#include <linux/mm.h>
  #include <linux/hugetlb.h>

  #include <linux/huge_mm.h>

  #include <linux/mount.h>
  #include <linux/seq_file.h>

  #include <linux/highmem.h>

  #include <linux/ptrace.h>

  #include <linux/slab.h>

  #include <linux/pagemap.h>
  #include <linux/mempolicy.h>

  #include <linux/rmap.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  #include <asm/elf.h>
  #include <asm/uaccess.h>

  #include <asm/tlbflush.h>

  #include "internal.h"

  void task_mem(struct seq_file *m, struct mm_struct *mm)

  {

  	unsigned long data, text, lib, swap;

  	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
  
  	/*
  	 * Note: to minimize their overhead, mm maintains hiwater_vm and
  	 * hiwater_rss only when about to *lower* total_vm or rss.  Any
  	 * collector of these hiwater stats must therefore get total_vm
  	 * and rss too, which will usually be the higher.  Barriers? not
  	 * worth the effort, such snapshots can always be inconsistent.
  	 */
  	hiwater_vm = total_vm = mm->total_vm;
  	if (hiwater_vm < mm->hiwater_vm)
  		hiwater_vm = mm->hiwater_vm;
  	hiwater_rss = total_rss = get_mm_rss(mm);
  	if (hiwater_rss < mm->hiwater_rss)
  		hiwater_rss = mm->hiwater_rss;

  
  	data = mm->total_vm - mm->shared_vm - mm->stack_vm;
  	text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
  	lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;

  	swap = get_mm_counter(mm, MM_SWAPENTS);

  	seq_printf(m,

  		"VmPeak:\t%8lu kB
  "

  		"VmSize:\t%8lu kB
  "
  		"VmLck:\t%8lu kB
  "

  		"VmPin:\t%8lu kB
  "

  		"VmHWM:\t%8lu kB
  "

  		"VmRSS:\t%8lu kB
  "
  		"VmData:\t%8lu kB
  "
  		"VmStk:\t%8lu kB
  "
  		"VmExe:\t%8lu kB
  "
  		"VmLib:\t%8lu kB
  "

  		"VmPTE:\t%8lu kB
  "
  		"VmSwap:\t%8lu kB
  ",

  		hiwater_vm << (PAGE_SHIFT-10),
  		(total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),

  		mm->locked_vm << (PAGE_SHIFT-10),

  		mm->pinned_vm << (PAGE_SHIFT-10),

  		hiwater_rss << (PAGE_SHIFT-10),
  		total_rss << (PAGE_SHIFT-10),

  		data << (PAGE_SHIFT-10),
  		mm->stack_vm << (PAGE_SHIFT-10), text, lib,

  		(PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10,
  		swap << (PAGE_SHIFT-10));

  }
  
  unsigned long task_vsize(struct mm_struct *mm)
  {
  	return PAGE_SIZE * mm->total_vm;
  }

  unsigned long task_statm(struct mm_struct *mm,
  			 unsigned long *shared, unsigned long *text,
  			 unsigned long *data, unsigned long *resident)

  {

  	*shared = get_mm_counter(mm, MM_FILEPAGES);

  	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
  								>> PAGE_SHIFT;
  	*data = mm->total_vm - mm->shared_vm;

  	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);

  	return mm->total_vm;
  }

  static void pad_len_spaces(struct seq_file *m, int len)
  {
  	len = 25 + sizeof(void*) * 6 - len;
  	if (len < 1)
  		len = 1;
  	seq_printf(m, "%*c", len, ' ');
  }

  static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
  {
  	if (vma && vma != priv->tail_vma) {
  		struct mm_struct *mm = vma->vm_mm;
  		up_read(&mm->mmap_sem);
  		mmput(mm);
  	}
  }

  static void *m_start(struct seq_file *m, loff_t *pos)

  {

  	struct proc_maps_private *priv = m->private;
  	unsigned long last_addr = m->version;
  	struct mm_struct *mm;
  	struct vm_area_struct *vma, *tail_vma = NULL;
  	loff_t l = *pos;
  
  	/* Clear the per syscall fields in priv */
  	priv->task = NULL;
  	priv->tail_vma = NULL;
  
  	/*
  	 * We remember last_addr rather than next_addr to hit with
  	 * mmap_cache most of the time. We have zero last_addr at
  	 * the beginning and also after lseek. We will have -1 last_addr
  	 * after the end of the vmas.
  	 */
  
  	if (last_addr == -1UL)
  		return NULL;
  
  	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
  	if (!priv->task)

  		return ERR_PTR(-ESRCH);

  
  	mm = mm_for_maps(priv->task);

  	if (!mm || IS_ERR(mm))
  		return mm;

  	down_read(&mm->mmap_sem);

  	tail_vma = get_gate_vma(priv->task->mm);

  	priv->tail_vma = tail_vma;
  
  	/* Start with last addr hint */
  	vma = find_vma(mm, last_addr);
  	if (last_addr && vma) {
  		vma = vma->vm_next;
  		goto out;
  	}
  
  	/*
  	 * Check the vma index is within the range and do
  	 * sequential scan until m_index.
  	 */
  	vma = NULL;
  	if ((unsigned long)l < mm->map_count) {
  		vma = mm->mmap;
  		while (l-- && vma)
  			vma = vma->vm_next;
  		goto out;
  	}
  
  	if (l != mm->map_count)
  		tail_vma = NULL; /* After gate vma */
  
  out:
  	if (vma)
  		return vma;
  
  	/* End of vmas has been reached */
  	m->version = (tail_vma != NULL)? 0: -1UL;
  	up_read(&mm->mmap_sem);
  	mmput(mm);
  	return tail_vma;
  }
  
  static void *m_next(struct seq_file *m, void *v, loff_t *pos)
  {
  	struct proc_maps_private *priv = m->private;
  	struct vm_area_struct *vma = v;
  	struct vm_area_struct *tail_vma = priv->tail_vma;
  
  	(*pos)++;
  	if (vma && (vma != tail_vma) && vma->vm_next)
  		return vma->vm_next;
  	vma_stop(priv, vma);
  	return (vma != tail_vma)? tail_vma: NULL;
  }
  
  static void m_stop(struct seq_file *m, void *v)
  {
  	struct proc_maps_private *priv = m->private;
  	struct vm_area_struct *vma = v;

  	if (!IS_ERR(vma))
  		vma_stop(priv, vma);

  	if (priv->task)
  		put_task_struct(priv->task);
  }
  
  static int do_maps_open(struct inode *inode, struct file *file,

  			const struct seq_operations *ops)

  {
  	struct proc_maps_private *priv;
  	int ret = -ENOMEM;
  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  	if (priv) {
  		priv->pid = proc_pid(inode);
  		ret = seq_open(file, ops);
  		if (!ret) {
  			struct seq_file *m = file->private_data;
  			m->private = priv;
  		} else {
  			kfree(priv);
  		}
  	}
  	return ret;
  }

  static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)

  {

  	struct mm_struct *mm = vma->vm_mm;
  	struct file *file = vma->vm_file;

  	vm_flags_t flags = vma->vm_flags;

  	unsigned long ino = 0;

  	unsigned long long pgoff = 0;

  	unsigned long start, end;

  	dev_t dev = 0;
  	int len;
  
  	if (file) {

  		struct inode *inode = vma->vm_file->f_path.dentry->d_inode;

  		dev = inode->i_sb->s_dev;
  		ino = inode->i_ino;

  		pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;

  	}

  	/* We don't show the stack guard page in /proc/maps */
  	start = vma->vm_start;

  	if (stack_guard_page_start(vma, start))
  		start += PAGE_SIZE;
  	end = vma->vm_end;
  	if (stack_guard_page_end(vma, end))
  		end -= PAGE_SIZE;

  	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",

  			start,

  			end,

  			flags & VM_READ ? 'r' : '-',
  			flags & VM_WRITE ? 'w' : '-',
  			flags & VM_EXEC ? 'x' : '-',
  			flags & VM_MAYSHARE ? 's' : 'p',

  			pgoff,

  			MAJOR(dev), MINOR(dev), ino, &len);
  
  	/*
  	 * Print the dentry name for named mappings, and a
  	 * special [heap] marker for the heap:
  	 */

  	if (file) {

  		pad_len_spaces(m, len);

  		seq_path(m, &file->f_path, "
  ");

  	} else {

  		const char *name = arch_vma_name(vma);
  		if (!name) {
  			if (mm) {

  				if (vma->vm_start <= mm->brk &&
  						vma->vm_end >= mm->start_brk) {

  					name = "[heap]";
  				} else if (vma->vm_start <= mm->start_stack &&
  					   vma->vm_end >= mm->start_stack) {
  					name = "[stack]";

  				}

  			} else {
  				name = "[vdso]";

  			}

  		}
  		if (name) {

  			pad_len_spaces(m, len);

  			seq_puts(m, name);

  		}
  	}
  	seq_putc(m, '
  ');

  }
  
  static int show_map(struct seq_file *m, void *v)
  {
  	struct vm_area_struct *vma = v;
  	struct proc_maps_private *priv = m->private;
  	struct task_struct *task = priv->task;
  
  	show_map_vma(m, vma);

  	if (m->count < m->size)  /* vma is copied successfully */

  		m->version = (vma != get_gate_vma(task->mm))
  			? vma->vm_start : 0;

  	return 0;
  }

  static const struct seq_operations proc_pid_maps_op = {

  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_map
  };
  
  static int maps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_pid_maps_op);
  }
  
  const struct file_operations proc_maps_operations = {
  	.open		= maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release_private,
  };
  
  /*
   * Proportional Set Size(PSS): my share of RSS.
   *
   * PSS of a process is the count of pages it has in memory, where each
   * page is divided by the number of processes sharing it.  So if a
   * process has 1000 pages all to itself, and 1000 shared with one other
   * process, its PSS will be 1500.
   *
   * To keep (accumulated) division errors low, we adopt a 64bit
   * fixed-point pss counter to minimize division errors. So (pss >>
   * PSS_SHIFT) would be the real byte count.
   *
   * A shift of 12 before division means (assuming 4K page size):
   * 	- 1M 3-user-pages add up to 8KB errors;
   * 	- supports mapcount up to 2^24, or 16M;
   * 	- supports PSS up to 2^52 bytes, or 4PB.
   */
  #define PSS_SHIFT 12

  #ifdef CONFIG_PROC_PAGE_MONITOR

  struct mem_size_stats {

  	struct vm_area_struct *vma;
  	unsigned long resident;
  	unsigned long shared_clean;
  	unsigned long shared_dirty;
  	unsigned long private_clean;
  	unsigned long private_dirty;
  	unsigned long referenced;

  	unsigned long anonymous;

  	unsigned long anonymous_thp;

  	unsigned long swap;

  	u64 pss;
  };

  
  static void smaps_pte_entry(pte_t ptent, unsigned long addr,

  		unsigned long ptent_size, struct mm_walk *walk)

  {
  	struct mem_size_stats *mss = walk->private;
  	struct vm_area_struct *vma = mss->vma;
  	struct page *page;
  	int mapcount;
  
  	if (is_swap_pte(ptent)) {

  		mss->swap += ptent_size;

  		return;
  	}
  
  	if (!pte_present(ptent))
  		return;
  
  	page = vm_normal_page(vma, addr, ptent);
  	if (!page)
  		return;
  
  	if (PageAnon(page))

  		mss->anonymous += ptent_size;

  	mss->resident += ptent_size;

  	/* Accumulate the size in pages that have been accessed. */
  	if (pte_young(ptent) || PageReferenced(page))

  		mss->referenced += ptent_size;

  	mapcount = page_mapcount(page);
  	if (mapcount >= 2) {
  		if (pte_dirty(ptent) || PageDirty(page))

  			mss->shared_dirty += ptent_size;

  		else

  			mss->shared_clean += ptent_size;
  		mss->pss += (ptent_size << PSS_SHIFT) / mapcount;

  	} else {
  		if (pte_dirty(ptent) || PageDirty(page))

  			mss->private_dirty += ptent_size;

  		else

  			mss->private_clean += ptent_size;
  		mss->pss += (ptent_size << PSS_SHIFT);

  	}
  }

  static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,

  			   struct mm_walk *walk)

  {

  	struct mem_size_stats *mss = walk->private;

  	struct vm_area_struct *vma = mss->vma;

  	pte_t *pte;

  	spinlock_t *ptl;

  	spin_lock(&walk->mm->page_table_lock);
  	if (pmd_trans_huge(*pmd)) {
  		if (pmd_trans_splitting(*pmd)) {
  			spin_unlock(&walk->mm->page_table_lock);
  			wait_split_huge_page(vma->anon_vma, pmd);
  		} else {
  			smaps_pte_entry(*(pte_t *)pmd, addr,
  					HPAGE_PMD_SIZE, walk);
  			spin_unlock(&walk->mm->page_table_lock);

  			mss->anonymous_thp += HPAGE_PMD_SIZE;

  			return 0;
  		}
  	} else {
  		spin_unlock(&walk->mm->page_table_lock);
  	}
  	/*
  	 * The mmap_sem held all the way back in m_start() is what
  	 * keeps khugepaged out of here and from collapsing things
  	 * in here.
  	 */

  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

  	for (; addr != end; pte++, addr += PAGE_SIZE)

  		smaps_pte_entry(*pte, addr, PAGE_SIZE, walk);

  	pte_unmap_unlock(pte - 1, ptl);
  	cond_resched();

  	return 0;

  }

  static int show_smap(struct seq_file *m, void *v)
  {

  	struct proc_maps_private *priv = m->private;
  	struct task_struct *task = priv->task;

  	struct vm_area_struct *vma = v;

  	struct mem_size_stats mss;

  	struct mm_walk smaps_walk = {
  		.pmd_entry = smaps_pte_range,
  		.mm = vma->vm_mm,
  		.private = &mss,
  	};

  
  	memset(&mss, 0, sizeof mss);

  	mss.vma = vma;

  	/* mmap_sem is held in m_start */

  	if (vma->vm_mm && !is_vm_hugetlb_page(vma))

  		walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);

  	show_map_vma(m, vma);

  
  	seq_printf(m,
  		   "Size:           %8lu kB
  "
  		   "Rss:            %8lu kB
  "
  		   "Pss:            %8lu kB
  "
  		   "Shared_Clean:   %8lu kB
  "
  		   "Shared_Dirty:   %8lu kB
  "
  		   "Private_Clean:  %8lu kB
  "
  		   "Private_Dirty:  %8lu kB
  "

  		   "Referenced:     %8lu kB
  "

  		   "Anonymous:      %8lu kB
  "

  		   "AnonHugePages:  %8lu kB
  "

  		   "Swap:           %8lu kB
  "

  		   "KernelPageSize: %8lu kB
  "

  		   "MMUPageSize:    %8lu kB
  "
  		   "Locked:         %8lu kB
  ",

  		   (vma->vm_end - vma->vm_start) >> 10,
  		   mss.resident >> 10,
  		   (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
  		   mss.shared_clean  >> 10,
  		   mss.shared_dirty  >> 10,
  		   mss.private_clean >> 10,
  		   mss.private_dirty >> 10,

  		   mss.referenced >> 10,

  		   mss.anonymous >> 10,

  		   mss.anonymous_thp >> 10,

  		   mss.swap >> 10,

  		   vma_kernel_pagesize(vma) >> 10,

  		   vma_mmu_pagesize(vma) >> 10,
  		   (vma->vm_flags & VM_LOCKED) ?
  			(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);

  	if (m->count < m->size)  /* vma is copied successfully */

  		m->version = (vma != get_gate_vma(task->mm))
  			? vma->vm_start : 0;

  	return 0;

  }

  static const struct seq_operations proc_pid_smaps_op = {

  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_smap
  };
  
  static int smaps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_pid_smaps_op);
  }
  
  const struct file_operations proc_smaps_operations = {
  	.open		= smaps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release_private,
  };
  
  static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,

  				unsigned long end, struct mm_walk *walk)

  {

  	struct vm_area_struct *vma = walk->private;

  	pte_t *pte, ptent;
  	spinlock_t *ptl;
  	struct page *page;

  	split_huge_page_pmd(walk->mm, pmd);

  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  	for (; addr != end; pte++, addr += PAGE_SIZE) {
  		ptent = *pte;
  		if (!pte_present(ptent))
  			continue;
  
  		page = vm_normal_page(vma, addr, ptent);
  		if (!page)
  			continue;
  
  		/* Clear accessed and referenced bits. */
  		ptep_test_and_clear_young(vma, addr, pte);
  		ClearPageReferenced(page);
  	}
  	pte_unmap_unlock(pte - 1, ptl);
  	cond_resched();
  	return 0;
  }

  #define CLEAR_REFS_ALL 1
  #define CLEAR_REFS_ANON 2
  #define CLEAR_REFS_MAPPED 3

  static ssize_t clear_refs_write(struct file *file, const char __user *buf,
  				size_t count, loff_t *ppos)

  {

  	struct task_struct *task;

  	char buffer[PROC_NUMBUF];

  	struct mm_struct *mm;

  	struct vm_area_struct *vma;

  	int type;
  	int rv;

  	memset(buffer, 0, sizeof(buffer));
  	if (count > sizeof(buffer) - 1)
  		count = sizeof(buffer) - 1;
  	if (copy_from_user(buffer, buf, count))
  		return -EFAULT;

  	rv = kstrtoint(strstrip(buffer), 10, &type);
  	if (rv < 0)
  		return rv;

  	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)

  		return -EINVAL;

  	task = get_proc_task(file->f_path.dentry->d_inode);
  	if (!task)
  		return -ESRCH;
  	mm = get_task_mm(task);
  	if (mm) {

  		struct mm_walk clear_refs_walk = {
  			.pmd_entry = clear_refs_pte_range,
  			.mm = mm,
  		};

  		down_read(&mm->mmap_sem);

  		for (vma = mm->mmap; vma; vma = vma->vm_next) {
  			clear_refs_walk.private = vma;

  			if (is_vm_hugetlb_page(vma))
  				continue;
  			/*
  			 * Writing 1 to /proc/pid/clear_refs affects all pages.
  			 *
  			 * Writing 2 to /proc/pid/clear_refs only affects
  			 * Anonymous pages.
  			 *
  			 * Writing 3 to /proc/pid/clear_refs only affects file
  			 * mapped pages.
  			 */
  			if (type == CLEAR_REFS_ANON && vma->vm_file)
  				continue;
  			if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
  				continue;
  			walk_page_range(vma->vm_start, vma->vm_end,
  					&clear_refs_walk);

  		}

  		flush_tlb_mm(mm);
  		up_read(&mm->mmap_sem);
  		mmput(mm);
  	}
  	put_task_struct(task);

  
  	return count;

  }

  const struct file_operations proc_clear_refs_operations = {
  	.write		= clear_refs_write,

  	.llseek		= noop_llseek,

  };

  struct pagemapread {

  	int pos, len;
  	u64 *buffer;

  };

  #define PM_ENTRY_BYTES      sizeof(u64)
  #define PM_STATUS_BITS      3
  #define PM_STATUS_OFFSET    (64 - PM_STATUS_BITS)
  #define PM_STATUS_MASK      (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
  #define PM_STATUS(nr)       (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
  #define PM_PSHIFT_BITS      6
  #define PM_PSHIFT_OFFSET    (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
  #define PM_PSHIFT_MASK      (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
  #define PM_PSHIFT(x)        (((u64) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
  #define PM_PFRAME_MASK      ((1LL << PM_PSHIFT_OFFSET) - 1)
  #define PM_PFRAME(x)        ((x) & PM_PFRAME_MASK)
  
  #define PM_PRESENT          PM_STATUS(4LL)
  #define PM_SWAP             PM_STATUS(2LL)
  #define PM_NOT_PRESENT      PM_PSHIFT(PAGE_SHIFT)

  #define PM_END_OF_BUFFER    1
  
  static int add_to_pagemap(unsigned long addr, u64 pfn,
  			  struct pagemapread *pm)
  {

  	pm->buffer[pm->pos++] = pfn;
  	if (pm->pos >= pm->len)

  		return PM_END_OF_BUFFER;

  	return 0;
  }
  
  static int pagemap_pte_hole(unsigned long start, unsigned long end,

  				struct mm_walk *walk)

  {

  	struct pagemapread *pm = walk->private;

  	unsigned long addr;
  	int err = 0;
  	for (addr = start; addr < end; addr += PAGE_SIZE) {
  		err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
  		if (err)
  			break;
  	}
  	return err;
  }

  static u64 swap_pte_to_pagemap_entry(pte_t pte)

  {
  	swp_entry_t e = pte_to_swp_entry(pte);

  	return swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);

  }

  static u64 pte_to_pagemap_entry(pte_t pte)

  {

  	u64 pme = 0;

  	if (is_swap_pte(pte))
  		pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte))
  			| PM_PSHIFT(PAGE_SHIFT) | PM_SWAP;
  	else if (pte_present(pte))
  		pme = PM_PFRAME(pte_pfn(pte))
  			| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
  	return pme;
  }

  static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,

  			     struct mm_walk *walk)

  {

  	struct vm_area_struct *vma;

  	struct pagemapread *pm = walk->private;

  	pte_t *pte;
  	int err = 0;

  	split_huge_page_pmd(walk->mm, pmd);

  	/* find the first VMA at or above 'addr' */
  	vma = find_vma(walk->mm, addr);

  	for (; addr != end; addr += PAGE_SIZE) {
  		u64 pfn = PM_NOT_PRESENT;

  
  		/* check to see if we've left 'vma' behind
  		 * and need a new, higher one */
  		if (vma && (addr >= vma->vm_end))
  			vma = find_vma(walk->mm, addr);
  
  		/* check that 'vma' actually covers this address,
  		 * and that it isn't a huge page vma */
  		if (vma && (vma->vm_start <= addr) &&
  		    !is_vm_hugetlb_page(vma)) {
  			pte = pte_offset_map(pmd, addr);
  			pfn = pte_to_pagemap_entry(*pte);
  			/* unmap before userspace copy */
  			pte_unmap(pte);
  		}

  		err = add_to_pagemap(addr, pfn, pm);
  		if (err)
  			return err;
  	}
  
  	cond_resched();
  
  	return err;
  }

  #ifdef CONFIG_HUGETLB_PAGE

  static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
  {
  	u64 pme = 0;
  	if (pte_present(pte))
  		pme = PM_PFRAME(pte_pfn(pte) + offset)
  			| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
  	return pme;
  }

  /* This function walks within one hugetlb entry in the single call */
  static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
  				 unsigned long addr, unsigned long end,
  				 struct mm_walk *walk)

  {

  	struct pagemapread *pm = walk->private;

  	int err = 0;

  	u64 pfn;

  	for (; addr != end; addr += PAGE_SIZE) {

  		int offset = (addr & ~hmask) >> PAGE_SHIFT;
  		pfn = huge_pte_to_pagemap_entry(*pte, offset);

  		err = add_to_pagemap(addr, pfn, pm);
  		if (err)
  			return err;
  	}
  
  	cond_resched();
  
  	return err;
  }

  #endif /* HUGETLB_PAGE */

  /*
   * /proc/pid/pagemap - an array mapping virtual pages to pfns
   *

   * For each page in the address space, this file contains one 64-bit entry
   * consisting of the following:
   *
   * Bits 0-55  page frame number (PFN) if present
   * Bits 0-4   swap type if swapped
   * Bits 5-55  swap offset if swapped
   * Bits 55-60 page shift (page size = 1<<page shift)
   * Bit  61    reserved for future use
   * Bit  62    page swapped
   * Bit  63    page present
   *
   * If the page is not present but in swap, then the PFN contains an
   * encoding of the swap file number and the page's offset into the
   * swap. Unmapped pages return a null PFN. This allows determining

   * precisely which pages are mapped (or in swap) and comparing mapped
   * pages between processes.
   *
   * Efficient users of this interface will use /proc/pid/maps to
   * determine which areas of memory are actually mapped and llseek to
   * skip over unmapped regions.
   */

  #define PAGEMAP_WALK_SIZE	(PMD_SIZE)

  #define PAGEMAP_WALK_MASK	(PMD_MASK)

  static ssize_t pagemap_read(struct file *file, char __user *buf,
  			    size_t count, loff_t *ppos)
  {
  	struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);

  	struct mm_struct *mm;
  	struct pagemapread pm;

  	int ret = -ESRCH;

  	struct mm_walk pagemap_walk = {};

  	unsigned long src;
  	unsigned long svpfn;
  	unsigned long start_vaddr;
  	unsigned long end_vaddr;

  	int copied = 0;

  
  	if (!task)
  		goto out;

  	ret = -EINVAL;
  	/* file position must be aligned */

  	if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))

  		goto out_task;

  
  	ret = 0;

  	if (!count)
  		goto out_task;

  	pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
  	pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);

  	ret = -ENOMEM;

  	if (!pm.buffer)

  		goto out_task;
  
  	mm = mm_for_maps(task);
  	ret = PTR_ERR(mm);
  	if (!mm || IS_ERR(mm))
  		goto out_free;

  	pagemap_walk.pmd_entry = pagemap_pte_range;
  	pagemap_walk.pte_hole = pagemap_pte_hole;

  #ifdef CONFIG_HUGETLB_PAGE

  	pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;

  #endif

  	pagemap_walk.mm = mm;
  	pagemap_walk.private = ±
  
  	src = *ppos;
  	svpfn = src / PM_ENTRY_BYTES;
  	start_vaddr = svpfn << PAGE_SHIFT;
  	end_vaddr = TASK_SIZE_OF(task);
  
  	/* watch out for wraparound */
  	if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT)
  		start_vaddr = end_vaddr;
  
  	/*
  	 * The odds are that this will stop walking way
  	 * before end_vaddr, because the length of the
  	 * user buffer is tracked in "pm", and the walk
  	 * will stop when we hit the end of the buffer.
  	 */

  	ret = 0;
  	while (count && (start_vaddr < end_vaddr)) {
  		int len;
  		unsigned long end;
  
  		pm.pos = 0;

  		end = (start_vaddr + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK;

  		/* overflow ? */
  		if (end < start_vaddr || end > end_vaddr)
  			end = end_vaddr;
  		down_read(&mm->mmap_sem);
  		ret = walk_page_range(start_vaddr, end, &pagemap_walk);
  		up_read(&mm->mmap_sem);
  		start_vaddr = end;
  
  		len = min(count, PM_ENTRY_BYTES * pm.pos);

  		if (copy_to_user(buf, pm.buffer, len)) {

  			ret = -EFAULT;

  			goto out_mm;

  		}
  		copied += len;
  		buf += len;
  		count -= len;

  	}

  	*ppos += copied;
  	if (!ret || ret == PM_END_OF_BUFFER)
  		ret = copied;

  out_mm:
  	mmput(mm);

  out_free:
  	kfree(pm.buffer);

  out_task:
  	put_task_struct(task);
  out:
  	return ret;
  }
  
  const struct file_operations proc_pagemap_operations = {
  	.llseek		= mem_lseek, /* borrow this */
  	.read		= pagemap_read,
  };

  #endif /* CONFIG_PROC_PAGE_MONITOR */

  #ifdef CONFIG_NUMA

  struct numa_maps {
  	struct vm_area_struct *vma;
  	unsigned long pages;
  	unsigned long anon;
  	unsigned long active;
  	unsigned long writeback;
  	unsigned long mapcount_max;
  	unsigned long dirty;
  	unsigned long swapcache;
  	unsigned long node[MAX_NUMNODES];
  };

  struct numa_maps_private {
  	struct proc_maps_private proc_maps;
  	struct numa_maps md;
  };

  static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
  			unsigned long nr_pages)

  {
  	int count = page_mapcount(page);

  	md->pages += nr_pages;

  	if (pte_dirty || PageDirty(page))

  		md->dirty += nr_pages;

  
  	if (PageSwapCache(page))

  		md->swapcache += nr_pages;

  
  	if (PageActive(page) || PageUnevictable(page))

  		md->active += nr_pages;

  
  	if (PageWriteback(page))

  		md->writeback += nr_pages;

  
  	if (PageAnon(page))

  		md->anon += nr_pages;

  
  	if (count > md->mapcount_max)
  		md->mapcount_max = count;

  	md->node[page_to_nid(page)] += nr_pages;

  }

  static struct page *can_gather_numa_stats(pte_t pte, struct vm_area_struct *vma,
  		unsigned long addr)
  {
  	struct page *page;
  	int nid;
  
  	if (!pte_present(pte))
  		return NULL;
  
  	page = vm_normal_page(vma, addr, pte);
  	if (!page)
  		return NULL;
  
  	if (PageReserved(page))
  		return NULL;
  
  	nid = page_to_nid(page);
  	if (!node_isset(nid, node_states[N_HIGH_MEMORY]))
  		return NULL;
  
  	return page;
  }

  static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
  		unsigned long end, struct mm_walk *walk)
  {
  	struct numa_maps *md;
  	spinlock_t *ptl;
  	pte_t *orig_pte;
  	pte_t *pte;
  
  	md = walk->private;

  	spin_lock(&walk->mm->page_table_lock);
  	if (pmd_trans_huge(*pmd)) {
  		if (pmd_trans_splitting(*pmd)) {
  			spin_unlock(&walk->mm->page_table_lock);
  			wait_split_huge_page(md->vma->anon_vma, pmd);
  		} else {
  			pte_t huge_pte = *(pte_t *)pmd;
  			struct page *page;
  
  			page = can_gather_numa_stats(huge_pte, md->vma, addr);
  			if (page)
  				gather_stats(page, md, pte_dirty(huge_pte),
  						HPAGE_PMD_SIZE/PAGE_SIZE);
  			spin_unlock(&walk->mm->page_table_lock);
  			return 0;
  		}
  	} else {
  		spin_unlock(&walk->mm->page_table_lock);
  	}

  	orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
  	do {

  		struct page *page = can_gather_numa_stats(*pte, md->vma, addr);

  		if (!page)
  			continue;

  		gather_stats(page, md, pte_dirty(*pte), 1);

  
  	} while (pte++, addr += PAGE_SIZE, addr != end);
  	pte_unmap_unlock(orig_pte, ptl);
  	return 0;
  }
  #ifdef CONFIG_HUGETLB_PAGE
  static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
  		unsigned long addr, unsigned long end, struct mm_walk *walk)
  {
  	struct numa_maps *md;
  	struct page *page;
  
  	if (pte_none(*pte))
  		return 0;
  
  	page = pte_page(*pte);
  	if (!page)
  		return 0;
  
  	md = walk->private;

  	gather_stats(page, md, pte_dirty(*pte), 1);

  	return 0;
  }
  
  #else
  static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
  		unsigned long addr, unsigned long end, struct mm_walk *walk)
  {
  	return 0;
  }
  #endif
  
  /*
   * Display pages allocated per node and memory policy via /proc.
   */
  static int show_numa_map(struct seq_file *m, void *v)
  {

  	struct numa_maps_private *numa_priv = m->private;
  	struct proc_maps_private *proc_priv = &numa_priv->proc_maps;

  	struct vm_area_struct *vma = v;

  	struct numa_maps *md = &numa_priv->md;

  	struct file *file = vma->vm_file;
  	struct mm_struct *mm = vma->vm_mm;
  	struct mm_walk walk = {};
  	struct mempolicy *pol;
  	int n;
  	char buffer[50];
  
  	if (!mm)
  		return 0;

  	/* Ensure we start with an empty set of numa_maps statistics. */
  	memset(md, 0, sizeof(*md));

  
  	md->vma = vma;
  
  	walk.hugetlb_entry = gather_hugetbl_stats;
  	walk.pmd_entry = gather_pte_stats;
  	walk.private = md;
  	walk.mm = mm;

  	pol = get_vma_policy(proc_priv->task, vma, vma->vm_start);

  	mpol_to_str(buffer, sizeof(buffer), pol, 0);
  	mpol_cond_put(pol);
  
  	seq_printf(m, "%08lx %s", vma->vm_start, buffer);
  
  	if (file) {
  		seq_printf(m, " file=");
  		seq_path(m, &file->f_path, "
  \t= ");
  	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
  		seq_printf(m, " heap");
  	} else if (vma->vm_start <= mm->start_stack &&
  			vma->vm_end >= mm->start_stack) {
  		seq_printf(m, " stack");
  	}

  	if (is_vm_hugetlb_page(vma))
  		seq_printf(m, " huge");

  	walk_page_range(vma->vm_start, vma->vm_end, &walk);
  
  	if (!md->pages)
  		goto out;
  
  	if (md->anon)
  		seq_printf(m, " anon=%lu", md->anon);
  
  	if (md->dirty)
  		seq_printf(m, " dirty=%lu", md->dirty);
  
  	if (md->pages != md->anon && md->pages != md->dirty)
  		seq_printf(m, " mapped=%lu", md->pages);
  
  	if (md->mapcount_max > 1)
  		seq_printf(m, " mapmax=%lu", md->mapcount_max);
  
  	if (md->swapcache)
  		seq_printf(m, " swapcache=%lu", md->swapcache);
  
  	if (md->active < md->pages && !is_vm_hugetlb_page(vma))
  		seq_printf(m, " active=%lu", md->active);
  
  	if (md->writeback)
  		seq_printf(m, " writeback=%lu", md->writeback);
  
  	for_each_node_state(n, N_HIGH_MEMORY)
  		if (md->node[n])
  			seq_printf(m, " N%d=%lu", n, md->node[n]);
  out:
  	seq_putc(m, '
  ');

  
  	if (m->count < m->size)

  		m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;

  	return 0;
  }

  static const struct seq_operations proc_pid_numa_maps_op = {

          .start  = m_start,
          .next   = m_next,
          .stop   = m_stop,

          .show   = show_numa_map,

  };

  
  static int numa_maps_open(struct inode *inode, struct file *file)
  {

  	struct numa_maps_private *priv;
  	int ret = -ENOMEM;
  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  	if (priv) {
  		priv->proc_maps.pid = proc_pid(inode);
  		ret = seq_open(file, &proc_pid_numa_maps_op);
  		if (!ret) {
  			struct seq_file *m = file->private_data;
  			m->private = priv;
  		} else {
  			kfree(priv);
  		}
  	}
  	return ret;

  }

  const struct file_operations proc_numa_maps_operations = {

  	.open		= numa_maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,

  	.release	= seq_release_private,

  };

  #endif /* CONFIG_NUMA */