v4.19.13 snapshot.
diff --git a/mm/vmacache.c b/mm/vmacache.c
new file mode 100644
index 0000000..cdc32a3
--- /dev/null
+++ b/mm/vmacache.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2014 Davidlohr Bueso.
+ */
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/mm.h>
+#include <linux/vmacache.h>
+#include <asm/pgtable.h>
+
+/*
+ * Hash based on the pmd of addr if configured with MMU, which provides a good
+ * hit rate for workloads with spatial locality. Otherwise, use pages.
+ */
+#ifdef CONFIG_MMU
+#define VMACACHE_SHIFT PMD_SHIFT
+#else
+#define VMACACHE_SHIFT PAGE_SHIFT
+#endif
+#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
+
+/*
+ * This task may be accessing a foreign mm via (for example)
+ * get_user_pages()->find_vma(). The vmacache is task-local and this
+ * task's vmacache pertains to a different mm (ie, its own). There is
+ * nothing we can do here.
+ *
+ * Also handle the case where a kernel thread has adopted this mm via use_mm().
+ * That kernel thread's vmacache is not applicable to this mm.
+ */
+static inline bool vmacache_valid_mm(struct mm_struct *mm)
+{
+ return current->mm == mm && !(current->flags & PF_KTHREAD);
+}
+
+void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
+{
+ if (vmacache_valid_mm(newvma->vm_mm))
+ current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
+}
+
+static bool vmacache_valid(struct mm_struct *mm)
+{
+ struct task_struct *curr;
+
+ if (!vmacache_valid_mm(mm))
+ return false;
+
+ curr = current;
+ if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
+ /*
+ * First attempt will always be invalid, initialize
+ * the new cache for this task here.
+ */
+ curr->vmacache.seqnum = mm->vmacache_seqnum;
+ vmacache_flush(curr);
+ return false;
+ }
+ return true;
+}
+
+struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
+{
+ int idx = VMACACHE_HASH(addr);
+ int i;
+
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
+ if (!vmacache_valid(mm))
+ return NULL;
+
+ for (i = 0; i < VMACACHE_SIZE; i++) {
+ struct vm_area_struct *vma = current->vmacache.vmas[idx];
+
+ if (vma) {
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+ if (WARN_ON_ONCE(vma->vm_mm != mm))
+ break;
+#endif
+ if (vma->vm_start <= addr && vma->vm_end > addr) {
+ count_vm_vmacache_event(VMACACHE_FIND_HITS);
+ return vma;
+ }
+ }
+ if (++idx == VMACACHE_SIZE)
+ idx = 0;
+ }
+
+ return NULL;
+}
+
+#ifndef CONFIG_MMU
+struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
+ unsigned long start,
+ unsigned long end)
+{
+ int idx = VMACACHE_HASH(start);
+ int i;
+
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
+ if (!vmacache_valid(mm))
+ return NULL;
+
+ for (i = 0; i < VMACACHE_SIZE; i++) {
+ struct vm_area_struct *vma = current->vmacache.vmas[idx];
+
+ if (vma && vma->vm_start == start && vma->vm_end == end) {
+ count_vm_vmacache_event(VMACACHE_FIND_HITS);
+ return vma;
+ }
+ if (++idx == VMACACHE_SIZE)
+ idx = 0;
+ }
+
+ return NULL;
+}
+#endif