Message-Id: <1365729237-29711-13-git-send-email-cody@linux.vnet.ibm.com>
Date:	Thu, 11 Apr 2013 18:13:44 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	Simon Jeons <simon.jeons@...il.com>
Subject: [RFC PATCH v2 12/25] mm: add memlayout & dnuma to track pfn->nid & transplant pages between nodes

On some systems, the hypervisor can (and will) relocate physical
addresses as seen in a VM between real NUMA nodes. For example, IBM
Power systems which are using particular revisions of PHYP (IBM's
proprietary hypervisor)

This change set introduces the infrastructure for tracking & dynamically
changing "memory layouts" (or "memlayouts"): the mapping between page
ranges & the actual backing NUMA node.

A memlayout is stored as an rbtree which maps pfns (really, ranges of
pfns) to a node. This mapping (combined with the LookupNode pageflag) is
used to "transplant" (move pages between nodes) pages when they are
freed back to the page allocator.

Additionally, when a new memlayout is commited the currently free pages
that are now in the 'wrong' zone's freelist are immidiately transplanted.

Hooks that tie it into the page alloctor to actually perform the
"transplant on free" are in later patches.

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
---
 include/linux/dnuma.h     |  97 ++++++++++
 include/linux/memlayout.h | 126 +++++++++++++
 mm/Kconfig                |  24 +++
 mm/Makefile               |   1 +
 mm/dnuma.c                | 439 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/memlayout.c            | 237 +++++++++++++++++++++++++
 6 files changed, 924 insertions(+)
 create mode 100644 include/linux/dnuma.h
 create mode 100644 include/linux/memlayout.h
 create mode 100644 mm/dnuma.c
 create mode 100644 mm/memlayout.c

diff --git a/include/linux/dnuma.h b/include/linux/dnuma.h
new file mode 100644
index 0000000..029a984
--- /dev/null
+++ b/include/linux/dnuma.h
@@ -0,0 +1,97 @@
+#ifndef LINUX_DNUMA_H_
+#define LINUX_DNUMA_H_
+
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/memlayout.h>
+#include <linux/spinlock.h>
+#include <linux/atomic.h>
+
+#ifdef CONFIG_DYNAMIC_NUMA
+/* Must be called _before_ setting a new_ml to the pfn_to_node_map */
+void dnuma_online_required_nodes_and_zones(struct memlayout *new_ml);
+
+/* Must be called _after_ setting a new_ml to the pfn_to_node_map */
+void dnuma_move_free_pages(struct memlayout *new_ml);
+void dnuma_mark_page_range(struct memlayout *new_ml);
+
+static inline bool dnuma_is_active(void)
+{
+	struct memlayout *ml;
+	bool ret;
+
+	rcu_read_lock();
+	ml = rcu_dereference(pfn_to_node_map);
+	ret = ml && (ml->type != ML_INITIAL);
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static inline bool dnuma_has_memlayout(void)
+{
+	return !!rcu_access_pointer(pfn_to_node_map);
+}
+
+static inline int dnuma_page_needs_move(struct page *page)
+{
+	int new_nid, old_nid;
+
+	if (!TestClearPageLookupNode(page))
+		return NUMA_NO_NODE;
+
+	/* FIXME: this does rcu_lock, deref, unlock */
+	if (WARN_ON(!dnuma_is_active()))
+		return NUMA_NO_NODE;
+
+	/* FIXME: and so does this (rcu lock, deref, and unlock) */
+	new_nid = memlayout_pfn_to_nid(page_to_pfn(page));
+	old_nid = page_to_nid(page);
+
+	if (new_nid == NUMA_NO_NODE) {
+		pr_alert("dnuma: pfn %05lx has moved from node %d to a non-memlayout range.\n",
+				page_to_pfn(page), old_nid);
+		return NUMA_NO_NODE;
+	}
+
+	if (new_nid == old_nid)
+		return NUMA_NO_NODE;
+
+	if (WARN_ON(!zone_is_initialized(
+			nid_zone(new_nid, page_zonenum(page)))))
+		return NUMA_NO_NODE;
+
+	return new_nid;
+}
+
+void dnuma_post_free_to_new_zone(struct page *page, int order);
+void dnuma_prior_free_to_new_zone(struct page *page, int order,
+				  struct zone *dest_zone,
+				  int dest_nid);
+
+#else /* !defined CONFIG_DYNAMIC_NUMA */
+
+static inline bool dnuma_is_active(void)
+{
+	return false;
+}
+
+static inline void dnuma_prior_free_to_new_zone(struct page *page, int order,
+						struct zone *dest_zone,
+						int dest_nid)
+{
+	BUG();
+}
+
+static inline void dnuma_post_free_to_new_zone(struct page *page, int order)
+{
+	BUG();
+}
+
+static inline int dnuma_page_needs_move(struct page *page)
+{
+	return NUMA_NO_NODE;
+}
+#endif /* !defined CONFIG_DYNAMIC_NUMA */
+
+#endif /* defined LINUX_DNUMA_H_ */
diff --git a/include/linux/memlayout.h b/include/linux/memlayout.h
new file mode 100644
index 0000000..6c26c52
--- /dev/null
+++ b/include/linux/memlayout.h
@@ -0,0 +1,126 @@
+#ifndef LINUX_MEMLAYOUT_H_
+#define LINUX_MEMLAYOUT_H_
+
+#include <linux/memblock.h> /* __init_memblock */
+#include <linux/mm.h>       /* NODE_DATA, page_zonenum */
+#include <linux/mmzone.h>   /* pfn_to_nid */
+#include <linux/rbtree.h>
+#include <linux/types.h>    /* size_t */
+
+#ifdef CONFIG_DYNAMIC_NUMA
+# ifdef NODE_NOT_IN_PAGE_FLAGS
+#  error "CONFIG_DYNAMIC_NUMA requires the NODE is in page flags. Try freeing up some flags by decreasing the maximum number of NUMA nodes, or switch to sparsmem-vmemmap"
+# endif
+
+enum memlayout_type {
+	ML_INITIAL,
+	ML_USER_DEBUG,
+	ML_NUM_TYPES
+};
+
+struct rangemap_entry {
+	struct rb_node node;
+	unsigned long pfn_start;
+	/* @pfn_end: inclusive, not stored as a count to make the lookup
+	 *           faster
+	 */
+	unsigned long pfn_end;
+	int nid;
+};
+
+#define RME_FMT "{%05lx-%05lx}:%d"
+#define RME_EXP(rme) rme->pfn_start, rme->pfn_end, rme->nid
+
+struct memlayout {
+	/*
+	 * - contains rangemap_entrys.
+	 * - assumes no 'ranges' overlap.
+	 */
+	struct rb_root root;
+	enum memlayout_type type;
+
+	/*
+	 * When a memlayout is commited, 'cache' is accessed (the field is read
+	 * from & written to) by multiple tasks without additional locking
+	 * (other than the rcu locking for accessing the memlayout).
+	 *
+	 * Do not assume that it will not change. Use ACCESS_ONCE() to avoid
+	 * potential races.
+	 */
+	struct rangemap_entry *cache;
+
+#ifdef CONFIG_DNUMA_DEBUGFS
+	unsigned seq;
+	struct dentry *d;
+#endif
+};
+
+extern __rcu struct memlayout *pfn_to_node_map;
+
+/* FIXME: overflow potential in completion check */
+#define ml_for_each_pfn_in_range(rme, pfn)	\
+	for (pfn = rme->pfn_start;		\
+	     pfn <= rme->pfn_end || pfn < rme->pfn_start; \
+	     pfn++)
+
+static inline bool rme_bounds_pfn(struct rangemap_entry *rme, unsigned long pfn)
+{
+	return rme->pfn_start <= pfn && pfn <= rme->pfn_end;
+}
+
+static inline struct rangemap_entry *rme_next(struct rangemap_entry *rme)
+{
+	struct rb_node *node = rb_next(&rme->node);
+	if (!node)
+		return NULL;
+	return rb_entry(node, typeof(*rme), node);
+}
+
+static inline struct rangemap_entry *rme_first(struct memlayout *ml)
+{
+	struct rb_node *node = rb_first(&ml->root);
+	if (!node)
+		return NULL;
+	return rb_entry(node, struct rangemap_entry, node);
+}
+
+#define ml_for_each_range(ml, rme) \
+	for (rme = rme_first(ml);	\
+	     &rme->node;		\
+	     rme = rme_next(rme))
+
+struct memlayout *memlayout_create(enum memlayout_type);
+void memlayout_destroy(struct memlayout *ml);
+
+int memlayout_new_range(struct memlayout *ml,
+		unsigned long pfn_start, unsigned long pfn_end, int nid);
+int memlayout_pfn_to_nid(unsigned long pfn);
+
+/*
+ * Put ranges added by memlayout_new_range() into use by
+ * memlayout_pfn_get_nid() and retire old memlayout.
+ *
+ * No modifications to a memlayout should be made after it is commited.
+ */
+void memlayout_commit(struct memlayout *ml);
+
+/*
+ * Sets up an inital memlayout in early boot.
+ * A weak default which uses memblock is provided.
+ */
+void memlayout_global_init(void);
+
+#else /* !defined(CONFIG_DYNAMIC_NUMA) */
+
+/* memlayout_new_range() & memlayout_commit() are purposefully omitted */
+
+static inline void memlayout_global_init(void)
+{}
+
+static inline int memlayout_pfn_to_nid(unsigned long pfn)
+{
+	return NUMA_NO_NODE;
+}
+#endif /* !defined(CONFIG_DYNAMIC_NUMA) */
+
+#endif
diff --git a/mm/Kconfig b/mm/Kconfig
index 3bea74f..86f0984 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -169,6 +169,30 @@ config MOVABLE_NODE
 config HAVE_BOOTMEM_INFO_NODE
 	def_bool n
 
+config DYNAMIC_NUMA
+	bool "Dynamic Numa: Allow NUMA layout to change after boot time"
+	depends on NUMA
+	depends on !DISCONTIGMEM
+	depends on MEMORY_HOTPLUG # locking + mem_online_node().
+	help
+	 Dynamic Numa (DNUMA) allows the movement of pages between NUMA nodes at
+	 run time.
+
+	 Typically, this is used on systems running under a hypervisor which
+	 may move the running VM based on the hypervisors needs. On such a
+	 system, this config option enables Linux to update it's knowledge of
+	 the memory layout.
+
+	 If the feature is not used but is enabled, there is a very small
+	 amount of overhead (an additional pageflag check) is added to all page frees.
+
+	 This is only useful if you enable some of the additional options to
+	 allow modifications of the numa memory layout (either through hypervisor events
+	 or a userspace interface).
+
+	 Choose Y if you have are running linux under a hypervisor that uses
+	 this feature, otherwise choose N if unsure.
+
 # eventually, we can have this option just 'select SPARSEMEM'
 config MEMORY_HOTPLUG
 	bool "Allow for memory hot-add"
diff --git a/mm/Makefile b/mm/Makefile
index 3a46287..82fe7c9b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -58,3 +58,4 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
 obj-$(CONFIG_CLEANCACHE) += cleancache.o
 obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
+obj-$(CONFIG_DYNAMIC_NUMA) += dnuma.o memlayout.o
diff --git a/mm/dnuma.c b/mm/dnuma.c
new file mode 100644
index 0000000..2ee0903
--- /dev/null
+++ b/mm/dnuma.c
@@ -0,0 +1,439 @@
+#define pr_fmt(fmt) "dnuma: " fmt
+
+#include <linux/atomic.h>
+#include <linux/bootmem.h>
+#include <linux/dnuma.h>
+#include <linux/memory.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include "internal.h"
+
+/* - must be called under lock_memory_hotplug() */
+/* TODO: avoid iterating over all PFNs. */
+void dnuma_online_required_nodes_and_zones(struct memlayout *new_ml)
+{
+	struct rangemap_entry *rme;
+	ml_for_each_range(new_ml, rme) {
+		unsigned long pfn;
+		int nid = rme->nid;
+
+		if (!node_online(nid)) {
+			pr_info("onlining node %d [start]\n", nid);
+
+			/* Consult hotadd_new_pgdat() */
+			__mem_online_node(nid);
+
+			/* XXX: we aren't really onlining memory, but some code
+			 * uses memory online notifications to tell if new
+			 * nodes have been created.
+			 *
+			 * Also note that the notifiers expect to be able to do
+			 * allocations, ie we must allow for might_sleep() */
+			{
+				int ret;
+
+				/* memory_notify() expects:
+				 *	- to add pages at the same time
+				 *	- to add zones at the same time
+				 * We can do neither of these things.
+				 *
+				 * XXX: - slab uses .status_change_nid
+				 *      - slub uses .status_change_nid_normal
+				 * FIXME: for slub, we may not be placing any
+				 *        "normal" memory in it, can we check
+				 *        for this?
+				 */
+				struct memory_notify arg = {
+					.status_change_nid = nid,
+					.status_change_nid_normal = nid,
+				};
+
+				ret = memory_notify(MEM_GOING_ONLINE, &arg);
+				ret = notifier_to_errno(ret);
+				if (WARN_ON(ret)) {
+					/* XXX: other stuff will bug out if we
+					 * keep going, need to actually cancel
+					 * memlayout changes
+					 */
+					memory_notify(MEM_CANCEL_ONLINE, &arg);
+				}
+			}
+
+			pr_info("onlining node %d [complete]\n", nid);
+		}
+
+		/* Determine the zones required */
+		for (pfn = rme->pfn_start; pfn <= rme->pfn_end; pfn++) {
+			struct zone *zone;
+			if (!pfn_valid(pfn))
+				continue;
+
+			zone = nid_zone(nid, page_zonenum(pfn_to_page(pfn)));
+			/* XXX: we (dnuma paths) can handle this (there will
+			 * just be quite a few WARNS in the logs), but if we
+			 * are indicating error above, should we bail out here
+			 * as well? */
+			WARN_ON(ensure_zone_is_initialized(zone, 0, 0));
+		}
+	}
+}
+
+/*
+ * Cannot be folded into dnuma_move_unallocated_pages() because unmarked pages
+ * could be freed back into the zone as dnuma_move_unallocated_pages() was in
+ * the process of iterating over it.
+ */
+void dnuma_mark_page_range(struct memlayout *new_ml)
+{
+	struct rangemap_entry *rme;
+	ml_for_each_range(new_ml, rme) {
+		unsigned long pfn;
+		for (pfn = rme->pfn_start; pfn <= rme->pfn_end; pfn++) {
+			if (!pfn_valid(pfn))
+				continue;
+			/* FIXME: should we be skipping compound / buddied
+			 *        pages? */
+			/* FIXME: if PageReserved(), can we just poke the nid
+			 *        directly? Should we? */
+			SetPageLookupNode(pfn_to_page(pfn));
+		}
+	}
+}
+
+#if 0
+static void node_states_set_node(int node, struct memory_notify *arg)
+{
+	if (arg->status_change_nid_normal >= 0)
+		node_set_state(node, N_NORMAL_MEMORY);
+
+	if (arg->status_change_nid_high >= 0)
+		node_set_state(node, N_HIGH_MEMORY);
+
+	node_set_state(node, N_MEMORY);
+}
+#endif
+
+void dnuma_post_free_to_new_zone(struct page *page, int order)
+{
+}
+
+static void dnuma_prior_return_to_new_zone(struct page *page, int order,
+					   struct zone *dest_zone,
+					   int dest_nid)
+{
+	int i;
+	unsigned long pfn = page_to_pfn(page);
+
+	grow_pgdat_and_zone(dest_zone, pfn, pfn + (1UL << order));
+
+	for (i = 0; i < 1UL << order; i++)
+		set_page_node(&page[i], dest_nid);
+}
+
+static void clear_lookup_node(struct page *page, int order)
+{
+	int i;
+	for (i = 0; i < 1UL << order; i++)
+		ClearPageLookupNode(&page[i]);
+}
+
+/* Does not assume it is called with any locking (but can be called with zone
+ * locks held, if needed) */
+void dnuma_prior_free_to_new_zone(struct page *page, int order,
+				  struct zone *dest_zone,
+				  int dest_nid)
+{
+	dnuma_prior_return_to_new_zone(page, order, dest_zone, dest_nid);
+}
+
+/* must be called with zone->lock held and memlayout's update_lock held */
+static void remove_free_pages_from_zone(struct zone *zone, struct page *page,
+					int order)
+{
+	/* zone free stats */
+	zone->free_area[order].nr_free--;
+	__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
+
+	list_del(&page->lru);
+	__ClearPageBuddy(page);
+
+	/* Allowed because we hold the memlayout update_lock. */
+	clear_lookup_node(page, order);
+
+	/* XXX: can we shrink spanned_pages & start_pfn without too much work?
+	 *  - not crutial because having a
+	 *    larger-than-necessary span simply means that more
+	 *    PFNs are iterated over.
+	 *  - would be nice to be able to do this to cut down
+	 *    on overhead caused by PFN iterators.
+	 */
+}
+
+/*
+ * __ref is to allow (__meminit) zone_pcp_update(), which we will have because
+ * DYNAMIC_NUMA depends on MEMORY_HOTPLUG (and all the MEMORY_HOTPLUG comments
+ * indicate __meminit is allowed when they are enabled).
+ */
+static void __ref add_free_page_to_node(int dest_nid, struct page *page,
+					int order)
+{
+	bool need_zonelists_rebuild = false;
+	struct zone *dest_zone = nid_zone(dest_nid, page_zonenum(page));
+	VM_BUG_ON(!zone_is_initialized(dest_zone));
+
+	if (zone_is_empty(dest_zone))
+		need_zonelists_rebuild = true;
+
+	/* Add page to new zone */
+	dnuma_prior_return_to_new_zone(page, order, dest_zone, dest_nid);
+	return_pages_to_zone(page, order, dest_zone);
+	dnuma_post_free_to_new_zone(order);
+
+	/* XXX: fixme, there are other states that need fixing up */
+	if (!node_state(dest_nid, N_MEMORY))
+		node_set_state(dest_nid, N_MEMORY);
+
+	if (need_zonelists_rebuild) {
+		/* XXX: also does stop_machine() */
+		zone_pcp_reset(dest_zone);
+		/* XXX: why is this locking actually needed? */
+		mutex_lock(&zonelists_mutex);
+#if 0
+		/* assumes that zone is unused */
+		setup_zone_pageset(dest_zone);
+		build_all_zonelists(NULL, NULL);
+#else
+		build_all_zonelists(NULL, dest_zone);
+#endif
+		mutex_unlock(&zonelists_mutex);
+	}
+}
+
+static struct rangemap_entry *add_split_pages_to_zones(
+		struct rangemap_entry *first_rme,
+		struct page *page, int order)
+{
+	int i;
+	struct rangemap_entry *rme = first_rme;
+	/*
+	 * We avoid doing any hard work to try to split the pages optimally
+	 * here because the page allocator splits them into 0-order pages
+	 * anyway.
+	 *
+	 * XXX: All of the checks for NULL rmes and the nid conditional are to
+	 * work around memlayouts potentially not covering all valid memory.
+	 */
+	for (i = 0; i < (1 << order); i++) {
+		unsigned long pfn = page_to_pfn(page);
+		int nid;
+		while (rme && pfn > rme->pfn_end)
+			rme = rme_next(rme);
+
+		if (rme && pfn >= rme->pfn_start)
+			nid = rme->nid;
+		else
+			nid = page_to_nid(page + i);
+
+		add_free_page_to_node(nid, page + i, 0);
+	}
+
+	return rme;
+}
+
+#define _page_count_idx(managed, nid, zone_num) \
+	(managed + 2 * (zone_num + MAX_NR_ZONES * (nid)))
+#define page_count_idx(nid, zone_num) _page_count_idx(0, nid, zone_num)
+
+/* Because we hold lock_memory_hotplug(), we assume that no else will be
+ * changing present_pages and managed_pages.
+ */
+static void update_page_counts(struct memlayout *new_ml)
+{
+	/* Perform a combined iteration of pgdat+zones and memlayout.
+	 * - memlayouts are ordered, their lookup from pfn is slow, and they
+	 *   might have holes over valid pfns.
+	 * - pgdat+zones are unordered, have O(1) lookups, and don't have holes
+	 *   over valid pfns.
+	 */
+	struct rangemap_entry *rme;
+	unsigned long pfn = 0;
+	unsigned long *counts = kzalloc(2 * nr_node_ids * MAX_NR_ZONES *
+						sizeof(*counts),
+					GFP_KERNEL);
+	if (WARN_ON(!counts))
+		return;
+	rme = rme_first(new_ml);
+	for (pfn = 0; pfn < max_pfn; pfn++) {
+		int nid;
+		struct page *page;
+		size_t idx;
+
+		if (!pfn_valid(pfn))
+			continue;
+
+		page = pfn_to_page(pfn);
+recheck_rme:
+		if (!rme || pfn < rme->pfn_start) {
+			/* We are before the start of the current rme, or we
+			 * are past the last rme, fallback on pgdat+zone+page
+			 * data. */
+			nid = page_to_nid(page);
+			pr_debug("FALLBACK: pfn %05lx, put in node %d. current rme "RME_FMT"\n",
+					pfn, nid, RME_EXP(rme));
+		} else if (pfn > rme->pfn_end) {
+			rme = rme_next(rme);
+			goto recheck_rme;
+		} else {
+			nid = rme->nid;
+		}
+
+		idx = page_count_idx(nid, page_zonenum(page));
+		/* XXX: what happens if pages become
+		   reserved/unreserved during this
+		   process? */
+		if (!PageReserved(page))
+			counts[idx]++; /* managed_pages */
+		counts[idx + 1]++;     /* present_pages */
+	}
+
+	{
+		int nid;
+		for (nid = 0; nid < nr_node_ids; nid++) {
+			unsigned long nid_present = 0;
+			int zone_num;
+			pg_data_t *node = NODE_DATA(nid);
+			if (!node)
+				continue;
+			for (zone_num = 0; zone_num < node->nr_zones;
+					zone_num++) {
+				struct zone *zone = &node->node_zones[zone_num];
+				size_t idx = page_count_idx(nid, zone_num);
+				pr_debug("nid %d zone %d mp=%lu pp=%lu -> mp=%lu pp=%lu\n",
+						nid, zone_num,
+						zone->managed_pages,
+						zone->present_pages,
+						counts[idx], counts[idx+1]);
+				zone->managed_pages = counts[idx];
+				zone->present_pages = counts[idx + 1];
+				nid_present += zone->present_pages;
+
+				/*
+				 * recalculate pcp ->batch & ->high using
+				 * zone->managed_pages
+				 */
+				zone_pcp_update(zone);
+			}
+
+			pr_debug(" node %d zone * present_pages %lu to %lu\n",
+					node->node_id, node->node_present_pages,
+					nid_present);
+			node->node_present_pages = nid_present;
+		}
+	}
+
+	kfree(counts);
+}
+
+void __ref dnuma_move_free_pages(struct memlayout *new_ml)
+{
+	struct rangemap_entry *rme;
+
+	update_page_counts(new_ml);
+	init_per_zone_wmark_min();
+
+	/* FIXME: how does this removal of pages from a zone interact with
+	 * migrate types? ISOLATION? */
+	ml_for_each_range(new_ml, rme) {
+		unsigned long pfn = rme->pfn_start;
+		int range_nid;
+		struct page *page;
+new_rme:
+		range_nid = rme->nid;
+
+		for (; pfn <= rme->pfn_end; pfn++) {
+			struct zone *zone;
+			int page_nid, order;
+			unsigned long flags, last_pfn, first_pfn;
+			if (!pfn_valid(pfn))
+				continue;
+
+			page = pfn_to_page(pfn);
+#if 0
+			/* XXX: can we ensure this is safe? Pages marked
+			 * reserved could be freed into the page allocator if
+			 * they mark memory areas that were allocated via
+			 * earlier allocators. */
+			if (PageReserved(page)) {
+				set_page_node(page, range_nid);
+				/* TODO: adjust spanned_pages & present_pages &
+				 * start_pfn. */
+			}
+#endif
+
+			/* Currently allocated, will be fixed up when freed. */
+			if (!PageBuddy(page))
+				continue;
+
+			page_nid = page_to_nid(page);
+			if (page_nid == range_nid)
+				continue;
+
+			zone = page_zone(page);
+			spin_lock_irqsave(&zone->lock, flags);
+
+			/* Someone allocated it since we last checked. It will
+			 * be fixed up when it is freed */
+			if (!PageBuddy(page))
+				goto skip_unlock;
+
+			/* It has already been transplanted "somewhere",
+			 * somewhere should be the proper zone. */
+			if (page_zone(page) != zone) {
+				VM_BUG_ON(zone != nid_zone(range_nid,
+							page_zonenum(page)));
+				goto skip_unlock;
+			}
+
+			order = page_order(page);
+			first_pfn = pfn & ~((1 << order) - 1);
+			last_pfn  = pfn |  ((1 << order) - 1);
+			if (WARN(pfn != first_pfn,
+					"pfn %05lx is not first_pfn %05lx\n",
+					pfn, first_pfn)) {
+				pfn = last_pfn;
+				goto skip_unlock;
+			}
+
+			if (last_pfn > rme->pfn_end) {
+				/*
+				 * this higher order page doesn't fit into the
+				 * current range even though it starts there.
+				 */
+				pr_warn("order-%02d page (pfn %05lx-%05lx) extends beyond end of rme "RME_FMT"\n",
+						order, first_pfn, last_pfn,
+						RME_EXP(rme));
+
+				remove_free_pages_from_zone(zone, page, order);
+				spin_unlock_irqrestore(&zone->lock, flags);
+
+				rme = add_split_pages_to_zones(rme, page,
+						order);
+				pfn = last_pfn + 1;
+				goto new_rme;
+			}
+
+			remove_free_pages_from_zone(zone, page, order);
+			spin_unlock_irqrestore(&zone->lock, flags);
+
+			add_free_page_to_node(range_nid, page, order);
+			pfn = last_pfn;
+			continue;
+skip_unlock:
+			spin_unlock_irqrestore(&zone->lock, flags);
+		}
+	}
+}
diff --git a/mm/memlayout.c b/mm/memlayout.c
new file mode 100644
index 0000000..7d2905b
--- /dev/null
+++ b/mm/memlayout.c
@@ -0,0 +1,237 @@
+/*
+ * memlayout - provides a mapping of PFN ranges to nodes with the requirements
+ * that looking up a node from a PFN is fast, and changes to the mapping will
+ * occour relatively infrequently.
+ *
+ */
+#define pr_fmt(fmt) "memlayout: " fmt
+
+#include <linux/dnuma.h>
+#include <linux/export.h>
+#include <linux/memblock.h>
+#include <linux/printk.h>
+#include <linux/rbtree.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+
+/* protected by memlayout_lock */
+__rcu struct memlayout *pfn_to_node_map;
+DEFINE_MUTEX(memlayout_lock);
+
+static void free_rme_tree(struct rb_root *root)
+{
+	struct rangemap_entry *pos, *n;
+	rbtree_postorder_for_each_entry_safe(pos, n, root, node) {
+		kfree(pos);
+	}
+}
+
+static void ml_destroy_mem(struct memlayout *ml)
+{
+	if (!ml)
+		return;
+	free_rme_tree(&ml->root);
+	kfree(ml);
+}
+
+static int find_insertion_point(struct memlayout *ml, unsigned long pfn_start,
+		unsigned long pfn_end, int nid, struct rb_node ***o_new,
+		struct rb_node **o_parent)
+{
+	struct rb_node **new = &ml->root.rb_node, *parent = NULL;
+	struct rangemap_entry *rme;
+	pr_debug("adding range: {%lX-%lX}:%d\n", pfn_start, pfn_end, nid);
+	while (*new) {
+		rme = rb_entry(*new, typeof(*rme), node);
+
+		parent = *new;
+		if (pfn_end < rme->pfn_start && pfn_start < rme->pfn_end)
+			new = &((*new)->rb_left);
+		else if (pfn_start > rme->pfn_end && pfn_end > rme->pfn_end)
+			new = &((*new)->rb_right);
+		else {
+			/* an embedded region, need to use an interval or
+			 * sequence tree. */
+			pr_warn("tried to embed {%lX,%lX}:%d inside {%lX-%lX}:%d\n",
+				 pfn_start, pfn_end, nid,
+				 rme->pfn_start, rme->pfn_end, rme->nid);
+			return 1;
+		}
+	}
+
+	*o_new = new;
+	*o_parent = parent;
+	return 0;
+}
+
+int memlayout_new_range(struct memlayout *ml, unsigned long pfn_start,
+		unsigned long pfn_end, int nid)
+{
+	struct rb_node **new, *parent;
+	struct rangemap_entry *rme;
+
+	if (WARN_ON(nid < 0))
+		return -EINVAL;
+	if (WARN_ON(nid >= nr_node_ids))
+		return -EINVAL;
+
+	if (find_insertion_point(ml, pfn_start, pfn_end, nid, &new, &parent))
+		return 1;
+
+	rme = kmalloc(sizeof(*rme), GFP_KERNEL);
+	if (!rme)
+		return -ENOMEM;
+
+	rme->pfn_start = pfn_start;
+	rme->pfn_end = pfn_end;
+	rme->nid = nid;
+
+	rb_link_node(&rme->node, parent, new);
+	rb_insert_color(&rme->node, &ml->root);
+	return 0;
+}
+
+int memlayout_pfn_to_nid(unsigned long pfn)
+{
+	struct rb_node *node;
+	struct memlayout *ml;
+	struct rangemap_entry *rme;
+	rcu_read_lock();
+	ml = rcu_dereference(pfn_to_node_map);
+	if (!ml || (ml->type == ML_INITIAL))
+		goto out;
+
+	rme = ACCESS_ONCE(ml->cache);
+	if (rme && rme_bounds_pfn(rme, pfn)) {
+		rcu_read_unlock();
+		return rme->nid;
+	}
+
+	node = ml->root.rb_node;
+	while (node) {
+		struct rangemap_entry *rme = rb_entry(node, typeof(*rme), node);
+		bool greater_than_start = rme->pfn_start <= pfn;
+		bool less_than_end = pfn <= rme->pfn_end;
+
+		if (greater_than_start && !less_than_end)
+			node = node->rb_right;
+		else if (less_than_end && !greater_than_start)
+			node = node->rb_left;
+		else {
+			/* greater_than_start && less_than_end.
+			 *  the case (!greater_than_start  && !less_than_end)
+			 *  is impossible */
+			int nid = rme->nid;
+			ACCESS_ONCE(ml->cache) = rme;
+			rcu_read_unlock();
+			return nid;
+		}
+	}
+
+out:
+	rcu_read_unlock();
+	return NUMA_NO_NODE;
+}
+
+void memlayout_destroy(struct memlayout *ml)
+{
+	ml_destroy_mem(ml);
+}
+
+struct memlayout *memlayout_create(enum memlayout_type type)
+{
+	struct memlayout *ml;
+
+	if (WARN_ON(type < 0 || type >= ML_NUM_TYPES))
+		return NULL;
+
+	ml = kmalloc(sizeof(*ml), GFP_KERNEL);
+	if (!ml)
+		return NULL;
+
+	ml->root = RB_ROOT;
+	ml->type = type;
+	ml->cache = NULL;
+
+	return ml;
+}
+
+void memlayout_commit(struct memlayout *ml)
+{
+	struct memlayout *old_ml;
+
+	if (ml->type == ML_INITIAL) {
+		if (WARN(dnuma_has_memlayout(),
+				"memlayout marked first is not first, ignoring.\n")) {
+			memlayout_destroy(ml);
+			ml_backlog_feed(ml);
+			return;
+		}
+
+		mutex_lock(&memlayout_lock);
+		rcu_assign_pointer(pfn_to_node_map, ml);
+		mutex_unlock(&memlayout_lock);
+		return;
+	}
+
+	lock_memory_hotplug();
+	dnuma_online_required_nodes_and_zones(ml);
+	unlock_memory_hotplug();
+
+	mutex_lock(&memlayout_lock);
+	old_ml = rcu_dereference_protected(pfn_to_node_map,
+			mutex_is_locked(&memlayout_lock));
+
+	rcu_assign_pointer(pfn_to_node_map, ml);
+
+	synchronize_rcu();
+	memlayout_destroy(old_ml);
+
+	/* Must be called only after the new value for pfn_to_node_map has
+	 * propogated to all tasks, otherwise some pages may lookup the old
+	 * pfn_to_node_map on free & not transplant themselves to their new-new
+	 * node. */
+	dnuma_mark_page_range(ml);
+
+	/* Do this after the free path is set up so that pages are free'd into
+	 * their "new" zones so that after this completes, no free pages in the
+	 * wrong zone remain. */
+	dnuma_move_free_pages(ml);
+
+	/* All new _non pcp_ page allocations now match the memlayout*/
+	drain_all_pages();
+	/* All new page allocations now match the memlayout */
+
+	mutex_unlock(&memlayout_lock);
+}
+
+/*
+ * The default memlayout global initializer, using memblock to determine
+ * affinities
+ *
+ * reqires: slab_is_available() && memblock is not (yet) freed.
+ * sleeps: definitely: memlayout_commit() -> synchronize_rcu()
+ *	   potentially: kmalloc()
+ */
+__weak __meminit
+void memlayout_global_init(void)
+{
+	int i, nid, errs = 0;
+	unsigned long start, end;
+	struct memlayout *ml = memlayout_create(ML_INITIAL);
+	if (WARN_ON(!ml))
+		return;
+
+	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid) {
+		int r = memlayout_new_range(ml, start, end - 1, nid);
+		if (r) {
+			pr_err("failed to add range [%05lx, %05lx] in node %d to mapping\n",
+					start, end, nid);
+			errs++;
+		} else
+			pr_devel("added range [%05lx, %05lx] in node %d\n",
+					start, end, nid);
+	}
+
+	memlayout_commit(ml);
+}
-- 
1.8.2.1

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