Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 1599 insertions, 0 deletions

diff --git a/kernel/mm/rmap.c b/kernel/mm/rmap.c
new file mode 100644
index 000000000..24dd3f9fe
--- /dev/null
+++ b/kernel/mm/rmap.c
@@ -0,0 +1,1599 @@
+/*
+ * mm/rmap.c - physical to virtual reverse mappings
+ *
+ * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
+ * Released under the General Public License (GPL).
+ *
+ * Simple, low overhead reverse mapping scheme.
+ * Please try to keep this thing as modular as possible.
+ *
+ * Provides methods for unmapping each kind of mapped page:
+ * the anon methods track anonymous pages, and
+ * the file methods track pages belonging to an inode.
+ *
+ * Original design by Rik van Riel <riel@conectiva.com.br> 2001
+ * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
+ * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
+ * Contributions by Hugh Dickins 2003, 2004
+ */
+
+/*
+ * Lock ordering in mm:
+ *
+ * inode->i_mutex	(while writing or truncating, not reading or faulting)
+ *   mm->mmap_sem
+ *     page->flags PG_locked (lock_page)
+ *       mapping->i_mmap_rwsem
+ *         anon_vma->rwsem
+ *           mm->page_table_lock or pte_lock
+ *             zone->lru_lock (in mark_page_accessed, isolate_lru_page)
+ *             swap_lock (in swap_duplicate, swap_info_get)
+ *               mmlist_lock (in mmput, drain_mmlist and others)
+ *               mapping->private_lock (in __set_page_dirty_buffers)
+ *               inode->i_lock (in set_page_dirty's __mark_inode_dirty)
+ *               bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
+ *                 sb_lock (within inode_lock in fs/fs-writeback.c)
+ *                 mapping->tree_lock (widely used, in set_page_dirty,
+ *                           in arch-dependent flush_dcache_mmap_lock,
+ *                           within bdi.wb->list_lock in __sync_single_inode)
+ *
+ * anon_vma->rwsem,mapping->i_mutex      (memory_failure, collect_procs_anon)
+ *   ->tasklist_lock
+ *     pte map lock
+ */
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/ksm.h>
+#include <linux/rmap.h>
+#include <linux/rcupdate.h>
+#include <linux/export.h>
+#include <linux/memcontrol.h>
+#include <linux/mmu_notifier.h>
+#include <linux/migrate.h>
+#include <linux/hugetlb.h>
+#include <linux/backing-dev.h>
+
+#include <asm/tlbflush.h>
+
+#include "internal.h"
+
+static struct kmem_cache *anon_vma_cachep;
+static struct kmem_cache *anon_vma_chain_cachep;
+
+static inline struct anon_vma *anon_vma_alloc(void)
+{
+	struct anon_vma *anon_vma;
+
+	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
+	if (anon_vma) {
+		atomic_set(&anon_vma->refcount, 1);
+		anon_vma->degree = 1;	/* Reference for first vma */
+		anon_vma->parent = anon_vma;
+		/*
+		 * Initialise the anon_vma root to point to itself. If called
+		 * from fork, the root will be reset to the parents anon_vma.
+		 */
+		anon_vma->root = anon_vma;
+	}
+
+	return anon_vma;
+}
+
+static inline void anon_vma_free(struct anon_vma *anon_vma)
+{
+	VM_BUG_ON(atomic_read(&anon_vma->refcount));
+
+	/*
+	 * Synchronize against page_lock_anon_vma_read() such that
+	 * we can safely hold the lock without the anon_vma getting
+	 * freed.
+	 *
+	 * Relies on the full mb implied by the atomic_dec_and_test() from
+	 * put_anon_vma() against the acquire barrier implied by
+	 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
+	 *
+	 * page_lock_anon_vma_read()	VS	put_anon_vma()
+	 *   down_read_trylock()		  atomic_dec_and_test()
+	 *   LOCK				  MB
+	 *   atomic_read()			  rwsem_is_locked()
+	 *
+	 * LOCK should suffice since the actual taking of the lock must
+	 * happen _before_ what follows.
+	 */
+	might_sleep();
+	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
+		anon_vma_lock_write(anon_vma);
+		anon_vma_unlock_write(anon_vma);
+	}
+
+	kmem_cache_free(anon_vma_cachep, anon_vma);
+}
+
+static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
+{
+	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
+}
+
+static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
+{
+	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
+}
+
+static void anon_vma_chain_link(struct vm_area_struct *vma,
+				struct anon_vma_chain *avc,
+				struct anon_vma *anon_vma)
+{
+	avc->vma = vma;
+	avc->anon_vma = anon_vma;
+	list_add(&avc->same_vma, &vma->anon_vma_chain);
+	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
+}
+
+/**
+ * anon_vma_prepare - attach an anon_vma to a memory region
+ * @vma: the memory region in question
+ *
+ * This makes sure the memory mapping described by 'vma' has
+ * an 'anon_vma' attached to it, so that we can associate the
+ * anonymous pages mapped into it with that anon_vma.
+ *
+ * The common case will be that we already have one, but if
+ * not we either need to find an adjacent mapping that we
+ * can re-use the anon_vma from (very common when the only
+ * reason for splitting a vma has been mprotect()), or we
+ * allocate a new one.
+ *
+ * Anon-vma allocations are very subtle, because we may have
+ * optimistically looked up an anon_vma in page_lock_anon_vma_read()
+ * and that may actually touch the spinlock even in the newly
+ * allocated vma (it depends on RCU to make sure that the
+ * anon_vma isn't actually destroyed).
+ *
+ * As a result, we need to do proper anon_vma locking even
+ * for the new allocation. At the same time, we do not want
+ * to do any locking for the common case of already having
+ * an anon_vma.
+ *
+ * This must be called with the mmap_sem held for reading.
+ */
+int anon_vma_prepare(struct vm_area_struct *vma)
+{
+	struct anon_vma *anon_vma = vma->anon_vma;
+	struct anon_vma_chain *avc;
+
+	might_sleep();
+	if (unlikely(!anon_vma)) {
+		struct mm_struct *mm = vma->vm_mm;
+		struct anon_vma *allocated;
+
+		avc = anon_vma_chain_alloc(GFP_KERNEL);
+		if (!avc)
+			goto out_enomem;
+
+		anon_vma = find_mergeable_anon_vma(vma);
+		allocated = NULL;
+		if (!anon_vma) {
+			anon_vma = anon_vma_alloc();
+			if (unlikely(!anon_vma))
+				goto out_enomem_free_avc;
+			allocated = anon_vma;
+		}
+
+		anon_vma_lock_write(anon_vma);
+		/* page_table_lock to protect against threads */
+		spin_lock(&mm->page_table_lock);
+		if (likely(!vma->anon_vma)) {
+			vma->anon_vma = anon_vma;
+			anon_vma_chain_link(vma, avc, anon_vma);
+			/* vma reference or self-parent link for new root */
+			anon_vma->degree++;
+			allocated = NULL;
+			avc = NULL;
+		}
+		spin_unlock(&mm->page_table_lock);
+		anon_vma_unlock_write(anon_vma);
+
+		if (unlikely(allocated))
+			put_anon_vma(allocated);
+		if (unlikely(avc))
+			anon_vma_chain_free(avc);
+	}
+	return 0;
+
+ out_enomem_free_avc:
+	anon_vma_chain_free(avc);
+ out_enomem:
+	return -ENOMEM;
+}
+
+/*
+ * This is a useful helper function for locking the anon_vma root as
+ * we traverse the vma->anon_vma_chain, looping over anon_vma's that
+ * have the same vma.
+ *
+ * Such anon_vma's should have the same root, so you'd expect to see
+ * just a single mutex_lock for the whole traversal.
+ */
+static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
+{
+	struct anon_vma *new_root = anon_vma->root;
+	if (new_root != root) {
+		if (WARN_ON_ONCE(root))
+			up_write(&root->rwsem);
+		root = new_root;
+		down_write(&root->rwsem);
+	}
+	return root;
+}
+
+static inline void unlock_anon_vma_root(struct anon_vma *root)
+{
+	if (root)
+		up_write(&root->rwsem);
+}
+
+/*
+ * Attach the anon_vmas from src to dst.
+ * Returns 0 on success, -ENOMEM on failure.
+ *
+ * If dst->anon_vma is NULL this function tries to find and reuse existing
+ * anon_vma which has no vmas and only one child anon_vma. This prevents
+ * degradation of anon_vma hierarchy to endless linear chain in case of
+ * constantly forking task. On the other hand, an anon_vma with more than one
+ * child isn't reused even if there was no alive vma, thus rmap walker has a
+ * good chance of avoiding scanning the whole hierarchy when it searches where
+ * page is mapped.
+ */
+int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
+{
+	struct anon_vma_chain *avc, *pavc;
+	struct anon_vma *root = NULL;
+
+	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
+		struct anon_vma *anon_vma;
+
+		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
+		if (unlikely(!avc)) {
+			unlock_anon_vma_root(root);
+			root = NULL;
+			avc = anon_vma_chain_alloc(GFP_KERNEL);
+			if (!avc)
+				goto enomem_failure;
+		}
+		anon_vma = pavc->anon_vma;
+		root = lock_anon_vma_root(root, anon_vma);
+		anon_vma_chain_link(dst, avc, anon_vma);
+
+		/*
+		 * Reuse existing anon_vma if its degree lower than two,
+		 * that means it has no vma and only one anon_vma child.
+		 *
+		 * Do not chose parent anon_vma, otherwise first child
+		 * will always reuse it. Root anon_vma is never reused:
+		 * it has self-parent reference and at least one child.
+		 */
+		if (!dst->anon_vma && anon_vma != src->anon_vma &&
+				anon_vma->degree < 2)
+			dst->anon_vma = anon_vma;
+	}
+	if (dst->anon_vma)
+		dst->anon_vma->degree++;
+	unlock_anon_vma_root(root);
+	return 0;
+
+ enomem_failure:
+	/*
+	 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
+	 * decremented in unlink_anon_vmas().
+	 * We can safely do this because callers of anon_vma_clone() don't care
+	 * about dst->anon_vma if anon_vma_clone() failed.
+	 */
+	dst->anon_vma = NULL;
+	unlink_anon_vmas(dst);
+	return -ENOMEM;
+}
+
+/*
+ * Attach vma to its own anon_vma, as well as to the anon_vmas that
+ * the corresponding VMA in the parent process is attached to.
+ * Returns 0 on success, non-zero on failure.
+ */
+int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
+{
+	struct anon_vma_chain *avc;
+	struct anon_vma *anon_vma;
+	int error;
+
+	/* Don't bother if the parent process has no anon_vma here. */
+	if (!pvma->anon_vma)
+		return 0;
+
+	/* Drop inherited anon_vma, we'll reuse existing or allocate new. */
+	vma->anon_vma = NULL;
+
+	/*
+	 * First, attach the new VMA to the parent VMA's anon_vmas,
+	 * so rmap can find non-COWed pages in child processes.
+	 */
+	error = anon_vma_clone(vma, pvma);
+	if (error)
+		return error;
+
+	/* An existing anon_vma has been reused, all done then. */
+	if (vma->anon_vma)
+		return 0;
+
+	/* Then add our own anon_vma. */
+	anon_vma = anon_vma_alloc();
+	if (!anon_vma)
+		goto out_error;
+	avc = anon_vma_chain_alloc(GFP_KERNEL);
+	if (!avc)
+		goto out_error_free_anon_vma;
+
+	/*
+	 * The root anon_vma's spinlock is the lock actually used when we
+	 * lock any of the anon_vmas in this anon_vma tree.
+	 */
+	anon_vma->root = pvma->anon_vma->root;
+	anon_vma->parent = pvma->anon_vma;
+	/*
+	 * With refcounts, an anon_vma can stay around longer than the
+	 * process it belongs to. The root anon_vma needs to be pinned until
+	 * this anon_vma is freed, because the lock lives in the root.
+	 */
+	get_anon_vma(anon_vma->root);
+	/* Mark this anon_vma as the one where our new (COWed) pages go. */
+	vma->anon_vma = anon_vma;
+	anon_vma_lock_write(anon_vma);
+	anon_vma_chain_link(vma, avc, anon_vma);
+	anon_vma->parent->degree++;
+	anon_vma_unlock_write(anon_vma);
+
+	return 0;
+
+ out_error_free_anon_vma:
+	put_anon_vma(anon_vma);
+ out_error:
+	unlink_anon_vmas(vma);
+	return -ENOMEM;
+}
+
+void unlink_anon_vmas(struct vm_area_struct *vma)
+{
+	struct anon_vma_chain *avc, *next;
+	struct anon_vma *root = NULL;
+
+	/*
+	 * Unlink each anon_vma chained to the VMA.  This list is ordered
+	 * from newest to oldest, ensuring the root anon_vma gets freed last.
+	 */
+	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
+		struct anon_vma *anon_vma = avc->anon_vma;
+
+		root = lock_anon_vma_root(root, anon_vma);
+		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
+
+		/*
+		 * Leave empty anon_vmas on the list - we'll need
+		 * to free them outside the lock.
+		 */
+		if (RB_EMPTY_ROOT(&anon_vma->rb_root)) {
+			anon_vma->parent->degree--;
+			continue;
+		}
+
+		list_del(&avc->same_vma);
+		anon_vma_chain_free(avc);
+	}
+	if (vma->anon_vma)
+		vma->anon_vma->degree--;
+	unlock_anon_vma_root(root);
+
+	/*
+	 * Iterate the list once more, it now only contains empty and unlinked
+	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
+	 * needing to write-acquire the anon_vma->root->rwsem.
+	 */
+	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
+		struct anon_vma *anon_vma = avc->anon_vma;
+
+		BUG_ON(anon_vma->degree);
+		put_anon_vma(anon_vma);
+
+		list_del(&avc->same_vma);
+		anon_vma_chain_free(avc);
+	}
+}
+
+static void anon_vma_ctor(void *data)
+{
+	struct anon_vma *anon_vma = data;
+
+	init_rwsem(&anon_vma->rwsem);
+	atomic_set(&anon_vma->refcount, 0);
+	anon_vma->rb_root = RB_ROOT;
+}
+
+void __init anon_vma_init(void)
+{
+	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
+			0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
+	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
+}
+
+/*
+ * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
+ *
+ * Since there is no serialization what so ever against page_remove_rmap()
+ * the best this function can do is return a locked anon_vma that might
+ * have been relevant to this page.
+ *
+ * The page might have been remapped to a different anon_vma or the anon_vma
+ * returned may already be freed (and even reused).
+ *
+ * In case it was remapped to a different anon_vma, the new anon_vma will be a
+ * child of the old anon_vma, and the anon_vma lifetime rules will therefore
+ * ensure that any anon_vma obtained from the page will still be valid for as
+ * long as we observe page_mapped() [ hence all those page_mapped() tests ].
+ *
+ * All users of this function must be very careful when walking the anon_vma
+ * chain and verify that the page in question is indeed mapped in it
+ * [ something equivalent to page_mapped_in_vma() ].
+ *
+ * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
+ * that the anon_vma pointer from page->mapping is valid if there is a
+ * mapcount, we can dereference the anon_vma after observing those.
+ */
+struct anon_vma *page_get_anon_vma(struct page *page)
+{
+	struct anon_vma *anon_vma = NULL;
+	unsigned long anon_mapping;
+
+	rcu_read_lock();
+	anon_mapping = (unsigned long)READ_ONCE(page->mapping);
+	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+		goto out;
+	if (!page_mapped(page))
+		goto out;
+
+	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
+	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
+		anon_vma = NULL;
+		goto out;
+	}
+
+	/*
+	 * If this page is still mapped, then its anon_vma cannot have been
+	 * freed.  But if it has been unmapped, we have no security against the
+	 * anon_vma structure being freed and reused (for another anon_vma:
+	 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
+	 * above cannot corrupt).
+	 */
+	if (!page_mapped(page)) {
+		rcu_read_unlock();
+		put_anon_vma(anon_vma);
+		return NULL;
+	}
+out:
+	rcu_read_unlock();
+
+	return anon_vma;
+}
+
+/*
+ * Similar to page_get_anon_vma() except it locks the anon_vma.
+ *
+ * Its a little more complex as it tries to keep the fast path to a single
+ * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
+ * reference like with page_get_anon_vma() and then block on the mutex.
+ */
+struct anon_vma *page_lock_anon_vma_read(struct page *page)
+{
+	struct anon_vma *anon_vma = NULL;
+	struct anon_vma *root_anon_vma;
+	unsigned long anon_mapping;
+
+	rcu_read_lock();
+	anon_mapping = (unsigned long)READ_ONCE(page->mapping);
+	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+		goto out;
+	if (!page_mapped(page))
+		goto out;
+
+	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
+	root_anon_vma = READ_ONCE(anon_vma->root);
+	if (down_read_trylock(&root_anon_vma->rwsem)) {
+		/*
+		 * If the page is still mapped, then this anon_vma is still
+		 * its anon_vma, and holding the mutex ensures that it will
+		 * not go away, see anon_vma_free().
+		 */
+		if (!page_mapped(page)) {
+			up_read(&root_anon_vma->rwsem);
+			anon_vma = NULL;
+		}
+		goto out;
+	}
+
+	/* trylock failed, we got to sleep */
+	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
+		anon_vma = NULL;
+		goto out;
+	}
+
+	if (!page_mapped(page)) {
+		rcu_read_unlock();
+		put_anon_vma(anon_vma);
+		return NULL;
+	}
+
+	/* we pinned the anon_vma, its safe to sleep */
+	rcu_read_unlock();
+	anon_vma_lock_read(anon_vma);
+
+	if (atomic_dec_and_test(&anon_vma->refcount)) {
+		/*
+		 * Oops, we held the last refcount, release the lock
+		 * and bail -- can't simply use put_anon_vma() because
+		 * we'll deadlock on the anon_vma_lock_write() recursion.
+		 */
+		anon_vma_unlock_read(anon_vma);
+		__put_anon_vma(anon_vma);
+		anon_vma = NULL;
+	}
+
+	return anon_vma;
+
+out:
+	rcu_read_unlock();
+	return anon_vma;
+}
+
+void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
+{
+	anon_vma_unlock_read(anon_vma);
+}
+
+/*
+ * At what user virtual address is page expected in @vma?
+ */
+static inline unsigned long
+__vma_address(struct page *page, struct vm_area_struct *vma)
+{
+	pgoff_t pgoff = page_to_pgoff(page);
+	return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+}
+
+inline unsigned long
+vma_address(struct page *page, struct vm_area_struct *vma)
+{
+	unsigned long address = __vma_address(page, vma);
+
+	/* page should be within @vma mapping range */
+	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+
+	return address;
+}
+
+/*
+ * At what user virtual address is page expected in vma?
+ * Caller should check the page is actually part of the vma.
+ */
+unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+	unsigned long address;
+	if (PageAnon(page)) {
+		struct anon_vma *page__anon_vma = page_anon_vma(page);
+		/*
+		 * Note: swapoff's unuse_vma() is more efficient with this
+		 * check, and needs it to match anon_vma when KSM is active.
+		 */
+		if (!vma->anon_vma || !page__anon_vma ||
+		    vma->anon_vma->root != page__anon_vma->root)
+			return -EFAULT;
+	} else if (page->mapping) {
+		if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
+			return -EFAULT;
+	} else
+		return -EFAULT;
+	address = __vma_address(page, vma);
+	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
+		return -EFAULT;
+	return address;
+}
+
+pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd = NULL;
+	pmd_t pmde;
+
+	pgd = pgd_offset(mm, address);
+	if (!pgd_present(*pgd))
+		goto out;
+
+	pud = pud_offset(pgd, address);
+	if (!pud_present(*pud))
+		goto out;
+
+	pmd = pmd_offset(pud, address);
+	/*
+	 * Some THP functions use the sequence pmdp_clear_flush(), set_pmd_at()
+	 * without holding anon_vma lock for write.  So when looking for a
+	 * genuine pmde (in which to find pte), test present and !THP together.
+	 */
+	pmde = *pmd;
+	barrier();
+	if (!pmd_present(pmde) || pmd_trans_huge(pmde))
+		pmd = NULL;
+out:
+	return pmd;
+}
+
+/*
+ * Check that @page is mapped at @address into @mm.
+ *
+ * If @sync is false, page_check_address may perform a racy check to avoid
+ * the page table lock when the pte is not present (helpful when reclaiming
+ * highly shared pages).
+ *
+ * On success returns with pte mapped and locked.
+ */
+pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
+			  unsigned long address, spinlock_t **ptlp, int sync)
+{
+	pmd_t *pmd;
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	if (unlikely(PageHuge(page))) {
+		/* when pud is not present, pte will be NULL */
+		pte = huge_pte_offset(mm, address);
+		if (!pte)
+			return NULL;
+
+		ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
+		goto check;
+	}
+
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
+		return NULL;
+
+	pte = pte_offset_map(pmd, address);
+	/* Make a quick check before getting the lock */
+	if (!sync && !pte_present(*pte)) {
+		pte_unmap(pte);
+		return NULL;
+	}
+
+	ptl = pte_lockptr(mm, pmd);
+check:
+	spin_lock(ptl);
+	if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
+		*ptlp = ptl;
+		return pte;
+	}
+	pte_unmap_unlock(pte, ptl);
+	return NULL;
+}
+
+/**
+ * page_mapped_in_vma - check whether a page is really mapped in a VMA
+ * @page: the page to test
+ * @vma: the VMA to test
+ *
+ * Returns 1 if the page is mapped into the page tables of the VMA, 0
+ * if the page is not mapped into the page tables of this VMA.  Only
+ * valid for normal file or anonymous VMAs.
+ */
+int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+	unsigned long address;
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	address = __vma_address(page, vma);
+	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
+		return 0;
+	pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
+	if (!pte)			/* the page is not in this mm */
+		return 0;
+	pte_unmap_unlock(pte, ptl);
+
+	return 1;
+}
+
+struct page_referenced_arg {
+	int mapcount;
+	int referenced;
+	unsigned long vm_flags;
+	struct mem_cgroup *memcg;
+};
+/*
+ * arg: page_referenced_arg will be passed
+ */
+static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
+			unsigned long address, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	spinlock_t *ptl;
+	int referenced = 0;
+	struct page_referenced_arg *pra = arg;
+
+	if (unlikely(PageTransHuge(page))) {
+		pmd_t *pmd;
+
+		/*
+		 * rmap might return false positives; we must filter
+		 * these out using page_check_address_pmd().
+		 */
+		pmd = page_check_address_pmd(page, mm, address,
+					     PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+		if (!pmd)
+			return SWAP_AGAIN;
+
+		if (vma->vm_flags & VM_LOCKED) {
+			spin_unlock(ptl);
+			pra->vm_flags |= VM_LOCKED;
+			return SWAP_FAIL; /* To break the loop */
+		}
+
+		/* go ahead even if the pmd is pmd_trans_splitting() */
+		if (pmdp_clear_flush_young_notify(vma, address, pmd))
+			referenced++;
+		spin_unlock(ptl);
+	} else {
+		pte_t *pte;
+
+		/*
+		 * rmap might return false positives; we must filter
+		 * these out using page_check_address().
+		 */
+		pte = page_check_address(page, mm, address, &ptl, 0);
+		if (!pte)
+			return SWAP_AGAIN;
+
+		if (vma->vm_flags & VM_LOCKED) {
+			pte_unmap_unlock(pte, ptl);
+			pra->vm_flags |= VM_LOCKED;
+			return SWAP_FAIL; /* To break the loop */
+		}
+
+		if (ptep_clear_flush_young_notify(vma, address, pte)) {
+			/*
+			 * Don't treat a reference through a sequentially read
+			 * mapping as such.  If the page has been used in
+			 * another mapping, we will catch it; if this other
+			 * mapping is already gone, the unmap path will have
+			 * set PG_referenced or activated the page.
+			 */
+			if (likely(!(vma->vm_flags & VM_SEQ_READ)))
+				referenced++;
+		}
+		pte_unmap_unlock(pte, ptl);
+	}
+
+	if (referenced) {
+		pra->referenced++;
+		pra->vm_flags |= vma->vm_flags;
+	}
+
+	pra->mapcount--;
+	if (!pra->mapcount)
+		return SWAP_SUCCESS; /* To break the loop */
+
+	return SWAP_AGAIN;
+}
+
+static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
+{
+	struct page_referenced_arg *pra = arg;
+	struct mem_cgroup *memcg = pra->memcg;
+
+	if (!mm_match_cgroup(vma->vm_mm, memcg))
+		return true;
+
+	return false;
+}
+
+/**
+ * page_referenced - test if the page was referenced
+ * @page: the page to test
+ * @is_locked: caller holds lock on the page
+ * @memcg: target memory cgroup
+ * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
+ *
+ * Quick test_and_clear_referenced for all mappings to a page,
+ * returns the number of ptes which referenced the page.
+ */
+int page_referenced(struct page *page,
+		    int is_locked,
+		    struct mem_cgroup *memcg,
+		    unsigned long *vm_flags)
+{
+	int ret;
+	int we_locked = 0;
+	struct page_referenced_arg pra = {
+		.mapcount = page_mapcount(page),
+		.memcg = memcg,
+	};
+	struct rmap_walk_control rwc = {
+		.rmap_one = page_referenced_one,
+		.arg = (void *)&pra,
+		.anon_lock = page_lock_anon_vma_read,
+	};
+
+	*vm_flags = 0;
+	if (!page_mapped(page))
+		return 0;
+
+	if (!page_rmapping(page))
+		return 0;
+
+	if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
+		we_locked = trylock_page(page);
+		if (!we_locked)
+			return 1;
+	}
+
+	/*
+	 * If we are reclaiming on behalf of a cgroup, skip
+	 * counting on behalf of references from different
+	 * cgroups
+	 */
+	if (memcg) {
+		rwc.invalid_vma = invalid_page_referenced_vma;
+	}
+
+	ret = rmap_walk(page, &rwc);
+	*vm_flags = pra.vm_flags;
+
+	if (we_locked)
+		unlock_page(page);
+
+	return pra.referenced;
+}
+
+static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
+			    unsigned long address, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	pte_t *pte;
+	spinlock_t *ptl;
+	int ret = 0;
+	int *cleaned = arg;
+
+	pte = page_check_address(page, mm, address, &ptl, 1);
+	if (!pte)
+		goto out;
+
+	if (pte_dirty(*pte) || pte_write(*pte)) {
+		pte_t entry;
+
+		flush_cache_page(vma, address, pte_pfn(*pte));
+		entry = ptep_clear_flush(vma, address, pte);
+		entry = pte_wrprotect(entry);
+		entry = pte_mkclean(entry);
+		set_pte_at(mm, address, pte, entry);
+		ret = 1;
+	}
+
+	pte_unmap_unlock(pte, ptl);
+
+	if (ret) {
+		mmu_notifier_invalidate_page(mm, address);
+		(*cleaned)++;
+	}
+out:
+	return SWAP_AGAIN;
+}
+
+static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
+{
+	if (vma->vm_flags & VM_SHARED)
+		return false;
+
+	return true;
+}
+
+int page_mkclean(struct page *page)
+{
+	int cleaned = 0;
+	struct address_space *mapping;
+	struct rmap_walk_control rwc = {
+		.arg = (void *)&cleaned,
+		.rmap_one = page_mkclean_one,
+		.invalid_vma = invalid_mkclean_vma,
+	};
+
+	BUG_ON(!PageLocked(page));
+
+	if (!page_mapped(page))
+		return 0;
+
+	mapping = page_mapping(page);
+	if (!mapping)
+		return 0;
+
+	rmap_walk(page, &rwc);
+
+	return cleaned;
+}
+EXPORT_SYMBOL_GPL(page_mkclean);
+
+/**
+ * page_move_anon_rmap - move a page to our anon_vma
+ * @page:	the page to move to our anon_vma
+ * @vma:	the vma the page belongs to
+ * @address:	the user virtual address mapped
+ *
+ * When a page belongs exclusively to one process after a COW event,
+ * that page can be moved into the anon_vma that belongs to just that
+ * process, so the rmap code will not search the parent or sibling
+ * processes.
+ */
+void page_move_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address)
+{
+	struct anon_vma *anon_vma = vma->anon_vma;
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	VM_BUG_ON_VMA(!anon_vma, vma);
+	VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
+
+	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+	page->mapping = (struct address_space *) anon_vma;
+}
+
+/**
+ * __page_set_anon_rmap - set up new anonymous rmap
+ * @page:	Page to add to rmap	
+ * @vma:	VM area to add page to.
+ * @address:	User virtual address of the mapping	
+ * @exclusive:	the page is exclusively owned by the current process
+ */
+static void __page_set_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address, int exclusive)
+{
+	struct anon_vma *anon_vma = vma->anon_vma;
+
+	BUG_ON(!anon_vma);
+
+	if (PageAnon(page))
+		return;
+
+	/*
+	 * If the page isn't exclusively mapped into this vma,
+	 * we must use the _oldest_ possible anon_vma for the
+	 * page mapping!
+	 */
+	if (!exclusive)
+		anon_vma = anon_vma->root;
+
+	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+	page->mapping = (struct address_space *) anon_vma;
+	page->index = linear_page_index(vma, address);
+}
+
+/**
+ * __page_check_anon_rmap - sanity check anonymous rmap addition
+ * @page:	the page to add the mapping to
+ * @vma:	the vm area in which the mapping is added
+ * @address:	the user virtual address mapped
+ */
+static void __page_check_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address)
+{
+#ifdef CONFIG_DEBUG_VM
+	/*
+	 * The page's anon-rmap details (mapping and index) are guaranteed to
+	 * be set up correctly at this point.
+	 *
+	 * We have exclusion against page_add_anon_rmap because the caller
+	 * always holds the page locked, except if called from page_dup_rmap,
+	 * in which case the page is already known to be setup.
+	 *
+	 * We have exclusion against page_add_new_anon_rmap because those pages
+	 * are initially only visible via the pagetables, and the pte is locked
+	 * over the call to page_add_new_anon_rmap.
+	 */
+	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
+	BUG_ON(page->index != linear_page_index(vma, address));
+#endif
+}
+
+/**
+ * page_add_anon_rmap - add pte mapping to an anonymous page
+ * @page:	the page to add the mapping to
+ * @vma:	the vm area in which the mapping is added
+ * @address:	the user virtual address mapped
+ *
+ * The caller needs to hold the pte lock, and the page must be locked in
+ * the anon_vma case: to serialize mapping,index checking after setting,
+ * and to ensure that PageAnon is not being upgraded racily to PageKsm
+ * (but PageKsm is never downgraded to PageAnon).
+ */
+void page_add_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address)
+{
+	do_page_add_anon_rmap(page, vma, address, 0);
+}
+
+/*
+ * Special version of the above for do_swap_page, which often runs
+ * into pages that are exclusively owned by the current process.
+ * Everybody else should continue to use page_add_anon_rmap above.
+ */
+void do_page_add_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address, int exclusive)
+{
+	int first = atomic_inc_and_test(&page->_mapcount);
+	if (first) {
+		/*
+		 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
+		 * these counters are not modified in interrupt context, and
+		 * pte lock(a spinlock) is held, which implies preemption
+		 * disabled.
+		 */
+		if (PageTransHuge(page))
+			__inc_zone_page_state(page,
+					      NR_ANON_TRANSPARENT_HUGEPAGES);
+		__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
+				hpage_nr_pages(page));
+	}
+	if (unlikely(PageKsm(page)))
+		return;
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	/* address might be in next vma when migration races vma_adjust */
+	if (first)
+		__page_set_anon_rmap(page, vma, address, exclusive);
+	else
+		__page_check_anon_rmap(page, vma, address);
+}
+
+/**
+ * page_add_new_anon_rmap - add pte mapping to a new anonymous page
+ * @page:	the page to add the mapping to
+ * @vma:	the vm area in which the mapping is added
+ * @address:	the user virtual address mapped
+ *
+ * Same as page_add_anon_rmap but must only be called on *new* pages.
+ * This means the inc-and-test can be bypassed.
+ * Page does not have to be locked.
+ */
+void page_add_new_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address)
+{
+	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+	SetPageSwapBacked(page);
+	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
+	if (PageTransHuge(page))
+		__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
+	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
+			hpage_nr_pages(page));
+	__page_set_anon_rmap(page, vma, address, 1);
+}
+
+/**
+ * page_add_file_rmap - add pte mapping to a file page
+ * @page: the page to add the mapping to
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_add_file_rmap(struct page *page)
+{
+	struct mem_cgroup *memcg;
+
+	memcg = mem_cgroup_begin_page_stat(page);
+	if (atomic_inc_and_test(&page->_mapcount)) {
+		__inc_zone_page_state(page, NR_FILE_MAPPED);
+		mem_cgroup_inc_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
+	}
+	mem_cgroup_end_page_stat(memcg);
+}
+
+static void page_remove_file_rmap(struct page *page)
+{
+	struct mem_cgroup *memcg;
+
+	memcg = mem_cgroup_begin_page_stat(page);
+
+	/* page still mapped by someone else? */
+	if (!atomic_add_negative(-1, &page->_mapcount))
+		goto out;
+
+	/* Hugepages are not counted in NR_FILE_MAPPED for now. */
+	if (unlikely(PageHuge(page)))
+		goto out;
+
+	/*
+	 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
+	 * these counters are not modified in interrupt context, and
+	 * pte lock(a spinlock) is held, which implies preemption disabled.
+	 */
+	__dec_zone_page_state(page, NR_FILE_MAPPED);
+	mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
+
+	if (unlikely(PageMlocked(page)))
+		clear_page_mlock(page);
+out:
+	mem_cgroup_end_page_stat(memcg);
+}
+
+/**
+ * page_remove_rmap - take down pte mapping from a page
+ * @page: page to remove mapping from
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_remove_rmap(struct page *page)
+{
+	if (!PageAnon(page)) {
+		page_remove_file_rmap(page);
+		return;
+	}
+
+	/* page still mapped by someone else? */
+	if (!atomic_add_negative(-1, &page->_mapcount))
+		return;
+
+	/* Hugepages are not counted in NR_ANON_PAGES for now. */
+	if (unlikely(PageHuge(page)))
+		return;
+
+	/*
+	 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
+	 * these counters are not modified in interrupt context, and
+	 * pte lock(a spinlock) is held, which implies preemption disabled.
+	 */
+	if (PageTransHuge(page))
+		__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
+
+	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
+			      -hpage_nr_pages(page));
+
+	if (unlikely(PageMlocked(page)))
+		clear_page_mlock(page);
+
+	/*
+	 * It would be tidy to reset the PageAnon mapping here,
+	 * but that might overwrite a racing page_add_anon_rmap
+	 * which increments mapcount after us but sets mapping
+	 * before us: so leave the reset to free_hot_cold_page,
+	 * and remember that it's only reliable while mapped.
+	 * Leaving it set also helps swapoff to reinstate ptes
+	 * faster for those pages still in swapcache.
+	 */
+}
+
+/*
+ * @arg: enum ttu_flags will be passed to this argument
+ */
+static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
+		     unsigned long address, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	pte_t *pte;
+	pte_t pteval;
+	spinlock_t *ptl;
+	int ret = SWAP_AGAIN;
+	enum ttu_flags flags = (enum ttu_flags)arg;
+
+	pte = page_check_address(page, mm, address, &ptl, 0);
+	if (!pte)
+		goto out;
+
+	/*
+	 * If the page is mlock()d, we cannot swap it out.
+	 * If it's recently referenced (perhaps page_referenced
+	 * skipped over this mm) then we should reactivate it.
+	 */
+	if (!(flags & TTU_IGNORE_MLOCK)) {
+		if (vma->vm_flags & VM_LOCKED)
+			goto out_mlock;
+
+		if (flags & TTU_MUNLOCK)
+			goto out_unmap;
+	}
+	if (!(flags & TTU_IGNORE_ACCESS)) {
+		if (ptep_clear_flush_young_notify(vma, address, pte)) {
+			ret = SWAP_FAIL;
+			goto out_unmap;
+		}
+  	}
+
+	/* Nuke the page table entry. */
+	flush_cache_page(vma, address, page_to_pfn(page));
+	pteval = ptep_clear_flush(vma, address, pte);
+
+	/* Move the dirty bit to the physical page now the pte is gone. */
+	if (pte_dirty(pteval))
+		set_page_dirty(page);
+
+	/* Update high watermark before we lower rss */
+	update_hiwater_rss(mm);
+
+	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
+		if (!PageHuge(page)) {
+			if (PageAnon(page))
+				dec_mm_counter(mm, MM_ANONPAGES);
+			else
+				dec_mm_counter(mm, MM_FILEPAGES);
+		}
+		set_pte_at(mm, address, pte,
+			   swp_entry_to_pte(make_hwpoison_entry(page)));
+	} else if (pte_unused(pteval)) {
+		/*
+		 * The guest indicated that the page content is of no
+		 * interest anymore. Simply discard the pte, vmscan
+		 * will take care of the rest.
+		 */
+		if (PageAnon(page))
+			dec_mm_counter(mm, MM_ANONPAGES);
+		else
+			dec_mm_counter(mm, MM_FILEPAGES);
+	} else if (PageAnon(page)) {
+		swp_entry_t entry = { .val = page_private(page) };
+		pte_t swp_pte;
+
+		if (PageSwapCache(page)) {
+			/*
+			 * Store the swap location in the pte.
+			 * See handle_pte_fault() ...
+			 */
+			if (swap_duplicate(entry) < 0) {
+				set_pte_at(mm, address, pte, pteval);
+				ret = SWAP_FAIL;
+				goto out_unmap;
+			}
+			if (list_empty(&mm->mmlist)) {
+				spin_lock(&mmlist_lock);
+				if (list_empty(&mm->mmlist))
+					list_add(&mm->mmlist, &init_mm.mmlist);
+				spin_unlock(&mmlist_lock);
+			}
+			dec_mm_counter(mm, MM_ANONPAGES);
+			inc_mm_counter(mm, MM_SWAPENTS);
+		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
+			/*
+			 * Store the pfn of the page in a special migration
+			 * pte. do_swap_page() will wait until the migration
+			 * pte is removed and then restart fault handling.
+			 */
+			BUG_ON(!(flags & TTU_MIGRATION));
+			entry = make_migration_entry(page, pte_write(pteval));
+		}
+		swp_pte = swp_entry_to_pte(entry);
+		if (pte_soft_dirty(pteval))
+			swp_pte = pte_swp_mksoft_dirty(swp_pte);
+		set_pte_at(mm, address, pte, swp_pte);
+	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
+		   (flags & TTU_MIGRATION)) {
+		/* Establish migration entry for a file page */
+		swp_entry_t entry;
+		entry = make_migration_entry(page, pte_write(pteval));
+		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
+	} else
+		dec_mm_counter(mm, MM_FILEPAGES);
+
+	page_remove_rmap(page);
+	page_cache_release(page);
+
+out_unmap:
+	pte_unmap_unlock(pte, ptl);
+	if (ret != SWAP_FAIL && !(flags & TTU_MUNLOCK))
+		mmu_notifier_invalidate_page(mm, address);
+out:
+	return ret;
+
+out_mlock:
+	pte_unmap_unlock(pte, ptl);
+
+
+	/*
+	 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
+	 * unstable result and race. Plus, We can't wait here because
+	 * we now hold anon_vma->rwsem or mapping->i_mmap_rwsem.
+	 * if trylock failed, the page remain in evictable lru and later
+	 * vmscan could retry to move the page to unevictable lru if the
+	 * page is actually mlocked.
+	 */
+	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
+		if (vma->vm_flags & VM_LOCKED) {
+			mlock_vma_page(page);
+			ret = SWAP_MLOCK;
+		}
+		up_read(&vma->vm_mm->mmap_sem);
+	}
+	return ret;
+}
+
+bool is_vma_temporary_stack(struct vm_area_struct *vma)
+{
+	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
+
+	if (!maybe_stack)
+		return false;
+
+	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
+						VM_STACK_INCOMPLETE_SETUP)
+		return true;
+
+	return false;
+}
+
+static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
+{
+	return is_vma_temporary_stack(vma);
+}
+
+static int page_not_mapped(struct page *page)
+{
+	return !page_mapped(page);
+};
+
+/**
+ * try_to_unmap - try to remove all page table mappings to a page
+ * @page: the page to get unmapped
+ * @flags: action and flags
+ *
+ * Tries to remove all the page table entries which are mapping this
+ * page, used in the pageout path.  Caller must hold the page lock.
+ * Return values are:
+ *
+ * SWAP_SUCCESS	- we succeeded in removing all mappings
+ * SWAP_AGAIN	- we missed a mapping, try again later
+ * SWAP_FAIL	- the page is unswappable
+ * SWAP_MLOCK	- page is mlocked.
+ */
+int try_to_unmap(struct page *page, enum ttu_flags flags)
+{
+	int ret;
+	struct rmap_walk_control rwc = {
+		.rmap_one = try_to_unmap_one,
+		.arg = (void *)flags,
+		.done = page_not_mapped,
+		.anon_lock = page_lock_anon_vma_read,
+	};
+
+	VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page);
+
+	/*
+	 * During exec, a temporary VMA is setup and later moved.
+	 * The VMA is moved under the anon_vma lock but not the
+	 * page tables leading to a race where migration cannot
+	 * find the migration ptes. Rather than increasing the
+	 * locking requirements of exec(), migration skips
+	 * temporary VMAs until after exec() completes.
+	 */
+	if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
+		rwc.invalid_vma = invalid_migration_vma;
+
+	ret = rmap_walk(page, &rwc);
+
+	if (ret != SWAP_MLOCK && !page_mapped(page))
+		ret = SWAP_SUCCESS;
+	return ret;
+}
+
+/**
+ * try_to_munlock - try to munlock a page
+ * @page: the page to be munlocked
+ *
+ * Called from munlock code.  Checks all of the VMAs mapping the page
+ * to make sure nobody else has this page mlocked. The page will be
+ * returned with PG_mlocked cleared if no other vmas have it mlocked.
+ *
+ * Return values are:
+ *
+ * SWAP_AGAIN	- no vma is holding page mlocked, or,
+ * SWAP_AGAIN	- page mapped in mlocked vma -- couldn't acquire mmap sem
+ * SWAP_FAIL	- page cannot be located at present
+ * SWAP_MLOCK	- page is now mlocked.
+ */
+int try_to_munlock(struct page *page)
+{
+	int ret;
+	struct rmap_walk_control rwc = {
+		.rmap_one = try_to_unmap_one,
+		.arg = (void *)TTU_MUNLOCK,
+		.done = page_not_mapped,
+		.anon_lock = page_lock_anon_vma_read,
+
+	};
+
+	VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
+
+	ret = rmap_walk(page, &rwc);
+	return ret;
+}
+
+void __put_anon_vma(struct anon_vma *anon_vma)
+{
+	struct anon_vma *root = anon_vma->root;
+
+	anon_vma_free(anon_vma);
+	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
+		anon_vma_free(root);
+}
+
+static struct anon_vma *rmap_walk_anon_lock(struct page *page,
+					struct rmap_walk_control *rwc)
+{
+	struct anon_vma *anon_vma;
+
+	if (rwc->anon_lock)
+		return rwc->anon_lock(page);
+
+	/*
+	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
+	 * because that depends on page_mapped(); but not all its usages
+	 * are holding mmap_sem. Users without mmap_sem are required to
+	 * take a reference count to prevent the anon_vma disappearing
+	 */
+	anon_vma = page_anon_vma(page);
+	if (!anon_vma)
+		return NULL;
+
+	anon_vma_lock_read(anon_vma);
+	return anon_vma;
+}
+
+/*
+ * rmap_walk_anon - do something to anonymous page using the object-based
+ * rmap method
+ * @page: the page to be handled
+ * @rwc: control variable according to each walk type
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the anon_vma struct it points to.
+ *
+ * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
+ * where the page was found will be held for write.  So, we won't recheck
+ * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
+ * LOCKED.
+ */
+static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
+{
+	struct anon_vma *anon_vma;
+	pgoff_t pgoff;
+	struct anon_vma_chain *avc;
+	int ret = SWAP_AGAIN;
+
+	anon_vma = rmap_walk_anon_lock(page, rwc);
+	if (!anon_vma)
+		return ret;
+
+	pgoff = page_to_pgoff(page);
+	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
+		struct vm_area_struct *vma = avc->vma;
+		unsigned long address = vma_address(page, vma);
+
+		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+			continue;
+
+		ret = rwc->rmap_one(page, vma, address, rwc->arg);
+		if (ret != SWAP_AGAIN)
+			break;
+		if (rwc->done && rwc->done(page))
+			break;
+	}
+	anon_vma_unlock_read(anon_vma);
+	return ret;
+}
+
+/*
+ * rmap_walk_file - do something to file page using the object-based rmap method
+ * @page: the page to be handled
+ * @rwc: control variable according to each walk type
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the address_space struct it points to.
+ *
+ * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
+ * where the page was found will be held for write.  So, we won't recheck
+ * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
+ * LOCKED.
+ */
+static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
+{
+	struct address_space *mapping = page->mapping;
+	pgoff_t pgoff;
+	struct vm_area_struct *vma;
+	int ret = SWAP_AGAIN;
+
+	/*
+	 * The page lock not only makes sure that page->mapping cannot
+	 * suddenly be NULLified by truncation, it makes sure that the
+	 * structure at mapping cannot be freed and reused yet,
+	 * so we can safely take mapping->i_mmap_rwsem.
+	 */
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+	if (!mapping)
+		return ret;
+
+	pgoff = page_to_pgoff(page);
+	i_mmap_lock_read(mapping);
+	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
+		unsigned long address = vma_address(page, vma);
+
+		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+			continue;
+
+		ret = rwc->rmap_one(page, vma, address, rwc->arg);
+		if (ret != SWAP_AGAIN)
+			goto done;
+		if (rwc->done && rwc->done(page))
+			goto done;
+	}
+
+done:
+	i_mmap_unlock_read(mapping);
+	return ret;
+}
+
+int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
+{
+	if (unlikely(PageKsm(page)))
+		return rmap_walk_ksm(page, rwc);
+	else if (PageAnon(page))
+		return rmap_walk_anon(page, rwc);
+	else
+		return rmap_walk_file(page, rwc);
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+/*
+ * The following three functions are for anonymous (private mapped) hugepages.
+ * Unlike common anonymous pages, anonymous hugepages have no accounting code
+ * and no lru code, because we handle hugepages differently from common pages.
+ */
+static void __hugepage_set_anon_rmap(struct page *page,
+	struct vm_area_struct *vma, unsigned long address, int exclusive)
+{
+	struct anon_vma *anon_vma = vma->anon_vma;
+
+	BUG_ON(!anon_vma);
+
+	if (PageAnon(page))
+		return;
+	if (!exclusive)
+		anon_vma = anon_vma->root;
+
+	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+	page->mapping = (struct address_space *) anon_vma;
+	page->index = linear_page_index(vma, address);
+}
+
+void hugepage_add_anon_rmap(struct page *page,
+			    struct vm_area_struct *vma, unsigned long address)
+{
+	struct anon_vma *anon_vma = vma->anon_vma;
+	int first;
+
+	BUG_ON(!PageLocked(page));
+	BUG_ON(!anon_vma);
+	/* address might be in next vma when migration races vma_adjust */
+	first = atomic_inc_and_test(&page->_mapcount);
+	if (first)
+		__hugepage_set_anon_rmap(page, vma, address, 0);
+}
+
+void hugepage_add_new_anon_rmap(struct page *page,
+			struct vm_area_struct *vma, unsigned long address)
+{
+	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
+	atomic_set(&page->_mapcount, 0);
+	__hugepage_set_anon_rmap(page, vma, address, 1);
+}
+#endif /* CONFIG_HUGETLB_PAGE */