v4.19.13 snapshot.
diff --git a/mm/rmap.c b/mm/rmap.c
new file mode 100644
index 0000000..85b7f94
--- /dev/null
+++ b/mm/rmap.c
@@ -0,0 +1,1955 @@
+/*
+ * 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)
+ * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
+ * 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)
+ * mem_cgroup_{begin,end}_page_stat (memcg->move_lock)
+ * i_pages lock (widely used)
+ * 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_mutex (memory_failure, collect_procs_anon)
+ * ->tasklist_lock
+ * pte map lock
+ */
+
+#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/backing-dev.h>
+#include <linux/page_idle.h>
+#include <linux/memremap.h>
+#include <linux/userfaultfd_k.h>
+
+#include <asm/tlbflush.h>
+
+#include <trace/events/tlb.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, 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 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 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;
+ 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.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;
+
+ VM_WARN_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_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 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_TYPESAFE_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);
+}
+
+#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 = ¤t->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 = ¤t->tlb_ubc;
+
+ if (tlb_ubc->writable)
+ try_to_unmap_flush();
+}
+
+static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
+{
+ struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
+
+ 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();
+ mm->tlb_flush_batched = true;
+
+ /*
+ * 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)
+{
+ if (mm->tlb_flush_batched) {
+ flush_tlb_mm(mm);
+
+ /*
+ * Do not allow the compiler to re-order the clearing of
+ * tlb_flush_batched before the tlb is flushed.
+ */
+ barrier();
+ mm->tlb_flush_batched = false;
+ }
+}
+#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)
+{
+ 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;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd = NULL;
+ pmd_t pmde;
+
+ 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);
+ /*
+ * Some THP functions use the sequence pmdp_huge_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;
+}
+
+struct page_referenced_arg {
+ int mapcount;
+ int referenced;
+ unsigned long vm_flags;
+ struct mem_cgroup *memcg;
+};
+/*
+ * arg: page_referenced_arg will be passed
+ */
+static bool page_referenced_one(struct page *page, struct vm_area_struct *vma,
+ unsigned long address, void *arg)
+{
+ struct page_referenced_arg *pra = arg;
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ .address = address,
+ };
+ int referenced = 0;
+
+ while (page_vma_mapped_walk(&pvmw)) {
+ address = pvmw.address;
+
+ if (vma->vm_flags & VM_LOCKED) {
+ page_vma_mapped_walk_done(&pvmw);
+ pra->vm_flags |= VM_LOCKED;
+ return false; /* To break the loop */
+ }
+
+ if (pvmw.pte) {
+ if (ptep_clear_flush_young_notify(vma, address,
+ pvmw.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++;
+ }
+ } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+ if (pmdp_clear_flush_young_notify(vma, address,
+ pvmw.pmd))
+ referenced++;
+ } else {
+ /* unexpected pmd-mapped page? */
+ WARN_ON_ONCE(1);
+ }
+
+ pra->mapcount--;
+ }
+
+ if (referenced)
+ clear_page_idle(page);
+ if (test_and_clear_page_young(page))
+ referenced++;
+
+ if (referenced) {
+ pra->referenced++;
+ pra->vm_flags |= vma->vm_flags;
+ }
+
+ if (!pra->mapcount)
+ return false; /* To break the loop */
+
+ return true;
+}
+
+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 we_locked = 0;
+ struct page_referenced_arg pra = {
+ .mapcount = total_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;
+ }
+
+ rmap_walk(page, &rwc);
+ *vm_flags = pra.vm_flags;
+
+ if (we_locked)
+ unlock_page(page);
+
+ return pra.referenced;
+}
+
+static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
+ unsigned long address, void *arg)
+{
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ .address = address,
+ .flags = PVMW_SYNC,
+ };
+ unsigned long start = address, end;
+ int *cleaned = arg;
+
+ /*
+ * We have to assume the worse case ie pmd for invalidation. Note that
+ * the page can not be free from this function.
+ */
+ end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
+ mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
+
+ while (page_vma_mapped_walk(&pvmw)) {
+ unsigned long cstart;
+ int ret = 0;
+
+ cstart = 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_HUGE_PAGECACHE
+ pmd_t *pmd = pvmw.pmd;
+ pmd_t entry;
+
+ if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
+ continue;
+
+ flush_cache_page(vma, address, page_to_pfn(page));
+ entry = pmdp_huge_clear_flush(vma, address, pmd);
+ entry = pmd_wrprotect(entry);
+ entry = pmd_mkclean(entry);
+ set_pmd_at(vma->vm_mm, address, pmd, entry);
+ cstart &= PMD_MASK;
+ ret = 1;
+#else
+ /* unexpected pmd-mapped page? */
+ 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/vm/mmu_notifier.rst
+ */
+ if (ret)
+ (*cleaned)++;
+ }
+
+ mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
+
+ 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 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
+ *
+ * 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)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+
+ page = compound_head(page);
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_VMA(!anon_vma, vma);
+
+ anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+ /*
+ * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
+ * simultaneously, so a concurrent reader (eg page_referenced()'s
+ * PageAnon()) will not see one without the other.
+ */
+ WRITE_ONCE(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_to_pgoff(page) != 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
+ * @compound: charge the page as compound or small page
+ *
+ * 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, bool compound)
+{
+ do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 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 flags)
+{
+ bool compound = flags & RMAP_COMPOUND;
+ bool first;
+
+ 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);
+ }
+
+ if (first) {
+ int nr = compound ? hpage_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)
+ __inc_node_page_state(page, NR_ANON_THPS);
+ __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
+ }
+ 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,
+ flags & RMAP_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
+ * @compound: charge the page as compound or small page
+ *
+ * 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, bool compound)
+{
+ int nr = compound ? hpage_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);
+ __inc_node_page_state(page, NR_ANON_THPS);
+ } else {
+ /* Anon THP always mapped first with PMD */
+ VM_BUG_ON_PAGE(PageTransCompound(page), page);
+ /* increment count (starts at -1) */
+ atomic_set(&page->_mapcount, 0);
+ }
+ __mod_node_page_state(page_pgdat(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
+ * @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, bool compound)
+{
+ int i, nr = 1;
+
+ VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
+ lock_page_memcg(page);
+ if (compound && PageTransHuge(page)) {
+ for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
+ if (atomic_inc_and_test(&page[i]._mapcount))
+ nr++;
+ }
+ if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
+ goto out;
+ VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+ __inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
+ } else {
+ if (PageTransCompound(page) && page_mapping(page)) {
+ VM_WARN_ON_ONCE(!PageLocked(page));
+
+ SetPageDoubleMap(compound_head(page));
+ if (PageMlocked(page))
+ clear_page_mlock(compound_head(page));
+ }
+ if (!atomic_inc_and_test(&page->_mapcount))
+ goto out;
+ }
+ __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
+out:
+ unlock_page_memcg(page);
+}
+
+static void page_remove_file_rmap(struct page *page, bool compound)
+{
+ int i, nr = 1;
+
+ VM_BUG_ON_PAGE(compound && !PageHead(page), page);
+ lock_page_memcg(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));
+ goto out;
+ }
+
+ /* page still mapped by someone else? */
+ if (compound && PageTransHuge(page)) {
+ for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
+ if (atomic_add_negative(-1, &page[i]._mapcount))
+ nr++;
+ }
+ if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
+ goto out;
+ VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+ __dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
+ } else {
+ if (!atomic_add_negative(-1, &page->_mapcount))
+ goto out;
+ }
+
+ /*
+ * We use the irq-unsafe __{inc|mod}_lruvec_page_state because
+ * these counters are not modified in interrupt context, and
+ * pte lock(a spinlock) is held, which implies preemption disabled.
+ */
+ __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr);
+
+ if (unlikely(PageMlocked(page)))
+ clear_page_mlock(page);
+out:
+ unlock_page_memcg(page);
+}
+
+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;
+
+ __dec_node_page_state(page, NR_ANON_THPS);
+
+ if (TestClearPageDoubleMap(page)) {
+ /*
+ * Subpages can be mapped with PTEs too. Check how many of
+ * themi are still mapped.
+ */
+ for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
+ if (atomic_add_negative(-1, &page[i]._mapcount))
+ nr++;
+ }
+ } else {
+ nr = HPAGE_PMD_NR;
+ }
+
+ if (unlikely(PageMlocked(page)))
+ clear_page_mlock(page);
+
+ if (nr) {
+ __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
+ deferred_split_huge_page(page);
+ }
+}
+
+/**
+ * page_remove_rmap - take down pte mapping from a page
+ * @page: page to remove mapping from
+ * @compound: uncharge the page as compound or small page
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_remove_rmap(struct page *page, bool compound)
+{
+ if (!PageAnon(page))
+ return page_remove_file_rmap(page, compound);
+
+ if (compound)
+ return page_remove_anon_compound_rmap(page);
+
+ /* page still mapped by someone else? */
+ if (!atomic_add_negative(-1, &page->_mapcount))
+ 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.
+ */
+ __dec_node_page_state(page, NR_ANON_MAPPED);
+
+ if (unlikely(PageMlocked(page)))
+ clear_page_mlock(page);
+
+ 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.
+ */
+}
+
+/*
+ * @arg: enum ttu_flags will be passed to this argument
+ */
+static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
+ unsigned long address, void *arg)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ .address = address,
+ };
+ pte_t pteval;
+ struct page *subpage;
+ bool ret = true;
+ unsigned long start = address, end;
+ enum ttu_flags flags = (enum ttu_flags)arg;
+
+ /* munlock has nothing to gain from examining un-locked vmas */
+ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
+ return true;
+
+ if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
+ is_zone_device_page(page) && !is_device_private_page(page))
+ return true;
+
+ if (flags & TTU_SPLIT_HUGE_PMD) {
+ split_huge_pmd_address(vma, address,
+ flags & TTU_SPLIT_FREEZE, page);
+ }
+
+ /*
+ * 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.
+ */
+ end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
+ if (PageHuge(page)) {
+ /*
+ * If sharing is possible, start and end will be adjusted
+ * accordingly.
+ */
+ adjust_range_if_pmd_sharing_possible(vma, &start, &end);
+ }
+ mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
+
+ while (page_vma_mapped_walk(&pvmw)) {
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ /* PMD-mapped THP migration entry */
+ if (!pvmw.pte && (flags & TTU_MIGRATION)) {
+ VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
+
+ set_pmd_migration_entry(&pvmw, page);
+ continue;
+ }
+#endif
+
+ /*
+ * 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) {
+ /* PTE-mapped THP are never mlocked */
+ if (!PageTransCompound(page)) {
+ /*
+ * Holding pte lock, we do *not* need
+ * mmap_sem here
+ */
+ mlock_vma_page(page);
+ }
+ ret = false;
+ page_vma_mapped_walk_done(&pvmw);
+ break;
+ }
+ if (flags & TTU_MUNLOCK)
+ continue;
+ }
+
+ /* Unexpected PMD-mapped THP? */
+ VM_BUG_ON_PAGE(!pvmw.pte, page);
+
+ subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
+ address = pvmw.address;
+
+ if (PageHuge(page)) {
+ if (huge_pmd_unshare(mm, &address, pvmw.pte)) {
+ /*
+ * huge_pmd_unshare unmapped 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, start, end);
+ flush_tlb_range(vma, start, end);
+ mmu_notifier_invalidate_range(mm, start, 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;
+ }
+ }
+
+ if (IS_ENABLED(CONFIG_MIGRATION) &&
+ (flags & TTU_MIGRATION) &&
+ is_zone_device_page(page)) {
+ swp_entry_t entry;
+ pte_t swp_pte;
+
+ pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.pte);
+
+ /*
+ * 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 = make_migration_entry(page, 0);
+ swp_pte = swp_entry_to_pte(entry);
+ if (pte_soft_dirty(pteval))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
+ /*
+ * No need to invalidate here it will synchronize on
+ * against the special swap migration pte.
+ */
+ goto discard;
+ }
+
+ if (!(flags & TTU_IGNORE_ACCESS)) {
+ if (ptep_clear_flush_young_notify(vma, address,
+ pvmw.pte)) {
+ ret = false;
+ page_vma_mapped_walk_done(&pvmw);
+ break;
+ }
+ }
+
+ /* Nuke the page table entry. */
+ flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+ 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 page.
+ * 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);
+ }
+
+ /* Move the dirty bit to the 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)) {
+ pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
+ if (PageHuge(page)) {
+ int nr = 1 << compound_order(page);
+ hugetlb_count_sub(nr, mm);
+ set_huge_swap_pte_at(mm, address,
+ pvmw.pte, pteval,
+ vma_mmu_pagesize(vma));
+ } else {
+ dec_mm_counter(mm, mm_counter(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(page));
+ /* We have to invalidate as we cleared the pte */
+ mmu_notifier_invalidate_range(mm, address,
+ address + PAGE_SIZE);
+ } else if (IS_ENABLED(CONFIG_MIGRATION) &&
+ (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) {
+ swp_entry_t entry;
+ pte_t swp_pte;
+
+ if (arch_unmap_one(mm, vma, address, pteval) < 0) {
+ 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.
+ */
+ entry = make_migration_entry(subpage,
+ 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, pvmw.pte, swp_pte);
+ /*
+ * No need to invalidate here it will synchronize on
+ * against the special swap migration pte.
+ */
+ } else if (PageAnon(page)) {
+ 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(PageSwapBacked(page) != PageSwapCache(page))) {
+ 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 (!PageSwapBacked(page)) {
+ if (!PageDirty(page)) {
+ /* 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 page was redirtied, it cannot be
+ * discarded. Remap the page to page table.
+ */
+ set_pte_at(mm, address, pvmw.pte, pteval);
+ SetPageSwapBacked(page);
+ 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) {
+ set_pte_at(mm, address, pvmw.pte, pteval);
+ ret = false;
+ page_vma_mapped_walk_done(&pvmw);
+ break;
+ }
+ 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 (pte_soft_dirty(pteval))
+ swp_pte = pte_swp_mksoft_dirty(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 page, thus it cannot
+ * be removed from the page cache and replaced by a new
+ * page before mmu_notifier_invalidate_range_end, so no
+ * concurrent thread might update its page table to
+ * point at new page while a device still is using this
+ * page.
+ *
+ * See Documentation/vm/mmu_notifier.rst
+ */
+ dec_mm_counter(mm, mm_counter_file(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/vm/mmu_notifier.rst
+ */
+ page_remove_rmap(subpage, PageHuge(page));
+ put_page(page);
+ }
+
+ mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
+
+ 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_mapcount_is_zero(struct page *page)
+{
+ return !total_mapcount(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.
+ *
+ * If unmap is successful, return true. Otherwise, false.
+ */
+bool try_to_unmap(struct page *page, enum ttu_flags flags)
+{
+ struct rmap_walk_control rwc = {
+ .rmap_one = try_to_unmap_one,
+ .arg = (void *)flags,
+ .done = page_mapcount_is_zero,
+ .anon_lock = page_lock_anon_vma_read,
+ };
+
+ /*
+ * 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|TTU_SPLIT_FREEZE))
+ && !PageKsm(page) && PageAnon(page))
+ rwc.invalid_vma = invalid_migration_vma;
+
+ if (flags & TTU_RMAP_LOCKED)
+ rmap_walk_locked(page, &rwc);
+ else
+ rmap_walk(page, &rwc);
+
+ return !page_mapcount(page) ? true : false;
+}
+
+static int page_not_mapped(struct page *page)
+{
+ return !page_mapped(page);
+};
+
+/**
+ * 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.
+ */
+
+void try_to_munlock(struct page *page)
+{
+ 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);
+ VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
+
+ rmap_walk(page, &rwc);
+}
+
+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 void rmap_walk_anon(struct page *page, 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 = page_anon_vma(page);
+ /* anon_vma disappear under us? */
+ VM_BUG_ON_PAGE(!anon_vma, page);
+ } else {
+ anon_vma = rmap_walk_anon_lock(page, rwc);
+ }
+ if (!anon_vma)
+ return;
+
+ pgoff_start = page_to_pgoff(page);
+ pgoff_end = pgoff_start + hpage_nr_pages(page) - 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(page, vma);
+
+ cond_resched();
+
+ if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+ continue;
+
+ if (!rwc->rmap_one(page, vma, address, rwc->arg))
+ break;
+ if (rwc->done && rwc->done(page))
+ 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.
+ *
+ * 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 void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
+ bool locked)
+{
+ struct address_space *mapping = page_mapping(page);
+ 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_PAGE(!PageLocked(page), page);
+
+ if (!mapping)
+ return;
+
+ pgoff_start = page_to_pgoff(page);
+ pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
+ if (!locked)
+ i_mmap_lock_read(mapping);
+ vma_interval_tree_foreach(vma, &mapping->i_mmap,
+ pgoff_start, pgoff_end) {
+ unsigned long address = vma_address(page, vma);
+
+ cond_resched();
+
+ if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+ continue;
+
+ if (!rwc->rmap_one(page, vma, address, rwc->arg))
+ goto done;
+ if (rwc->done && rwc->done(page))
+ goto done;
+ }
+
+done:
+ if (!locked)
+ i_mmap_unlock_read(mapping);
+}
+
+void rmap_walk(struct page *page, struct rmap_walk_control *rwc)
+{
+ if (unlikely(PageKsm(page)))
+ rmap_walk_ksm(page, rwc);
+ else if (PageAnon(page))
+ rmap_walk_anon(page, rwc, false);
+ else
+ rmap_walk_file(page, rwc, false);
+}
+
+/* Like rmap_walk, but caller holds relevant rmap lock */
+void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
+{
+ /* no ksm support for now */
+ VM_BUG_ON_PAGE(PageKsm(page), page);
+ if (PageAnon(page))
+ rmap_walk_anon(page, rwc, true);
+ else
+ rmap_walk_file(page, rwc, true);
+}
+
+#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(compound_mapcount_ptr(page));
+ 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(compound_mapcount_ptr(page), 0);
+ __hugepage_set_anon_rmap(page, vma, address, 1);
+}
+#endif /* CONFIG_HUGETLB_PAGE */