Adding upstream version 4.19.249.upstream/4.19.249upstream

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

1 files changed, 2981 insertions, 0 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
new file mode 100644
index 000000000..5ada8897e
--- /dev/null
+++ b/mm/mempolicy.c
@@ -0,0 +1,2981 @@
+/*
+ * Simple NUMA memory policy for the Linux kernel.
+ *
+ * Copyright 2003,2004 Andi Kleen, SuSE Labs.
+ * (C) Copyright 2005 Christoph Lameter, Silicon Graphics, Inc.
+ * Subject to the GNU Public License, version 2.
+ *
+ * NUMA policy allows the user to give hints in which node(s) memory should
+ * be allocated.
+ *
+ * Support four policies per VMA and per process:
+ *
+ * The VMA policy has priority over the process policy for a page fault.
+ *
+ * interleave     Allocate memory interleaved over a set of nodes,
+ *                with normal fallback if it fails.
+ *                For VMA based allocations this interleaves based on the
+ *                offset into the backing object or offset into the mapping
+ *                for anonymous memory. For process policy an process counter
+ *                is used.
+ *
+ * bind           Only allocate memory on a specific set of nodes,
+ *                no fallback.
+ *                FIXME: memory is allocated starting with the first node
+ *                to the last. It would be better if bind would truly restrict
+ *                the allocation to memory nodes instead
+ *
+ * preferred       Try a specific node first before normal fallback.
+ *                As a special case NUMA_NO_NODE here means do the allocation
+ *                on the local CPU. This is normally identical to default,
+ *                but useful to set in a VMA when you have a non default
+ *                process policy.
+ *
+ * default        Allocate on the local node first, or when on a VMA
+ *                use the process policy. This is what Linux always did
+ *		  in a NUMA aware kernel and still does by, ahem, default.
+ *
+ * The process policy is applied for most non interrupt memory allocations
+ * in that process' context. Interrupts ignore the policies and always
+ * try to allocate on the local CPU. The VMA policy is only applied for memory
+ * allocations for a VMA in the VM.
+ *
+ * Currently there are a few corner cases in swapping where the policy
+ * is not applied, but the majority should be handled. When process policy
+ * is used it is not remembered over swap outs/swap ins.
+ *
+ * Only the highest zone in the zone hierarchy gets policied. Allocations
+ * requesting a lower zone just use default policy. This implies that
+ * on systems with highmem kernel lowmem allocation don't get policied.
+ * Same with GFP_DMA allocations.
+ *
+ * For shmfs/tmpfs/hugetlbfs shared memory the policy is shared between
+ * all users and remembered even when nobody has memory mapped.
+ */
+
+/* Notebook:
+   fix mmap readahead to honour policy and enable policy for any page cache
+   object
+   statistics for bigpages
+   global policy for page cache? currently it uses process policy. Requires
+   first item above.
+   handle mremap for shared memory (currently ignored for the policy)
+   grows down?
+   make bind policy root only? It can trigger oom much faster and the
+   kernel is not always grateful with that.
+*/
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mempolicy.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/hugetlb.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/numa_balancing.h>
+#include <linux/sched/task.h>
+#include <linux/nodemask.h>
+#include <linux/cpuset.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/export.h>
+#include <linux/nsproxy.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/compat.h>
+#include <linux/ptrace.h>
+#include <linux/swap.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+#include <linux/migrate.h>
+#include <linux/ksm.h>
+#include <linux/rmap.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/ctype.h>
+#include <linux/mm_inline.h>
+#include <linux/mmu_notifier.h>
+#include <linux/printk.h>
+#include <linux/swapops.h>
+
+#include <asm/tlbflush.h>
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+/* Internal flags */
+#define MPOL_MF_DISCONTIG_OK (MPOL_MF_INTERNAL << 0)	/* Skip checks for continuous vmas */
+#define MPOL_MF_INVERT (MPOL_MF_INTERNAL << 1)		/* Invert check for nodemask */
+
+static struct kmem_cache *policy_cache;
+static struct kmem_cache *sn_cache;
+
+/* Highest zone. An specific allocation for a zone below that is not
+   policied. */
+enum zone_type policy_zone = 0;
+
+/*
+ * run-time system-wide default policy => local allocation
+ */
+static struct mempolicy default_policy = {
+	.refcnt = ATOMIC_INIT(1), /* never free it */
+	.mode = MPOL_PREFERRED,
+	.flags = MPOL_F_LOCAL,
+};
+
+static struct mempolicy preferred_node_policy[MAX_NUMNODES];
+
+struct mempolicy *get_task_policy(struct task_struct *p)
+{
+	struct mempolicy *pol = p->mempolicy;
+	int node;
+
+	if (pol)
+		return pol;
+
+	node = numa_node_id();
+	if (node != NUMA_NO_NODE) {
+		pol = &preferred_node_policy[node];
+		/* preferred_node_policy is not initialised early in boot */
+		if (pol->mode)
+			return pol;
+	}
+
+	return &default_policy;
+}
+
+static const struct mempolicy_operations {
+	int (*create)(struct mempolicy *pol, const nodemask_t *nodes);
+	void (*rebind)(struct mempolicy *pol, const nodemask_t *nodes);
+} mpol_ops[MPOL_MAX];
+
+static inline int mpol_store_user_nodemask(const struct mempolicy *pol)
+{
+	return pol->flags & MPOL_MODE_FLAGS;
+}
+
+static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig,
+				   const nodemask_t *rel)
+{
+	nodemask_t tmp;
+	nodes_fold(tmp, *orig, nodes_weight(*rel));
+	nodes_onto(*ret, tmp, *rel);
+}
+
+static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
+{
+	if (nodes_empty(*nodes))
+		return -EINVAL;
+	pol->v.nodes = *nodes;
+	return 0;
+}
+
+static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
+{
+	if (!nodes)
+		pol->flags |= MPOL_F_LOCAL;	/* local allocation */
+	else if (nodes_empty(*nodes))
+		return -EINVAL;			/*  no allowed nodes */
+	else
+		pol->v.preferred_node = first_node(*nodes);
+	return 0;
+}
+
+static int mpol_new_bind(struct mempolicy *pol, const nodemask_t *nodes)
+{
+	if (nodes_empty(*nodes))
+		return -EINVAL;
+	pol->v.nodes = *nodes;
+	return 0;
+}
+
+/*
+ * mpol_set_nodemask is called after mpol_new() to set up the nodemask, if
+ * any, for the new policy.  mpol_new() has already validated the nodes
+ * parameter with respect to the policy mode and flags.  But, we need to
+ * handle an empty nodemask with MPOL_PREFERRED here.
+ *
+ * Must be called holding task's alloc_lock to protect task's mems_allowed
+ * and mempolicy.  May also be called holding the mmap_semaphore for write.
+ */
+static int mpol_set_nodemask(struct mempolicy *pol,
+		     const nodemask_t *nodes, struct nodemask_scratch *nsc)
+{
+	int ret;
+
+	/* if mode is MPOL_DEFAULT, pol is NULL. This is right. */
+	if (pol == NULL)
+		return 0;
+	/* Check N_MEMORY */
+	nodes_and(nsc->mask1,
+		  cpuset_current_mems_allowed, node_states[N_MEMORY]);
+
+	VM_BUG_ON(!nodes);
+	if (pol->mode == MPOL_PREFERRED && nodes_empty(*nodes))
+		nodes = NULL;	/* explicit local allocation */
+	else {
+		if (pol->flags & MPOL_F_RELATIVE_NODES)
+			mpol_relative_nodemask(&nsc->mask2, nodes, &nsc->mask1);
+		else
+			nodes_and(nsc->mask2, *nodes, nsc->mask1);
+
+		if (mpol_store_user_nodemask(pol))
+			pol->w.user_nodemask = *nodes;
+		else
+			pol->w.cpuset_mems_allowed =
+						cpuset_current_mems_allowed;
+	}
+
+	if (nodes)
+		ret = mpol_ops[pol->mode].create(pol, &nsc->mask2);
+	else
+		ret = mpol_ops[pol->mode].create(pol, NULL);
+	return ret;
+}
+
+/*
+ * This function just creates a new policy, does some check and simple
+ * initialization. You must invoke mpol_set_nodemask() to set nodes.
+ */
+static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
+				  nodemask_t *nodes)
+{
+	struct mempolicy *policy;
+
+	pr_debug("setting mode %d flags %d nodes[0] %lx\n",
+		 mode, flags, nodes ? nodes_addr(*nodes)[0] : NUMA_NO_NODE);
+
+	if (mode == MPOL_DEFAULT) {
+		if (nodes && !nodes_empty(*nodes))
+			return ERR_PTR(-EINVAL);
+		return NULL;
+	}
+	VM_BUG_ON(!nodes);
+
+	/*
+	 * MPOL_PREFERRED cannot be used with MPOL_F_STATIC_NODES or
+	 * MPOL_F_RELATIVE_NODES if the nodemask is empty (local allocation).
+	 * All other modes require a valid pointer to a non-empty nodemask.
+	 */
+	if (mode == MPOL_PREFERRED) {
+		if (nodes_empty(*nodes)) {
+			if (((flags & MPOL_F_STATIC_NODES) ||
+			     (flags & MPOL_F_RELATIVE_NODES)))
+				return ERR_PTR(-EINVAL);
+		}
+	} else if (mode == MPOL_LOCAL) {
+		if (!nodes_empty(*nodes) ||
+		    (flags & MPOL_F_STATIC_NODES) ||
+		    (flags & MPOL_F_RELATIVE_NODES))
+			return ERR_PTR(-EINVAL);
+		mode = MPOL_PREFERRED;
+	} else if (nodes_empty(*nodes))
+		return ERR_PTR(-EINVAL);
+	policy = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+	if (!policy)
+		return ERR_PTR(-ENOMEM);
+	atomic_set(&policy->refcnt, 1);
+	policy->mode = mode;
+	policy->flags = flags;
+
+	return policy;
+}
+
+/* Slow path of a mpol destructor. */
+void __mpol_put(struct mempolicy *p)
+{
+	if (!atomic_dec_and_test(&p->refcnt))
+		return;
+	kmem_cache_free(policy_cache, p);
+}
+
+static void mpol_rebind_default(struct mempolicy *pol, const nodemask_t *nodes)
+{
+}
+
+static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
+{
+	nodemask_t tmp;
+
+	if (pol->flags & MPOL_F_STATIC_NODES)
+		nodes_and(tmp, pol->w.user_nodemask, *nodes);
+	else if (pol->flags & MPOL_F_RELATIVE_NODES)
+		mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes);
+	else {
+		nodes_remap(tmp, pol->v.nodes,pol->w.cpuset_mems_allowed,
+								*nodes);
+		pol->w.cpuset_mems_allowed = *nodes;
+	}
+
+	if (nodes_empty(tmp))
+		tmp = *nodes;
+
+	pol->v.nodes = tmp;
+}
+
+static void mpol_rebind_preferred(struct mempolicy *pol,
+						const nodemask_t *nodes)
+{
+	nodemask_t tmp;
+
+	if (pol->flags & MPOL_F_STATIC_NODES) {
+		int node = first_node(pol->w.user_nodemask);
+
+		if (node_isset(node, *nodes)) {
+			pol->v.preferred_node = node;
+			pol->flags &= ~MPOL_F_LOCAL;
+		} else
+			pol->flags |= MPOL_F_LOCAL;
+	} else if (pol->flags & MPOL_F_RELATIVE_NODES) {
+		mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes);
+		pol->v.preferred_node = first_node(tmp);
+	} else if (!(pol->flags & MPOL_F_LOCAL)) {
+		pol->v.preferred_node = node_remap(pol->v.preferred_node,
+						   pol->w.cpuset_mems_allowed,
+						   *nodes);
+		pol->w.cpuset_mems_allowed = *nodes;
+	}
+}
+
+/*
+ * mpol_rebind_policy - Migrate a policy to a different set of nodes
+ *
+ * Per-vma policies are protected by mmap_sem. Allocations using per-task
+ * policies are protected by task->mems_allowed_seq to prevent a premature
+ * OOM/allocation failure due to parallel nodemask modification.
+ */
+static void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
+{
+	if (!pol)
+		return;
+	if (!mpol_store_user_nodemask(pol) && !(pol->flags & MPOL_F_LOCAL) &&
+	    nodes_equal(pol->w.cpuset_mems_allowed, *newmask))
+		return;
+
+	mpol_ops[pol->mode].rebind(pol, newmask);
+}
+
+/*
+ * Wrapper for mpol_rebind_policy() that just requires task
+ * pointer, and updates task mempolicy.
+ *
+ * Called with task's alloc_lock held.
+ */
+
+void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new)
+{
+	mpol_rebind_policy(tsk->mempolicy, new);
+}
+
+/*
+ * Rebind each vma in mm to new nodemask.
+ *
+ * Call holding a reference to mm.  Takes mm->mmap_sem during call.
+ */
+
+void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
+{
+	struct vm_area_struct *vma;
+
+	down_write(&mm->mmap_sem);
+	for (vma = mm->mmap; vma; vma = vma->vm_next)
+		mpol_rebind_policy(vma->vm_policy, new);
+	up_write(&mm->mmap_sem);
+}
+
+static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
+	[MPOL_DEFAULT] = {
+		.rebind = mpol_rebind_default,
+	},
+	[MPOL_INTERLEAVE] = {
+		.create = mpol_new_interleave,
+		.rebind = mpol_rebind_nodemask,
+	},
+	[MPOL_PREFERRED] = {
+		.create = mpol_new_preferred,
+		.rebind = mpol_rebind_preferred,
+	},
+	[MPOL_BIND] = {
+		.create = mpol_new_bind,
+		.rebind = mpol_rebind_nodemask,
+	},
+};
+
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
+				unsigned long flags);
+
+struct queue_pages {
+	struct list_head *pagelist;
+	unsigned long flags;
+	nodemask_t *nmask;
+	struct vm_area_struct *prev;
+};
+
+/*
+ * Check if the page's nid is in qp->nmask.
+ *
+ * If MPOL_MF_INVERT is set in qp->flags, check if the nid is
+ * in the invert of qp->nmask.
+ */
+static inline bool queue_pages_required(struct page *page,
+					struct queue_pages *qp)
+{
+	int nid = page_to_nid(page);
+	unsigned long flags = qp->flags;
+
+	return node_isset(nid, *qp->nmask) == !(flags & MPOL_MF_INVERT);
+}
+
+/*
+ * queue_pages_pmd() has four possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ *     specified.
+ * 2 - THP was split.
+ * -EIO - is migration entry or only MPOL_MF_STRICT was specified and an
+ *        existing page was already on a node that does not follow the
+ *        policy.
+ */
+static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
+				unsigned long end, struct mm_walk *walk)
+{
+	int ret = 0;
+	struct page *page;
+	struct queue_pages *qp = walk->private;
+	unsigned long flags;
+
+	if (unlikely(is_pmd_migration_entry(*pmd))) {
+		ret = -EIO;
+		goto unlock;
+	}
+	page = pmd_page(*pmd);
+	if (is_huge_zero_page(page)) {
+		spin_unlock(ptl);
+		__split_huge_pmd(walk->vma, pmd, addr, false, NULL);
+		ret = 2;
+		goto out;
+	}
+	if (!queue_pages_required(page, qp))
+		goto unlock;
+
+	flags = qp->flags;
+	/* go to thp migration */
+	if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
+		if (!vma_migratable(walk->vma) ||
+		    migrate_page_add(page, qp->pagelist, flags)) {
+			ret = 1;
+			goto unlock;
+		}
+	} else
+		ret = -EIO;
+unlock:
+	spin_unlock(ptl);
+out:
+	return ret;
+}
+
+/*
+ * Scan through pages checking if pages follow certain conditions,
+ * and move them to the pagelist if they do.
+ *
+ * queue_pages_pte_range() has three possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ *     specified.
+ * -EIO - only MPOL_MF_STRICT was specified and an existing page was already
+ *        on a node that does not follow the policy.
+ */
+static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
+			unsigned long end, struct mm_walk *walk)
+{
+	struct vm_area_struct *vma = walk->vma;
+	struct page *page;
+	struct queue_pages *qp = walk->private;
+	unsigned long flags = qp->flags;
+	int ret;
+	bool has_unmovable = false;
+	pte_t *pte, *mapped_pte;
+	spinlock_t *ptl;
+
+	ptl = pmd_trans_huge_lock(pmd, vma);
+	if (ptl) {
+		ret = queue_pages_pmd(pmd, ptl, addr, end, walk);
+		if (ret != 2)
+			return ret;
+	}
+	/* THP was split, fall through to pte walk */
+
+	if (pmd_trans_unstable(pmd))
+		return 0;
+
+	mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	for (; addr != end; pte++, addr += PAGE_SIZE) {
+		if (!pte_present(*pte))
+			continue;
+		page = vm_normal_page(vma, addr, *pte);
+		if (!page)
+			continue;
+		/*
+		 * vm_normal_page() filters out zero pages, but there might
+		 * still be PageReserved pages to skip, perhaps in a VDSO.
+		 */
+		if (PageReserved(page))
+			continue;
+		if (!queue_pages_required(page, qp))
+			continue;
+		if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
+			/* MPOL_MF_STRICT must be specified if we get here */
+			if (!vma_migratable(vma)) {
+				has_unmovable = true;
+				break;
+			}
+
+			/*
+			 * Do not abort immediately since there may be
+			 * temporary off LRU pages in the range.  Still
+			 * need migrate other LRU pages.
+			 */
+			if (migrate_page_add(page, qp->pagelist, flags))
+				has_unmovable = true;
+		} else
+			break;
+	}
+	pte_unmap_unlock(mapped_pte, ptl);
+	cond_resched();
+
+	if (has_unmovable)
+		return 1;
+
+	return addr != end ? -EIO : 0;
+}
+
+static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
+			       unsigned long addr, unsigned long end,
+			       struct mm_walk *walk)
+{
+#ifdef CONFIG_HUGETLB_PAGE
+	struct queue_pages *qp = walk->private;
+	unsigned long flags = qp->flags;
+	struct page *page;
+	spinlock_t *ptl;
+	pte_t entry;
+
+	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
+	entry = huge_ptep_get(pte);
+	if (!pte_present(entry))
+		goto unlock;
+	page = pte_page(entry);
+	if (!queue_pages_required(page, qp))
+		goto unlock;
+	/* With MPOL_MF_MOVE, we migrate only unshared hugepage. */
+	if (flags & (MPOL_MF_MOVE_ALL) ||
+	    (flags & MPOL_MF_MOVE && page_mapcount(page) == 1))
+		isolate_huge_page(page, qp->pagelist);
+unlock:
+	spin_unlock(ptl);
+#else
+	BUG();
+#endif
+	return 0;
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * This is used to mark a range of virtual addresses to be inaccessible.
+ * These are later cleared by a NUMA hinting fault. Depending on these
+ * faults, pages may be migrated for better NUMA placement.
+ *
+ * This is assuming that NUMA faults are handled using PROT_NONE. If
+ * an architecture makes a different choice, it will need further
+ * changes to the core.
+ */
+unsigned long change_prot_numa(struct vm_area_struct *vma,
+			unsigned long addr, unsigned long end)
+{
+	int nr_updated;
+
+	nr_updated = change_protection(vma, addr, end, PAGE_NONE, 0, 1);
+	if (nr_updated)
+		count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated);
+
+	return nr_updated;
+}
+#else
+static unsigned long change_prot_numa(struct vm_area_struct *vma,
+			unsigned long addr, unsigned long end)
+{
+	return 0;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+static int queue_pages_test_walk(unsigned long start, unsigned long end,
+				struct mm_walk *walk)
+{
+	struct vm_area_struct *vma = walk->vma;
+	struct queue_pages *qp = walk->private;
+	unsigned long endvma = vma->vm_end;
+	unsigned long flags = qp->flags;
+
+	/*
+	 * Need check MPOL_MF_STRICT to return -EIO if possible
+	 * regardless of vma_migratable
+	 */
+	if (!vma_migratable(vma) &&
+	    !(flags & MPOL_MF_STRICT))
+		return 1;
+
+	if (endvma > end)
+		endvma = end;
+	if (vma->vm_start > start)
+		start = vma->vm_start;
+
+	if (!(flags & MPOL_MF_DISCONTIG_OK)) {
+		if (!vma->vm_next && vma->vm_end < end)
+			return -EFAULT;
+		if (qp->prev && qp->prev->vm_end < vma->vm_start)
+			return -EFAULT;
+	}
+
+	qp->prev = vma;
+
+	if (flags & MPOL_MF_LAZY) {
+		/* Similar to task_numa_work, skip inaccessible VMAs */
+		if (!is_vm_hugetlb_page(vma) &&
+			(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) &&
+			!(vma->vm_flags & VM_MIXEDMAP))
+			change_prot_numa(vma, start, endvma);
+		return 1;
+	}
+
+	/* queue pages from current vma */
+	if (flags & MPOL_MF_VALID)
+		return 0;
+	return 1;
+}
+
+/*
+ * Walk through page tables and collect pages to be migrated.
+ *
+ * If pages found in a given range are on a set of nodes (determined by
+ * @nodes and @flags,) it's isolated and queued to the pagelist which is
+ * passed via @private.
+ *
+ * queue_pages_range() has three possible return values:
+ * 1 - there is unmovable page, but MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ *     specified.
+ * 0 - queue pages successfully or no misplaced page.
+ * errno - i.e. misplaced pages with MPOL_MF_STRICT specified (-EIO) or
+ *         memory range specified by nodemask and maxnode points outside
+ *         your accessible address space (-EFAULT)
+ */
+static int
+queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
+		nodemask_t *nodes, unsigned long flags,
+		struct list_head *pagelist)
+{
+	struct queue_pages qp = {
+		.pagelist = pagelist,
+		.flags = flags,
+		.nmask = nodes,
+		.prev = NULL,
+	};
+	struct mm_walk queue_pages_walk = {
+		.hugetlb_entry = queue_pages_hugetlb,
+		.pmd_entry = queue_pages_pte_range,
+		.test_walk = queue_pages_test_walk,
+		.mm = mm,
+		.private = &qp,
+	};
+
+	return walk_page_range(start, end, &queue_pages_walk);
+}
+
+/*
+ * Apply policy to a single VMA
+ * This must be called with the mmap_sem held for writing.
+ */
+static int vma_replace_policy(struct vm_area_struct *vma,
+						struct mempolicy *pol)
+{
+	int err;
+	struct mempolicy *old;
+	struct mempolicy *new;
+
+	pr_debug("vma %lx-%lx/%lx vm_ops %p vm_file %p set_policy %p\n",
+		 vma->vm_start, vma->vm_end, vma->vm_pgoff,
+		 vma->vm_ops, vma->vm_file,
+		 vma->vm_ops ? vma->vm_ops->set_policy : NULL);
+
+	new = mpol_dup(pol);
+	if (IS_ERR(new))
+		return PTR_ERR(new);
+
+	if (vma->vm_ops && vma->vm_ops->set_policy) {
+		err = vma->vm_ops->set_policy(vma, new);
+		if (err)
+			goto err_out;
+	}
+
+	old = vma->vm_policy;
+	vma->vm_policy = new; /* protected by mmap_sem */
+	mpol_put(old);
+
+	return 0;
+ err_out:
+	mpol_put(new);
+	return err;
+}
+
+/* Step 2: apply policy to a range and do splits. */
+static int mbind_range(struct mm_struct *mm, unsigned long start,
+		       unsigned long end, struct mempolicy *new_pol)
+{
+	struct vm_area_struct *prev;
+	struct vm_area_struct *vma;
+	int err = 0;
+	pgoff_t pgoff;
+	unsigned long vmstart;
+	unsigned long vmend;
+
+	vma = find_vma(mm, start);
+	if (!vma || vma->vm_start > start)
+		return -EFAULT;
+
+	prev = vma->vm_prev;
+	if (start > vma->vm_start)
+		prev = vma;
+
+	for (; vma && vma->vm_start < end; prev = vma, vma = vma->vm_next) {
+		vmstart = max(start, vma->vm_start);
+		vmend   = min(end, vma->vm_end);
+
+		if (mpol_equal(vma_policy(vma), new_pol))
+			continue;
+
+		pgoff = vma->vm_pgoff +
+			((vmstart - vma->vm_start) >> PAGE_SHIFT);
+		prev = vma_merge(mm, prev, vmstart, vmend, vma->vm_flags,
+				 vma->anon_vma, vma->vm_file, pgoff,
+				 new_pol, vma->vm_userfaultfd_ctx);
+		if (prev) {
+			vma = prev;
+			goto replace;
+		}
+		if (vma->vm_start != vmstart) {
+			err = split_vma(vma->vm_mm, vma, vmstart, 1);
+			if (err)
+				goto out;
+		}
+		if (vma->vm_end != vmend) {
+			err = split_vma(vma->vm_mm, vma, vmend, 0);
+			if (err)
+				goto out;
+		}
+ replace:
+		err = vma_replace_policy(vma, new_pol);
+		if (err)
+			goto out;
+	}
+
+ out:
+	return err;
+}
+
+/* Set the process memory policy */
+static long do_set_mempolicy(unsigned short mode, unsigned short flags,
+			     nodemask_t *nodes)
+{
+	struct mempolicy *new, *old;
+	NODEMASK_SCRATCH(scratch);
+	int ret;
+
+	if (!scratch)
+		return -ENOMEM;
+
+	new = mpol_new(mode, flags, nodes);
+	if (IS_ERR(new)) {
+		ret = PTR_ERR(new);
+		goto out;
+	}
+
+	task_lock(current);
+	ret = mpol_set_nodemask(new, nodes, scratch);
+	if (ret) {
+		task_unlock(current);
+		mpol_put(new);
+		goto out;
+	}
+	old = current->mempolicy;
+	current->mempolicy = new;
+	if (new && new->mode == MPOL_INTERLEAVE)
+		current->il_prev = MAX_NUMNODES-1;
+	task_unlock(current);
+	mpol_put(old);
+	ret = 0;
+out:
+	NODEMASK_SCRATCH_FREE(scratch);
+	return ret;
+}
+
+/*
+ * Return nodemask for policy for get_mempolicy() query
+ *
+ * Called with task's alloc_lock held
+ */
+static void get_policy_nodemask(struct mempolicy *p, nodemask_t *nodes)
+{
+	nodes_clear(*nodes);
+	if (p == &default_policy)
+		return;
+
+	switch (p->mode) {
+	case MPOL_BIND:
+		/* Fall through */
+	case MPOL_INTERLEAVE:
+		*nodes = p->v.nodes;
+		break;
+	case MPOL_PREFERRED:
+		if (!(p->flags & MPOL_F_LOCAL))
+			node_set(p->v.preferred_node, *nodes);
+		/* else return empty node mask for local allocation */
+		break;
+	default:
+		BUG();
+	}
+}
+
+static int lookup_node(unsigned long addr)
+{
+	struct page *p;
+	int err;
+
+	err = get_user_pages(addr & PAGE_MASK, 1, 0, &p, NULL);
+	if (err >= 0) {
+		err = page_to_nid(p);
+		put_page(p);
+	}
+	return err;
+}
+
+/* Retrieve NUMA policy */
+static long do_get_mempolicy(int *policy, nodemask_t *nmask,
+			     unsigned long addr, unsigned long flags)
+{
+	int err;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma = NULL;
+	struct mempolicy *pol = current->mempolicy;
+
+	if (flags &
+		~(unsigned long)(MPOL_F_NODE|MPOL_F_ADDR|MPOL_F_MEMS_ALLOWED))
+		return -EINVAL;
+
+	if (flags & MPOL_F_MEMS_ALLOWED) {
+		if (flags & (MPOL_F_NODE|MPOL_F_ADDR))
+			return -EINVAL;
+		*policy = 0;	/* just so it's initialized */
+		task_lock(current);
+		*nmask  = cpuset_current_mems_allowed;
+		task_unlock(current);
+		return 0;
+	}
+
+	if (flags & MPOL_F_ADDR) {
+		/*
+		 * Do NOT fall back to task policy if the
+		 * vma/shared policy at addr is NULL.  We
+		 * want to return MPOL_DEFAULT in this case.
+		 */
+		down_read(&mm->mmap_sem);
+		vma = find_vma_intersection(mm, addr, addr+1);
+		if (!vma) {
+			up_read(&mm->mmap_sem);
+			return -EFAULT;
+		}
+		if (vma->vm_ops && vma->vm_ops->get_policy)
+			pol = vma->vm_ops->get_policy(vma, addr);
+		else
+			pol = vma->vm_policy;
+	} else if (addr)
+		return -EINVAL;
+
+	if (!pol)
+		pol = &default_policy;	/* indicates default behavior */
+
+	if (flags & MPOL_F_NODE) {
+		if (flags & MPOL_F_ADDR) {
+			err = lookup_node(addr);
+			if (err < 0)
+				goto out;
+			*policy = err;
+		} else if (pol == current->mempolicy &&
+				pol->mode == MPOL_INTERLEAVE) {
+			*policy = next_node_in(current->il_prev, pol->v.nodes);
+		} else {
+			err = -EINVAL;
+			goto out;
+		}
+	} else {
+		*policy = pol == &default_policy ? MPOL_DEFAULT :
+						pol->mode;
+		/*
+		 * Internal mempolicy flags must be masked off before exposing
+		 * the policy to userspace.
+		 */
+		*policy |= (pol->flags & MPOL_MODE_FLAGS);
+	}
+
+	err = 0;
+	if (nmask) {
+		if (mpol_store_user_nodemask(pol)) {
+			*nmask = pol->w.user_nodemask;
+		} else {
+			task_lock(current);
+			get_policy_nodemask(pol, nmask);
+			task_unlock(current);
+		}
+	}
+
+ out:
+	mpol_cond_put(pol);
+	if (vma)
+		up_read(&current->mm->mmap_sem);
+	return err;
+}
+
+#ifdef CONFIG_MIGRATION
+/*
+ * page migration, thp tail pages can be passed.
+ */
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
+				unsigned long flags)
+{
+	struct page *head = compound_head(page);
+	/*
+	 * Avoid migrating a page that is shared with others.
+	 */
+	if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(head) == 1) {
+		if (!isolate_lru_page(head)) {
+			list_add_tail(&head->lru, pagelist);
+			mod_node_page_state(page_pgdat(head),
+				NR_ISOLATED_ANON + page_is_file_cache(head),
+				hpage_nr_pages(head));
+		} else if (flags & MPOL_MF_STRICT) {
+			/*
+			 * Non-movable page may reach here.  And, there may be
+			 * temporary off LRU pages or non-LRU movable pages.
+			 * Treat them as unmovable pages since they can't be
+			 * isolated, so they can't be moved at the moment.  It
+			 * should return -EIO for this case too.
+			 */
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
+/* page allocation callback for NUMA node migration */
+struct page *alloc_new_node_page(struct page *page, unsigned long node)
+{
+	if (PageHuge(page))
+		return alloc_huge_page_node(page_hstate(compound_head(page)),
+					node);
+	else if (PageTransHuge(page)) {
+		struct page *thp;
+
+		thp = alloc_pages_node(node,
+			(GFP_TRANSHUGE | __GFP_THISNODE),
+			HPAGE_PMD_ORDER);
+		if (!thp)
+			return NULL;
+		prep_transhuge_page(thp);
+		return thp;
+	} else
+		return __alloc_pages_node(node, GFP_HIGHUSER_MOVABLE |
+						    __GFP_THISNODE, 0);
+}
+
+/*
+ * Migrate pages from one node to a target node.
+ * Returns error or the number of pages not migrated.
+ */
+static int migrate_to_node(struct mm_struct *mm, int source, int dest,
+			   int flags)
+{
+	nodemask_t nmask;
+	LIST_HEAD(pagelist);
+	int err = 0;
+
+	nodes_clear(nmask);
+	node_set(source, nmask);
+
+	/*
+	 * This does not "check" the range but isolates all pages that
+	 * need migration.  Between passing in the full user address
+	 * space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
+	 */
+	VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
+	queue_pages_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
+			flags | MPOL_MF_DISCONTIG_OK, &pagelist);
+
+	if (!list_empty(&pagelist)) {
+		err = migrate_pages(&pagelist, alloc_new_node_page, NULL, dest,
+					MIGRATE_SYNC, MR_SYSCALL);
+		if (err)
+			putback_movable_pages(&pagelist);
+	}
+
+	return err;
+}
+
+/*
+ * Move pages between the two nodesets so as to preserve the physical
+ * layout as much as possible.
+ *
+ * Returns the number of page that could not be moved.
+ */
+int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
+		     const nodemask_t *to, int flags)
+{
+	int busy = 0;
+	int err;
+	nodemask_t tmp;
+
+	err = migrate_prep();
+	if (err)
+		return err;
+
+	down_read(&mm->mmap_sem);
+
+	/*
+	 * Find a 'source' bit set in 'tmp' whose corresponding 'dest'
+	 * bit in 'to' is not also set in 'tmp'.  Clear the found 'source'
+	 * bit in 'tmp', and return that <source, dest> pair for migration.
+	 * The pair of nodemasks 'to' and 'from' define the map.
+	 *
+	 * If no pair of bits is found that way, fallback to picking some
+	 * pair of 'source' and 'dest' bits that are not the same.  If the
+	 * 'source' and 'dest' bits are the same, this represents a node
+	 * that will be migrating to itself, so no pages need move.
+	 *
+	 * If no bits are left in 'tmp', or if all remaining bits left
+	 * in 'tmp' correspond to the same bit in 'to', return false
+	 * (nothing left to migrate).
+	 *
+	 * This lets us pick a pair of nodes to migrate between, such that
+	 * if possible the dest node is not already occupied by some other
+	 * source node, minimizing the risk of overloading the memory on a
+	 * node that would happen if we migrated incoming memory to a node
+	 * before migrating outgoing memory source that same node.
+	 *
+	 * A single scan of tmp is sufficient.  As we go, we remember the
+	 * most recent <s, d> pair that moved (s != d).  If we find a pair
+	 * that not only moved, but what's better, moved to an empty slot
+	 * (d is not set in tmp), then we break out then, with that pair.
+	 * Otherwise when we finish scanning from_tmp, we at least have the
+	 * most recent <s, d> pair that moved.  If we get all the way through
+	 * the scan of tmp without finding any node that moved, much less
+	 * moved to an empty node, then there is nothing left worth migrating.
+	 */
+
+	tmp = *from;
+	while (!nodes_empty(tmp)) {
+		int s,d;
+		int source = NUMA_NO_NODE;
+		int dest = 0;
+
+		for_each_node_mask(s, tmp) {
+
+			/*
+			 * do_migrate_pages() tries to maintain the relative
+			 * node relationship of the pages established between
+			 * threads and memory areas.
+                         *
+			 * However if the number of source nodes is not equal to
+			 * the number of destination nodes we can not preserve
+			 * this node relative relationship.  In that case, skip
+			 * copying memory from a node that is in the destination
+			 * mask.
+			 *
+			 * Example: [2,3,4] -> [3,4,5] moves everything.
+			 *          [0-7] - > [3,4,5] moves only 0,1,2,6,7.
+			 */
+
+			if ((nodes_weight(*from) != nodes_weight(*to)) &&
+						(node_isset(s, *to)))
+				continue;
+
+			d = node_remap(s, *from, *to);
+			if (s == d)
+				continue;
+
+			source = s;	/* Node moved. Memorize */
+			dest = d;
+
+			/* dest not in remaining from nodes? */
+			if (!node_isset(dest, tmp))
+				break;
+		}
+		if (source == NUMA_NO_NODE)
+			break;
+
+		node_clear(source, tmp);
+		err = migrate_to_node(mm, source, dest, flags);
+		if (err > 0)
+			busy += err;
+		if (err < 0)
+			break;
+	}
+	up_read(&mm->mmap_sem);
+	if (err < 0)
+		return err;
+	return busy;
+
+}
+
+/*
+ * Allocate a new page for page migration based on vma policy.
+ * Start by assuming the page is mapped by the same vma as contains @start.
+ * Search forward from there, if not.  N.B., this assumes that the
+ * list of pages handed to migrate_pages()--which is how we get here--
+ * is in virtual address order.
+ */
+static struct page *new_page(struct page *page, unsigned long start)
+{
+	struct vm_area_struct *vma;
+	unsigned long uninitialized_var(address);
+
+	vma = find_vma(current->mm, start);
+	while (vma) {
+		address = page_address_in_vma(page, vma);
+		if (address != -EFAULT)
+			break;
+		vma = vma->vm_next;
+	}
+
+	if (PageHuge(page)) {
+		return alloc_huge_page_vma(page_hstate(compound_head(page)),
+				vma, address);
+	} else if (PageTransHuge(page)) {
+		struct page *thp;
+
+		thp = alloc_hugepage_vma(GFP_TRANSHUGE, vma, address,
+					 HPAGE_PMD_ORDER);
+		if (!thp)
+			return NULL;
+		prep_transhuge_page(thp);
+		return thp;
+	}
+	/*
+	 * if !vma, alloc_page_vma() will use task or system default policy
+	 */
+	return alloc_page_vma(GFP_HIGHUSER_MOVABLE | __GFP_RETRY_MAYFAIL,
+			vma, address);
+}
+#else
+
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
+				unsigned long flags)
+{
+	return -EIO;
+}
+
+int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
+		     const nodemask_t *to, int flags)
+{
+	return -ENOSYS;
+}
+
+static struct page *new_page(struct page *page, unsigned long start)
+{
+	return NULL;
+}
+#endif
+
+static long do_mbind(unsigned long start, unsigned long len,
+		     unsigned short mode, unsigned short mode_flags,
+		     nodemask_t *nmask, unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+	struct mempolicy *new;
+	unsigned long end;
+	int err;
+	int ret;
+	LIST_HEAD(pagelist);
+
+	if (flags & ~(unsigned long)MPOL_MF_VALID)
+		return -EINVAL;
+	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
+		return -EPERM;
+
+	if (start & ~PAGE_MASK)
+		return -EINVAL;
+
+	if (mode == MPOL_DEFAULT)
+		flags &= ~MPOL_MF_STRICT;
+
+	len = (len + PAGE_SIZE - 1) & PAGE_MASK;
+	end = start + len;
+
+	if (end < start)
+		return -EINVAL;
+	if (end == start)
+		return 0;
+
+	new = mpol_new(mode, mode_flags, nmask);
+	if (IS_ERR(new))
+		return PTR_ERR(new);
+
+	if (flags & MPOL_MF_LAZY)
+		new->flags |= MPOL_F_MOF;
+
+	/*
+	 * If we are using the default policy then operation
+	 * on discontinuous address spaces is okay after all
+	 */
+	if (!new)
+		flags |= MPOL_MF_DISCONTIG_OK;
+
+	pr_debug("mbind %lx-%lx mode:%d flags:%d nodes:%lx\n",
+		 start, start + len, mode, mode_flags,
+		 nmask ? nodes_addr(*nmask)[0] : NUMA_NO_NODE);
+
+	if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
+
+		err = migrate_prep();
+		if (err)
+			goto mpol_out;
+	}
+	{
+		NODEMASK_SCRATCH(scratch);
+		if (scratch) {
+			down_write(&mm->mmap_sem);
+			task_lock(current);
+			err = mpol_set_nodemask(new, nmask, scratch);
+			task_unlock(current);
+			if (err)
+				up_write(&mm->mmap_sem);
+		} else
+			err = -ENOMEM;
+		NODEMASK_SCRATCH_FREE(scratch);
+	}
+	if (err)
+		goto mpol_out;
+
+	ret = queue_pages_range(mm, start, end, nmask,
+			  flags | MPOL_MF_INVERT, &pagelist);
+
+	if (ret < 0) {
+		err = ret;
+		goto up_out;
+	}
+
+	err = mbind_range(mm, start, end, new);
+
+	if (!err) {
+		int nr_failed = 0;
+
+		if (!list_empty(&pagelist)) {
+			WARN_ON_ONCE(flags & MPOL_MF_LAZY);
+			nr_failed = migrate_pages(&pagelist, new_page, NULL,
+				start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
+			if (nr_failed)
+				putback_movable_pages(&pagelist);
+		}
+
+		if ((ret > 0) || (nr_failed && (flags & MPOL_MF_STRICT)))
+			err = -EIO;
+	} else {
+up_out:
+		if (!list_empty(&pagelist))
+			putback_movable_pages(&pagelist);
+	}
+
+	up_write(&mm->mmap_sem);
+mpol_out:
+	mpol_put(new);
+	return err;
+}
+
+/*
+ * User space interface with variable sized bitmaps for nodelists.
+ */
+
+/* Copy a node mask from user space. */
+static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
+		     unsigned long maxnode)
+{
+	unsigned long k;
+	unsigned long t;
+	unsigned long nlongs;
+	unsigned long endmask;
+
+	--maxnode;
+	nodes_clear(*nodes);
+	if (maxnode == 0 || !nmask)
+		return 0;
+	if (maxnode > PAGE_SIZE*BITS_PER_BYTE)
+		return -EINVAL;
+
+	nlongs = BITS_TO_LONGS(maxnode);
+	if ((maxnode % BITS_PER_LONG) == 0)
+		endmask = ~0UL;
+	else
+		endmask = (1UL << (maxnode % BITS_PER_LONG)) - 1;
+
+	/*
+	 * When the user specified more nodes than supported just check
+	 * if the non supported part is all zero.
+	 *
+	 * If maxnode have more longs than MAX_NUMNODES, check
+	 * the bits in that area first. And then go through to
+	 * check the rest bits which equal or bigger than MAX_NUMNODES.
+	 * Otherwise, just check bits [MAX_NUMNODES, maxnode).
+	 */
+	if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
+		for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
+			if (get_user(t, nmask + k))
+				return -EFAULT;
+			if (k == nlongs - 1) {
+				if (t & endmask)
+					return -EINVAL;
+			} else if (t)
+				return -EINVAL;
+		}
+		nlongs = BITS_TO_LONGS(MAX_NUMNODES);
+		endmask = ~0UL;
+	}
+
+	if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
+		unsigned long valid_mask = endmask;
+
+		valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);
+		if (get_user(t, nmask + nlongs - 1))
+			return -EFAULT;
+		if (t & valid_mask)
+			return -EINVAL;
+	}
+
+	if (copy_from_user(nodes_addr(*nodes), nmask, nlongs*sizeof(unsigned long)))
+		return -EFAULT;
+	nodes_addr(*nodes)[nlongs-1] &= endmask;
+	return 0;
+}
+
+/* Copy a kernel node mask to user space */
+static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
+			      nodemask_t *nodes)
+{
+	unsigned long copy = ALIGN(maxnode-1, 64) / 8;
+	unsigned int nbytes = BITS_TO_LONGS(nr_node_ids) * sizeof(long);
+
+	if (copy > nbytes) {
+		if (copy > PAGE_SIZE)
+			return -EINVAL;
+		if (clear_user((char __user *)mask + nbytes, copy - nbytes))
+			return -EFAULT;
+		copy = nbytes;
+	}
+	return copy_to_user(mask, nodes_addr(*nodes), copy) ? -EFAULT : 0;
+}
+
+static long kernel_mbind(unsigned long start, unsigned long len,
+			 unsigned long mode, const unsigned long __user *nmask,
+			 unsigned long maxnode, unsigned int flags)
+{
+	nodemask_t nodes;
+	int err;
+	unsigned short mode_flags;
+
+	mode_flags = mode & MPOL_MODE_FLAGS;
+	mode &= ~MPOL_MODE_FLAGS;
+	if (mode >= MPOL_MAX)
+		return -EINVAL;
+	if ((mode_flags & MPOL_F_STATIC_NODES) &&
+	    (mode_flags & MPOL_F_RELATIVE_NODES))
+		return -EINVAL;
+	err = get_nodes(&nodes, nmask, maxnode);
+	if (err)
+		return err;
+	return do_mbind(start, len, mode, mode_flags, &nodes, flags);
+}
+
+SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
+		unsigned long, mode, const unsigned long __user *, nmask,
+		unsigned long, maxnode, unsigned int, flags)
+{
+	return kernel_mbind(start, len, mode, nmask, maxnode, flags);
+}
+
+/* Set the process memory policy */
+static long kernel_set_mempolicy(int mode, const unsigned long __user *nmask,
+				 unsigned long maxnode)
+{
+	int err;
+	nodemask_t nodes;
+	unsigned short flags;
+
+	flags = mode & MPOL_MODE_FLAGS;
+	mode &= ~MPOL_MODE_FLAGS;
+	if ((unsigned int)mode >= MPOL_MAX)
+		return -EINVAL;
+	if ((flags & MPOL_F_STATIC_NODES) && (flags & MPOL_F_RELATIVE_NODES))
+		return -EINVAL;
+	err = get_nodes(&nodes, nmask, maxnode);
+	if (err)
+		return err;
+	return do_set_mempolicy(mode, flags, &nodes);
+}
+
+SYSCALL_DEFINE3(set_mempolicy, int, mode, const unsigned long __user *, nmask,
+		unsigned long, maxnode)
+{
+	return kernel_set_mempolicy(mode, nmask, maxnode);
+}
+
+static int kernel_migrate_pages(pid_t pid, unsigned long maxnode,
+				const unsigned long __user *old_nodes,
+				const unsigned long __user *new_nodes)
+{
+	struct mm_struct *mm = NULL;
+	struct task_struct *task;
+	nodemask_t task_nodes;
+	int err;
+	nodemask_t *old;
+	nodemask_t *new;
+	NODEMASK_SCRATCH(scratch);
+
+	if (!scratch)
+		return -ENOMEM;
+
+	old = &scratch->mask1;
+	new = &scratch->mask2;
+
+	err = get_nodes(old, old_nodes, maxnode);
+	if (err)
+		goto out;
+
+	err = get_nodes(new, new_nodes, maxnode);
+	if (err)
+		goto out;
+
+	/* Find the mm_struct */
+	rcu_read_lock();
+	task = pid ? find_task_by_vpid(pid) : current;
+	if (!task) {
+		rcu_read_unlock();
+		err = -ESRCH;
+		goto out;
+	}
+	get_task_struct(task);
+
+	err = -EINVAL;
+
+	/*
+	 * Check if this process has the right to modify the specified process.
+	 * Use the regular "ptrace_may_access()" checks.
+	 */
+	if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
+		rcu_read_unlock();
+		err = -EPERM;
+		goto out_put;
+	}
+	rcu_read_unlock();
+
+	task_nodes = cpuset_mems_allowed(task);
+	/* Is the user allowed to access the target nodes? */
+	if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) {
+		err = -EPERM;
+		goto out_put;
+	}
+
+	task_nodes = cpuset_mems_allowed(current);
+	nodes_and(*new, *new, task_nodes);
+	if (nodes_empty(*new))
+		goto out_put;
+
+	nodes_and(*new, *new, node_states[N_MEMORY]);
+	if (nodes_empty(*new))
+		goto out_put;
+
+	err = security_task_movememory(task);
+	if (err)
+		goto out_put;
+
+	mm = get_task_mm(task);
+	put_task_struct(task);
+
+	if (!mm) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = do_migrate_pages(mm, old, new,
+		capable(CAP_SYS_NICE) ? MPOL_MF_MOVE_ALL : MPOL_MF_MOVE);
+
+	mmput(mm);
+out:
+	NODEMASK_SCRATCH_FREE(scratch);
+
+	return err;
+
+out_put:
+	put_task_struct(task);
+	goto out;
+
+}
+
+SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
+		const unsigned long __user *, old_nodes,
+		const unsigned long __user *, new_nodes)
+{
+	return kernel_migrate_pages(pid, maxnode, old_nodes, new_nodes);
+}
+
+
+/* Retrieve NUMA policy */
+static int kernel_get_mempolicy(int __user *policy,
+				unsigned long __user *nmask,
+				unsigned long maxnode,
+				unsigned long addr,
+				unsigned long flags)
+{
+	int err;
+	int uninitialized_var(pval);
+	nodemask_t nodes;
+
+	if (nmask != NULL && maxnode < nr_node_ids)
+		return -EINVAL;
+
+	err = do_get_mempolicy(&pval, &nodes, addr, flags);
+
+	if (err)
+		return err;
+
+	if (policy && put_user(pval, policy))
+		return -EFAULT;
+
+	if (nmask)
+		err = copy_nodes_to_user(nmask, maxnode, &nodes);
+
+	return err;
+}
+
+SYSCALL_DEFINE5(get_mempolicy, int __user *, policy,
+		unsigned long __user *, nmask, unsigned long, maxnode,
+		unsigned long, addr, unsigned long, flags)
+{
+	return kernel_get_mempolicy(policy, nmask, maxnode, addr, flags);
+}
+
+#ifdef CONFIG_COMPAT
+
+COMPAT_SYSCALL_DEFINE5(get_mempolicy, int __user *, policy,
+		       compat_ulong_t __user *, nmask,
+		       compat_ulong_t, maxnode,
+		       compat_ulong_t, addr, compat_ulong_t, flags)
+{
+	long err;
+	unsigned long __user *nm = NULL;
+	unsigned long nr_bits, alloc_size;
+	DECLARE_BITMAP(bm, MAX_NUMNODES);
+
+	nr_bits = min_t(unsigned long, maxnode-1, nr_node_ids);
+	alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
+
+	if (nmask)
+		nm = compat_alloc_user_space(alloc_size);
+
+	err = kernel_get_mempolicy(policy, nm, nr_bits+1, addr, flags);
+
+	if (!err && nmask) {
+		unsigned long copy_size;
+		copy_size = min_t(unsigned long, sizeof(bm), alloc_size);
+		err = copy_from_user(bm, nm, copy_size);
+		/* ensure entire bitmap is zeroed */
+		err |= clear_user(nmask, ALIGN(maxnode-1, 8) / 8);
+		err |= compat_put_bitmap(nmask, bm, nr_bits);
+	}
+
+	return err;
+}
+
+COMPAT_SYSCALL_DEFINE3(set_mempolicy, int, mode, compat_ulong_t __user *, nmask,
+		       compat_ulong_t, maxnode)
+{
+	unsigned long __user *nm = NULL;
+	unsigned long nr_bits, alloc_size;
+	DECLARE_BITMAP(bm, MAX_NUMNODES);
+
+	nr_bits = min_t(unsigned long, maxnode-1, MAX_NUMNODES);
+	alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
+
+	if (nmask) {
+		if (compat_get_bitmap(bm, nmask, nr_bits))
+			return -EFAULT;
+		nm = compat_alloc_user_space(alloc_size);
+		if (copy_to_user(nm, bm, alloc_size))
+			return -EFAULT;
+	}
+
+	return kernel_set_mempolicy(mode, nm, nr_bits+1);
+}
+
+COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
+		       compat_ulong_t, mode, compat_ulong_t __user *, nmask,
+		       compat_ulong_t, maxnode, compat_ulong_t, flags)
+{
+	unsigned long __user *nm = NULL;
+	unsigned long nr_bits, alloc_size;
+	nodemask_t bm;
+
+	nr_bits = min_t(unsigned long, maxnode-1, MAX_NUMNODES);
+	alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
+
+	if (nmask) {
+		if (compat_get_bitmap(nodes_addr(bm), nmask, nr_bits))
+			return -EFAULT;
+		nm = compat_alloc_user_space(alloc_size);
+		if (copy_to_user(nm, nodes_addr(bm), alloc_size))
+			return -EFAULT;
+	}
+
+	return kernel_mbind(start, len, mode, nm, nr_bits+1, flags);
+}
+
+COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
+		       compat_ulong_t, maxnode,
+		       const compat_ulong_t __user *, old_nodes,
+		       const compat_ulong_t __user *, new_nodes)
+{
+	unsigned long __user *old = NULL;
+	unsigned long __user *new = NULL;
+	nodemask_t tmp_mask;
+	unsigned long nr_bits;
+	unsigned long size;
+
+	nr_bits = min_t(unsigned long, maxnode - 1, MAX_NUMNODES);
+	size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
+	if (old_nodes) {
+		if (compat_get_bitmap(nodes_addr(tmp_mask), old_nodes, nr_bits))
+			return -EFAULT;
+		old = compat_alloc_user_space(new_nodes ? size * 2 : size);
+		if (new_nodes)
+			new = old + size / sizeof(unsigned long);
+		if (copy_to_user(old, nodes_addr(tmp_mask), size))
+			return -EFAULT;
+	}
+	if (new_nodes) {
+		if (compat_get_bitmap(nodes_addr(tmp_mask), new_nodes, nr_bits))
+			return -EFAULT;
+		if (new == NULL)
+			new = compat_alloc_user_space(size);
+		if (copy_to_user(new, nodes_addr(tmp_mask), size))
+			return -EFAULT;
+	}
+	return kernel_migrate_pages(pid, nr_bits + 1, old, new);
+}
+
+#endif /* CONFIG_COMPAT */
+
+struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
+						unsigned long addr)
+{
+	struct mempolicy *pol = NULL;
+
+	if (vma) {
+		if (vma->vm_ops && vma->vm_ops->get_policy) {
+			pol = vma->vm_ops->get_policy(vma, addr);
+		} else if (vma->vm_policy) {
+			pol = vma->vm_policy;
+
+			/*
+			 * shmem_alloc_page() passes MPOL_F_SHARED policy with
+			 * a pseudo vma whose vma->vm_ops=NULL. Take a reference
+			 * count on these policies which will be dropped by
+			 * mpol_cond_put() later
+			 */
+			if (mpol_needs_cond_ref(pol))
+				mpol_get(pol);
+		}
+	}
+
+	return pol;
+}
+
+/*
+ * get_vma_policy(@vma, @addr)
+ * @vma: virtual memory area whose policy is sought
+ * @addr: address in @vma for shared policy lookup
+ *
+ * Returns effective policy for a VMA at specified address.
+ * Falls back to current->mempolicy or system default policy, as necessary.
+ * Shared policies [those marked as MPOL_F_SHARED] require an extra reference
+ * count--added by the get_policy() vm_op, as appropriate--to protect against
+ * freeing by another task.  It is the caller's responsibility to free the
+ * extra reference for shared policies.
+ */
+static struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
+						unsigned long addr)
+{
+	struct mempolicy *pol = __get_vma_policy(vma, addr);
+
+	if (!pol)
+		pol = get_task_policy(current);
+
+	return pol;
+}
+
+bool vma_policy_mof(struct vm_area_struct *vma)
+{
+	struct mempolicy *pol;
+
+	if (vma->vm_ops && vma->vm_ops->get_policy) {
+		bool ret = false;
+
+		pol = vma->vm_ops->get_policy(vma, vma->vm_start);
+		if (pol && (pol->flags & MPOL_F_MOF))
+			ret = true;
+		mpol_cond_put(pol);
+
+		return ret;
+	}
+
+	pol = vma->vm_policy;
+	if (!pol)
+		pol = get_task_policy(current);
+
+	return pol->flags & MPOL_F_MOF;
+}
+
+static int apply_policy_zone(struct mempolicy *policy, enum zone_type zone)
+{
+	enum zone_type dynamic_policy_zone = policy_zone;
+
+	BUG_ON(dynamic_policy_zone == ZONE_MOVABLE);
+
+	/*
+	 * if policy->v.nodes has movable memory only,
+	 * we apply policy when gfp_zone(gfp) = ZONE_MOVABLE only.
+	 *
+	 * policy->v.nodes is intersect with node_states[N_MEMORY].
+	 * so if the following test faile, it implies
+	 * policy->v.nodes has movable memory only.
+	 */
+	if (!nodes_intersects(policy->v.nodes, node_states[N_HIGH_MEMORY]))
+		dynamic_policy_zone = ZONE_MOVABLE;
+
+	return zone >= dynamic_policy_zone;
+}
+
+/*
+ * Return a nodemask representing a mempolicy for filtering nodes for
+ * page allocation
+ */
+static nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy)
+{
+	/* Lower zones don't get a nodemask applied for MPOL_BIND */
+	if (unlikely(policy->mode == MPOL_BIND) &&
+			apply_policy_zone(policy, gfp_zone(gfp)) &&
+			cpuset_nodemask_valid_mems_allowed(&policy->v.nodes))
+		return &policy->v.nodes;
+
+	return NULL;
+}
+
+/* Return the node id preferred by the given mempolicy, or the given id */
+static int policy_node(gfp_t gfp, struct mempolicy *policy,
+								int nd)
+{
+	if (policy->mode == MPOL_PREFERRED && !(policy->flags & MPOL_F_LOCAL))
+		nd = policy->v.preferred_node;
+	else {
+		/*
+		 * __GFP_THISNODE shouldn't even be used with the bind policy
+		 * because we might easily break the expectation to stay on the
+		 * requested node and not break the policy.
+		 */
+		WARN_ON_ONCE(policy->mode == MPOL_BIND && (gfp & __GFP_THISNODE));
+	}
+
+	return nd;
+}
+
+/* Do dynamic interleaving for a process */
+static unsigned interleave_nodes(struct mempolicy *policy)
+{
+	unsigned next;
+	struct task_struct *me = current;
+
+	next = next_node_in(me->il_prev, policy->v.nodes);
+	if (next < MAX_NUMNODES)
+		me->il_prev = next;
+	return next;
+}
+
+/*
+ * Depending on the memory policy provide a node from which to allocate the
+ * next slab entry.
+ */
+unsigned int mempolicy_slab_node(void)
+{
+	struct mempolicy *policy;
+	int node = numa_mem_id();
+
+	if (in_interrupt())
+		return node;
+
+	policy = current->mempolicy;
+	if (!policy || policy->flags & MPOL_F_LOCAL)
+		return node;
+
+	switch (policy->mode) {
+	case MPOL_PREFERRED:
+		/*
+		 * handled MPOL_F_LOCAL above
+		 */
+		return policy->v.preferred_node;
+
+	case MPOL_INTERLEAVE:
+		return interleave_nodes(policy);
+
+	case MPOL_BIND: {
+		struct zoneref *z;
+
+		/*
+		 * Follow bind policy behavior and start allocation at the
+		 * first node.
+		 */
+		struct zonelist *zonelist;
+		enum zone_type highest_zoneidx = gfp_zone(GFP_KERNEL);
+		zonelist = &NODE_DATA(node)->node_zonelists[ZONELIST_FALLBACK];
+		z = first_zones_zonelist(zonelist, highest_zoneidx,
+							&policy->v.nodes);
+		return z->zone ? zone_to_nid(z->zone) : node;
+	}
+
+	default:
+		BUG();
+	}
+}
+
+/*
+ * Do static interleaving for a VMA with known offset @n.  Returns the n'th
+ * node in pol->v.nodes (starting from n=0), wrapping around if n exceeds the
+ * number of present nodes.
+ */
+static unsigned offset_il_node(struct mempolicy *pol, unsigned long n)
+{
+	unsigned nnodes = nodes_weight(pol->v.nodes);
+	unsigned target;
+	int i;
+	int nid;
+
+	if (!nnodes)
+		return numa_node_id();
+	target = (unsigned int)n % nnodes;
+	nid = first_node(pol->v.nodes);
+	for (i = 0; i < target; i++)
+		nid = next_node(nid, pol->v.nodes);
+	return nid;
+}
+
+/* Determine a node number for interleave */
+static inline unsigned interleave_nid(struct mempolicy *pol,
+		 struct vm_area_struct *vma, unsigned long addr, int shift)
+{
+	if (vma) {
+		unsigned long off;
+
+		/*
+		 * for small pages, there is no difference between
+		 * shift and PAGE_SHIFT, so the bit-shift is safe.
+		 * for huge pages, since vm_pgoff is in units of small
+		 * pages, we need to shift off the always 0 bits to get
+		 * a useful offset.
+		 */
+		BUG_ON(shift < PAGE_SHIFT);
+		off = vma->vm_pgoff >> (shift - PAGE_SHIFT);
+		off += (addr - vma->vm_start) >> shift;
+		return offset_il_node(pol, off);
+	} else
+		return interleave_nodes(pol);
+}
+
+#ifdef CONFIG_HUGETLBFS
+/*
+ * huge_node(@vma, @addr, @gfp_flags, @mpol)
+ * @vma: virtual memory area whose policy is sought
+ * @addr: address in @vma for shared policy lookup and interleave policy
+ * @gfp_flags: for requested zone
+ * @mpol: pointer to mempolicy pointer for reference counted mempolicy
+ * @nodemask: pointer to nodemask pointer for MPOL_BIND nodemask
+ *
+ * Returns a nid suitable for a huge page allocation and a pointer
+ * to the struct mempolicy for conditional unref after allocation.
+ * If the effective policy is 'BIND, returns a pointer to the mempolicy's
+ * @nodemask for filtering the zonelist.
+ *
+ * Must be protected by read_mems_allowed_begin()
+ */
+int huge_node(struct vm_area_struct *vma, unsigned long addr, gfp_t gfp_flags,
+				struct mempolicy **mpol, nodemask_t **nodemask)
+{
+	int nid;
+
+	*mpol = get_vma_policy(vma, addr);
+	*nodemask = NULL;	/* assume !MPOL_BIND */
+
+	if (unlikely((*mpol)->mode == MPOL_INTERLEAVE)) {
+		nid = interleave_nid(*mpol, vma, addr,
+					huge_page_shift(hstate_vma(vma)));
+	} else {
+		nid = policy_node(gfp_flags, *mpol, numa_node_id());
+		if ((*mpol)->mode == MPOL_BIND)
+			*nodemask = &(*mpol)->v.nodes;
+	}
+	return nid;
+}
+
+/*
+ * init_nodemask_of_mempolicy
+ *
+ * If the current task's mempolicy is "default" [NULL], return 'false'
+ * to indicate default policy.  Otherwise, extract the policy nodemask
+ * for 'bind' or 'interleave' policy into the argument nodemask, or
+ * initialize the argument nodemask to contain the single node for
+ * 'preferred' or 'local' policy and return 'true' to indicate presence
+ * of non-default mempolicy.
+ *
+ * We don't bother with reference counting the mempolicy [mpol_get/put]
+ * because the current task is examining it's own mempolicy and a task's
+ * mempolicy is only ever changed by the task itself.
+ *
+ * N.B., it is the caller's responsibility to free a returned nodemask.
+ */
+bool init_nodemask_of_mempolicy(nodemask_t *mask)
+{
+	struct mempolicy *mempolicy;
+	int nid;
+
+	if (!(mask && current->mempolicy))
+		return false;
+
+	task_lock(current);
+	mempolicy = current->mempolicy;
+	switch (mempolicy->mode) {
+	case MPOL_PREFERRED:
+		if (mempolicy->flags & MPOL_F_LOCAL)
+			nid = numa_node_id();
+		else
+			nid = mempolicy->v.preferred_node;
+		init_nodemask_of_node(mask, nid);
+		break;
+
+	case MPOL_BIND:
+		/* Fall through */
+	case MPOL_INTERLEAVE:
+		*mask =  mempolicy->v.nodes;
+		break;
+
+	default:
+		BUG();
+	}
+	task_unlock(current);
+
+	return true;
+}
+#endif
+
+/*
+ * mempolicy_nodemask_intersects
+ *
+ * If tsk's mempolicy is "default" [NULL], return 'true' to indicate default
+ * policy.  Otherwise, check for intersection between mask and the policy
+ * nodemask for 'bind' or 'interleave' policy.  For 'perferred' or 'local'
+ * policy, always return true since it may allocate elsewhere on fallback.
+ *
+ * Takes task_lock(tsk) to prevent freeing of its mempolicy.
+ */
+bool mempolicy_nodemask_intersects(struct task_struct *tsk,
+					const nodemask_t *mask)
+{
+	struct mempolicy *mempolicy;
+	bool ret = true;
+
+	if (!mask)
+		return ret;
+	task_lock(tsk);
+	mempolicy = tsk->mempolicy;
+	if (!mempolicy)
+		goto out;
+
+	switch (mempolicy->mode) {
+	case MPOL_PREFERRED:
+		/*
+		 * MPOL_PREFERRED and MPOL_F_LOCAL are only preferred nodes to
+		 * allocate from, they may fallback to other nodes when oom.
+		 * Thus, it's possible for tsk to have allocated memory from
+		 * nodes in mask.
+		 */
+		break;
+	case MPOL_BIND:
+	case MPOL_INTERLEAVE:
+		ret = nodes_intersects(mempolicy->v.nodes, *mask);
+		break;
+	default:
+		BUG();
+	}
+out:
+	task_unlock(tsk);
+	return ret;
+}
+
+/* Allocate a page in interleaved policy.
+   Own path because it needs to do special accounting. */
+static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
+					unsigned nid)
+{
+	struct page *page;
+
+	page = __alloc_pages(gfp, order, nid);
+	/* skip NUMA_INTERLEAVE_HIT counter update if numa stats is disabled */
+	if (!static_branch_likely(&vm_numa_stat_key))
+		return page;
+	if (page && page_to_nid(page) == nid) {
+		preempt_disable();
+		__inc_numa_state(page_zone(page), NUMA_INTERLEAVE_HIT);
+		preempt_enable();
+	}
+	return page;
+}
+
+/**
+ * 	alloc_pages_vma	- Allocate a page for a VMA.
+ *
+ * 	@gfp:
+ *      %GFP_USER    user allocation.
+ *      %GFP_KERNEL  kernel allocations,
+ *      %GFP_HIGHMEM highmem/user allocations,
+ *      %GFP_FS      allocation should not call back into a file system.
+ *      %GFP_ATOMIC  don't sleep.
+ *
+ *	@order:Order of the GFP allocation.
+ * 	@vma:  Pointer to VMA or NULL if not available.
+ *	@addr: Virtual Address of the allocation. Must be inside the VMA.
+ *	@node: Which node to prefer for allocation (modulo policy).
+ *	@hugepage: for hugepages try only the preferred node if possible
+ *
+ * 	This function allocates a page from the kernel page pool and applies
+ *	a NUMA policy associated with the VMA or the current process.
+ *	When VMA is not NULL caller must hold down_read on the mmap_sem of the
+ *	mm_struct of the VMA to prevent it from going away. Should be used for
+ *	all allocations for pages that will be mapped into user space. Returns
+ *	NULL when no page can be allocated.
+ */
+struct page *
+alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
+		unsigned long addr, int node, bool hugepage)
+{
+	struct mempolicy *pol;
+	struct page *page;
+	int preferred_nid;
+	nodemask_t *nmask;
+
+	pol = get_vma_policy(vma, addr);
+
+	if (pol->mode == MPOL_INTERLEAVE) {
+		unsigned nid;
+
+		nid = interleave_nid(pol, vma, addr, PAGE_SHIFT + order);
+		mpol_cond_put(pol);
+		page = alloc_page_interleave(gfp, order, nid);
+		goto out;
+	}
+
+	if (unlikely(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage)) {
+		int hpage_node = node;
+
+		/*
+		 * For hugepage allocation and non-interleave policy which
+		 * allows the current node (or other explicitly preferred
+		 * node) we only try to allocate from the current/preferred
+		 * node and don't fall back to other nodes, as the cost of
+		 * remote accesses would likely offset THP benefits.
+		 *
+		 * If the policy is interleave, or does not allow the current
+		 * node in its nodemask, we allocate the standard way.
+		 */
+		if (pol->mode == MPOL_PREFERRED &&
+						!(pol->flags & MPOL_F_LOCAL))
+			hpage_node = pol->v.preferred_node;
+
+		nmask = policy_nodemask(gfp, pol);
+		if (!nmask || node_isset(hpage_node, *nmask)) {
+			mpol_cond_put(pol);
+			/*
+			 * We cannot invoke reclaim if __GFP_THISNODE
+			 * is set. Invoking reclaim with
+			 * __GFP_THISNODE set, would cause THP
+			 * allocations to trigger heavy swapping
+			 * despite there may be tons of free memory
+			 * (including potentially plenty of THP
+			 * already available in the buddy) on all the
+			 * other NUMA nodes.
+			 *
+			 * At most we could invoke compaction when
+			 * __GFP_THISNODE is set (but we would need to
+			 * refrain from invoking reclaim even if
+			 * compaction returned COMPACT_SKIPPED because
+			 * there wasn't not enough memory to succeed
+			 * compaction). For now just avoid
+			 * __GFP_THISNODE instead of limiting the
+			 * allocation path to a strict and single
+			 * compaction invocation.
+			 *
+			 * Supposedly if direct reclaim was enabled by
+			 * the caller, the app prefers THP regardless
+			 * of the node it comes from so this would be
+			 * more desiderable behavior than only
+			 * providing THP originated from the local
+			 * node in such case.
+			 */
+			if (!(gfp & __GFP_DIRECT_RECLAIM))
+				gfp |= __GFP_THISNODE;
+			page = __alloc_pages_node(hpage_node, gfp, order);
+			goto out;
+		}
+	}
+
+	nmask = policy_nodemask(gfp, pol);
+	preferred_nid = policy_node(gfp, pol, node);
+	page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
+	mpol_cond_put(pol);
+out:
+	return page;
+}
+
+/**
+ * 	alloc_pages_current - Allocate pages.
+ *
+ *	@gfp:
+ *		%GFP_USER   user allocation,
+ *      	%GFP_KERNEL kernel allocation,
+ *      	%GFP_HIGHMEM highmem allocation,
+ *      	%GFP_FS     don't call back into a file system.
+ *      	%GFP_ATOMIC don't sleep.
+ *	@order: Power of two of allocation size in pages. 0 is a single page.
+ *
+ *	Allocate a page from the kernel page pool.  When not in
+ *	interrupt context and apply the current process NUMA policy.
+ *	Returns NULL when no page can be allocated.
+ */
+struct page *alloc_pages_current(gfp_t gfp, unsigned order)
+{
+	struct mempolicy *pol = &default_policy;
+	struct page *page;
+
+	if (!in_interrupt() && !(gfp & __GFP_THISNODE))
+		pol = get_task_policy(current);
+
+	/*
+	 * No reference counting needed for current->mempolicy
+	 * nor system default_policy
+	 */
+	if (pol->mode == MPOL_INTERLEAVE)
+		page = alloc_page_interleave(gfp, order, interleave_nodes(pol));
+	else
+		page = __alloc_pages_nodemask(gfp, order,
+				policy_node(gfp, pol, numa_node_id()),
+				policy_nodemask(gfp, pol));
+
+	return page;
+}
+EXPORT_SYMBOL(alloc_pages_current);
+
+int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
+{
+	struct mempolicy *pol = mpol_dup(vma_policy(src));
+
+	if (IS_ERR(pol))
+		return PTR_ERR(pol);
+	dst->vm_policy = pol;
+	return 0;
+}
+
+/*
+ * If mpol_dup() sees current->cpuset == cpuset_being_rebound, then it
+ * rebinds the mempolicy its copying by calling mpol_rebind_policy()
+ * with the mems_allowed returned by cpuset_mems_allowed().  This
+ * keeps mempolicies cpuset relative after its cpuset moves.  See
+ * further kernel/cpuset.c update_nodemask().
+ *
+ * current's mempolicy may be rebinded by the other task(the task that changes
+ * cpuset's mems), so we needn't do rebind work for current task.
+ */
+
+/* Slow path of a mempolicy duplicate */
+struct mempolicy *__mpol_dup(struct mempolicy *old)
+{
+	struct mempolicy *new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+
+	if (!new)
+		return ERR_PTR(-ENOMEM);
+
+	/* task's mempolicy is protected by alloc_lock */
+	if (old == current->mempolicy) {
+		task_lock(current);
+		*new = *old;
+		task_unlock(current);
+	} else
+		*new = *old;
+
+	if (current_cpuset_is_being_rebound()) {
+		nodemask_t mems = cpuset_mems_allowed(current);
+		mpol_rebind_policy(new, &mems);
+	}
+	atomic_set(&new->refcnt, 1);
+	return new;
+}
+
+/* Slow path of a mempolicy comparison */
+bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
+{
+	if (!a || !b)
+		return false;
+	if (a->mode != b->mode)
+		return false;
+	if (a->flags != b->flags)
+		return false;
+	if (mpol_store_user_nodemask(a))
+		if (!nodes_equal(a->w.user_nodemask, b->w.user_nodemask))
+			return false;
+
+	switch (a->mode) {
+	case MPOL_BIND:
+		/* Fall through */
+	case MPOL_INTERLEAVE:
+		return !!nodes_equal(a->v.nodes, b->v.nodes);
+	case MPOL_PREFERRED:
+		/* a's ->flags is the same as b's */
+		if (a->flags & MPOL_F_LOCAL)
+			return true;
+		return a->v.preferred_node == b->v.preferred_node;
+	default:
+		BUG();
+		return false;
+	}
+}
+
+/*
+ * Shared memory backing store policy support.
+ *
+ * Remember policies even when nobody has shared memory mapped.
+ * The policies are kept in Red-Black tree linked from the inode.
+ * They are protected by the sp->lock rwlock, which should be held
+ * for any accesses to the tree.
+ */
+
+/*
+ * lookup first element intersecting start-end.  Caller holds sp->lock for
+ * reading or for writing
+ */
+static struct sp_node *
+sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
+{
+	struct rb_node *n = sp->root.rb_node;
+
+	while (n) {
+		struct sp_node *p = rb_entry(n, struct sp_node, nd);
+
+		if (start >= p->end)
+			n = n->rb_right;
+		else if (end <= p->start)
+			n = n->rb_left;
+		else
+			break;
+	}
+	if (!n)
+		return NULL;
+	for (;;) {
+		struct sp_node *w = NULL;
+		struct rb_node *prev = rb_prev(n);
+		if (!prev)
+			break;
+		w = rb_entry(prev, struct sp_node, nd);
+		if (w->end <= start)
+			break;
+		n = prev;
+	}
+	return rb_entry(n, struct sp_node, nd);
+}
+
+/*
+ * Insert a new shared policy into the list.  Caller holds sp->lock for
+ * writing.
+ */
+static void sp_insert(struct shared_policy *sp, struct sp_node *new)
+{
+	struct rb_node **p = &sp->root.rb_node;
+	struct rb_node *parent = NULL;
+	struct sp_node *nd;
+
+	while (*p) {
+		parent = *p;
+		nd = rb_entry(parent, struct sp_node, nd);
+		if (new->start < nd->start)
+			p = &(*p)->rb_left;
+		else if (new->end > nd->end)
+			p = &(*p)->rb_right;
+		else
+			BUG();
+	}
+	rb_link_node(&new->nd, parent, p);
+	rb_insert_color(&new->nd, &sp->root);
+	pr_debug("inserting %lx-%lx: %d\n", new->start, new->end,
+		 new->policy ? new->policy->mode : 0);
+}
+
+/* Find shared policy intersecting idx */
+struct mempolicy *
+mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
+{
+	struct mempolicy *pol = NULL;
+	struct sp_node *sn;
+
+	if (!sp->root.rb_node)
+		return NULL;
+	read_lock(&sp->lock);
+	sn = sp_lookup(sp, idx, idx+1);
+	if (sn) {
+		mpol_get(sn->policy);
+		pol = sn->policy;
+	}
+	read_unlock(&sp->lock);
+	return pol;
+}
+
+static void sp_free(struct sp_node *n)
+{
+	mpol_put(n->policy);
+	kmem_cache_free(sn_cache, n);
+}
+
+/**
+ * mpol_misplaced - check whether current page node is valid in policy
+ *
+ * @page: page to be checked
+ * @vma: vm area where page mapped
+ * @addr: virtual address where page mapped
+ *
+ * Lookup current policy node id for vma,addr and "compare to" page's
+ * node id.
+ *
+ * Returns:
+ *	-1	- not misplaced, page is in the right node
+ *	node	- node id where the page should be
+ *
+ * Policy determination "mimics" alloc_page_vma().
+ * Called from fault path where we know the vma and faulting address.
+ */
+int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol;
+	struct zoneref *z;
+	int curnid = page_to_nid(page);
+	unsigned long pgoff;
+	int thiscpu = raw_smp_processor_id();
+	int thisnid = cpu_to_node(thiscpu);
+	int polnid = -1;
+	int ret = -1;
+
+	pol = get_vma_policy(vma, addr);
+	if (!(pol->flags & MPOL_F_MOF))
+		goto out;
+
+	switch (pol->mode) {
+	case MPOL_INTERLEAVE:
+		pgoff = vma->vm_pgoff;
+		pgoff += (addr - vma->vm_start) >> PAGE_SHIFT;
+		polnid = offset_il_node(pol, pgoff);
+		break;
+
+	case MPOL_PREFERRED:
+		if (pol->flags & MPOL_F_LOCAL)
+			polnid = numa_node_id();
+		else
+			polnid = pol->v.preferred_node;
+		break;
+
+	case MPOL_BIND:
+
+		/*
+		 * allows binding to multiple nodes.
+		 * use current page if in policy nodemask,
+		 * else select nearest allowed node, if any.
+		 * If no allowed nodes, use current [!misplaced].
+		 */
+		if (node_isset(curnid, pol->v.nodes))
+			goto out;
+		z = first_zones_zonelist(
+				node_zonelist(numa_node_id(), GFP_HIGHUSER),
+				gfp_zone(GFP_HIGHUSER),
+				&pol->v.nodes);
+		polnid = zone_to_nid(z->zone);
+		break;
+
+	default:
+		BUG();
+	}
+
+	/* Migrate the page towards the node whose CPU is referencing it */
+	if (pol->flags & MPOL_F_MORON) {
+		polnid = thisnid;
+
+		if (!should_numa_migrate_memory(current, page, curnid, thiscpu))
+			goto out;
+	}
+
+	if (curnid != polnid)
+		ret = polnid;
+out:
+	mpol_cond_put(pol);
+
+	return ret;
+}
+
+/*
+ * Drop the (possibly final) reference to task->mempolicy.  It needs to be
+ * dropped after task->mempolicy is set to NULL so that any allocation done as
+ * part of its kmem_cache_free(), such as by KASAN, doesn't reference a freed
+ * policy.
+ */
+void mpol_put_task_policy(struct task_struct *task)
+{
+	struct mempolicy *pol;
+
+	task_lock(task);
+	pol = task->mempolicy;
+	task->mempolicy = NULL;
+	task_unlock(task);
+	mpol_put(pol);
+}
+
+static void sp_delete(struct shared_policy *sp, struct sp_node *n)
+{
+	pr_debug("deleting %lx-l%lx\n", n->start, n->end);
+	rb_erase(&n->nd, &sp->root);
+	sp_free(n);
+}
+
+static void sp_node_init(struct sp_node *node, unsigned long start,
+			unsigned long end, struct mempolicy *pol)
+{
+	node->start = start;
+	node->end = end;
+	node->policy = pol;
+}
+
+static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
+				struct mempolicy *pol)
+{
+	struct sp_node *n;
+	struct mempolicy *newpol;
+
+	n = kmem_cache_alloc(sn_cache, GFP_KERNEL);
+	if (!n)
+		return NULL;
+
+	newpol = mpol_dup(pol);
+	if (IS_ERR(newpol)) {
+		kmem_cache_free(sn_cache, n);
+		return NULL;
+	}
+	newpol->flags |= MPOL_F_SHARED;
+	sp_node_init(n, start, end, newpol);
+
+	return n;
+}
+
+/* Replace a policy range. */
+static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
+				 unsigned long end, struct sp_node *new)
+{
+	struct sp_node *n;
+	struct sp_node *n_new = NULL;
+	struct mempolicy *mpol_new = NULL;
+	int ret = 0;
+
+restart:
+	write_lock(&sp->lock);
+	n = sp_lookup(sp, start, end);
+	/* Take care of old policies in the same range. */
+	while (n && n->start < end) {
+		struct rb_node *next = rb_next(&n->nd);
+		if (n->start >= start) {
+			if (n->end <= end)
+				sp_delete(sp, n);
+			else
+				n->start = end;
+		} else {
+			/* Old policy spanning whole new range. */
+			if (n->end > end) {
+				if (!n_new)
+					goto alloc_new;
+
+				*mpol_new = *n->policy;
+				atomic_set(&mpol_new->refcnt, 1);
+				sp_node_init(n_new, end, n->end, mpol_new);
+				n->end = start;
+				sp_insert(sp, n_new);
+				n_new = NULL;
+				mpol_new = NULL;
+				break;
+			} else
+				n->end = start;
+		}
+		if (!next)
+			break;
+		n = rb_entry(next, struct sp_node, nd);
+	}
+	if (new)
+		sp_insert(sp, new);
+	write_unlock(&sp->lock);
+	ret = 0;
+
+err_out:
+	if (mpol_new)
+		mpol_put(mpol_new);
+	if (n_new)
+		kmem_cache_free(sn_cache, n_new);
+
+	return ret;
+
+alloc_new:
+	write_unlock(&sp->lock);
+	ret = -ENOMEM;
+	n_new = kmem_cache_alloc(sn_cache, GFP_KERNEL);
+	if (!n_new)
+		goto err_out;
+	mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+	if (!mpol_new)
+		goto err_out;
+	atomic_set(&mpol_new->refcnt, 1);
+	goto restart;
+}
+
+/**
+ * mpol_shared_policy_init - initialize shared policy for inode
+ * @sp: pointer to inode shared policy
+ * @mpol:  struct mempolicy to install
+ *
+ * Install non-NULL @mpol in inode's shared policy rb-tree.
+ * On entry, the current task has a reference on a non-NULL @mpol.
+ * This must be released on exit.
+ * This is called at get_inode() calls and we can use GFP_KERNEL.
+ */
+void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
+{
+	int ret;
+
+	sp->root = RB_ROOT;		/* empty tree == default mempolicy */
+	rwlock_init(&sp->lock);
+
+	if (mpol) {
+		struct vm_area_struct pvma;
+		struct mempolicy *new;
+		NODEMASK_SCRATCH(scratch);
+
+		if (!scratch)
+			goto put_mpol;
+		/* contextualize the tmpfs mount point mempolicy */
+		new = mpol_new(mpol->mode, mpol->flags, &mpol->w.user_nodemask);
+		if (IS_ERR(new))
+			goto free_scratch; /* no valid nodemask intersection */
+
+		task_lock(current);
+		ret = mpol_set_nodemask(new, &mpol->w.user_nodemask, scratch);
+		task_unlock(current);
+		if (ret)
+			goto put_new;
+
+		/* Create pseudo-vma that contains just the policy */
+		vma_init(&pvma, NULL);
+		pvma.vm_end = TASK_SIZE;	/* policy covers entire file */
+		mpol_set_shared_policy(sp, &pvma, new); /* adds ref */
+
+put_new:
+		mpol_put(new);			/* drop initial ref */
+free_scratch:
+		NODEMASK_SCRATCH_FREE(scratch);
+put_mpol:
+		mpol_put(mpol);	/* drop our incoming ref on sb mpol */
+	}
+}
+
+int mpol_set_shared_policy(struct shared_policy *info,
+			struct vm_area_struct *vma, struct mempolicy *npol)
+{
+	int err;
+	struct sp_node *new = NULL;
+	unsigned long sz = vma_pages(vma);
+
+	pr_debug("set_shared_policy %lx sz %lu %d %d %lx\n",
+		 vma->vm_pgoff,
+		 sz, npol ? npol->mode : -1,
+		 npol ? npol->flags : -1,
+		 npol ? nodes_addr(npol->v.nodes)[0] : NUMA_NO_NODE);
+
+	if (npol) {
+		new = sp_alloc(vma->vm_pgoff, vma->vm_pgoff + sz, npol);
+		if (!new)
+			return -ENOMEM;
+	}
+	err = shared_policy_replace(info, vma->vm_pgoff, vma->vm_pgoff+sz, new);
+	if (err && new)
+		sp_free(new);
+	return err;
+}
+
+/* Free a backing policy store on inode delete. */
+void mpol_free_shared_policy(struct shared_policy *p)
+{
+	struct sp_node *n;
+	struct rb_node *next;
+
+	if (!p->root.rb_node)
+		return;
+	write_lock(&p->lock);
+	next = rb_first(&p->root);
+	while (next) {
+		n = rb_entry(next, struct sp_node, nd);
+		next = rb_next(&n->nd);
+		sp_delete(p, n);
+	}
+	write_unlock(&p->lock);
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+static int __initdata numabalancing_override;
+
+static void __init check_numabalancing_enable(void)
+{
+	bool numabalancing_default = false;
+
+	if (IS_ENABLED(CONFIG_NUMA_BALANCING_DEFAULT_ENABLED))
+		numabalancing_default = true;
+
+	/* Parsed by setup_numabalancing. override == 1 enables, -1 disables */
+	if (numabalancing_override)
+		set_numabalancing_state(numabalancing_override == 1);
+
+	if (num_online_nodes() > 1 && !numabalancing_override) {
+		pr_info("%s automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl\n",
+			numabalancing_default ? "Enabling" : "Disabling");
+		set_numabalancing_state(numabalancing_default);
+	}
+}
+
+static int __init setup_numabalancing(char *str)
+{
+	int ret = 0;
+	if (!str)
+		goto out;
+
+	if (!strcmp(str, "enable")) {
+		numabalancing_override = 1;
+		ret = 1;
+	} else if (!strcmp(str, "disable")) {
+		numabalancing_override = -1;
+		ret = 1;
+	}
+out:
+	if (!ret)
+		pr_warn("Unable to parse numa_balancing=\n");
+
+	return ret;
+}
+__setup("numa_balancing=", setup_numabalancing);
+#else
+static inline void __init check_numabalancing_enable(void)
+{
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+/* assumes fs == KERNEL_DS */
+void __init numa_policy_init(void)
+{
+	nodemask_t interleave_nodes;
+	unsigned long largest = 0;
+	int nid, prefer = 0;
+
+	policy_cache = kmem_cache_create("numa_policy",
+					 sizeof(struct mempolicy),
+					 0, SLAB_PANIC, NULL);
+
+	sn_cache = kmem_cache_create("shared_policy_node",
+				     sizeof(struct sp_node),
+				     0, SLAB_PANIC, NULL);
+
+	for_each_node(nid) {
+		preferred_node_policy[nid] = (struct mempolicy) {
+			.refcnt = ATOMIC_INIT(1),
+			.mode = MPOL_PREFERRED,
+			.flags = MPOL_F_MOF | MPOL_F_MORON,
+			.v = { .preferred_node = nid, },
+		};
+	}
+
+	/*
+	 * Set interleaving policy for system init. Interleaving is only
+	 * enabled across suitably sized nodes (default is >= 16MB), or
+	 * fall back to the largest node if they're all smaller.
+	 */
+	nodes_clear(interleave_nodes);
+	for_each_node_state(nid, N_MEMORY) {
+		unsigned long total_pages = node_present_pages(nid);
+
+		/* Preserve the largest node */
+		if (largest < total_pages) {
+			largest = total_pages;
+			prefer = nid;
+		}
+
+		/* Interleave this node? */
+		if ((total_pages << PAGE_SHIFT) >= (16 << 20))
+			node_set(nid, interleave_nodes);
+	}
+
+	/* All too small, use the largest */
+	if (unlikely(nodes_empty(interleave_nodes)))
+		node_set(prefer, interleave_nodes);
+
+	if (do_set_mempolicy(MPOL_INTERLEAVE, 0, &interleave_nodes))
+		pr_err("%s: interleaving failed\n", __func__);
+
+	check_numabalancing_enable();
+}
+
+/* Reset policy of current process to default */
+void numa_default_policy(void)
+{
+	do_set_mempolicy(MPOL_DEFAULT, 0, NULL);
+}
+
+/*
+ * Parse and format mempolicy from/to strings
+ */
+
+/*
+ * "local" is implemented internally by MPOL_PREFERRED with MPOL_F_LOCAL flag.
+ */
+static const char * const policy_modes[] =
+{
+	[MPOL_DEFAULT]    = "default",
+	[MPOL_PREFERRED]  = "prefer",
+	[MPOL_BIND]       = "bind",
+	[MPOL_INTERLEAVE] = "interleave",
+	[MPOL_LOCAL]      = "local",
+};
+
+
+#ifdef CONFIG_TMPFS
+/**
+ * mpol_parse_str - parse string to mempolicy, for tmpfs mpol mount option.
+ * @str:  string containing mempolicy to parse
+ * @mpol:  pointer to struct mempolicy pointer, returned on success.
+ *
+ * Format of input:
+ *	<mode>[=<flags>][:<nodelist>]
+ *
+ * On success, returns 0, else 1
+ */
+int mpol_parse_str(char *str, struct mempolicy **mpol)
+{
+	struct mempolicy *new = NULL;
+	unsigned short mode;
+	unsigned short mode_flags;
+	nodemask_t nodes;
+	char *nodelist = strchr(str, ':');
+	char *flags = strchr(str, '=');
+	int err = 1;
+
+	if (flags)
+		*flags++ = '\0';	/* terminate mode string */
+
+	if (nodelist) {
+		/* NUL-terminate mode or flags string */
+		*nodelist++ = '\0';
+		if (nodelist_parse(nodelist, nodes))
+			goto out;
+		if (!nodes_subset(nodes, node_states[N_MEMORY]))
+			goto out;
+	} else
+		nodes_clear(nodes);
+
+	for (mode = 0; mode < MPOL_MAX; mode++) {
+		if (!strcmp(str, policy_modes[mode])) {
+			break;
+		}
+	}
+	if (mode >= MPOL_MAX)
+		goto out;
+
+	switch (mode) {
+	case MPOL_PREFERRED:
+		/*
+		 * Insist on a nodelist of one node only, although later
+		 * we use first_node(nodes) to grab a single node, so here
+		 * nodelist (or nodes) cannot be empty.
+		 */
+		if (nodelist) {
+			char *rest = nodelist;
+			while (isdigit(*rest))
+				rest++;
+			if (*rest)
+				goto out;
+			if (nodes_empty(nodes))
+				goto out;
+		}
+		break;
+	case MPOL_INTERLEAVE:
+		/*
+		 * Default to online nodes with memory if no nodelist
+		 */
+		if (!nodelist)
+			nodes = node_states[N_MEMORY];
+		break;
+	case MPOL_LOCAL:
+		/*
+		 * Don't allow a nodelist;  mpol_new() checks flags
+		 */
+		if (nodelist)
+			goto out;
+		mode = MPOL_PREFERRED;
+		break;
+	case MPOL_DEFAULT:
+		/*
+		 * Insist on a empty nodelist
+		 */
+		if (!nodelist)
+			err = 0;
+		goto out;
+	case MPOL_BIND:
+		/*
+		 * Insist on a nodelist
+		 */
+		if (!nodelist)
+			goto out;
+	}
+
+	mode_flags = 0;
+	if (flags) {
+		/*
+		 * Currently, we only support two mutually exclusive
+		 * mode flags.
+		 */
+		if (!strcmp(flags, "static"))
+			mode_flags |= MPOL_F_STATIC_NODES;
+		else if (!strcmp(flags, "relative"))
+			mode_flags |= MPOL_F_RELATIVE_NODES;
+		else
+			goto out;
+	}
+
+	new = mpol_new(mode, mode_flags, &nodes);
+	if (IS_ERR(new))
+		goto out;
+
+	/*
+	 * Save nodes for mpol_to_str() to show the tmpfs mount options
+	 * for /proc/mounts, /proc/pid/mounts and /proc/pid/mountinfo.
+	 */
+	if (mode != MPOL_PREFERRED)
+		new->v.nodes = nodes;
+	else if (nodelist)
+		new->v.preferred_node = first_node(nodes);
+	else
+		new->flags |= MPOL_F_LOCAL;
+
+	/*
+	 * Save nodes for contextualization: this will be used to "clone"
+	 * the mempolicy in a specific context [cpuset] at a later time.
+	 */
+	new->w.user_nodemask = nodes;
+
+	err = 0;
+
+out:
+	/* Restore string for error message */
+	if (nodelist)
+		*--nodelist = ':';
+	if (flags)
+		*--flags = '=';
+	if (!err)
+		*mpol = new;
+	return err;
+}
+#endif /* CONFIG_TMPFS */
+
+/**
+ * mpol_to_str - format a mempolicy structure for printing
+ * @buffer:  to contain formatted mempolicy string
+ * @maxlen:  length of @buffer
+ * @pol:  pointer to mempolicy to be formatted
+ *
+ * Convert @pol into a string.  If @buffer is too short, truncate the string.
+ * Recommend a @maxlen of at least 32 for the longest mode, "interleave", the
+ * longest flag, "relative", and to display at least a few node ids.
+ */
+void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
+{
+	char *p = buffer;
+	nodemask_t nodes = NODE_MASK_NONE;
+	unsigned short mode = MPOL_DEFAULT;
+	unsigned short flags = 0;
+
+	if (pol && pol != &default_policy && !(pol->flags & MPOL_F_MORON)) {
+		mode = pol->mode;
+		flags = pol->flags;
+	}
+
+	switch (mode) {
+	case MPOL_DEFAULT:
+		break;
+	case MPOL_PREFERRED:
+		if (flags & MPOL_F_LOCAL)
+			mode = MPOL_LOCAL;
+		else
+			node_set(pol->v.preferred_node, nodes);
+		break;
+	case MPOL_BIND:
+	case MPOL_INTERLEAVE:
+		nodes = pol->v.nodes;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		snprintf(p, maxlen, "unknown");
+		return;
+	}
+
+	p += snprintf(p, maxlen, "%s", policy_modes[mode]);
+
+	if (flags & MPOL_MODE_FLAGS) {
+		p += snprintf(p, buffer + maxlen - p, "=");
+
+		/*
+		 * Currently, the only defined flags are mutually exclusive
+		 */
+		if (flags & MPOL_F_STATIC_NODES)
+			p += snprintf(p, buffer + maxlen - p, "static");
+		else if (flags & MPOL_F_RELATIVE_NODES)
+			p += snprintf(p, buffer + maxlen - p, "relative");
+	}
+
+	if (!nodes_empty(nodes))
+		p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
+			       nodemask_pr_args(&nodes));
+}