Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2577 insertions, 0 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
new file mode 100644
index 000000000..7da2d8d09
--- /dev/null
+++ b/mm/rmap.c
@@ -0,0 +1,2577 @@
+/*
+ * 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_rwsem	(while writing or truncating, not reading or faulting)
+ *   mm->mmap_lock
+ *     mapping->invalidate_lock (in filemap_fault)
+ *       page->flags PG_locked (lock_page)
+ *         hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
+ *           mapping->i_mmap_rwsem
+ *             anon_vma->rwsem
+ *               mm->page_table_lock or pte_lock
+ *                 swap_lock (in swap_duplicate, swap_info_get)
+ *                   mmlist_lock (in mmput, drain_mmlist and others)
+ *                   mapping->private_lock (in block_dirty_folio)
+ *                     folio_lock_memcg move_lock (in block_dirty_folio)
+ *                       i_pages lock (widely used)
+ *                         lruvec->lru_lock (in folio_lruvec_lock_irq)
+ *                   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)
+ *                     i_pages 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_mmap_rwsem   (memory_failure, collect_procs_anon)
+ *   ->tasklist_lock
+ *     pte map lock
+ *
+ * hugetlbfs PageHuge() take locks in this order:
+ *   hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
+ *     vma_lock (hugetlb specific lock for pmd_sharing)
+ *       mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
+ *         page->flags PG_locked (lock_page)
+ */
+
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/task.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/huge_mm.h>
+#include <linux/backing-dev.h>
+#include <linux/page_idle.h>
+#include <linux/memremap.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/mm_inline.h>
+
+#include <asm/tlbflush.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/tlb.h>
+#include <trace/events/migrate.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->num_children = 0;
+		anon_vma->num_active_vmas = 0;
+		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 folio_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 folio_lock_anon_vma_read(). This orders:
+	 *
+	 * folio_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, which
+ * is handled inline by anon_vma_prepare(). 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 folio_lock_anon_vma_read()
+ * and that may actually touch the rwsem 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_lock held for reading.
+ */
+int __anon_vma_prepare(struct vm_area_struct *vma)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct anon_vma *anon_vma, *allocated;
+	struct anon_vma_chain *avc;
+
+	might_sleep();
+
+	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;
+		anon_vma->num_children++; /* self-parent link for new root */
+		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);
+		anon_vma->num_active_vmas++;
+		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.
+ *
+ * anon_vma_clone() is called by __vma_adjust(), __split_vma(), copy_vma() and
+ * anon_vma_fork(). The first three want an exact copy of src, while the last
+ * one, anon_vma_fork(), may try to reuse an existing anon_vma to prevent
+ * endless growth of anon_vma. Since dst->anon_vma is set to NULL before call,
+ * we can identify this case by checking (!dst->anon_vma && src->anon_vma).
+ *
+ * If (!dst->anon_vma && src->anon_vma) is true, 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 it has no vma and only one
+		 * anon_vma child.
+		 *
+		 * Root anon_vma is never reused:
+		 * it has self-parent reference and at least one child.
+		 */
+		if (!dst->anon_vma && src->anon_vma &&
+		    anon_vma->num_children < 2 &&
+		    anon_vma->num_active_vmas == 0)
+			dst->anon_vma = anon_vma;
+	}
+	if (dst->anon_vma)
+		dst->anon_vma->num_active_vmas++;
+	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;
+	anon_vma->num_active_vmas++;
+	avc = anon_vma_chain_alloc(GFP_KERNEL);
+	if (!avc)
+		goto out_error_free_anon_vma;
+
+	/*
+	 * The root anon_vma's rwsem 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->num_children++;
+	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.rb_root)) {
+			anon_vma->parent->num_children--;
+			continue;
+		}
+
+		list_del(&avc->same_vma);
+		anon_vma_chain_free(avc);
+	}
+	if (vma->anon_vma) {
+		vma->anon_vma->num_active_vmas--;
+
+		/*
+		 * vma would still be needed after unlink, and anon_vma will be prepared
+		 * when handle fault.
+		 */
+		vma->anon_vma = NULL;
+	}
+	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;
+
+		VM_WARN_ON(anon_vma->num_children);
+		VM_WARN_ON(anon_vma->num_active_vmas);
+		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_CACHED;
+}
+
+void __init anon_vma_init(void)
+{
+	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
+			0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
+			anon_vma_ctor);
+	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
+			SLAB_PANIC|SLAB_ACCOUNT);
+}
+
+/*
+ * 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 refcount increased 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 SLAB_TYPESAFE_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 *folio_get_anon_vma(struct folio *folio)
+{
+	struct anon_vma *anon_vma = NULL;
+	unsigned long anon_mapping;
+
+	rcu_read_lock();
+	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
+	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+		goto out;
+	if (!folio_mapped(folio))
+		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 folio 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_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
+	 * above cannot corrupt).
+	 */
+	if (!folio_mapped(folio)) {
+		rcu_read_unlock();
+		put_anon_vma(anon_vma);
+		return NULL;
+	}
+out:
+	rcu_read_unlock();
+
+	return anon_vma;
+}
+
+/*
+ * Similar to folio_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 folio_get_anon_vma() and then block on the mutex
+ * on !rwc->try_lock case.
+ */
+struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
+					  struct rmap_walk_control *rwc)
+{
+	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(folio->mapping);
+	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+		goto out;
+	if (!folio_mapped(folio))
+		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 folio 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 (!folio_mapped(folio)) {
+			up_read(&root_anon_vma->rwsem);
+			anon_vma = NULL;
+		}
+		goto out;
+	}
+
+	if (rwc && rwc->try_lock) {
+		anon_vma = NULL;
+		rwc->contended = true;
+		goto out;
+	}
+
+	/* trylock failed, we got to sleep */
+	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
+		anon_vma = NULL;
+		goto out;
+	}
+
+	if (!folio_mapped(folio)) {
+		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;
+}
+
+#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
+/*
+ * Flush TLB entries for recently unmapped pages from remote CPUs. It is
+ * important if a PTE was dirty when it was unmapped that it's flushed
+ * before any IO is initiated on the page to prevent lost writes. Similarly,
+ * it must be flushed before freeing to prevent data leakage.
+ */
+void try_to_unmap_flush(void)
+{
+	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+
+	if (!tlb_ubc->flush_required)
+		return;
+
+	arch_tlbbatch_flush(&tlb_ubc->arch);
+	tlb_ubc->flush_required = false;
+	tlb_ubc->writable = false;
+}
+
+/* Flush iff there are potentially writable TLB entries that can race with IO */
+void try_to_unmap_flush_dirty(void)
+{
+	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+
+	if (tlb_ubc->writable)
+		try_to_unmap_flush();
+}
+
+/*
+ * Bits 0-14 of mm->tlb_flush_batched record pending generations.
+ * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
+ */
+#define TLB_FLUSH_BATCH_FLUSHED_SHIFT	16
+#define TLB_FLUSH_BATCH_PENDING_MASK			\
+	((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
+#define TLB_FLUSH_BATCH_PENDING_LARGE			\
+	(TLB_FLUSH_BATCH_PENDING_MASK / 2)
+
+static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
+{
+	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+	int batch, nbatch;
+
+	arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
+	tlb_ubc->flush_required = true;
+
+	/*
+	 * Ensure compiler does not re-order the setting of tlb_flush_batched
+	 * before the PTE is cleared.
+	 */
+	barrier();
+	batch = atomic_read(&mm->tlb_flush_batched);
+retry:
+	if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
+		/*
+		 * Prevent `pending' from catching up with `flushed' because of
+		 * overflow.  Reset `pending' and `flushed' to be 1 and 0 if
+		 * `pending' becomes large.
+		 */
+		nbatch = atomic_cmpxchg(&mm->tlb_flush_batched, batch, 1);
+		if (nbatch != batch) {
+			batch = nbatch;
+			goto retry;
+		}
+	} else {
+		atomic_inc(&mm->tlb_flush_batched);
+	}
+
+	/*
+	 * If the PTE was dirty then it's best to assume it's writable. The
+	 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
+	 * before the page is queued for IO.
+	 */
+	if (writable)
+		tlb_ubc->writable = true;
+}
+
+/*
+ * Returns true if the TLB flush should be deferred to the end of a batch of
+ * unmap operations to reduce IPIs.
+ */
+static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
+{
+	bool should_defer = false;
+
+	if (!(flags & TTU_BATCH_FLUSH))
+		return false;
+
+	/* If remote CPUs need to be flushed then defer batch the flush */
+	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
+		should_defer = true;
+	put_cpu();
+
+	return should_defer;
+}
+
+/*
+ * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
+ * releasing the PTL if TLB flushes are batched. It's possible for a parallel
+ * operation such as mprotect or munmap to race between reclaim unmapping
+ * the page and flushing the page. If this race occurs, it potentially allows
+ * access to data via a stale TLB entry. Tracking all mm's that have TLB
+ * batching in flight would be expensive during reclaim so instead track
+ * whether TLB batching occurred in the past and if so then do a flush here
+ * if required. This will cost one additional flush per reclaim cycle paid
+ * by the first operation at risk such as mprotect and mumap.
+ *
+ * This must be called under the PTL so that an access to tlb_flush_batched
+ * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
+ * via the PTL.
+ */
+void flush_tlb_batched_pending(struct mm_struct *mm)
+{
+	int batch = atomic_read(&mm->tlb_flush_batched);
+	int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
+	int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
+
+	if (pending != flushed) {
+		flush_tlb_mm(mm);
+		/*
+		 * If the new TLB flushing is pending during flushing, leave
+		 * mm->tlb_flush_batched as is, to avoid losing flushing.
+		 */
+		atomic_cmpxchg(&mm->tlb_flush_batched, batch,
+			       pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
+	}
+}
+#else
+static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
+{
+}
+
+static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
+{
+	return false;
+}
+#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
+
+/*
+ * 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)
+{
+	struct folio *folio = page_folio(page);
+	if (folio_test_anon(folio)) {
+		struct anon_vma *page__anon_vma = folio_anon_vma(folio);
+		/*
+		 * 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 (!vma->vm_file) {
+		return -EFAULT;
+	} else if (vma->vm_file->f_mapping != folio->mapping) {
+		return -EFAULT;
+	}
+
+	return vma_address(page, vma);
+}
+
+/*
+ * Returns the actual pmd_t* where we expect 'address' to be mapped from, or
+ * NULL if it doesn't exist.  No guarantees / checks on what the pmd_t*
+ * represents.
+ */
+pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd = NULL;
+
+	pgd = pgd_offset(mm, address);
+	if (!pgd_present(*pgd))
+		goto out;
+
+	p4d = p4d_offset(pgd, address);
+	if (!p4d_present(*p4d))
+		goto out;
+
+	pud = pud_offset(p4d, address);
+	if (!pud_present(*pud))
+		goto out;
+
+	pmd = pmd_offset(pud, address);
+out:
+	return pmd;
+}
+
+struct folio_referenced_arg {
+	int mapcount;
+	int referenced;
+	unsigned long vm_flags;
+	struct mem_cgroup *memcg;
+};
+/*
+ * arg: folio_referenced_arg will be passed
+ */
+static bool folio_referenced_one(struct folio *folio,
+		struct vm_area_struct *vma, unsigned long address, void *arg)
+{
+	struct folio_referenced_arg *pra = arg;
+	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
+	int referenced = 0;
+
+	while (page_vma_mapped_walk(&pvmw)) {
+		address = pvmw.address;
+
+		if ((vma->vm_flags & VM_LOCKED) &&
+		    (!folio_test_large(folio) || !pvmw.pte)) {
+			/* Restore the mlock which got missed */
+			mlock_vma_folio(folio, vma, !pvmw.pte);
+			page_vma_mapped_walk_done(&pvmw);
+			pra->vm_flags |= VM_LOCKED;
+			return false; /* To break the loop */
+		}
+
+		if (pvmw.pte) {
+			if (lru_gen_enabled() && pte_young(*pvmw.pte) &&
+			    !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))) {
+				lru_gen_look_around(&pvmw);
+				referenced++;
+			}
+
+			if (ptep_clear_flush_young_notify(vma, address,
+						pvmw.pte)) {
+				/*
+				 * Don't treat a reference through
+				 * a sequentially read mapping as such.
+				 * If the folio has been used in another mapping,
+				 * we will catch it; if this other mapping is
+				 * already gone, the unmap path will have set
+				 * the referenced flag or activated the folio.
+				 */
+				if (likely(!(vma->vm_flags & VM_SEQ_READ)))
+					referenced++;
+			}
+		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+			if (pmdp_clear_flush_young_notify(vma, address,
+						pvmw.pmd))
+				referenced++;
+		} else {
+			/* unexpected pmd-mapped folio? */
+			WARN_ON_ONCE(1);
+		}
+
+		pra->mapcount--;
+	}
+
+	if (referenced)
+		folio_clear_idle(folio);
+	if (folio_test_clear_young(folio))
+		referenced++;
+
+	if (referenced) {
+		pra->referenced++;
+		pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
+	}
+
+	if (!pra->mapcount)
+		return false; /* To break the loop */
+
+	return true;
+}
+
+static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
+{
+	struct folio_referenced_arg *pra = arg;
+	struct mem_cgroup *memcg = pra->memcg;
+
+	if (!mm_match_cgroup(vma->vm_mm, memcg))
+		return true;
+
+	return false;
+}
+
+/**
+ * folio_referenced() - Test if the folio was referenced.
+ * @folio: The folio to test.
+ * @is_locked: Caller holds lock on the folio.
+ * @memcg: target memory cgroup
+ * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
+ *
+ * Quick test_and_clear_referenced for all mappings of a folio,
+ *
+ * Return: The number of mappings which referenced the folio. Return -1 if
+ * the function bailed out due to rmap lock contention.
+ */
+int folio_referenced(struct folio *folio, int is_locked,
+		     struct mem_cgroup *memcg, unsigned long *vm_flags)
+{
+	int we_locked = 0;
+	struct folio_referenced_arg pra = {
+		.mapcount = folio_mapcount(folio),
+		.memcg = memcg,
+	};
+	struct rmap_walk_control rwc = {
+		.rmap_one = folio_referenced_one,
+		.arg = (void *)&pra,
+		.anon_lock = folio_lock_anon_vma_read,
+		.try_lock = true,
+	};
+
+	*vm_flags = 0;
+	if (!pra.mapcount)
+		return 0;
+
+	if (!folio_raw_mapping(folio))
+		return 0;
+
+	if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
+		we_locked = folio_trylock(folio);
+		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_folio_referenced_vma;
+	}
+
+	rmap_walk(folio, &rwc);
+	*vm_flags = pra.vm_flags;
+
+	if (we_locked)
+		folio_unlock(folio);
+
+	return rwc.contended ? -1 : pra.referenced;
+}
+
+static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
+{
+	int cleaned = 0;
+	struct vm_area_struct *vma = pvmw->vma;
+	struct mmu_notifier_range range;
+	unsigned long address = pvmw->address;
+
+	/*
+	 * We have to assume the worse case ie pmd for invalidation. Note that
+	 * the folio can not be freed from this function.
+	 */
+	mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE,
+				0, vma, vma->vm_mm, address,
+				vma_address_end(pvmw));
+	mmu_notifier_invalidate_range_start(&range);
+
+	while (page_vma_mapped_walk(pvmw)) {
+		int ret = 0;
+
+		address = pvmw->address;
+		if (pvmw->pte) {
+			pte_t entry;
+			pte_t *pte = pvmw->pte;
+
+			if (!pte_dirty(*pte) && !pte_write(*pte))
+				continue;
+
+			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(vma->vm_mm, address, pte, entry);
+			ret = 1;
+		} else {
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+			pmd_t *pmd = pvmw->pmd;
+			pmd_t entry;
+
+			if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
+				continue;
+
+			flush_cache_range(vma, address,
+					  address + HPAGE_PMD_SIZE);
+			entry = pmdp_invalidate(vma, address, pmd);
+			entry = pmd_wrprotect(entry);
+			entry = pmd_mkclean(entry);
+			set_pmd_at(vma->vm_mm, address, pmd, entry);
+			ret = 1;
+#else
+			/* unexpected pmd-mapped folio? */
+			WARN_ON_ONCE(1);
+#endif
+		}
+
+		/*
+		 * No need to call mmu_notifier_invalidate_range() as we are
+		 * downgrading page table protection not changing it to point
+		 * to a new page.
+		 *
+		 * See Documentation/mm/mmu_notifier.rst
+		 */
+		if (ret)
+			cleaned++;
+	}
+
+	mmu_notifier_invalidate_range_end(&range);
+
+	return cleaned;
+}
+
+static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
+			     unsigned long address, void *arg)
+{
+	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
+	int *cleaned = arg;
+
+	*cleaned += page_vma_mkclean_one(&pvmw);
+
+	return true;
+}
+
+static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
+{
+	if (vma->vm_flags & VM_SHARED)
+		return false;
+
+	return true;
+}
+
+int folio_mkclean(struct folio *folio)
+{
+	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(!folio_test_locked(folio));
+
+	if (!folio_mapped(folio))
+		return 0;
+
+	mapping = folio_mapping(folio);
+	if (!mapping)
+		return 0;
+
+	rmap_walk(folio, &rwc);
+
+	return cleaned;
+}
+EXPORT_SYMBOL_GPL(folio_mkclean);
+
+/**
+ * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
+ *                     [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
+ *                     within the @vma of shared mappings. And since clean PTEs
+ *                     should also be readonly, write protects them too.
+ * @pfn: start pfn.
+ * @nr_pages: number of physically contiguous pages srarting with @pfn.
+ * @pgoff: page offset that the @pfn mapped with.
+ * @vma: vma that @pfn mapped within.
+ *
+ * Returns the number of cleaned PTEs (including PMDs).
+ */
+int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
+		      struct vm_area_struct *vma)
+{
+	struct page_vma_mapped_walk pvmw = {
+		.pfn		= pfn,
+		.nr_pages	= nr_pages,
+		.pgoff		= pgoff,
+		.vma		= vma,
+		.flags		= PVMW_SYNC,
+	};
+
+	if (invalid_mkclean_vma(vma, NULL))
+		return 0;
+
+	pvmw.address = vma_pgoff_address(pgoff, nr_pages, vma);
+	VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
+
+	return page_vma_mkclean_one(&pvmw);
+}
+
+/**
+ * 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
+ *
+ * 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)
+{
+	void *anon_vma = vma->anon_vma;
+	struct folio *folio = page_folio(page);
+
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	VM_BUG_ON_VMA(!anon_vma, vma);
+
+	anon_vma += PAGE_MAPPING_ANON;
+	/*
+	 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
+	 * simultaneously, so a concurrent reader (eg folio_referenced()'s
+	 * folio_test_anon()) will not see one without the other.
+	 */
+	WRITE_ONCE(folio->mapping, anon_vma);
+	SetPageAnonExclusive(page);
+}
+
+/**
+ * __page_set_anon_rmap - set up new anonymous rmap
+ * @page:	Page or Hugepage 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))
+		goto out;
+
+	/*
+	 * 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;
+
+	/*
+	 * page_idle does a lockless/optimistic rmap scan on page->mapping.
+	 * Make sure the compiler doesn't split the stores of anon_vma and
+	 * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
+	 * could mistake the mapping for a struct address_space and crash.
+	 */
+	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+	WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
+	page->index = linear_page_index(vma, address);
+out:
+	if (exclusive)
+		SetPageAnonExclusive(page);
+}
+
+/**
+ * __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)
+{
+	struct folio *folio = page_folio(page);
+	/*
+	 * 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.
+	 *
+	 * 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.
+	 */
+	VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
+			folio);
+	VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
+		       page);
+}
+
+/**
+ * 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
+ * @flags:	the rmap flags
+ *
+ * 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, rmap_t flags)
+{
+	bool compound = flags & RMAP_COMPOUND;
+	bool first;
+
+	if (unlikely(PageKsm(page)))
+		lock_page_memcg(page);
+	else
+		VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+	if (compound) {
+		atomic_t *mapcount;
+		VM_BUG_ON_PAGE(!PageLocked(page), page);
+		VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+		mapcount = compound_mapcount_ptr(page);
+		first = atomic_inc_and_test(mapcount);
+	} else {
+		first = atomic_inc_and_test(&page->_mapcount);
+	}
+	VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
+	VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
+
+	if (first) {
+		int nr = compound ? thp_nr_pages(page) : 1;
+		/*
+		 * 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 (compound)
+			__mod_lruvec_page_state(page, NR_ANON_THPS, nr);
+		__mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
+	}
+
+	if (unlikely(PageKsm(page)))
+		unlock_page_memcg(page);
+
+	/* address might be in next vma when migration races vma_adjust */
+	else if (first)
+		__page_set_anon_rmap(page, vma, address,
+				     !!(flags & RMAP_EXCLUSIVE));
+	else
+		__page_check_anon_rmap(page, vma, address);
+
+	mlock_vma_page(page, vma, compound);
+}
+
+/**
+ * page_add_new_anon_rmap - add 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
+ *
+ * If it's a compound page, it is accounted as a compound page. As the page
+ * is new, it's assume to get mapped exclusively by a single process.
+ *
+ * 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)
+{
+	const bool compound = PageCompound(page);
+	int nr = compound ? thp_nr_pages(page) : 1;
+
+	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+	__SetPageSwapBacked(page);
+	if (compound) {
+		VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+		/* increment count (starts at -1) */
+		atomic_set(compound_mapcount_ptr(page), 0);
+		atomic_set(compound_pincount_ptr(page), 0);
+
+		__mod_lruvec_page_state(page, NR_ANON_THPS, nr);
+	} else {
+		/* increment count (starts at -1) */
+		atomic_set(&page->_mapcount, 0);
+	}
+	__mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
+	__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
+ * @vma:	the vm area in which the mapping is added
+ * @compound:	charge the page as compound or small page
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_add_file_rmap(struct page *page,
+	struct vm_area_struct *vma, bool compound)
+{
+	int i, nr = 0;
+
+	VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
+	lock_page_memcg(page);
+	if (compound && PageTransHuge(page)) {
+		int nr_pages = thp_nr_pages(page);
+
+		for (i = 0; i < nr_pages; i++) {
+			if (atomic_inc_and_test(&page[i]._mapcount))
+				nr++;
+		}
+		if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
+			goto out;
+
+		/*
+		 * It is racy to ClearPageDoubleMap in page_remove_file_rmap();
+		 * but page lock is held by all page_add_file_rmap() compound
+		 * callers, and SetPageDoubleMap below warns if !PageLocked:
+		 * so here is a place that DoubleMap can be safely cleared.
+		 */
+		VM_WARN_ON_ONCE(!PageLocked(page));
+		if (nr == nr_pages && PageDoubleMap(page))
+			ClearPageDoubleMap(page);
+
+		if (PageSwapBacked(page))
+			__mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED,
+						nr_pages);
+		else
+			__mod_lruvec_page_state(page, NR_FILE_PMDMAPPED,
+						nr_pages);
+	} else {
+		if (PageTransCompound(page) && page_mapping(page)) {
+			VM_WARN_ON_ONCE(!PageLocked(page));
+			SetPageDoubleMap(compound_head(page));
+		}
+		if (atomic_inc_and_test(&page->_mapcount))
+			nr++;
+	}
+out:
+	if (nr)
+		__mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
+	unlock_page_memcg(page);
+
+	mlock_vma_page(page, vma, compound);
+}
+
+static void page_remove_file_rmap(struct page *page, bool compound)
+{
+	int i, nr = 0;
+
+	VM_BUG_ON_PAGE(compound && !PageHead(page), page);
+
+	/* Hugepages are not counted in NR_FILE_MAPPED for now. */
+	if (unlikely(PageHuge(page))) {
+		/* hugetlb pages are always mapped with pmds */
+		atomic_dec(compound_mapcount_ptr(page));
+		return;
+	}
+
+	/* page still mapped by someone else? */
+	if (compound && PageTransHuge(page)) {
+		int nr_pages = thp_nr_pages(page);
+
+		for (i = 0; i < nr_pages; i++) {
+			if (atomic_add_negative(-1, &page[i]._mapcount))
+				nr++;
+		}
+		if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
+			goto out;
+		if (PageSwapBacked(page))
+			__mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED,
+						-nr_pages);
+		else
+			__mod_lruvec_page_state(page, NR_FILE_PMDMAPPED,
+						-nr_pages);
+	} else {
+		if (atomic_add_negative(-1, &page->_mapcount))
+			nr++;
+	}
+out:
+	if (nr)
+		__mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr);
+}
+
+static void page_remove_anon_compound_rmap(struct page *page)
+{
+	int i, nr;
+
+	if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
+		return;
+
+	/* Hugepages are not counted in NR_ANON_PAGES for now. */
+	if (unlikely(PageHuge(page)))
+		return;
+
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+		return;
+
+	__mod_lruvec_page_state(page, NR_ANON_THPS, -thp_nr_pages(page));
+
+	if (TestClearPageDoubleMap(page)) {
+		/*
+		 * Subpages can be mapped with PTEs too. Check how many of
+		 * them are still mapped.
+		 */
+		for (i = 0, nr = 0; i < thp_nr_pages(page); i++) {
+			if (atomic_add_negative(-1, &page[i]._mapcount))
+				nr++;
+		}
+
+		/*
+		 * Queue the page for deferred split if at least one small
+		 * page of the compound page is unmapped, but at least one
+		 * small page is still mapped.
+		 */
+		if (nr && nr < thp_nr_pages(page))
+			deferred_split_huge_page(page);
+	} else {
+		nr = thp_nr_pages(page);
+	}
+
+	if (nr)
+		__mod_lruvec_page_state(page, NR_ANON_MAPPED, -nr);
+}
+
+/**
+ * page_remove_rmap - take down pte mapping from a page
+ * @page:	page to remove mapping from
+ * @vma:	the vm area from which the mapping is removed
+ * @compound:	uncharge the page as compound or small page
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_remove_rmap(struct page *page,
+	struct vm_area_struct *vma, bool compound)
+{
+	lock_page_memcg(page);
+
+	if (!PageAnon(page)) {
+		page_remove_file_rmap(page, compound);
+		goto out;
+	}
+
+	if (compound) {
+		page_remove_anon_compound_rmap(page);
+		goto out;
+	}
+
+	/* page still mapped by someone else? */
+	if (!atomic_add_negative(-1, &page->_mapcount))
+		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_lruvec_page_state(page, NR_ANON_MAPPED);
+
+	if (PageTransCompound(page))
+		deferred_split_huge_page(compound_head(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_unref_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.
+	 */
+out:
+	unlock_page_memcg(page);
+
+	munlock_vma_page(page, vma, compound);
+}
+
+/*
+ * @arg: enum ttu_flags will be passed to this argument
+ */
+static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
+		     unsigned long address, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
+	pte_t pteval;
+	struct page *subpage;
+	bool anon_exclusive, ret = true;
+	struct mmu_notifier_range range;
+	enum ttu_flags flags = (enum ttu_flags)(long)arg;
+
+	/*
+	 * When racing against e.g. zap_pte_range() on another cpu,
+	 * in between its ptep_get_and_clear_full() and page_remove_rmap(),
+	 * try_to_unmap() may return before page_mapped() has become false,
+	 * if page table locking is skipped: use TTU_SYNC to wait for that.
+	 */
+	if (flags & TTU_SYNC)
+		pvmw.flags = PVMW_SYNC;
+
+	if (flags & TTU_SPLIT_HUGE_PMD)
+		split_huge_pmd_address(vma, address, false, folio);
+
+	/*
+	 * For THP, we have to assume the worse case ie pmd for invalidation.
+	 * For hugetlb, it could be much worse if we need to do pud
+	 * invalidation in the case of pmd sharing.
+	 *
+	 * Note that the folio can not be freed in this function as call of
+	 * try_to_unmap() must hold a reference on the folio.
+	 */
+	range.end = vma_address_end(&pvmw);
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
+				address, range.end);
+	if (folio_test_hugetlb(folio)) {
+		/*
+		 * If sharing is possible, start and end will be adjusted
+		 * accordingly.
+		 */
+		adjust_range_if_pmd_sharing_possible(vma, &range.start,
+						     &range.end);
+	}
+	mmu_notifier_invalidate_range_start(&range);
+
+	while (page_vma_mapped_walk(&pvmw)) {
+		/* Unexpected PMD-mapped THP? */
+		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
+
+		/*
+		 * If the folio is in an mlock()d vma, we must not swap it out.
+		 */
+		if (!(flags & TTU_IGNORE_MLOCK) &&
+		    (vma->vm_flags & VM_LOCKED)) {
+			/* Restore the mlock which got missed */
+			mlock_vma_folio(folio, vma, false);
+			page_vma_mapped_walk_done(&pvmw);
+			ret = false;
+			break;
+		}
+
+		subpage = folio_page(folio,
+					pte_pfn(*pvmw.pte) - folio_pfn(folio));
+		address = pvmw.address;
+		anon_exclusive = folio_test_anon(folio) &&
+				 PageAnonExclusive(subpage);
+
+		if (folio_test_hugetlb(folio)) {
+			bool anon = folio_test_anon(folio);
+
+			/*
+			 * The try_to_unmap() is only passed a hugetlb page
+			 * in the case where the hugetlb page is poisoned.
+			 */
+			VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
+			/*
+			 * huge_pmd_unshare may unmap an entire PMD page.
+			 * There is no way of knowing exactly which PMDs may
+			 * be cached for this mm, so we must flush them all.
+			 * start/end were already adjusted above to cover this
+			 * range.
+			 */
+			flush_cache_range(vma, range.start, range.end);
+
+			/*
+			 * To call huge_pmd_unshare, i_mmap_rwsem must be
+			 * held in write mode.  Caller needs to explicitly
+			 * do this outside rmap routines.
+			 *
+			 * We also must hold hugetlb vma_lock in write mode.
+			 * Lock order dictates acquiring vma_lock BEFORE
+			 * i_mmap_rwsem.  We can only try lock here and fail
+			 * if unsuccessful.
+			 */
+			if (!anon) {
+				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+				if (!hugetlb_vma_trylock_write(vma)) {
+					page_vma_mapped_walk_done(&pvmw);
+					ret = false;
+					break;
+				}
+				if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
+					hugetlb_vma_unlock_write(vma);
+					flush_tlb_range(vma,
+						range.start, range.end);
+					mmu_notifier_invalidate_range(mm,
+						range.start, range.end);
+					/*
+					 * The ref count of the PMD page was
+					 * dropped which is part of the way map
+					 * counting is done for shared PMDs.
+					 * Return 'true' here.  When there is
+					 * no other sharing, huge_pmd_unshare
+					 * returns false and we will unmap the
+					 * actual page and drop map count
+					 * to zero.
+					 */
+					page_vma_mapped_walk_done(&pvmw);
+					break;
+				}
+				hugetlb_vma_unlock_write(vma);
+			}
+			pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
+		} else {
+			flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+			/* Nuke the page table entry. */
+			if (should_defer_flush(mm, flags)) {
+				/*
+				 * We clear the PTE but do not flush so potentially
+				 * a remote CPU could still be writing to the folio.
+				 * If the entry was previously clean then the
+				 * architecture must guarantee that a clear->dirty
+				 * transition on a cached TLB entry is written through
+				 * and traps if the PTE is unmapped.
+				 */
+				pteval = ptep_get_and_clear(mm, address, pvmw.pte);
+
+				set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
+			} else {
+				pteval = ptep_clear_flush(vma, address, pvmw.pte);
+			}
+		}
+
+		/*
+		 * Now the pte is cleared. If this pte was uffd-wp armed,
+		 * we may want to replace a none pte with a marker pte if
+		 * it's file-backed, so we don't lose the tracking info.
+		 */
+		pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval);
+
+		/* Set the dirty flag on the folio now the pte is gone. */
+		if (pte_dirty(pteval))
+			folio_mark_dirty(folio);
+
+		/* Update high watermark before we lower rss */
+		update_hiwater_rss(mm);
+
+		if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
+			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
+			if (folio_test_hugetlb(folio)) {
+				hugetlb_count_sub(folio_nr_pages(folio), mm);
+				set_huge_pte_at(mm, address, pvmw.pte, pteval);
+			} else {
+				dec_mm_counter(mm, mm_counter(&folio->page));
+				set_pte_at(mm, address, pvmw.pte, pteval);
+			}
+
+		} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
+			/*
+			 * The guest indicated that the page content is of no
+			 * interest anymore. Simply discard the pte, vmscan
+			 * will take care of the rest.
+			 * A future reference will then fault in a new zero
+			 * page. When userfaultfd is active, we must not drop
+			 * this page though, as its main user (postcopy
+			 * migration) will not expect userfaults on already
+			 * copied pages.
+			 */
+			dec_mm_counter(mm, mm_counter(&folio->page));
+			/* We have to invalidate as we cleared the pte */
+			mmu_notifier_invalidate_range(mm, address,
+						      address + PAGE_SIZE);
+		} else if (folio_test_anon(folio)) {
+			swp_entry_t entry = { .val = page_private(subpage) };
+			pte_t swp_pte;
+			/*
+			 * Store the swap location in the pte.
+			 * See handle_pte_fault() ...
+			 */
+			if (unlikely(folio_test_swapbacked(folio) !=
+					folio_test_swapcache(folio))) {
+				WARN_ON_ONCE(1);
+				ret = false;
+				/* We have to invalidate as we cleared the pte */
+				mmu_notifier_invalidate_range(mm, address,
+							address + PAGE_SIZE);
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+
+			/* MADV_FREE page check */
+			if (!folio_test_swapbacked(folio)) {
+				int ref_count, map_count;
+
+				/*
+				 * Synchronize with gup_pte_range():
+				 * - clear PTE; barrier; read refcount
+				 * - inc refcount; barrier; read PTE
+				 */
+				smp_mb();
+
+				ref_count = folio_ref_count(folio);
+				map_count = folio_mapcount(folio);
+
+				/*
+				 * Order reads for page refcount and dirty flag
+				 * (see comments in __remove_mapping()).
+				 */
+				smp_rmb();
+
+				/*
+				 * The only page refs must be one from isolation
+				 * plus the rmap(s) (dropped by discard:).
+				 */
+				if (ref_count == 1 + map_count &&
+				    !folio_test_dirty(folio)) {
+					/* Invalidate as we cleared the pte */
+					mmu_notifier_invalidate_range(mm,
+						address, address + PAGE_SIZE);
+					dec_mm_counter(mm, MM_ANONPAGES);
+					goto discard;
+				}
+
+				/*
+				 * If the folio was redirtied, it cannot be
+				 * discarded. Remap the page to page table.
+				 */
+				set_pte_at(mm, address, pvmw.pte, pteval);
+				folio_set_swapbacked(folio);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+
+			if (swap_duplicate(entry) < 0) {
+				set_pte_at(mm, address, pvmw.pte, pteval);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
+				swap_free(entry);
+				set_pte_at(mm, address, pvmw.pte, pteval);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+
+			/* See page_try_share_anon_rmap(): clear PTE first. */
+			if (anon_exclusive &&
+			    page_try_share_anon_rmap(subpage)) {
+				swap_free(entry);
+				set_pte_at(mm, address, pvmw.pte, pteval);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+			/*
+			 * Note: We *don't* remember if the page was mapped
+			 * exclusively in the swap pte if the architecture
+			 * doesn't support __HAVE_ARCH_PTE_SWP_EXCLUSIVE. In
+			 * that case, swapin code has to re-determine that
+			 * manually and might detect the page as possibly
+			 * shared, for example, if there are other references on
+			 * the page or if the page is under writeback. We made
+			 * sure that there are no GUP pins on the page that
+			 * would rely on it, so for GUP pins this is fine.
+			 */
+			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);
+			swp_pte = swp_entry_to_pte(entry);
+			if (anon_exclusive)
+				swp_pte = pte_swp_mkexclusive(swp_pte);
+			if (pte_soft_dirty(pteval))
+				swp_pte = pte_swp_mksoft_dirty(swp_pte);
+			if (pte_uffd_wp(pteval))
+				swp_pte = pte_swp_mkuffd_wp(swp_pte);
+			set_pte_at(mm, address, pvmw.pte, swp_pte);
+			/* Invalidate as we cleared the pte */
+			mmu_notifier_invalidate_range(mm, address,
+						      address + PAGE_SIZE);
+		} else {
+			/*
+			 * This is a locked file-backed folio,
+			 * so it cannot be removed from the page
+			 * cache and replaced by a new folio before
+			 * mmu_notifier_invalidate_range_end, so no
+			 * concurrent thread might update its page table
+			 * to point at a new folio while a device is
+			 * still using this folio.
+			 *
+			 * See Documentation/mm/mmu_notifier.rst
+			 */
+			dec_mm_counter(mm, mm_counter_file(&folio->page));
+		}
+discard:
+		/*
+		 * No need to call mmu_notifier_invalidate_range() it has be
+		 * done above for all cases requiring it to happen under page
+		 * table lock before mmu_notifier_invalidate_range_end()
+		 *
+		 * See Documentation/mm/mmu_notifier.rst
+		 */
+		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
+		if (vma->vm_flags & VM_LOCKED)
+			mlock_page_drain_local();
+		folio_put(folio);
+	}
+
+	mmu_notifier_invalidate_range_end(&range);
+
+	return ret;
+}
+
+static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
+{
+	return vma_is_temporary_stack(vma);
+}
+
+static int page_not_mapped(struct folio *folio)
+{
+	return !folio_mapped(folio);
+}
+
+/**
+ * try_to_unmap - Try to remove all page table mappings to a folio.
+ * @folio: The folio to unmap.
+ * @flags: action and flags
+ *
+ * Tries to remove all the page table entries which are mapping this
+ * folio.  It is the caller's responsibility to check if the folio is
+ * still mapped if needed (use TTU_SYNC to prevent accounting races).
+ *
+ * Context: Caller must hold the folio lock.
+ */
+void try_to_unmap(struct folio *folio, enum ttu_flags flags)
+{
+	struct rmap_walk_control rwc = {
+		.rmap_one = try_to_unmap_one,
+		.arg = (void *)flags,
+		.done = page_not_mapped,
+		.anon_lock = folio_lock_anon_vma_read,
+	};
+
+	if (flags & TTU_RMAP_LOCKED)
+		rmap_walk_locked(folio, &rwc);
+	else
+		rmap_walk(folio, &rwc);
+}
+
+/*
+ * @arg: enum ttu_flags will be passed to this argument.
+ *
+ * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
+ * containing migration entries.
+ */
+static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
+		     unsigned long address, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
+	pte_t pteval;
+	struct page *subpage;
+	bool anon_exclusive, ret = true;
+	struct mmu_notifier_range range;
+	enum ttu_flags flags = (enum ttu_flags)(long)arg;
+
+	/*
+	 * When racing against e.g. zap_pte_range() on another cpu,
+	 * in between its ptep_get_and_clear_full() and page_remove_rmap(),
+	 * try_to_migrate() may return before page_mapped() has become false,
+	 * if page table locking is skipped: use TTU_SYNC to wait for that.
+	 */
+	if (flags & TTU_SYNC)
+		pvmw.flags = PVMW_SYNC;
+
+	/*
+	 * unmap_page() in mm/huge_memory.c is the only user of migration with
+	 * TTU_SPLIT_HUGE_PMD and it wants to freeze.
+	 */
+	if (flags & TTU_SPLIT_HUGE_PMD)
+		split_huge_pmd_address(vma, address, true, folio);
+
+	/*
+	 * For THP, we have to assume the worse case ie pmd for invalidation.
+	 * For hugetlb, it could be much worse if we need to do pud
+	 * invalidation in the case of pmd sharing.
+	 *
+	 * Note that the page can not be free in this function as call of
+	 * try_to_unmap() must hold a reference on the page.
+	 */
+	range.end = vma_address_end(&pvmw);
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
+				address, range.end);
+	if (folio_test_hugetlb(folio)) {
+		/*
+		 * If sharing is possible, start and end will be adjusted
+		 * accordingly.
+		 */
+		adjust_range_if_pmd_sharing_possible(vma, &range.start,
+						     &range.end);
+	}
+	mmu_notifier_invalidate_range_start(&range);
+
+	while (page_vma_mapped_walk(&pvmw)) {
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+		/* PMD-mapped THP migration entry */
+		if (!pvmw.pte) {
+			subpage = folio_page(folio,
+				pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
+			VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
+					!folio_test_pmd_mappable(folio), folio);
+
+			if (set_pmd_migration_entry(&pvmw, subpage)) {
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+			continue;
+		}
+#endif
+
+		/* Unexpected PMD-mapped THP? */
+		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
+
+		if (folio_is_zone_device(folio)) {
+			/*
+			 * Our PTE is a non-present device exclusive entry and
+			 * calculating the subpage as for the common case would
+			 * result in an invalid pointer.
+			 *
+			 * Since only PAGE_SIZE pages can currently be
+			 * migrated, just set it to page. This will need to be
+			 * changed when hugepage migrations to device private
+			 * memory are supported.
+			 */
+			VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
+			subpage = &folio->page;
+		} else {
+			subpage = folio_page(folio,
+					pte_pfn(*pvmw.pte) - folio_pfn(folio));
+		}
+		address = pvmw.address;
+		anon_exclusive = folio_test_anon(folio) &&
+				 PageAnonExclusive(subpage);
+
+		if (folio_test_hugetlb(folio)) {
+			bool anon = folio_test_anon(folio);
+
+			/*
+			 * huge_pmd_unshare may unmap an entire PMD page.
+			 * There is no way of knowing exactly which PMDs may
+			 * be cached for this mm, so we must flush them all.
+			 * start/end were already adjusted above to cover this
+			 * range.
+			 */
+			flush_cache_range(vma, range.start, range.end);
+
+			/*
+			 * To call huge_pmd_unshare, i_mmap_rwsem must be
+			 * held in write mode.  Caller needs to explicitly
+			 * do this outside rmap routines.
+			 *
+			 * We also must hold hugetlb vma_lock in write mode.
+			 * Lock order dictates acquiring vma_lock BEFORE
+			 * i_mmap_rwsem.  We can only try lock here and
+			 * fail if unsuccessful.
+			 */
+			if (!anon) {
+				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+				if (!hugetlb_vma_trylock_write(vma)) {
+					page_vma_mapped_walk_done(&pvmw);
+					ret = false;
+					break;
+				}
+				if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
+					hugetlb_vma_unlock_write(vma);
+					flush_tlb_range(vma,
+						range.start, range.end);
+					mmu_notifier_invalidate_range(mm,
+						range.start, range.end);
+
+					/*
+					 * The ref count of the PMD page was
+					 * dropped which is part of the way map
+					 * counting is done for shared PMDs.
+					 * Return 'true' here.  When there is
+					 * no other sharing, huge_pmd_unshare
+					 * returns false and we will unmap the
+					 * actual page and drop map count
+					 * to zero.
+					 */
+					page_vma_mapped_walk_done(&pvmw);
+					break;
+				}
+				hugetlb_vma_unlock_write(vma);
+			}
+			/* Nuke the hugetlb page table entry */
+			pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
+		} else {
+			flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+			/* Nuke the page table entry. */
+			pteval = ptep_clear_flush(vma, address, pvmw.pte);
+		}
+
+		/* Set the dirty flag on the folio now the pte is gone. */
+		if (pte_dirty(pteval))
+			folio_mark_dirty(folio);
+
+		/* Update high watermark before we lower rss */
+		update_hiwater_rss(mm);
+
+		if (folio_is_device_private(folio)) {
+			unsigned long pfn = folio_pfn(folio);
+			swp_entry_t entry;
+			pte_t swp_pte;
+
+			if (anon_exclusive)
+				BUG_ON(page_try_share_anon_rmap(subpage));
+
+			/*
+			 * 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.
+			 */
+			entry = pte_to_swp_entry(pteval);
+			if (is_writable_device_private_entry(entry))
+				entry = make_writable_migration_entry(pfn);
+			else if (anon_exclusive)
+				entry = make_readable_exclusive_migration_entry(pfn);
+			else
+				entry = make_readable_migration_entry(pfn);
+			swp_pte = swp_entry_to_pte(entry);
+
+			/*
+			 * pteval maps a zone device page and is therefore
+			 * a swap pte.
+			 */
+			if (pte_swp_soft_dirty(pteval))
+				swp_pte = pte_swp_mksoft_dirty(swp_pte);
+			if (pte_swp_uffd_wp(pteval))
+				swp_pte = pte_swp_mkuffd_wp(swp_pte);
+			set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
+			trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
+						compound_order(&folio->page));
+			/*
+			 * No need to invalidate here it will synchronize on
+			 * against the special swap migration pte.
+			 */
+		} else if (PageHWPoison(subpage)) {
+			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
+			if (folio_test_hugetlb(folio)) {
+				hugetlb_count_sub(folio_nr_pages(folio), mm);
+				set_huge_pte_at(mm, address, pvmw.pte, pteval);
+			} else {
+				dec_mm_counter(mm, mm_counter(&folio->page));
+				set_pte_at(mm, address, pvmw.pte, pteval);
+			}
+
+		} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
+			/*
+			 * The guest indicated that the page content is of no
+			 * interest anymore. Simply discard the pte, vmscan
+			 * will take care of the rest.
+			 * A future reference will then fault in a new zero
+			 * page. When userfaultfd is active, we must not drop
+			 * this page though, as its main user (postcopy
+			 * migration) will not expect userfaults on already
+			 * copied pages.
+			 */
+			dec_mm_counter(mm, mm_counter(&folio->page));
+			/* We have to invalidate as we cleared the pte */
+			mmu_notifier_invalidate_range(mm, address,
+						      address + PAGE_SIZE);
+		} else {
+			swp_entry_t entry;
+			pte_t swp_pte;
+
+			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
+				if (folio_test_hugetlb(folio))
+					set_huge_pte_at(mm, address, pvmw.pte, pteval);
+				else
+					set_pte_at(mm, address, pvmw.pte, pteval);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+			VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
+				       !anon_exclusive, subpage);
+
+			/* See page_try_share_anon_rmap(): clear PTE first. */
+			if (anon_exclusive &&
+			    page_try_share_anon_rmap(subpage)) {
+				if (folio_test_hugetlb(folio))
+					set_huge_pte_at(mm, address, pvmw.pte, pteval);
+				else
+					set_pte_at(mm, address, pvmw.pte, pteval);
+				ret = false;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+
+			/*
+			 * 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.
+			 */
+			if (pte_write(pteval))
+				entry = make_writable_migration_entry(
+							page_to_pfn(subpage));
+			else if (anon_exclusive)
+				entry = make_readable_exclusive_migration_entry(
+							page_to_pfn(subpage));
+			else
+				entry = make_readable_migration_entry(
+							page_to_pfn(subpage));
+			if (pte_young(pteval))
+				entry = make_migration_entry_young(entry);
+			if (pte_dirty(pteval))
+				entry = make_migration_entry_dirty(entry);
+			swp_pte = swp_entry_to_pte(entry);
+			if (pte_soft_dirty(pteval))
+				swp_pte = pte_swp_mksoft_dirty(swp_pte);
+			if (pte_uffd_wp(pteval))
+				swp_pte = pte_swp_mkuffd_wp(swp_pte);
+			if (folio_test_hugetlb(folio))
+				set_huge_pte_at(mm, address, pvmw.pte, swp_pte);
+			else
+				set_pte_at(mm, address, pvmw.pte, swp_pte);
+			trace_set_migration_pte(address, pte_val(swp_pte),
+						compound_order(&folio->page));
+			/*
+			 * No need to invalidate here it will synchronize on
+			 * against the special swap migration pte.
+			 */
+		}
+
+		/*
+		 * No need to call mmu_notifier_invalidate_range() it has be
+		 * done above for all cases requiring it to happen under page
+		 * table lock before mmu_notifier_invalidate_range_end()
+		 *
+		 * See Documentation/mm/mmu_notifier.rst
+		 */
+		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
+		if (vma->vm_flags & VM_LOCKED)
+			mlock_page_drain_local();
+		folio_put(folio);
+	}
+
+	mmu_notifier_invalidate_range_end(&range);
+
+	return ret;
+}
+
+/**
+ * try_to_migrate - try to replace all page table mappings with swap entries
+ * @folio: the folio to replace page table entries for
+ * @flags: action and flags
+ *
+ * Tries to remove all the page table entries which are mapping this folio and
+ * replace them with special swap entries. Caller must hold the folio lock.
+ */
+void try_to_migrate(struct folio *folio, enum ttu_flags flags)
+{
+	struct rmap_walk_control rwc = {
+		.rmap_one = try_to_migrate_one,
+		.arg = (void *)flags,
+		.done = page_not_mapped,
+		.anon_lock = folio_lock_anon_vma_read,
+	};
+
+	/*
+	 * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
+	 * TTU_SPLIT_HUGE_PMD and TTU_SYNC flags.
+	 */
+	if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
+					TTU_SYNC)))
+		return;
+
+	if (folio_is_zone_device(folio) &&
+	    (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
+		return;
+
+	/*
+	 * 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 (!folio_test_ksm(folio) && folio_test_anon(folio))
+		rwc.invalid_vma = invalid_migration_vma;
+
+	if (flags & TTU_RMAP_LOCKED)
+		rmap_walk_locked(folio, &rwc);
+	else
+		rmap_walk(folio, &rwc);
+}
+
+#ifdef CONFIG_DEVICE_PRIVATE
+struct make_exclusive_args {
+	struct mm_struct *mm;
+	unsigned long address;
+	void *owner;
+	bool valid;
+};
+
+static bool page_make_device_exclusive_one(struct folio *folio,
+		struct vm_area_struct *vma, unsigned long address, void *priv)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
+	struct make_exclusive_args *args = priv;
+	pte_t pteval;
+	struct page *subpage;
+	bool ret = true;
+	struct mmu_notifier_range range;
+	swp_entry_t entry;
+	pte_t swp_pte;
+
+	mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma,
+				      vma->vm_mm, address, min(vma->vm_end,
+				      address + folio_size(folio)),
+				      args->owner);
+	mmu_notifier_invalidate_range_start(&range);
+
+	while (page_vma_mapped_walk(&pvmw)) {
+		/* Unexpected PMD-mapped THP? */
+		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
+
+		if (!pte_present(*pvmw.pte)) {
+			ret = false;
+			page_vma_mapped_walk_done(&pvmw);
+			break;
+		}
+
+		subpage = folio_page(folio,
+				pte_pfn(*pvmw.pte) - folio_pfn(folio));
+		address = pvmw.address;
+
+		/* Nuke the page table entry. */
+		flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+		pteval = ptep_clear_flush(vma, address, pvmw.pte);
+
+		/* Set the dirty flag on the folio now the pte is gone. */
+		if (pte_dirty(pteval))
+			folio_mark_dirty(folio);
+
+		/*
+		 * Check that our target page is still mapped at the expected
+		 * address.
+		 */
+		if (args->mm == mm && args->address == address &&
+		    pte_write(pteval))
+			args->valid = true;
+
+		/*
+		 * 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.
+		 */
+		if (pte_write(pteval))
+			entry = make_writable_device_exclusive_entry(
+							page_to_pfn(subpage));
+		else
+			entry = make_readable_device_exclusive_entry(
+							page_to_pfn(subpage));
+		swp_pte = swp_entry_to_pte(entry);
+		if (pte_soft_dirty(pteval))
+			swp_pte = pte_swp_mksoft_dirty(swp_pte);
+		if (pte_uffd_wp(pteval))
+			swp_pte = pte_swp_mkuffd_wp(swp_pte);
+
+		set_pte_at(mm, address, pvmw.pte, swp_pte);
+
+		/*
+		 * There is a reference on the page for the swap entry which has
+		 * been removed, so shouldn't take another.
+		 */
+		page_remove_rmap(subpage, vma, false);
+	}
+
+	mmu_notifier_invalidate_range_end(&range);
+
+	return ret;
+}
+
+/**
+ * folio_make_device_exclusive - Mark the folio exclusively owned by a device.
+ * @folio: The folio to replace page table entries for.
+ * @mm: The mm_struct where the folio is expected to be mapped.
+ * @address: Address where the folio is expected to be mapped.
+ * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
+ *
+ * Tries to remove all the page table entries which are mapping this
+ * folio and replace them with special device exclusive swap entries to
+ * grant a device exclusive access to the folio.
+ *
+ * Context: Caller must hold the folio lock.
+ * Return: false if the page is still mapped, or if it could not be unmapped
+ * from the expected address. Otherwise returns true (success).
+ */
+static bool folio_make_device_exclusive(struct folio *folio,
+		struct mm_struct *mm, unsigned long address, void *owner)
+{
+	struct make_exclusive_args args = {
+		.mm = mm,
+		.address = address,
+		.owner = owner,
+		.valid = false,
+	};
+	struct rmap_walk_control rwc = {
+		.rmap_one = page_make_device_exclusive_one,
+		.done = page_not_mapped,
+		.anon_lock = folio_lock_anon_vma_read,
+		.arg = &args,
+	};
+
+	/*
+	 * Restrict to anonymous folios for now to avoid potential writeback
+	 * issues.
+	 */
+	if (!folio_test_anon(folio))
+		return false;
+
+	rmap_walk(folio, &rwc);
+
+	return args.valid && !folio_mapcount(folio);
+}
+
+/**
+ * make_device_exclusive_range() - Mark a range for exclusive use by a device
+ * @mm: mm_struct of associated target process
+ * @start: start of the region to mark for exclusive device access
+ * @end: end address of region
+ * @pages: returns the pages which were successfully marked for exclusive access
+ * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
+ *
+ * Returns: number of pages found in the range by GUP. A page is marked for
+ * exclusive access only if the page pointer is non-NULL.
+ *
+ * This function finds ptes mapping page(s) to the given address range, locks
+ * them and replaces mappings with special swap entries preventing userspace CPU
+ * access. On fault these entries are replaced with the original mapping after
+ * calling MMU notifiers.
+ *
+ * A driver using this to program access from a device must use a mmu notifier
+ * critical section to hold a device specific lock during programming. Once
+ * programming is complete it should drop the page lock and reference after
+ * which point CPU access to the page will revoke the exclusive access.
+ */
+int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
+				unsigned long end, struct page **pages,
+				void *owner)
+{
+	long npages = (end - start) >> PAGE_SHIFT;
+	long i;
+
+	npages = get_user_pages_remote(mm, start, npages,
+				       FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
+				       pages, NULL, NULL);
+	if (npages < 0)
+		return npages;
+
+	for (i = 0; i < npages; i++, start += PAGE_SIZE) {
+		struct folio *folio = page_folio(pages[i]);
+		if (PageTail(pages[i]) || !folio_trylock(folio)) {
+			folio_put(folio);
+			pages[i] = NULL;
+			continue;
+		}
+
+		if (!folio_make_device_exclusive(folio, mm, start, owner)) {
+			folio_unlock(folio);
+			folio_put(folio);
+			pages[i] = NULL;
+		}
+	}
+
+	return npages;
+}
+EXPORT_SYMBOL_GPL(make_device_exclusive_range);
+#endif
+
+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 folio *folio,
+					    struct rmap_walk_control *rwc)
+{
+	struct anon_vma *anon_vma;
+
+	if (rwc->anon_lock)
+		return rwc->anon_lock(folio, rwc);
+
+	/*
+	 * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
+	 * because that depends on page_mapped(); but not all its usages
+	 * are holding mmap_lock. Users without mmap_lock are required to
+	 * take a reference count to prevent the anon_vma disappearing
+	 */
+	anon_vma = folio_anon_vma(folio);
+	if (!anon_vma)
+		return NULL;
+
+	if (anon_vma_trylock_read(anon_vma))
+		goto out;
+
+	if (rwc->try_lock) {
+		anon_vma = NULL;
+		rwc->contended = true;
+		goto out;
+	}
+
+	anon_vma_lock_read(anon_vma);
+out:
+	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.
+ */
+static void rmap_walk_anon(struct folio *folio,
+		struct rmap_walk_control *rwc, bool locked)
+{
+	struct anon_vma *anon_vma;
+	pgoff_t pgoff_start, pgoff_end;
+	struct anon_vma_chain *avc;
+
+	if (locked) {
+		anon_vma = folio_anon_vma(folio);
+		/* anon_vma disappear under us? */
+		VM_BUG_ON_FOLIO(!anon_vma, folio);
+	} else {
+		anon_vma = rmap_walk_anon_lock(folio, rwc);
+	}
+	if (!anon_vma)
+		return;
+
+	pgoff_start = folio_pgoff(folio);
+	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
+	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
+			pgoff_start, pgoff_end) {
+		struct vm_area_struct *vma = avc->vma;
+		unsigned long address = vma_address(&folio->page, vma);
+
+		VM_BUG_ON_VMA(address == -EFAULT, vma);
+		cond_resched();
+
+		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+			continue;
+
+		if (!rwc->rmap_one(folio, vma, address, rwc->arg))
+			break;
+		if (rwc->done && rwc->done(folio))
+			break;
+	}
+
+	if (!locked)
+		anon_vma_unlock_read(anon_vma);
+}
+
+/*
+ * 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.
+ */
+static void rmap_walk_file(struct folio *folio,
+		struct rmap_walk_control *rwc, bool locked)
+{
+	struct address_space *mapping = folio_mapping(folio);
+	pgoff_t pgoff_start, pgoff_end;
+	struct vm_area_struct *vma;
+
+	/*
+	 * 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_FOLIO(!folio_test_locked(folio), folio);
+
+	if (!mapping)
+		return;
+
+	pgoff_start = folio_pgoff(folio);
+	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
+	if (!locked) {
+		if (i_mmap_trylock_read(mapping))
+			goto lookup;
+
+		if (rwc->try_lock) {
+			rwc->contended = true;
+			return;
+		}
+
+		i_mmap_lock_read(mapping);
+	}
+lookup:
+	vma_interval_tree_foreach(vma, &mapping->i_mmap,
+			pgoff_start, pgoff_end) {
+		unsigned long address = vma_address(&folio->page, vma);
+
+		VM_BUG_ON_VMA(address == -EFAULT, vma);
+		cond_resched();
+
+		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+			continue;
+
+		if (!rwc->rmap_one(folio, vma, address, rwc->arg))
+			goto done;
+		if (rwc->done && rwc->done(folio))
+			goto done;
+	}
+
+done:
+	if (!locked)
+		i_mmap_unlock_read(mapping);
+}
+
+void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
+{
+	if (unlikely(folio_test_ksm(folio)))
+		rmap_walk_ksm(folio, rwc);
+	else if (folio_test_anon(folio))
+		rmap_walk_anon(folio, rwc, false);
+	else
+		rmap_walk_file(folio, rwc, false);
+}
+
+/* Like rmap_walk, but caller holds relevant rmap lock */
+void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
+{
+	/* no ksm support for now */
+	VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
+	if (folio_test_anon(folio))
+		rmap_walk_anon(folio, rwc, true);
+	else
+		rmap_walk_file(folio, rwc, true);
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+/*
+ * The following two 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.
+ *
+ * RMAP_COMPOUND is ignored.
+ */
+void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
+			    unsigned long address, rmap_t flags)
+{
+	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(compound_mapcount_ptr(page));
+	VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
+	VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
+	if (first)
+		__page_set_anon_rmap(page, vma, address,
+				     !!(flags & RMAP_EXCLUSIVE));
+}
+
+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(compound_mapcount_ptr(page), 0);
+	atomic_set(compound_pincount_ptr(page), 0);
+
+	__page_set_anon_rmap(page, vma, address, 1);
+}
+#endif /* CONFIG_HUGETLB_PAGE */