[PATCH] numa api: Core NUMA API code

From: Andi Kleen <ak@suse.de>

The following patches add support for configurable NUMA memory policy
for user processes. It is based on the proposal from last kernel summit
with feedback from various people.

This NUMA API doesn't not attempt to implement page migration or anything
else complicated: all it does is to police the allocation when a page
is first allocation or when a page is reallocated after swapping. Currently
only support for shared memory and anonymous memory is there; policy for
file based mappings is not implemented yet (although they get implicitely
policied by the default process policy)

It adds three new system calls: mbind to change the policy of a VMA,
set_mempolicy to change the policy of a process, get_mempolicy to retrieve
memory policy. User tools (numactl, libnuma, test programs, manpages) can be
found in  ftp://ftp.suse.com/pub/people/ak/numa/numactl-0.6.tar.gz

For details on the system calls see the manpages
http://www.firstfloor.org/~andi/mbind.html
http://www.firstfloor.org/~andi/set_mempolicy.html
http://www.firstfloor.org/~andi/get_mempolicy.html
Most user programs should actually not use the system calls directly,
but use the higher level functions in libnuma
(http://www.firstfloor.org/~andi/numa.html) or the command line tools
(http://www.firstfloor.org/~andi/numactl.html

The system calls allow user programs and administors to set various NUMA memory
policies for putting memory on specific nodes. Here is a short description
of the policies copied from the kernel patch:

 * 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.
 * preferred      Try a specific node first before normal fallback.
 *                As a special case node -1 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.




This patch:

This is the core NUMA API code. This includes NUMA policy aware
wrappers for get_free_pages and alloc_page_vma(). On non NUMA kernels
these are defined away.

The system calls mbind (see http://www.firstfloor.org/~andi/mbind.html),
get_mempolicy (http://www.firstfloor.org/~andi/get_mempolicy.html) and
set_mempolicy (http://www.firstfloor.org/~andi/set_mempolicy.html) are
implemented here.

Adds a vm_policy field to the VMA and to the process. The process
also has field for interleaving. VMA interleaving uses the offset
into the VMA, but that's not possible for process allocations.

From: Andi Kleen <ak@muc.de>

  > Andi, how come policy_vma() calls ->set_policy under i_shared_sem?

  I think this can be actually dropped now.  In an earlier version I did
  walk the vma shared list to change the policies of other mappings to the
  same shared memory region.  This turned out too complicated with all the
  corner cases, so I eventually gave in and added ->get_policy to the fast
  path.  Also there is still the mmap_sem which prevents races in the same MM.
   

  Patch to remove it attached.  Also adds documentation and removes the
  bogus __alloc_page_vma() prototype noticed by hch.

From: Andi Kleen <ak@suse.de>

  A few incremental fixes for NUMA API.

  - Fix a few comments

  - Add a compat_ function for get_mem_policy I considered changing the
    ABI to avoid this, but that would have made the API too ugly.  I put it
    directly into the file because a mm/compat.c didn't seem worth it just for
    this.

  - Fix the algorithm for VMA interleave.

From: Matthew Dobson <colpatch@us.ibm.com>

  1) Move the extern of alloc_pages_current() into #ifdef CONFIG_NUMA.
    The only references to the function are in NUMA code in mempolicy.c

  2) Remove the definitions of __alloc_page_vma().  They aren't used.

  3) Move forward declaration of struct vm_area_struct to top of file.

2 files changed, 1018 insertions, 0 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 5f3baecd85a7f3..6927986abd75a0 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -13,3 +13,4 @@ obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
 
 obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o
 obj-$(CONFIG_HUGETLBFS)	+= hugetlb.o
+obj-$(CONFIG_NUMA) 	+= mempolicy.o
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
new file mode 100644
index 00000000000000..39bfe0d2ab49d3
--- /dev/null
+++ b/mm/mempolicy.c
@@ -0,0 +1,1017 @@
+/*
+ * Simple NUMA memory policy for the Linux kernel.
+ *
+ * Copyright 2003,2004 Andi Kleen, SuSE Labs.
+ * 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.
+ * preferred       Try a specific node first before normal fallback.
+ *                As a special case node -1 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.
+   could replace all the switch()es with a mempolicy_ops structure.
+*/
+
+#include <linux/mempolicy.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/compat.h>
+#include <asm/uaccess.h>
+
+static kmem_cache_t *policy_cache;
+static kmem_cache_t *sn_cache;
+
+#define PDprintk(fmt...)
+
+/* Highest zone. An specific allocation for a zone below that is not
+   policied. */
+static int policy_zone;
+
+static struct mempolicy default_policy = {
+	.refcnt = ATOMIC_INIT(1), /* never free it */
+	.policy = MPOL_DEFAULT,
+};
+
+/* Check if all specified nodes are online */
+static int nodes_online(unsigned long *nodes)
+{
+	DECLARE_BITMAP(offline, MAX_NUMNODES);
+
+	bitmap_copy(offline, node_online_map, MAX_NUMNODES);
+	if (bitmap_empty(offline, MAX_NUMNODES))
+		set_bit(0, offline);
+	bitmap_complement(offline, MAX_NUMNODES);
+	bitmap_and(offline, offline, nodes, MAX_NUMNODES);
+	if (!bitmap_empty(offline, MAX_NUMNODES))
+		return -EINVAL;
+	return 0;
+}
+
+/* Do sanity checking on a policy */
+static int mpol_check_policy(int mode, unsigned long *nodes)
+{
+	int empty = bitmap_empty(nodes, MAX_NUMNODES);
+
+	switch (mode) {
+	case MPOL_DEFAULT:
+		if (!empty)
+			return -EINVAL;
+		break;
+	case MPOL_BIND:
+	case MPOL_INTERLEAVE:
+		/* Preferred will only use the first bit, but allow
+		   more for now. */
+		if (empty)
+			return -EINVAL;
+		break;
+	}
+	return nodes_online(nodes);
+}
+
+/* Copy a node mask from user space. */
+static int get_nodes(unsigned long *nodes, unsigned long *nmask,
+		     unsigned long maxnode, int mode)
+{
+	unsigned long k;
+	unsigned long nlongs;
+	unsigned long endmask;
+
+	--maxnode;
+	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 (nmask && nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
+		for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
+			unsigned long t;
+			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;
+	}
+
+	bitmap_zero(nodes, MAX_NUMNODES);
+	if (nmask && copy_from_user(nodes, nmask, nlongs*sizeof(unsigned long)))
+		return -EFAULT;
+	nodes[nlongs-1] &= endmask;
+	return mpol_check_policy(mode, nodes);
+}
+
+/* Generate a custom zonelist for the BIND policy. */
+static struct zonelist *bind_zonelist(unsigned long *nodes)
+{
+	struct zonelist *zl;
+	int num, max, nd;
+
+	max = 1 + MAX_NR_ZONES * bitmap_weight(nodes, MAX_NUMNODES);
+	zl = kmalloc(sizeof(void *) * max, GFP_KERNEL);
+	if (!zl)
+		return NULL;
+	num = 0;
+	for (nd = find_first_bit(nodes, MAX_NUMNODES);
+	     nd < MAX_NUMNODES;
+	     nd = find_next_bit(nodes, MAX_NUMNODES, 1+nd)) {
+		int k;
+		for (k = MAX_NR_ZONES-1; k >= 0; k--) {
+			struct zone *z = &NODE_DATA(nd)->node_zones[k];
+			if (!z->present_pages)
+				continue;
+			zl->zones[num++] = z;
+			if (k > policy_zone)
+				policy_zone = k;
+		}
+	}
+	BUG_ON(num >= max);
+	zl->zones[num] = NULL;
+	return zl;
+}
+
+/* Create a new policy */
+static struct mempolicy *mpol_new(int mode, unsigned long *nodes)
+{
+	struct mempolicy *policy;
+
+	PDprintk("setting mode %d nodes[0] %lx\n", mode, nodes[0]);
+	if (mode == MPOL_DEFAULT)
+		return NULL;
+	policy = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+	if (!policy)
+		return ERR_PTR(-ENOMEM);
+	atomic_set(&policy->refcnt, 1);
+	switch (mode) {
+	case MPOL_INTERLEAVE:
+		bitmap_copy(policy->v.nodes, nodes, MAX_NUMNODES);
+		break;
+	case MPOL_PREFERRED:
+		policy->v.preferred_node = find_first_bit(nodes, MAX_NUMNODES);
+		if (policy->v.preferred_node >= MAX_NUMNODES)
+			policy->v.preferred_node = -1;
+		break;
+	case MPOL_BIND:
+		policy->v.zonelist = bind_zonelist(nodes);
+		if (policy->v.zonelist == NULL) {
+			kmem_cache_free(policy_cache, policy);
+			return ERR_PTR(-ENOMEM);
+		}
+		break;
+	}
+	policy->policy = mode;
+	return policy;
+}
+
+/* Ensure all existing pages follow the policy. */
+static int
+verify_pages(unsigned long addr, unsigned long end, unsigned long *nodes)
+{
+	while (addr < end) {
+		struct page *p;
+		pte_t *pte;
+		pmd_t *pmd;
+		pgd_t *pgd = pgd_offset_k(addr);
+		if (pgd_none(*pgd)) {
+			addr = (addr + PGDIR_SIZE) & PGDIR_MASK;
+			continue;
+		}
+		pmd = pmd_offset(pgd, addr);
+		if (pmd_none(*pmd)) {
+			addr = (addr + PMD_SIZE) & PMD_MASK;
+			continue;
+		}
+		p = NULL;
+		pte = pte_offset_map(pmd, addr);
+		if (pte_present(*pte))
+			p = pte_page(*pte);
+		pte_unmap(pte);
+		if (p) {
+			unsigned nid = page_to_nid(p);
+			if (!test_bit(nid, nodes))
+				return -EIO;
+		}
+		addr += PAGE_SIZE;
+	}
+	return 0;
+}
+
+/* Step 1: check the range */
+static struct vm_area_struct *
+check_range(struct mm_struct *mm, unsigned long start, unsigned long end,
+	    unsigned long *nodes, unsigned long flags)
+{
+	int err;
+	struct vm_area_struct *first, *vma, *prev;
+
+	first = find_vma(mm, start);
+	if (!first)
+		return ERR_PTR(-EFAULT);
+	prev = NULL;
+	for (vma = first; vma->vm_start < end; vma = vma->vm_next) {
+		if (!vma->vm_next && vma->vm_end < end)
+			return ERR_PTR(-EFAULT);
+		if (prev && prev->vm_end < vma->vm_start)
+			return ERR_PTR(-EFAULT);
+		if ((flags & MPOL_MF_STRICT) && !is_vm_hugetlb_page(vma)) {
+			err = verify_pages(vma->vm_start, vma->vm_end, nodes);
+			if (err) {
+				first = ERR_PTR(err);
+				break;
+			}
+		}
+		prev = vma;
+	}
+	return first;
+}
+
+/* Apply policy to a single VMA */
+static int policy_vma(struct vm_area_struct *vma, struct mempolicy *new)
+{
+	int err = 0;
+	struct mempolicy *old = vma->vm_policy;
+
+	PDprintk("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);
+
+	if (vma->vm_ops && vma->vm_ops->set_policy)
+		err = vma->vm_ops->set_policy(vma, new);
+	if (!err) {
+		mpol_get(new);
+		vma->vm_policy = new;
+		mpol_free(old);
+	}
+	return err;
+}
+
+/* Step 2: apply policy to a range and do splits. */
+static int mbind_range(struct vm_area_struct *vma, unsigned long start,
+		       unsigned long end, struct mempolicy *new)
+{
+	struct vm_area_struct *next;
+	int err;
+
+	err = 0;
+	for (; vma->vm_start < end; vma = next) {
+		next = vma->vm_next;
+		if (vma->vm_start < start)
+			err = split_vma(vma->vm_mm, vma, start, 1);
+		if (!err && vma->vm_end > end)
+			err = split_vma(vma->vm_mm, vma, end, 0);
+		if (!err)
+			err = policy_vma(vma, new);
+		if (err)
+			break;
+	}
+	return err;
+}
+
+/* Change policy for a memory range */
+asmlinkage long sys_mbind(unsigned long start, unsigned long len,
+			  unsigned long mode,
+			  unsigned long *nmask, unsigned long maxnode,
+			  unsigned flags)
+{
+	struct vm_area_struct *vma;
+	struct mm_struct *mm = current->mm;
+	struct mempolicy *new;
+	unsigned long end;
+	DECLARE_BITMAP(nodes, MAX_NUMNODES);
+	int err;
+
+	if ((flags & ~(unsigned long)(MPOL_MF_STRICT)) || mode > MPOL_MAX)
+		return -EINVAL;
+	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;
+
+	err = get_nodes(nodes, nmask, maxnode, mode);
+	if (err)
+		return err;
+
+	new = mpol_new(mode, nodes);
+	if (IS_ERR(new))
+		return PTR_ERR(new);
+
+	PDprintk("mbind %lx-%lx mode:%ld nodes:%lx\n",start,start+len,
+			mode,nodes[0]);
+
+	down_write(&mm->mmap_sem);
+	vma = check_range(mm, start, end, nodes, flags);
+	err = PTR_ERR(vma);
+	if (!IS_ERR(vma))
+		err = mbind_range(vma, start, end, new);
+	up_write(&mm->mmap_sem);
+	mpol_free(new);
+	return err;
+}
+
+/* Set the process memory policy */
+asmlinkage long sys_set_mempolicy(int mode, unsigned long *nmask,
+				   unsigned long maxnode)
+{
+	int err;
+	struct mempolicy *new;
+	DECLARE_BITMAP(nodes, MAX_NUMNODES);
+
+	if (mode > MPOL_MAX)
+		return -EINVAL;
+	err = get_nodes(nodes, nmask, maxnode, mode);
+	if (err)
+		return err;
+	new = mpol_new(mode, nodes);
+	if (IS_ERR(new))
+		return PTR_ERR(new);
+	mpol_free(current->mempolicy);
+	current->mempolicy = new;
+	if (new && new->policy == MPOL_INTERLEAVE)
+		current->il_next = find_first_bit(new->v.nodes, MAX_NUMNODES);
+	return 0;
+}
+
+/* Fill a zone bitmap for a policy */
+static void get_zonemask(struct mempolicy *p, unsigned long *nodes)
+{
+	int i;
+
+	bitmap_zero(nodes, MAX_NUMNODES);
+	switch (p->policy) {
+	case MPOL_BIND:
+		for (i = 0; p->v.zonelist->zones[i]; i++)
+			__set_bit(p->v.zonelist->zones[i]->zone_pgdat->node_id, nodes);
+		break;
+	case MPOL_DEFAULT:
+		break;
+	case MPOL_INTERLEAVE:
+		bitmap_copy(nodes, p->v.nodes, MAX_NUMNODES);
+		break;
+	case MPOL_PREFERRED:
+		/* or use current node instead of online map? */
+		if (p->v.preferred_node < 0)
+			bitmap_copy(nodes, node_online_map, MAX_NUMNODES);
+		else
+			__set_bit(p->v.preferred_node, nodes);
+		break;
+	default:
+		BUG();
+	}
+}
+
+static int lookup_node(struct mm_struct *mm, unsigned long addr)
+{
+	struct page *p;
+	int err;
+
+	err = get_user_pages(current, mm, addr & PAGE_MASK, 1, 0, 0, &p, NULL);
+	if (err >= 0) {
+		err = page_zone(p)->zone_pgdat->node_id;
+		put_page(p);
+	}
+	return err;
+}
+
+/* Copy a kernel node mask to user space */
+static int copy_nodes_to_user(unsigned long *user_mask, unsigned long maxnode,
+			      unsigned long *nodes)
+{
+	unsigned long copy = ALIGN(maxnode-1, 64) / 8;
+
+	if (copy > sizeof(nodes)) {
+		if (copy > PAGE_SIZE)
+			return -EINVAL;
+		if (clear_user((char*)user_mask + sizeof(nodes),
+				copy - sizeof(nodes)))
+			return -EFAULT;
+		copy = sizeof(nodes);
+	}
+	return copy_to_user(user_mask, nodes, copy) ? -EFAULT : 0;
+}
+
+/* Retrieve NUMA policy */
+asmlinkage long sys_get_mempolicy(int *policy,
+				  unsigned long *nmask, unsigned long maxnode,
+				  unsigned long addr, unsigned long flags)
+{
+	int err, pval;
+	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))
+		return -EINVAL;
+	if (nmask != NULL && maxnode < numnodes)
+		return -EINVAL;
+	if (flags & MPOL_F_ADDR) {
+		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;
+
+	if (flags & MPOL_F_NODE) {
+		if (flags & MPOL_F_ADDR) {
+			err = lookup_node(mm, addr);
+			if (err < 0)
+				goto out;
+			pval = err;
+		} else if (pol == current->mempolicy &&
+				pol->policy == MPOL_INTERLEAVE) {
+			pval = current->il_next;
+		} else {
+			err = -EINVAL;
+			goto out;
+		}
+	} else
+		pval = pol->policy;
+
+	err = -EFAULT;
+	if (policy && put_user(pval, policy))
+		goto out;
+
+	err = 0;
+	if (nmask) {
+		DECLARE_BITMAP(nodes, MAX_NUMNODES);
+		get_zonemask(pol, nodes);
+		err = copy_nodes_to_user(nmask, maxnode, nodes);
+	}
+
+ out:
+	if (vma)
+		up_read(&current->mm->mmap_sem);
+	return err;
+}
+
+#ifdef CONFIG_COMPAT
+/* The other functions are compatible */
+asmlinkage long compat_get_mempolicy(int *policy,
+				  unsigned  *nmask, unsigned  maxnode,
+				  unsigned addr, unsigned  flags)
+{
+	long err;
+	unsigned long *nm = NULL;
+	if (nmask)
+		nm = compat_alloc_user_space(ALIGN(maxnode-1, 64) / 8);
+	err = sys_get_mempolicy(policy, nm, maxnode, addr, flags);
+	if (!err && copy_in_user(nmask, nm, ALIGN(maxnode-1, 32)/8))
+		err = -EFAULT;
+	return err;
+}
+#endif
+
+/* Return effective policy for a VMA */
+static struct mempolicy *
+get_vma_policy(struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol = current->mempolicy;
+
+	if (vma) {
+		if (vma->vm_ops && vma->vm_ops->get_policy)
+		        pol = vma->vm_ops->get_policy(vma, addr);
+		else if (vma->vm_policy &&
+				vma->vm_policy->policy != MPOL_DEFAULT)
+			pol = vma->vm_policy;
+	}
+	if (!pol)
+		pol = &default_policy;
+	return pol;
+}
+
+/* Return a zonelist representing a mempolicy */
+static struct zonelist *zonelist_policy(unsigned gfp, struct mempolicy *policy)
+{
+	int nd;
+
+	switch (policy->policy) {
+	case MPOL_PREFERRED:
+		nd = policy->v.preferred_node;
+		if (nd < 0)
+			nd = numa_node_id();
+		break;
+	case MPOL_BIND:
+		/* Lower zones don't get a policy applied */
+		if (gfp >= policy_zone)
+			return policy->v.zonelist;
+		/*FALL THROUGH*/
+	case MPOL_INTERLEAVE: /* should not happen */
+	case MPOL_DEFAULT:
+		nd = numa_node_id();
+		break;
+	default:
+		nd = 0;
+		BUG();
+	}
+	return NODE_DATA(nd)->node_zonelists + (gfp & GFP_ZONEMASK);
+}
+
+/* Do dynamic interleaving for a process */
+static unsigned interleave_nodes(struct mempolicy *policy)
+{
+	unsigned nid, next;
+	struct task_struct *me = current;
+
+	nid = me->il_next;
+	BUG_ON(nid >= MAX_NUMNODES);
+	next = find_next_bit(policy->v.nodes, MAX_NUMNODES, 1+nid);
+	if (next >= MAX_NUMNODES)
+		next = find_first_bit(policy->v.nodes, MAX_NUMNODES);
+	me->il_next = next;
+	return nid;
+}
+
+/* Do static interleaving for a VMA with known offset. */
+static unsigned offset_il_node(struct mempolicy *pol,
+		struct vm_area_struct *vma, unsigned long off)
+{
+	unsigned nnodes = bitmap_weight(pol->v.nodes, MAX_NUMNODES);
+	unsigned target = (unsigned)off % nnodes;
+	int c;
+	int nid = -1;
+
+	c = 0;
+	do {
+		nid = find_next_bit(pol->v.nodes, MAX_NUMNODES, nid+1);
+		c++;
+	} while (c <= target);
+	BUG_ON(nid >= MAX_NUMNODES);
+	BUG_ON(!test_bit(nid, pol->v.nodes));
+	return nid;
+}
+
+/* Allocate a page in interleaved policy.
+   Own path because it needs to do special accounting. */
+static struct page *alloc_page_interleave(unsigned gfp, unsigned nid)
+{
+	struct zonelist *zl;
+	struct page *page;
+
+	BUG_ON(!test_bit(nid, node_online_map));
+	zl = NODE_DATA(nid)->node_zonelists + (gfp & GFP_ZONEMASK);
+	page = __alloc_pages(gfp, 0, zl);
+	if (page && page_zone(page) == zl->zones[0]) {
+		zl->zones[0]->pageset[get_cpu()].interleave_hit++;
+		put_cpu();
+	}
+	return page;
+}
+
+/**
+ * 	alloc_page_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.
+ *
+ * 	@vma:  Pointer to VMA or NULL if not available.
+ *	@addr: Virtual Address of the allocation. Must be inside the VMA.
+ *
+ * 	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.
+ *
+ *	Should be called with the mm_sem of the vma hold.
+ */
+struct page *
+alloc_page_vma(unsigned gfp, struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol = get_vma_policy(vma, addr);
+
+	if (unlikely(pol->policy == MPOL_INTERLEAVE)) {
+		unsigned nid;
+		if (vma) {
+			unsigned long off;
+			BUG_ON(addr >= vma->vm_end);
+			BUG_ON(addr < vma->vm_start);
+			off = vma->vm_pgoff;
+			off += (addr - vma->vm_start) >> PAGE_SHIFT;
+			nid = offset_il_node(pol, vma, off);
+		} else {
+			/* fall back to process interleaving */
+			nid = interleave_nodes(pol);
+		}
+		return alloc_page_interleave(gfp, nid);
+	}
+	return __alloc_pages(gfp, 0, zonelist_policy(gfp, pol));
+}
+
+/**
+ * 	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(unsigned gfp, unsigned order)
+{
+	struct mempolicy *pol = current->mempolicy;
+
+	if (!pol || in_interrupt())
+		pol = &default_policy;
+	if (pol->policy == MPOL_INTERLEAVE && order == 0)
+		return alloc_page_interleave(gfp, interleave_nodes(pol));
+	return __alloc_pages(gfp, order, zonelist_policy(gfp, pol));
+}
+EXPORT_SYMBOL(alloc_pages_current);
+
+/* Slow path of a mempolicy copy */
+struct mempolicy *__mpol_copy(struct mempolicy *old)
+{
+	struct mempolicy *new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
+
+	if (!new)
+		return ERR_PTR(-ENOMEM);
+	*new = *old;
+	atomic_set(&new->refcnt, 1);
+	if (new->policy == MPOL_BIND) {
+		int sz = ksize(old->v.zonelist);
+		new->v.zonelist = kmalloc(sz, SLAB_KERNEL);
+		if (!new->v.zonelist) {
+			kmem_cache_free(policy_cache, new);
+			return ERR_PTR(-ENOMEM);
+		}
+		memcpy(new->v.zonelist, old->v.zonelist, sz);
+	}
+	return new;
+}
+
+/* Slow path of a mempolicy comparison */
+int __mpol_equal(struct mempolicy *a, struct mempolicy *b)
+{
+	if (!a || !b)
+		return 0;
+	if (a->policy != b->policy)
+		return 0;
+	switch (a->policy) {
+	case MPOL_DEFAULT:
+		return 1;
+	case MPOL_INTERLEAVE:
+		return bitmap_equal(a->v.nodes, b->v.nodes, MAX_NUMNODES);
+	case MPOL_PREFERRED:
+		return a->v.preferred_node == b->v.preferred_node;
+	case MPOL_BIND: {
+		int i;
+		for (i = 0; a->v.zonelist->zones[i]; i++)
+			if (a->v.zonelist->zones[i] != b->v.zonelist->zones[i])
+				return 0;
+		return b->v.zonelist->zones[i] == NULL;
+	}
+	default:
+		BUG();
+		return 0;
+	}
+}
+
+/* Slow path of a mpol destructor. */
+extern void __mpol_free(struct mempolicy *p)
+{
+	if (!atomic_dec_and_test(&p->refcnt))
+		return;
+	if (p->policy == MPOL_BIND)
+		kfree(p->v.zonelist);
+	p->policy = MPOL_DEFAULT;
+	kmem_cache_free(policy_cache, p);
+}
+
+/*
+ * Hugetlb policy. Same as above, just works with node numbers instead of
+ * zonelists.
+ */
+
+/* Find first node suitable for an allocation */
+int mpol_first_node(struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol = get_vma_policy(vma, addr);
+
+	switch (pol->policy) {
+	case MPOL_DEFAULT:
+		return numa_node_id();
+	case MPOL_BIND:
+		return pol->v.zonelist->zones[0]->zone_pgdat->node_id;
+	case MPOL_INTERLEAVE:
+		return interleave_nodes(pol);
+	case MPOL_PREFERRED:
+		return pol->v.preferred_node >= 0 ?
+				pol->v.preferred_node : numa_node_id();
+	}
+	BUG();
+	return 0;
+}
+
+/* Find secondary valid nodes for an allocation */
+int mpol_node_valid(int nid, struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol = get_vma_policy(vma, addr);
+
+	switch (pol->policy) {
+	case MPOL_PREFERRED:
+	case MPOL_DEFAULT:
+	case MPOL_INTERLEAVE:
+		return 1;
+	case MPOL_BIND: {
+		struct zone **z;
+		for (z = pol->v.zonelist->zones; *z; z++)
+			if ((*z)->zone_pgdat->node_id == nid)
+				return 1;
+		return 0;
+	}
+	default:
+		BUG();
+		return 0;
+	}
+}
+
+/*
+ * 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->sem semaphore, which should be held
+ * for any accesses to the tree.
+ */
+
+/* lookup first element intersecting start-end */
+/* Caller holds sp->sem */
+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->sem */
+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);
+	PDprintk("inserting %lx-%lx: %d\n", new->start, new->end,
+		 new->policy ? new->policy->policy : 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;
+
+	down(&sp->sem);
+	sn = sp_lookup(sp, idx, idx+1);
+	if (sn) {
+		mpol_get(sn->policy);
+		pol = sn->policy;
+	}
+	up(&sp->sem);
+	return pol;
+}
+
+static void sp_delete(struct shared_policy *sp, struct sp_node *n)
+{
+	PDprintk("deleting %lx-l%x\n", n->start, n->end);
+	rb_erase(&n->nd, &sp->root);
+	mpol_free(n->policy);
+	kmem_cache_free(sn_cache, n);
+}
+
+struct sp_node *
+sp_alloc(unsigned long start, unsigned long end, struct mempolicy *pol)
+{
+	struct sp_node *n = kmem_cache_alloc(sn_cache, GFP_KERNEL);
+
+	if (!n)
+		return NULL;
+	n->start = start;
+	n->end = end;
+	mpol_get(pol);
+	n->policy = pol;
+	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, *new2;
+
+	down(&sp->sem);
+	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) {
+				new2 = sp_alloc(end, n->end, n->policy);
+				if (!new2) {
+					up(&sp->sem);
+					return -ENOMEM;
+				}
+				n->end = end;
+				sp_insert(sp, new2);
+			}
+			/* Old crossing beginning, but not end (easy) */
+			if (n->start < start && n->end > start)
+				n->end = start;
+		}
+		if (!next)
+			break;
+		n = rb_entry(next, struct sp_node, nd);
+	}
+	if (new)
+		sp_insert(sp, new);
+	up(&sp->sem);
+	return 0;
+}
+
+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);
+
+	PDprintk("set_shared_policy %lx sz %lu %d %lx\n",
+		 vma->vm_pgoff,
+		 sz, npol? npol->policy : -1,
+		npol ? npol->v.nodes[0] : -1);
+
+	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)
+		kmem_cache_free(sn_cache, 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;
+
+	down(&p->sem);
+	next = rb_first(&p->root);
+	while (next) {
+		n = rb_entry(next, struct sp_node, nd);
+		next = rb_next(&n->nd);
+		rb_erase(&n->nd, &p->root);
+		mpol_free(n->policy);
+		kmem_cache_free(sn_cache, n);
+	}
+	up(&p->sem);
+}
+
+static __init int numa_policy_init(void)
+{
+	policy_cache = kmem_cache_create("numa_policy",
+					 sizeof(struct mempolicy),
+					 0, 0, NULL, NULL);
+
+	sn_cache = kmem_cache_create("shared_policy_node",
+				     sizeof(struct sp_node),
+				     0, 0, NULL, NULL);
+
+	if (!policy_cache || !sn_cache)
+		panic("Cannot create NUMA policy cache");
+	return 0;
+}
+module_init(numa_policy_init);