task_mmu.c

#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 <linux/mmu_notifier.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\n"
		"VmSize:\t%8lu kB\n"
		"VmLck:\t%8lu kB\n"
		"VmPin:\t%8lu kB\n"
		"VmHWM:\t%8lu kB\n"
		"VmRSS:\t%8lu kB\n"
		"VmData:\t%8lu kB\n"
		"VmStk:\t%8lu kB\n"
		"VmExe:\t%8lu kB\n"
		"VmLib:\t%8lu kB\n"
		"VmPTE:\t%8lu kB\n"
		"VmSwap:\t%8lu kB\n",
		hiwater_vm << (PAGE_SHIFT-10),
		total_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, ' ');
}

#ifdef CONFIG_NUMA
/*
 * These functions are for numa_maps but called in generic **maps seq_file
 * ->start(), ->stop() ops.
 *
 * numa_maps scans all vmas under mmap_sem and checks their mempolicy.
 * Each mempolicy object is controlled by reference counting. The problem here
 * is how to avoid accessing dead mempolicy object.
 *
 * Because we're holding mmap_sem while reading seq_file, it's safe to access
 * each vma's mempolicy, no vma objects will never drop refs to mempolicy.
 *
 * A task's mempolicy (task->mempolicy) has different behavior. task->mempolicy
 * is set and replaced under mmap_sem but unrefed and cleared under task_lock().
 * So, without task_lock(), we cannot trust get_vma_policy() because we cannot
 * gurantee the task never exits under us. But taking task_lock() around
 * get_vma_plicy() causes lock order problem.
 *
 * To access task->mempolicy without lock, we hold a reference count of an
 * object pointed by task->mempolicy and remember it. This will guarantee
 * that task->mempolicy points to an alive object or NULL in numa_maps accesses.
 */
static void hold_task_mempolicy(struct proc_maps_private *priv)
{
	struct task_struct *task = priv->task;

	task_lock(task);
	priv->task_mempolicy = task->mempolicy;
	mpol_get(priv->task_mempolicy);
	task_unlock(task);
}
static void release_task_mempolicy(struct proc_maps_private *priv)
{
	mpol_put(priv->task_mempolicy);
}
#else
static void hold_task_mempolicy(struct proc_maps_private *priv)
{
}
static void release_task_mempolicy(struct proc_maps_private *priv)
{
}
#endif

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;
		release_task_mempolicy(priv);
		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_access(priv->task, PTRACE_MODE_READ);
	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;
	hold_task_mempolicy(priv);
	/* 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;

	release_task_mempolicy(priv);
	/* 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, int is_pid)
{
	struct mm_struct *mm = vma->vm_mm;
	struct file *file = vma->vm_file;
	struct proc_maps_private *priv = m->private;
	struct task_struct *task = priv->task;
	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;
	const char *name = NULL;

	if (file) {
		struct inode *inode = file_inode(vma->vm_file);
		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, "\n");
		goto done;
	}

	name = arch_vma_name(vma);
	if (!name) {
		pid_t tid;

		if (!mm) {
			name = "[vdso]";
			goto done;
		}

		if (vma->vm_start <= mm->brk &&
		    vma->vm_end >= mm->start_brk) {
			name = "[heap]";
			goto done;
		}

		tid = vm_is_stack(task, vma, is_pid);

		if (tid != 0) {
			/*
			 * Thread stack in /proc/PID/task/TID/maps or
			 * the main process stack.
			 */
			if (!is_pid || (vma->vm_start <= mm->start_stack &&
			    vma->vm_end >= mm->start_stack)) {
				name = "[stack]";
			} else {
				/* Thread stack in /proc/PID/maps */
				pad_len_spaces(m, len);
				seq_printf(m, "[stack:%d]", tid);
			}
		}
	}

done:
	if (name) {
		pad_len_spaces(m, len);
		seq_puts(m, name);
	}
	seq_putc(m, '\n');
}

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

	show_map_vma(m, vma, is_pid);

	if (m->count < m->size)  /* vma is copied successfully */
		m->version = (vma != get_gate_vma(task->mm))
			? vma->vm_start : 0;
	return 0;
}

static int show_pid_map(struct seq_file *m, void *v)
{
	return show_map(m, v, 1);
}

static int show_tid_map(struct seq_file *m, void *v)
{
	return show_map(m, v, 0);
}

static const struct seq_operations proc_pid_maps_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_pid_map
};

static const struct seq_operations proc_tid_maps_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_tid_map
};

static int pid_maps_open(struct inode *inode, struct file *file)
{
	return do_maps_open(inode, file, &proc_pid_maps_op);
}

static int tid_maps_open(struct inode *inode, struct file *file)
{
	return do_maps_open(inode, file, &proc_tid_maps_op);
}

const struct file_operations proc_pid_maps_operations = {
	.open		= pid_maps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release_private,
};

const struct file_operations proc_tid_maps_operations = {
	.open		= tid_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;
	unsigned long nonlinear;
	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;
	pgoff_t pgoff = linear_page_index(vma, addr);
	struct page *page = NULL;
	int mapcount;

	if (pte_present(ptent)) {
		page = vm_normal_page(vma, addr, ptent);
	} else if (is_swap_pte(ptent)) {
		swp_entry_t swpent = pte_to_swp_entry(ptent);

		if (!non_swap_entry(swpent))
			mss->swap += ptent_size;
		else if (is_migration_entry(swpent))
			page = migration_entry_to_page(swpent);
	} else if (pte_file(ptent)) {
		if (pte_to_pgoff(ptent) != pgoff)
			mss->nonlinear += ptent_size;
	}

	if (!page)
		return;

	if (PageAnon(page))
		mss->anonymous += ptent_size;

	if (page->index != pgoff)
		mss->nonlinear += 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;

	if (pmd_trans_huge_lock(pmd, vma) == 1) {
		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;
	}

	if (pmd_trans_unstable(pmd))
		return 0;
	/*
	 * 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 void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
{
	/*
	 * Don't forget to update Documentation/ on changes.
	 */
	static const char mnemonics[BITS_PER_LONG][2] = {
		/*
		 * In case if we meet a flag we don't know about.
		 */
		[0 ... (BITS_PER_LONG-1)] = "??",

		[ilog2(VM_READ)]	= "rd",
		[ilog2(VM_WRITE)]	= "wr",
		[ilog2(VM_EXEC)]	= "ex",
		[ilog2(VM_SHARED)]	= "sh",
		[ilog2(VM_MAYREAD)]	= "mr",
		[ilog2(VM_MAYWRITE)]	= "mw",
		[ilog2(VM_MAYEXEC)]	= "me",
		[ilog2(VM_MAYSHARE)]	= "ms",
		[ilog2(VM_GROWSDOWN)]	= "gd",
		[ilog2(VM_PFNMAP)]	= "pf",
		[ilog2(VM_DENYWRITE)]	= "dw",
		[ilog2(VM_LOCKED)]	= "lo",
		[ilog2(VM_IO)]		= "io",
		[ilog2(VM_SEQ_READ)]	= "sr",
		[ilog2(VM_RAND_READ)]	= "rr",
		[ilog2(VM_DONTCOPY)]	= "dc",
		[ilog2(VM_DONTEXPAND)]	= "de",
		[ilog2(VM_ACCOUNT)]	= "ac",
		[ilog2(VM_NORESERVE)]	= "nr",
		[ilog2(VM_HUGETLB)]	= "ht",
		[ilog2(VM_NONLINEAR)]	= "nl",
		[ilog2(VM_ARCH_1)]	= "ar",
		[ilog2(VM_DONTDUMP)]	= "dd",
		[ilog2(VM_MIXEDMAP)]	= "mm",
		[ilog2(VM_HUGEPAGE)]	= "hg",
		[ilog2(VM_NOHUGEPAGE)]	= "nh",
		[ilog2(VM_MERGEABLE)]	= "mg",
	};
	size_t i;

	seq_puts(m, "VmFlags: ");
	for (i = 0; i < BITS_PER_LONG; i++) {
		if (vma->vm_flags & (1UL << i)) {
			seq_printf(m, "%c%c ",
				   mnemonics[i][0], mnemonics[i][1]);
		}
	}
	seq_putc(m, '\n');
}

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

	seq_printf(m,
		   "Size:           %8lu kB\n"
		   "Rss:            %8lu kB\n"
		   "Pss:            %8lu kB\n"
		   "Shared_Clean:   %8lu kB\n"
		   "Shared_Dirty:   %8lu kB\n"
		   "Private_Clean:  %8lu kB\n"
		   "Private_Dirty:  %8lu kB\n"
		   "Referenced:     %8lu kB\n"
		   "Anonymous:      %8lu kB\n"
		   "AnonHugePages:  %8lu kB\n"
		   "Swap:           %8lu kB\n"
		   "KernelPageSize: %8lu kB\n"
		   "MMUPageSize:    %8lu kB\n"
		   "Locked:         %8lu kB\n",
		   (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 (vma->vm_flags & VM_NONLINEAR)
		seq_printf(m, "Nonlinear:      %8lu kB\n",
				mss.nonlinear >> 10);

	show_smap_vma_flags(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 int show_pid_smap(struct seq_file *m, void *v)
{
	return show_smap(m, v, 1);
}

static int show_tid_smap(struct seq_file *m, void *v)
{
	return show_smap(m, v, 0);
}

static const struct seq_operations proc_pid_smaps_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_pid_smap
};

static const struct seq_operations proc_tid_smaps_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_tid_smap
};

static int pid_smaps_open(struct inode *inode, struct file *file)
{
	return do_maps_open(inode, file, &proc_pid_smaps_op);
}

static int tid_smaps_open(struct inode *inode, struct file *file)
{
	return do_maps_open(inode, file, &proc_tid_smaps_op);
}

const struct file_operations proc_pid_smaps_operations = {
	.open		= pid_smaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release_private,
};

const struct file_operations proc_tid_smaps_operations = {
	.open		= tid_smaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release_private,
};

/*
 * We do not want to have constant page-shift bits sitting in
 * pagemap entries and are about to reuse them some time soon.
 *
 * Here's the "migration strategy":
 * 1. when the system boots these bits remain what they are,
 *    but a warning about future change is printed in log;
 * 2. once anyone clears soft-dirty bits via clear_refs file,
 *    these flag is set to denote, that user is aware of the
 *    new API and those page-shift bits change their meaning.
 *    The respective warning is printed in dmesg;
 * 3. In a couple of releases we will remove all the mentions
 *    of page-shift in pagemap entries.
 */

static bool soft_dirty_cleared __read_mostly;

enum clear_refs_types {
	CLEAR_REFS_ALL = 1,
	CLEAR_REFS_ANON,
	CLEAR_REFS_MAPPED,
	CLEAR_REFS_SOFT_DIRTY,
	CLEAR_REFS_LAST,
};

struct clear_refs_private {
	struct vm_area_struct *vma;
	enum clear_refs_types type;
};

static inline void clear_soft_dirty(struct vm_area_struct *vma,
		unsigned long addr, pte_t *pte)
{
#ifdef CONFIG_MEM_SOFT_DIRTY
	/*
	 * The soft-dirty tracker uses #PF-s to catch writes
	 * to pages, so write-protect the pte as well. See the
	 * Documentation/vm/soft-dirty.txt for full description
	 * of how soft-dirty works.
	 */
	pte_t ptent = *pte;

	if (pte_present(ptent)) {
		ptent = pte_wrprotect(ptent);
		ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY);
	} else if (is_swap_pte(ptent)) {
		ptent = pte_swp_clear_soft_dirty(ptent);
	} else if (pte_file(ptent)) {
		ptent = pte_file_clear_soft_dirty(ptent);
	}

	set_pte_at(vma->vm_mm, addr, pte, ptent);
#endif
}

static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
				unsigned long end, struct mm_walk *walk)
{
	struct clear_refs_private *cp = walk->private;
	struct vm_area_struct *vma = cp->vma;
	pte_t *pte, ptent;
	spinlock_t *ptl;
	struct page *page;

	split_huge_page_pmd(vma, addr, pmd);
	if (pmd_trans_unstable(pmd))
		return 0;

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (; addr != end; pte++, addr += PAGE_SIZE) {
		ptent = *pte;

		if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
			clear_soft_dirty(vma, addr, pte);
			continue;
		}

		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;
}

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;
	enum clear_refs_types type;
	int itype;
	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, &itype);
	if (rv < 0)
		return rv;
	type = (enum clear_refs_types)itype;
	if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
		return -EINVAL;

	if (type == CLEAR_REFS_SOFT_DIRTY) {
		soft_dirty_cleared = true;
		pr_warn_once("The pagemap bits 55-60 has changed their meaning! "
				"See the linux/Documentation/vm/pagemap.txt for details.\n");
	}

	task = get_proc_task(file_inode(file));
	if (!task)
		return -ESRCH;
	mm = get_task_mm(task);
	if (mm) {
		struct clear_refs_private cp = {
			.type = type,
		};
		struct mm_walk clear_refs_walk = {
			.pmd_entry = clear_refs_pte_range,
			.mm = mm,
			.private = &cp,
		};
		down_read(&mm->mmap_sem);
		if (type == CLEAR_REFS_SOFT_DIRTY)
			mmu_notifier_invalidate_range_start(mm, 0, -1);
		for (vma = mm->mmap; vma; vma = vma->vm_next) {
			cp.vma = 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);
		}
		if (type == CLEAR_REFS_SOFT_DIRTY)
			mmu_notifier_invalidate_range_end(mm, 0, -1);
		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,
};

typedef struct {
	u64 pme;
} pagemap_entry_t;

struct pagemapread {
	int pos, len;
	pagemap_entry_t *buffer;
	bool v2;
};

#define PAGEMAP_WALK_SIZE	(PMD_SIZE)
#define PAGEMAP_WALK_MASK	(PMD_MASK)

#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)
/* in "new" pagemap pshift bits are occupied with more status bits */
#define PM_STATUS2(v2, x)   (__PM_PSHIFT(v2 ? x : PAGE_SHIFT))

#define __PM_SOFT_DIRTY      (1LL)
#define PM_PRESENT          PM_STATUS(4LL)
#define PM_SWAP             PM_STATUS(2LL)
#define PM_FILE             PM_STATUS(1LL)
#define PM_NOT_PRESENT(v2)  PM_STATUS2(v2, 0)
#define PM_END_OF_BUFFER    1

static inline pagemap_entry_t make_pme(u64 val)
{
	return (pagemap_entry_t) { .pme = val };
}

static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
			  struct pagemapread *pm)
{
	pm->buffer[pm->pos++] = *pme;
	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;
	pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));

	for (addr = start; addr < end; addr += PAGE_SIZE) {
		err = add_to_pagemap(addr, &pme, pm);
		if (err)
			break;
	}
	return err;
}

static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
		struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
	u64 frame, flags;
	struct page *page = NULL;
	int flags2 = 0;

	if (pte_present(pte)) {
		frame = pte_pfn(pte);
		flags = PM_PRESENT;
		page = vm_normal_page(vma, addr, pte);
	} else if (is_swap_pte(pte)) {
		swp_entry_t entry;
		if (pte_swp_soft_dirty(pte))
			flags2 |= __PM_SOFT_DIRTY;
		entry = pte_to_swp_entry(pte);
		frame = swp_type(entry) |
			(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
		flags = PM_SWAP;
		if (is_migration_entry(entry))
			page = migration_entry_to_page(entry);
	} else {
		*pme = make_pme(PM_NOT_PRESENT(pm->v2));
		return;
	}

	if (page && !PageAnon(page))
		flags |= PM_FILE;
	if (pte_soft_dirty(pte))
		flags2 |= __PM_SOFT_DIRTY;

	*pme = make_pme(PM_PFRAME(frame) | PM_STATUS2(pm->v2, flags2) | flags);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
		pmd_t pmd, int offset, int pmd_flags2)
{
	/*
	 * Currently pmd for thp is always present because thp can not be
	 * swapped-out, migrated, or HWPOISONed (split in such cases instead.)
	 * This if-check is just to prepare for future implementation.
	 */
	if (pmd_present(pmd))
		*pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
				| PM_STATUS2(pm->v2, pmd_flags2) | PM_PRESENT);
	else
		*pme = make_pme(PM_NOT_PRESENT(pm->v2));
}
#else
static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
		pmd_t pmd, int offset, int pmd_flags2)
{
}
#endif

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;
	pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));

	/* find the first VMA at or above 'addr' */
	vma = find_vma(walk->mm, addr);
	if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
		int pmd_flags2;

		pmd_flags2 = (pmd_soft_dirty(*pmd) ? __PM_SOFT_DIRTY : 0);