address, page_table);
+		page_add_new_anon_rmap(new_page, vma, address);
+		/*
+		 * We call the notify macro here because, when using secondary
+		 * mmu page tables (such as kvm shadow page tables), we want the
+		 * new page to be mapped directly into the secondary page table.
+		 */
+		set_pte_at_notify(mm, address, page_table, entry);
+		update_mmu_cache(vma, address, page_table);
+		if (old_page) {
+			/*
+			 * Only after switching the pte to the new page may
+			 * we remove the mapcount here. Otherwise another
+			 * process may come and find the rmap count decremented
+			 * before the pte is switched to the new page, and
+			 * "reuse" the old page writing into it while our pte
+			 * here still points into it and can be read by other
+			 * threads.
+			 *
+			 * The critical issue is to order this
+			 * page_remove_rmap with the ptp_clear_flush above.
+			 * Those stores are ordered by (if nothing else,)
+			 * the barrier present in the atomic_add_negative
+			 * in page_remove_rmap.
+			 *
+			 * Then the TLB flush in ptep_clear_flush ensures that
+			 * no process can access the old page before the
+			 * decremented mapcount is visible. And the old page
+			 * cannot be reused until after the decremented
+			 * mapcount is visible. So transitively, TLBs to
+			 * old page will be flushed before it can be reused.
+			 */
+			page_remove_rmap(old_page);
+		}
+
+		/* Free the old page.. */
+		new_page = old_page;
+		ret |= VM_FAULT_WRITE;
+	} else
+		mem_cgroup_uncharge_page(new_page);
+
+	if (new_page)
+		page_cache_release(new_page);
+unlock:
+	pte_unmap_unlock(page_table, ptl);
+	if (old_page) {
+		/*
+		 * Don't let another task, with possibly unlocked vma,
+		 * keep the mlocked page.
+		 */
+		if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
+			lock_page(old_page);	/* LRU manipulation */
+			munlock_vma_page(old_page);
+			unlock_page(old_page);
+		}
+		page_cache_release(old_page);
+	}
+	return ret;
+oom_free_new:
+	page_cache_release(new_page);
+oom:
+	if (old_page) {
+		if (page_mkwrite) {
+			unlock_page(old_page);
+			page_cache_release(old_page);
+		}
+		page_cache_release(old_page);
+	}
+	return VM_FAULT_OOM;
+
+unwritable_page:
+	page_cache_release(old_page);
+	return ret;
+}
+
+static void unmap_mapping_range_vma(struct vm_area_struct *vma,
+		unsigned long start_addr, unsigned long end_addr,
+		struct zap_details *details)
+{
+	zap_page_range(vma, start_addr, end_addr - start_addr, details);
+}
+
+static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
+					    struct zap_details *details)
+{
+	struct vm_area_struct *vma;
+	struct prio_tree_iter iter;
+	pgoff_t vba, vea, zba, zea;
+
+	vma_prio_tree_foreach(vma, &iter, root,
+			details->first_index, details->last_index) {
+
+		vba = vma->vm_pgoff;
+		vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
+		/* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
+		zba = details->first_index;
+		if (zba < vba)
+			zba = vba;
+		zea = details->last_index;
+		if (zea > vea)
+			zea = vea;
+
+		unmap_mapping_range_vma(vma,
+			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
+			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
+				details);
+	}
+}
+
+static inline void unmap_mapping_range_list(struct list_head *head,
+					    struct zap_details *details)
+{
+	struct vm_area_struct *vma;
+
+	/*
+	 * In nonlinear VMAs there is no correspondence between virtual address
+	 * offset and file offset.  So we must perform an exhaustive search
+	 * across *all* the pages in each nonlinear VMA, not just the pages
+	 * whose virtual address lies outside the file truncation point.
+	 */
+	list_for_each_entry(vma, head, shared.vm_set.list) {
+		details->nonlinear_vma = vma;
+		unmap_mapping_range_vma(vma, vma->vm_start, vma->vm_end, details);
+	}
+}
+
+/**
+ * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
+ * @mapping: the address space containing mmaps to be unmapped.
+ * @holebegin: byte in first page to unmap, relative to the start of
+ * the underlying file.  This will be rounded down to a PAGE_SIZE
+ * boundary.  Note that this is different from truncate_pagecache(), which
+ * must keep the partial page.  In contrast, we must get rid of
+ * partial pages.
+ * @holelen: size of prospective hole in bytes.  This will be rounded
+ * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
+ * end of the file.
+ * @even_cows: 1 when truncating a file, unmap even private COWed pages;
+ * but 0 when invalidating pagecache, don't throw away private data.
+ */
+void unmap_mapping_range(struct address_space *mapping,
+		loff_t const holebegin, loff_t const holelen, int even_cows)
+{
+	struct zap_details details;
+	pgoff_t hba = holebegin >> PAGE_SHIFT;
+	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+	/* Check for overflow. */
+	if (sizeof(holelen) > sizeof(hlen)) {
+		long long holeend =
+			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		if (holeend & ~(long long)ULONG_MAX)
+			hlen = ULONG_MAX - hba + 1;
+	}
+
+	details.check_mapping = even_cows? NULL: mapping;
+	details.nonlinear_vma = NULL;
+	details.first_index = hba;
+	details.last_index = hba + hlen - 1;
+	if (details.last_index < details.first_index)
+		details.last_index = ULONG_MAX;
+
+
+	mutex_lock(&mapping->i_mmap_mutex);
+	if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
+		unmap_mapping_range_tree(&mapping->i_mmap, &details);
+	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
+		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
+	mutex_unlock(&mapping->i_mmap_mutex);
+}
+EXPORT_SYMBOL(unmap_mapping_range);
+
+/*
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *page_table, pmd_t *pmd,
+		unsigned int flags, pte_t orig_pte)
+{
+	spinlock_t *ptl;
+	struct page *page, *swapcache = NULL;
+	swp_entry_t entry;
+	pte_t pte;
+	int locked;
+	struct mem_cgroup *ptr;
+	int exclusive = 0;
+	int ret = 0;
+
+	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
+		goto out;
+
+	entry = pte_to_swp_entry(orig_pte);
+	if (unlikely(non_swap_entry(entry))) {
+		if (is_migration_entry(entry)) {
+			migration_entry_wait(mm, pmd, address);
+		} else if (is_hwpoison_entry(entry)) {
+			ret = VM_FAULT_HWPOISON;
+		} else {
+			print_bad_pte(vma, address, orig_pte, NULL);
+			ret = VM_FAULT_SIGBUS;
+		}
+		goto out;
+	}
+	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
+	page = lookup_swap_cache(entry);
+	if (!page) {
+		grab_swap_token(mm); /* Contend for token _before_ read-in */
+		page = swapin_readahead(entry,
+					GFP_HIGHUSER_MOVABLE, vma, address);
+		if (!page) {
+			/*
+			 * Back out if somebody else faulted in this pte
+			 * while we released the pte lock.
+			 */
+			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+			if (likely(pte_same(*page_table, orig_pte)))
+				ret = VM_FAULT_OOM;
+			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
+			goto unlock;
+		}
+
+		/* Had to read the page from swap area: Major fault */
+		ret = VM_FAULT_MAJOR;
+		count_vm_event(PGMAJFAULT);
+		mem_cgroup_count_vm_event(mm, PGMAJFAULT);
+	} else if (PageHWPoison(page)) {
+		/*
+		 * hwpoisoned dirty swapcache pages are kept for killing
+		 * owner processes (which may be unknown at hwpoison time)
+		 */
+		ret = VM_FAULT_HWPOISON;
+		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
+		goto out_release;
+	}
+
+	locked = lock_page_or_retry(page, mm, flags);
+	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
+	if (!locked) {
+		ret |= VM_FAULT_RETRY;
+		goto out_release;
+	}
+
+	/*
+	 * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
+	 * release the swapcache from under us.  The page pin, and pte_same
+	 * test below, are not enough to exclude that.  Even if it is still
+	 * swapcache, we need to check that the page's swap has not changed.
+	 */
+	if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
+		goto out_page;
+
+	if (ksm_might_need_to_copy(page, vma, address)) {
+		swapcache = page;
+		page = ksm_does_need_to_copy(page, vma, address);
+
+		if (unlikely(!page)) {
+			ret = VM_FAULT_OOM;
+			page = swapcache;
+			swapcache = NULL;
+			goto out_page;
+		}
+	}
+
+	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
+		ret = VM_FAULT_OOM;
+		goto out_page;
+	}
+
+	/*
+	 * Back out if somebody else already faulted in this pte.
+	 */
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+	if (unlikely(!pte_same(*page_table, orig_pte)))
+		goto out_nomap;
+
+	if (unlikely(!PageUptodate(page))) {
+		ret = VM_FAULT_SIGBUS;
+		goto out_nomap;
+	}
+
+	/*
+	 * The page isn't present yet, go ahead with the fault.
+	 *
+	 * Be careful about the sequence of operations here.
+	 * To get its accounting right, reuse_swap_page() must be called
+	 * while the page is counted on swap but not yet in mapcount i.e.
+	 * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
+	 * must be called after the swap_free(), or it will never succeed.
+	 * Because delete_from_swap_page() may be called by reuse_swap_page(),
+	 * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
+	 * in page->private. In this case, a record in swap_cgroup  is silently
+	 * discarded at swap_free().
+	 */
+
+	inc_mm_counter_fast(mm, MM_ANONPAGES);
+	dec_mm_counter_fast(mm, MM_SWAPENTS);
+	pte = mk_pte(page, vma->vm_page_prot);
+	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
+		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
+		flags &= ~FAULT_FLAG_WRITE;
+		ret |= VM_FAULT_WRITE;
+		exclusive = 1;
+	}
+	flush_icache_page(vma, page);
+	set_pte_at(mm, address, page_table, pte);
+	do_page_add_anon_rmap(page, vma, address, exclusive);
+	/* It's better to call commit-charge after rmap is established */
+	mem_cgroup_commit_charge_swapin(page, ptr);
+
+	swap_free(entry);
+	if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
+		try_to_free_swap(page);
+	unlock_page(page);
+	if (swapcache) {
+		/*
+		 * Hold the lock to avoid the swap entry to be reused
+		 * until we take the PT lock for the pte_same() check
+		 * (to avoid false positives from pte_same). For
+		 * further safety release the lock after the swap_free
+		 * so that the swap count won't change under a
+		 * parallel locked swapcache.
+		 */
+		unlock_page(swapcache);
+		page_cache_release(swapcache);
+	}
+
+	if (flags & FAULT_FLAG_WRITE) {
+		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
+		if (ret & VM_FAULT_ERROR)
+			ret &= VM_FAULT_ERROR;
+		goto out;
+	}
+
+	/* No need to invalidate - it was non-present before */
+	update_mmu_cache(vma, address, page_table);
+unlock:
+	pte_unmap_unlock(page_table, ptl);
+out:
+	return ret;
+out_nomap:
+	mem_cgroup_cancel_charge_swapin(ptr);
+	pte_unmap_unlock(page_table, ptl);
+out_page:
+	unlock_page(page);
+out_release:
+	page_cache_release(page);
+	if (swapcache) {
+		unlock_page(swapcache);
+		page_cache_release(swapcache);
+	}
+	return ret;
+}
+
+/*
+ * This is like a special single-page "expand_{down|up}wards()",
+ * except we must first make sure that 'address{-|+}PAGE_SIZE'
+ * doesn't hit another vma.
+ */
+static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
+{
+	address &= PAGE_MASK;
+	if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
+		struct vm_area_struct *prev = vma->vm_prev;
+
+		/*
+		 * Is there a mapping abutting this one below?
+		 *
+		 * That's only ok if it's the same stack mapping
+		 * that has gotten split..
+		 */
+		if (prev && prev->vm_end == address)
+			return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
+
+		expand_downwards(vma, address - PAGE_SIZE);
+	}
+	if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
+		struct vm_area_struct *next = vma->vm_next;
+
+		/* As VM_GROWSDOWN but s/below/above/ */
+		if (next && next->vm_start == address + PAGE_SIZE)
+			return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
+
+		expand_upwards(vma, address + PAGE_SIZE);
+	}
+	return 0;
+}
+
+/*
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *page_table, pmd_t *pmd,
+		unsigned int flags)
+{
+	struct page *page;
+	spinlock_t *ptl;
+	pte_t entry;
+
+	pte_unmap(page_table);
+
+	/* Check if we need to add a guard page to the stack */
+	if (check_stack_guard_page(vma, address) < 0)
+		return VM_FAULT_SIGBUS;
+
+	/* Use the zero-page for reads */
+	if (!(flags & FAULT_FLAG_WRITE)) {
+		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
+						vma->vm_page_prot));
+		page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+		if (!pte_none(*page_table))
+			goto unlock;
+		goto setpte;
+	}
+
+	/* Allocate our own private page. */
+	if (unlikely(anon_vma_prepare(vma)))
+		goto oom;
+	page = alloc_zeroed_user_highpage_movable(vma, address);
+	if (!page)
+		goto oom;
+	__SetPageUptodate(page);
+
+	if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
+		goto oom_free_page;
+
+	entry = mk_pte(page, vma->vm_page_prot);
+	if (vma->vm_flags & VM_WRITE)
+		entry = pte_mkwrite(pte_mkdirty(entry));
+
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+	if (!pte_none(*page_table))
+		goto release;
+
+	inc_mm_counter_fast(mm, MM_ANONPAGES);
+	page_add_new_anon_rmap(page, vma, address);
+setpte:
+	set_pte_at(mm, address, page_table, entry);
+
+	/* No need to invalidate - it was non-present before */
+	update_mmu_cache(vma, address, page_table);
+unlock:
+	pte_unmap_unlock(page_table, ptl);
+	return 0;
+release:
+	mem_cgroup_uncharge_page(page);
+	page_cache_release(page);
+	goto unlock;
+oom_free_page:
+	page_cache_release(page);
+oom:
+	return VM_FAULT_OOM;
+}
+
+/*
+ * __do_fault() tries to create a new page mapping. It aggressively
+ * tries to share with existing pages, but makes a separate copy if
+ * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
+ * the next page fault.
+ *
+ * As this is called only for pages that do not currently exist, we
+ * do not need to flush old virtual caches or the TLB.
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte neither mapped nor locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd,
+		pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
+{
+	pte_t *page_table;
+	spinlock_t *ptl;
+	struct page *page;
+	pte_t entry;
+	int anon = 0;
+	int charged = 0;
+	struct page *dirty_page = NULL;
+	struct vm_fault vmf;
+	int ret;
+	int page_mkwrite = 0;
+
+	vmf.virtual_address = (void __user *)(address & PAGE_MASK);
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.page = NULL;
+
+	ret = vma->vm_ops->fault(vma, &vmf);
+	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
+			    VM_FAULT_RETRY)))
+		return ret;
+
+	if (unlikely(PageHWPoison(vmf.page))) {
+		if (ret & VM_FAULT_LOCKED)
+			unlock_page(vmf.page);
+		return VM_FAULT_HWPOISON;
+	}
+
+	/*
+	 * For consistency in subsequent calls, make the faulted page always
+	 * locked.
+	 */
+	if (unlikely(!(ret & VM_FAULT_LOCKED)))
+		lock_page(vmf.page);
+	else
+		VM_BUG_ON(!PageLocked(vmf.page));
+
+	/*
+	 * Should we do an early C-O-W break?
+	 */
+	page = vmf.page;
+	if (flags & FAULT_FLAG_WRITE) {
+		if (!(vma->vm_flags & VM_SHARED)) {
+			anon = 1;
+			if (unlikely(anon_vma_prepare(vma))) {
+				ret = VM_FAULT_OOM;
+				goto out;
+			}
+			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
+						vma, address);
+			if (!page) {
+				ret = VM_FAULT_OOM;
+				goto out;
+			}
+			if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
+				ret = VM_FAULT_OOM;
+				page_cache_release(page);
+				goto out;
+			}
+			charged = 1;
+			copy_user_highpage(page, vmf.page, address, vma);
+			__SetPageUptodate(page);
+		} else {
+			/*
+			 * If the page will be shareable, see if the backing
+			 * address space wants to know that the page is about
+			 * to become writable
+			 */
+			if (vma->vm_ops->page_mkwrite) {
+				int tmp;
+
+				unlock_page(page);
+				vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
+				tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
+				if (unlikely(tmp &
+					  (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
+					ret = tmp;
+					goto unwritable_page;
+				}
+				if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
+					lock_page(page);
+					if (!page->mapping) {
+						ret = 0; /* retry the fault */
+						unlock_page(page);
+						goto unwritable_page;
+					}
+				} else
+					VM_BUG_ON(!PageLocked(page));
+				page_mkwrite = 1;
+			}
+		}
+
+	}
+
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+
+	/*
+	 * This silly early PAGE_DIRTY setting removes a race
+	 * due to the bad i386 page protection. But it's valid
+	 * for other architectures too.
+	 *
+	 * Note that if FAULT_FLAG_WRITE is set, we either now have
+	 * an exclusive copy of the page, or this is a shared mapping,
+	 * so we can make it writable and dirty to avoid having to
+	 * handle that later.
+	 */
+	/* Only go through if we didn't race with anybody else... */
+	if (likely(pte_same(*page_table, orig_pte))) {
+		flush_icache_page(vma, page);
+		entry = mk_pte(page, vma->vm_page_prot);
+		if (flags & FAULT_FLAG_WRITE)
+			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+		if (anon) {
+			inc_mm_counter_fast(mm, MM_ANONPAGES);
+			page_add_new_anon_rmap(page, vma, address);
+		} else {
+			inc_mm_counter_fast(mm, MM_FILEPAGES);
+			page_add_file_rmap(page);
+			if (flags & FAULT_FLAG_WRITE) {
+				dirty_page = page;
+				get_page(dirty_page);
+			}
+		}
+		set_pte_at(mm, address, page_table, entry);
+
+		/* no need to invalidate: a not-present page won't be cached */
+		update_mmu_cache(vma, address, page_table);
+	} else {
+		if (charged)
+			mem_cgroup_uncharge_page(page);
+		if (anon)
+			page_cache_release(page);
+		else
+			anon = 1; /* no anon but release faulted_page */
+	}
+
+	pte_unmap_unlock(page_table, ptl);
+
+out:
+	if (dirty_page) {
+		struct address_space *mapping = page->mapping;
+
+		if (set_page_dirty(dirty_page))
+			page_mkwrite = 1;
+		unlock_page(dirty_page);
+		put_page(dirty_page);
+		if (page_mkwrite && mapping) {
+			/*
+			 * Some device drivers do not set page.mapping but still
+			 * dirty their pages
+			 */
+			balance_dirty_pages_ratelimited(mapping);
+		}
+
+		/* file_update_time outside page_lock */
+		if (vma->vm_file)
+			file_update_time(vma->vm_file);
+	} else {
+		unlock_page(vmf.page);
+		if (anon)
+			page_cache_release(vmf.page);
+	}
+
+	return ret;
+
+unwritable_page:
+	page_cache_release(page);
+	return ret;
+}
+
+static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *page_table, pmd_t *pmd,
+		unsigned int flags, pte_t orig_pte)
+{
+	pgoff_t pgoff = (((address & PAGE_MASK)
+			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+
+	pte_unmap(page_table);
+	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+}
+
+/*
+ * Fault of a previously existing named mapping. Repopulate the pte
+ * from the encoded file_pte if possible. This enables swappable
+ * nonlinear vmas.
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *page_table, pmd_t *pmd,
+		unsigned int flags, pte_t orig_pte)
+{
+	pgoff_t pgoff;
+
+	flags |= FAULT_FLAG_NONLINEAR;
+
+	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
+		return 0;
+
+	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
+		/*
+		 * Page table corrupted: show pte and kill process.
+		 */
+		print_bad_pte(vma, address, orig_pte, NULL);
+		return VM_FAULT_SIGBUS;
+	}
+
+	pgoff = pte_to_pgoff(orig_pte);
+	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+}
+
+/*
+ * These routines also need to handle stuff like marking pages dirty
+ * and/or accessed for architectures that don't do it in hardware (most
+ * RISC architectures).  The early dirtying is also good on the i386.
+ *
+ * There is also a hook called "update_mmu_cache()" that architectures
+ * with external mmu caches can use to update those (ie the Sparc or
+ * PowerPC hashed page tables that act as extended TLBs).
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
+ */
+int handle_pte_fault(struct mm_struct *mm,
+		     struct vm_area_struct *vma, unsigned long address,
+		     pte_t *pte, pmd_t *pmd, unsigned int flags)
+{
+	pte_t entry;
+	spinlock_t *ptl;
+
+	entry = *pte;
+	if (!pte_present(entry)) {
+		if (pte_none(entry)) {
+			if (vma->vm_ops) {
+				if (likely(vma->vm_ops->fault))
+					return do_linear_fault(mm, vma, address,
+						pte, pmd, flags, entry);
+			}
+			return do_anonymous_page(mm, vma, address,
+						 pte, pmd, flags);
+		}
+		if (pte_file(entry))
+			return do_nonlinear_fault(mm, vma, address,
+					pte, pmd, flags, entry);
+		return do_swap_page(mm, vma, address,
+					pte, pmd, flags, entry);
+	}
+
+	ptl = pte_lockptr(mm, pmd);
+	spin_lock(ptl);
+	if (unlikely(!pte_same(*pte, entry)))
+		goto unlock;
+	if (flags & FAULT_FLAG_WRITE) {
+		if (!pte_write(entry))
+			return do_wp_page(mm, vma, address,
+					pte, pmd, ptl, entry);
+		entry = pte_mkdirty(entry);
+	}
+	entry = pte_mkyoung(entry);
+	if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
+		update_mmu_cache(vma, address, pte);
+	} else {
+		/*
+		 * This is needed only for protection faults but the arch code
+		 * is not yet telling us if this is a protection fault or not.
+		 * This still avoids useless tlb flushes for .text page faults
+		 * with threads.
+		 */
+		if (flags & FAULT_FLAG_WRITE)
+			flush_tlb_fix_spurious_fault(vma, address);
+	}
+unlock:
+	pte_unmap_unlock(pte, ptl);
+	return 0;
+}
+
+/*
+ * By the time we get here, we already hold the mm semaphore
+ */
+int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, unsigned int flags)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	__set_current_state(TASK_RUNNING);
+
+	count_vm_event(PGFAULT);
+	mem_cgroup_count_vm_event(mm, PGFAULT);
+
+	/* do counter updates before entering really critical section. */
+	check_sync_rss_stat(current);
+
+	if (unlikely(is_vm_hugetlb_page(vma)))
+		return hugetlb_fault(mm, vma, address, flags);
+
+	pgd = pgd_offset(mm, address);
+	pud = pud_alloc(mm, pgd, address);
+	if (!pud)
+		return VM_FAULT_OOM;
+	pmd = pmd_alloc(mm, pud, address);
+	if (!pmd)
+		return VM_FAULT_OOM;
+	if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
+		if (!vma->vm_ops)
+			return do_huge_pmd_anonymous_page(mm, vma, address,
+							  pmd, flags);
+	} else {
+		pmd_t orig_pmd = *pmd;
+		barrier();
+		if (pmd_trans_huge(orig_pmd)) {
+			if (flags & FAULT_FLAG_WRITE &&
+			    !pmd_write(orig_pmd) &&
+			    !pmd_trans_splitting(orig_pmd))
+				return do_huge_pmd_wp_page(mm, vma, address,
+							   pmd, orig_pmd);
+			return 0;
+		}
+	}
+
+	/*
+	 * Use __pte_alloc instead of pte_alloc_map, because we can't
+	 * run pte_offset_map on the pmd, if an huge pmd could
+	 * materialize from under us from a different thread.
+	 */
+	if (unlikely(pmd_none(*pmd)) && __pte_alloc(mm, vma, pmd, address))
+		return VM_FAULT_OOM;
+	/* if an huge pmd materialized from under us just retry later */
+	if (unlikely(pmd_trans_huge(*pmd)))
+		return 0;
+	/*
+	 * A regular pmd is established and it can't morph into a huge pmd
+	 * from under us anymore at this point because we hold the mmap_sem
+	 * read mode and khugepaged takes it in write mode. So now it's
+	 * safe to run pte_offset_map().
+	 */
+	pte = pte_offset_map(pmd, address);
+
+	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
+}
+
+#ifndef __PAGETABLE_PUD_FOLDED
+/*
+ * Allocate page upper directory.
+ * We've already handled the fast-path in-line.
+ */
+int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
+{
+	pud_t *new = pud_alloc_one(mm, address);
+	if (!new)
+		return -ENOMEM;
+
+	smp_wmb(); /* See comment in __pte_alloc */
+
+	spin_lock(&mm->page_table_lock);
+	if (pgd_present(*pgd))		/* Another has populated it */
+		pud_free(mm, new);
+	else
+		pgd_populate(mm, pgd, new);
+	spin_unlock(&mm->page_table_lock);
+	return 0;
+}
+#endif /* __PAGETABLE_PUD_FOLDED */
+
+#ifndef __PAGETABLE_PMD_FOLDED
+/*
+ * Allocate page middle directory.
+ * We've already handled the fast-path in-line.
+ */
+int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
+{
+	pmd_t *new = pmd_alloc_one(mm, address);
+	if (!new)
+		return -ENOMEM;
+
+	smp_wmb(); /* See comment in __pte_alloc */
+
+	spin_lock(&mm->page_table_lock);
+#ifndef __ARCH_HAS_4LEVEL_HACK
+	if (pud_present(*pud))		/* Another has populated it */
+		pmd_free(mm, new);
+	else
+		pud_populate(mm, pud, new);
+#else
+	if (pgd_present(*pud))		/* Another has populated it */
+		pmd_free(mm, new);
+	else
+		pgd_populate(mm, pud, new);
+#endif /* __ARCH_HAS_4LEVEL_HACK */
+	spin_unlock(&mm->page_table_lock);
+	return 0;
+}
+#endif /* __PAGETABLE_PMD_FOLDED */
+
+int make_pages_present(unsigned long addr, unsigned long end)
+{
+	int ret, len, write;
+	struct vm_area_struct * vma;
+
+	vma = find_vma(current->mm, addr);
+	if (!vma)
+		return -ENOMEM;
+	/*
+	 * We want to touch writable mappings with a write fault in order
+	 * to break COW, except for shared mappings because these don't COW
+	 * and we would not want to dirty them for nothing.
+	 */
+	write = (vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE;
+	BUG_ON(addr >= end);
+	BUG_ON(end > vma->vm_end);
+	len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
+	ret = get_user_pages(current, current->mm, addr,
+			len, write, 0, NULL, NULL);
+	if (ret < 0)
+		return ret;
+	return ret == len ? 0 : -EFAULT;
+}
+
+#if !defined(__HAVE_ARCH_GATE_AREA)
+
+#if defined(AT_SYSINFO_EHDR)
+static struct vm_area_struct gate_vma;
+
+static int __init gate_vma_init(void)
+{
+	gate_vma.vm_mm = NULL;
+	gate_vma.vm_start = FIXADDR_USER_START;
+	gate_vma.vm_end = FIXADDR_USER_END;
+	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
+	gate_vma.vm_page_prot = __P101;
+	/*
+	 * Make sure the vDSO gets into every core dump.
+	 * Dumping its contents makes post-mortem fully interpretable later
+	 * without matching up the same kernel and hardware config to see
+	 * what PC values meant.
+	 */
+	gate_vma.vm_flags |= VM_ALWAYSDUMP;
+	return 0;
+}
+__initcall(gate_vma_init);
+#endif
+
+struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
+{
+#ifdef AT_SYSINFO_EHDR
+	return &gate_vma;
+#else
+	return NULL;
+#endif
+}
+
+int in_gate_area_no_mm(unsigned long addr)
+{
+#ifdef AT_SYSINFO_EHDR
+	if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
+		return 1;
+#endif
+	return 0;
+}
+
+#endif	/* __HAVE_ARCH_GATE_AREA */
+
+static int __follow_pte(struct mm_struct *mm, unsigned long address,
+		pte_t **ptepp, spinlock_t **ptlp)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *ptep;
+
+	pgd = pgd_offset(mm, address);
+	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+		goto out;
+
+	pud = pud_offset(pgd, address);
+	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
+		goto out;
+
+	pmd = pmd_offset(pud, address);
+	VM_BUG_ON(pmd_trans_huge(*pmd));
+	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
+		goto out;
+
+	/* We cannot handle huge page PFN maps. Luckily they don't exist. */
+	if (pmd_huge(*pmd))
+		goto out;
+
+	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
+	if (!ptep)
+		goto out;
+	if (!pte_present(*ptep))
+		goto unlock;
+	*ptepp = ptep;
+	return 0;
+unlock:
+	pte_unmap_unlock(ptep, *ptlp);
+out:
+	return -EINVAL;
+}
+
+static inline int follow_pte(struct mm_struct *mm, unsigned long address,
+			     pte_t **ptepp, spinlock_t **ptlp)
+{
+	int res;
+
+	/* (void) is needed to make gcc happy */
+	(void) __cond_lock(*ptlp,
+			   !(res = __follow_pte(mm, address, ptepp, ptlp)));
+	return res;
+}
+
+/**
+ * follow_pfn - look up PFN at a user virtual address
+ * @vma: memory mapping
+ * @address: user virtual address
+ * @pfn: location to store found PFN
+ *
+ * Only IO mappings and raw PFN mappings are allowed.
+ *
+ * Returns zero and the pfn at @pfn on success, -ve otherwise.
+ */
+int follow_pfn(struct vm_area_struct *vma, unsigned long address,
+	unsigned long *pfn)
+{
+	int ret = -EINVAL;
+	spinlock_t *ptl;
+	pte_t *ptep;
+
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return ret;
+
+	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
+	if (ret)
+		return ret;
+	*pfn = pte_pfn(*ptep);
+	pte_unmap_unlock(ptep, ptl);
+	return 0;
+}
+EXPORT_SYMBOL(follow_pfn);
+
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+int follow_phys(struct vm_area_struct *vma,
+		unsigned long address, unsigned int flags,
+		unsigned long *prot, resource_size_t *phys)
+{
+	int ret = -EINVAL;
+	pte_t *ptep, pte;
+	spinlock_t *ptl;
+
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		goto out;
+
+	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
+		goto out;
+	pte = *ptep;
+
+	if ((flags & FOLL_WRITE) && !pte_write(pte))
+		goto unlock;
+
+	*prot = pgprot_val(pte_pgprot(pte));
+	*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
+
+	ret = 0;
+unlock:
+	pte_unmap_unlock(ptep, ptl);
+out:
+	return ret;
+}
+
+int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+			void *buf, int len, int write)
+{
+	resource_size_t phys_addr;
+	unsigned long prot = 0;
+	void __iomem *maddr;
+	int offset = addr & (PAGE_SIZE-1);
+
+	if (follow_phys(vma, addr, write, &prot, &phys_addr))
+		return -EINVAL;
+
+	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
+	if (write)
+		memcpy_toio(maddr + offset, buf, len);
+	else
+		memcpy_fromio(buf, maddr + offset, len);
+	iounmap(maddr);
+
+	return len;
+}
+#endif
+
+/*
+ * Access another process' address space as given in mm.  If non-NULL, use the
+ * given task for page fault accounting.
+ */
+static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long addr, void *buf, int len, int write)
+{
+	struct vm_area_struct *vma;
+	void *old_buf = buf;
+
+	down_read(&mm->mmap_sem);
+	/* ignore errors, just check how much was successfully transferred */
+	while (len) {
+		int bytes, ret, offset;
+		void *maddr;
+		struct page *page = NULL;
+
+		ret = get_user_pages(tsk, mm, addr, 1,
+				write, 1, &page, &vma);
+		if (ret <= 0) {
+			/*
+			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
+			 * we can access using slightly different code.
+			 */
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+			vma = find_vma(mm, addr);
+			if (!vma || vma->vm_start > addr)
+				break;
+			if (vma->vm_ops && vma->vm_ops->access)
+				ret = vma->vm_ops->access(vma, addr, buf,
+							  len, write);
+			if (ret <= 0)
+#endif
+				break;
+			bytes = ret;
+		} else {
+			bytes = len;
+			offset = addr & (PAGE_SIZE-1);
+			if (bytes > PAGE_SIZE-offset)
+				bytes = PAGE_SIZE-offset;
+
+			maddr = kmap(page);
+			if (write) {
+				copy_to_user_page(vma, page, addr,
+						  maddr + offset, buf, bytes);
+				set_page_dirty_lock(page);
+			} else {
+				copy_from_user_page(vma, page, addr,
+						    buf, maddr + offset, bytes);
+			}
+			kunmap(page);
+			page_cache_release(page);
+		}
+		len -= bytes;
+		buf += bytes;
+		addr += bytes;
+	}
+	up_read(&mm->mmap_sem);
+
+	return buf - old_buf;
+}
+
+/**
+ * access_remote_vm - access another process' address space
+ * @mm:		the mm_struct of the target address space
+ * @addr:	start address to access
+ * @buf:	source or destination buffer
+ * @len:	number of bytes to transfer
+ * @write:	whether the access is a write
+ *
+ * The caller must hold a reference on @mm.
+ */
+int access_remote_vm(struct mm_struct *mm, unsigned long addr,
+		void *buf, int len, int write)
+{
+	return __access_remote_vm(NULL, mm, addr, buf, len, write);
+}
+
+/*
+ * Access another process' address space.
+ * Source/target buffer must be kernel space,
+ * Do not walk the page table directly, use get_user_pages
+ */
+int access_process_vm(struct task_struct *tsk, unsigned long addr,
+		void *buf, int len, int write)
+{
+	struct mm_struct *mm;
+	int ret;
+
+	mm = get_task_mm(tsk);
+	if (!mm)
+		return 0;
+
+	ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
+	mmput(mm);
+
+	return ret;
+}
+
+/*
+ * Print the name of a VMA.
+ */
+void print_vma_addr(char *prefix, unsigned long ip)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+
+	/*
+	 * Do not print if we are in atomic
+	 * contexts (in exception stacks, etc.):
+	 */
+	if (preempt_count())
+		return;
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, ip);
+	if (vma && vma->vm_file) {
+		struct file *f = vma->vm_file;
+		char *buf = (char *)__get_free_page(GFP_KERNEL);
+		if (buf) {
+			char *p, *s;
+
+			p = d_path(&f->f_path, buf, PAGE_SIZE);
+			if (IS_ERR(p))
+				p = "?";
+			s = strrchr(p, '/');
+			if (s)
+				p = s+1;
+			printk("%s%s[%lx+%lx]", prefix, p,
+					vma->vm_start,
+					vma->vm_end - vma->vm_start);
+			free_page((unsigned long)buf);
+		}
+	}
+	up_read(&current->mm->mmap_sem);
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+void might_fault(void)
+{
+	/*
+	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
+	 * holding the mmap_sem, this is safe because kernel memory doesn't
+	 * get paged out, therefore we'll never actually fault, and the
+	 * below annotations will generate false positives.
+	 */
+	if (segment_eq(get_fs(), KERNEL_DS))
+		return;
+
+	might_sleep();
+	/*
+	 * it would be nicer only to annotate paths which are not under
+	 * pagefault_disable, however that requires a larger audit and
+	 * providing helpers like get_user_atomic.
+	 */
+	if (!in_atomic() && current->mm)
+		might_lock_read(&current->mm->mmap_sem);
+}
+EXPORT_SYMBOL(might_fault);
+#endif
+
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
+static void clear_gigantic_page(struct page *page,
+				unsigned long addr,
+				unsigned int pages_per_huge_page)
+{
+	int i;
+	struct page *p = page;
+
+	might_sleep();
+	for (i = 0; i < pages_per_huge_page;
+	     i++, p = mem_map_next(p, page, i)) {
+		cond_resched();
+		clear_user_highpage(p, addr + i * PAGE_SIZE);
+	}
+}
+void clear_huge_page(struct page *page,
+		     unsigned long addr, unsigned int pages_per_huge_page)
+{
+	int i;
+
+	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
+		clear_gigantic_page(page, addr, pages_per_huge_page);
+		return;
+	}
+
+	might_sleep();
+	for (i = 0; i < pages_per_huge_page; i++) {
+		cond_resched();
+		clear_user_highpage(page + i, addr + i * PAGE_SIZE);
+	}
+}
+
+static void copy_user_gigantic_page(struct page *dst, struct page *src,
+				    unsigned long addr,
+				    struct vm_area_struct *vma,
+				    unsigned int pages_per_huge_page)
+{
+	int i;
+	struct page *dst_base = dst;
+	struct page *src_base = src;
+
+	for (i = 0; i < pages_per_huge_page; ) {
+		cond_resched();
+		copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
+
+		i++;
+		dst = mem_map_next(dst, dst_base, i);
+		src = mem_map_next(src, src_base, i);
+	}
+}
+
+void copy_user_huge_page(struct page *dst, struct page *src,
+			 unsigned long addr, struct vm_area_struct *vma,
+			 unsigned int pages_per_huge_page)
+{
+	int i;
+
+	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
+		copy_user_gigantic_page(dst, src, addr, vma,
+					pages_per_huge_page);
+		return;
+	}
+
+	might_sleep();
+	for (i = 0; i < pages_per_huge_page; i++) {
+		cond_resched();
+		copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
+	}
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */