diff --git a/mm/percpu.c b/mm/percpu.c
new file mode 100644
index 0000000..4617d97
--- /dev/null
+++ b/mm/percpu.c
@@ -0,0 +1,890 @@
+/*
+ * linux/mm/percpu.c - percpu memory allocator
+ *
+ * Copyright (C) 2009		SUSE Linux Products GmbH
+ * Copyright (C) 2009		Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ * This is percpu allocator which can handle both static and dynamic
+ * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
+ * chunk is consisted of num_possible_cpus() units and the first chunk
+ * is used for static percpu variables in the kernel image (special
+ * boot time alloc/init handling necessary as these areas need to be
+ * brought up before allocation services are running).  Unit grows as
+ * necessary and all units grow or shrink in unison.  When a chunk is
+ * filled up, another chunk is allocated.  ie. in vmalloc area
+ *
+ *  c0                           c1                         c2
+ *  -------------------          -------------------        ------------
+ * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
+ *  -------------------  ......  -------------------  ....  ------------
+ *
+ * Allocation is done in offset-size areas of single unit space.  Ie,
+ * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
+ * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring
+ * percpu base registers UNIT_SIZE apart.
+ *
+ * There are usually many small percpu allocations many of them as
+ * small as 4 bytes.  The allocator organizes chunks into lists
+ * according to free size and tries to allocate from the fullest one.
+ * Each chunk keeps the maximum contiguous area size hint which is
+ * guaranteed to be eqaul to or larger than the maximum contiguous
+ * area in the chunk.  This helps the allocator not to iterate the
+ * chunk maps unnecessarily.
+ *
+ * Allocation state in each chunk is kept using an array of integers
+ * on chunk->map.  A positive value in the map represents a free
+ * region and negative allocated.  Allocation inside a chunk is done
+ * by scanning this map sequentially and serving the first matching
+ * entry.  This is mostly copied from the percpu_modalloc() allocator.
+ * Chunks are also linked into a rb tree to ease address to chunk
+ * mapping during free.
+ *
+ * To use this allocator, arch code should do the followings.
+ *
+ * - define CONFIG_HAVE_DYNAMIC_PER_CPU_AREA
+ *
+ * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
+ *   regular address to percpu pointer and back
+ *
+ * - use pcpu_setup_static() during percpu area initialization to
+ *   setup kernel static percpu area
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bootmem.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/pfn.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+#define PCPU_MIN_UNIT_PAGES_SHIFT	4	/* also max alloc size */
+#define PCPU_SLOT_BASE_SHIFT		5	/* 1-31 shares the same slot */
+#define PCPU_DFL_MAP_ALLOC		16	/* start a map with 16 ents */
+
+struct pcpu_chunk {
+	struct list_head	list;		/* linked to pcpu_slot lists */
+	struct rb_node		rb_node;	/* key is chunk->vm->addr */
+	int			free_size;	/* free bytes in the chunk */
+	int			contig_hint;	/* max contiguous size hint */
+	struct vm_struct	*vm;		/* mapped vmalloc region */
+	int			map_used;	/* # of map entries used */
+	int			map_alloc;	/* # of map entries allocated */
+	int			*map;		/* allocation map */
+	struct page		*page[];	/* #cpus * UNIT_PAGES */
+};
+
+static int pcpu_unit_pages_shift;
+static int pcpu_unit_pages;
+static int pcpu_unit_shift;
+static int pcpu_unit_size;
+static int pcpu_chunk_size;
+static int pcpu_nr_slots;
+static size_t pcpu_chunk_struct_size;
+
+/* the address of the first chunk which starts with the kernel static area */
+void *pcpu_base_addr;
+EXPORT_SYMBOL_GPL(pcpu_base_addr);
+
+/* the size of kernel static area */
+static int pcpu_static_size;
+
+/*
+ * One mutex to rule them all.
+ *
+ * The following mutex is grabbed in the outermost public alloc/free
+ * interface functions and released only when the operation is
+ * complete.  As such, every function in this file other than the
+ * outermost functions are called under pcpu_mutex.
+ *
+ * It can easily be switched to use spinlock such that only the area
+ * allocation and page population commit are protected with it doing
+ * actual [de]allocation without holding any lock.  However, given
+ * what this allocator does, I think it's better to let them run
+ * sequentially.
+ */
+static DEFINE_MUTEX(pcpu_mutex);
+
+static struct list_head *pcpu_slot;		/* chunk list slots */
+static struct rb_root pcpu_addr_root = RB_ROOT;	/* chunks by address */
+
+static int pcpu_size_to_slot(int size)
+{
+	int highbit = fls(size);
+	return max(highbit - PCPU_SLOT_BASE_SHIFT + 2, 1);
+}
+
+static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
+{
+	if (chunk->free_size < sizeof(int) || chunk->contig_hint < sizeof(int))
+		return 0;
+
+	return pcpu_size_to_slot(chunk->free_size);
+}
+
+static int pcpu_page_idx(unsigned int cpu, int page_idx)
+{
+	return (cpu << pcpu_unit_pages_shift) + page_idx;
+}
+
+static struct page **pcpu_chunk_pagep(struct pcpu_chunk *chunk,
+				      unsigned int cpu, int page_idx)
+{
+	return &chunk->page[pcpu_page_idx(cpu, page_idx)];
+}
+
+static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
+				     unsigned int cpu, int page_idx)
+{
+	return (unsigned long)chunk->vm->addr +
+		(pcpu_page_idx(cpu, page_idx) << PAGE_SHIFT);
+}
+
+static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
+				     int page_idx)
+{
+	return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
+}
+
+/**
+ * pcpu_realloc - versatile realloc
+ * @p: the current pointer (can be NULL for new allocations)
+ * @size: the current size (can be 0 for new allocations)
+ * @new_size: the wanted new size (can be 0 for free)
+ *
+ * More robust realloc which can be used to allocate, resize or free a
+ * memory area of arbitrary size.  If the needed size goes over
+ * PAGE_SIZE, kernel VM is used.
+ *
+ * RETURNS:
+ * The new pointer on success, NULL on failure.
+ */
+static void *pcpu_realloc(void *p, size_t size, size_t new_size)
+{
+	void *new;
+
+	if (new_size <= PAGE_SIZE)
+		new = kmalloc(new_size, GFP_KERNEL);
+	else
+		new = vmalloc(new_size);
+	if (new_size && !new)
+		return NULL;
+
+	memcpy(new, p, min(size, new_size));
+	if (new_size > size)
+		memset(new + size, 0, new_size - size);
+
+	if (size <= PAGE_SIZE)
+		kfree(p);
+	else
+		vfree(p);
+
+	return new;
+}
+
+/**
+ * pcpu_chunk_relocate - put chunk in the appropriate chunk slot
+ * @chunk: chunk of interest
+ * @oslot: the previous slot it was on
+ *
+ * This function is called after an allocation or free changed @chunk.
+ * New slot according to the changed state is determined and @chunk is
+ * moved to the slot.
+ */
+static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
+{
+	int nslot = pcpu_chunk_slot(chunk);
+
+	if (oslot != nslot) {
+		if (oslot < nslot)
+			list_move(&chunk->list, &pcpu_slot[nslot]);
+		else
+			list_move_tail(&chunk->list, &pcpu_slot[nslot]);
+	}
+}
+
+static struct rb_node **pcpu_chunk_rb_search(void *addr,
+					     struct rb_node **parentp)
+{
+	struct rb_node **p = &pcpu_addr_root.rb_node;
+	struct rb_node *parent = NULL;
+	struct pcpu_chunk *chunk;
+
+	while (*p) {
+		parent = *p;
+		chunk = rb_entry(parent, struct pcpu_chunk, rb_node);
+
+		if (addr < chunk->vm->addr)
+			p = &(*p)->rb_left;
+		else if (addr > chunk->vm->addr)
+			p = &(*p)->rb_right;
+		else
+			break;
+	}
+
+	if (parentp)
+		*parentp = parent;
+	return p;
+}
+
+/**
+ * pcpu_chunk_addr_search - search for chunk containing specified address
+ * @addr: address to search for
+ *
+ * Look for chunk which might contain @addr.  More specifically, it
+ * searchs for the chunk with the highest start address which isn't
+ * beyond @addr.
+ *
+ * RETURNS:
+ * The address of the found chunk.
+ */
+static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
+{
+	struct rb_node *n, *parent;
+	struct pcpu_chunk *chunk;
+
+	n = *pcpu_chunk_rb_search(addr, &parent);
+	if (!n) {
+		/* no exactly matching chunk, the parent is the closest */
+		n = parent;
+		BUG_ON(!n);
+	}
+	chunk = rb_entry(n, struct pcpu_chunk, rb_node);
+
+	if (addr < chunk->vm->addr) {
+		/* the parent was the next one, look for the previous one */
+		n = rb_prev(n);
+		BUG_ON(!n);
+		chunk = rb_entry(n, struct pcpu_chunk, rb_node);
+	}
+
+	return chunk;
+}
+
+/**
+ * pcpu_chunk_addr_insert - insert chunk into address rb tree
+ * @new: chunk to insert
+ *
+ * Insert @new into address rb tree.
+ */
+static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
+{
+	struct rb_node **p, *parent;
+
+	p = pcpu_chunk_rb_search(new->vm->addr, &parent);
+	BUG_ON(*p);
+	rb_link_node(&new->rb_node, parent, p);
+	rb_insert_color(&new->rb_node, &pcpu_addr_root);
+}
+
+/**
+ * pcpu_split_block - split a map block
+ * @chunk: chunk of interest
+ * @i: index of map block to split
+ * @head: head size (can be 0)
+ * @tail: tail size (can be 0)
+ *
+ * Split the @i'th map block into two or three blocks.  If @head is
+ * non-zero, @head bytes block is inserted before block @i moving it
+ * to @i+1 and reducing its size by @head bytes.
+ *
+ * If @tail is non-zero, the target block, which can be @i or @i+1
+ * depending on @head, is reduced by @tail bytes and @tail byte block
+ * is inserted after the target block.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int pcpu_split_block(struct pcpu_chunk *chunk, int i, int head, int tail)
+{
+	int nr_extra = !!head + !!tail;
+	int target = chunk->map_used + nr_extra;
+
+	/* reallocation required? */
+	if (chunk->map_alloc < target) {
+		int new_alloc = chunk->map_alloc;
+		int *new;
+
+		while (new_alloc < target)
+			new_alloc *= 2;
+
+		new = pcpu_realloc(chunk->map,
+				   chunk->map_alloc * sizeof(new[0]),
+				   new_alloc * sizeof(new[0]));
+		if (!new)
+			return -ENOMEM;
+
+		chunk->map_alloc = new_alloc;
+		chunk->map = new;
+	}
+
+	/* insert a new subblock */
+	memmove(&chunk->map[i + nr_extra], &chunk->map[i],
+		sizeof(chunk->map[0]) * (chunk->map_used - i));
+	chunk->map_used += nr_extra;
+
+	if (head) {
+		chunk->map[i + 1] = chunk->map[i] - head;
+		chunk->map[i++] = head;
+	}
+	if (tail) {
+		chunk->map[i++] -= tail;
+		chunk->map[i] = tail;
+	}
+	return 0;
+}
+
+/**
+ * pcpu_alloc_area - allocate area from a pcpu_chunk
+ * @chunk: chunk of interest
+ * @size: wanted size
+ * @align: wanted align
+ *
+ * Try to allocate @size bytes area aligned at @align from @chunk.
+ * Note that this function only allocates the offset.  It doesn't
+ * populate or map the area.
+ *
+ * RETURNS:
+ * Allocated offset in @chunk on success, -errno on failure.
+ */
+static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
+{
+	int oslot = pcpu_chunk_slot(chunk);
+	int max_contig = 0;
+	int i, off;
+
+	/*
+	 * The static chunk initially doesn't have map attached
+	 * because kmalloc wasn't available during init.  Give it one.
+	 */
+	if (unlikely(!chunk->map)) {
+		chunk->map = pcpu_realloc(NULL, 0,
+				PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
+		if (!chunk->map)
+			return -ENOMEM;
+
+		chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
+		chunk->map[chunk->map_used++] = -pcpu_static_size;
+		if (chunk->free_size)
+			chunk->map[chunk->map_used++] = chunk->free_size;
+	}
+
+	for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
+		bool is_last = i + 1 == chunk->map_used;
+		int head, tail;
+
+		/* extra for alignment requirement */
+		head = ALIGN(off, align) - off;
+		BUG_ON(i == 0 && head != 0);
+
+		if (chunk->map[i] < 0)
+			continue;
+		if (chunk->map[i] < head + size) {
+			max_contig = max(chunk->map[i], max_contig);
+			continue;
+		}
+
+		/*
+		 * If head is small or the previous block is free,
+		 * merge'em.  Note that 'small' is defined as smaller
+		 * than sizeof(int), which is very small but isn't too
+		 * uncommon for percpu allocations.
+		 */
+		if (head && (head < sizeof(int) || chunk->map[i - 1] > 0)) {
+			if (chunk->map[i - 1] > 0)
+				chunk->map[i - 1] += head;
+			else {
+				chunk->map[i - 1] -= head;
+				chunk->free_size -= head;
+			}
+			chunk->map[i] -= head;
+			off += head;
+			head = 0;
+		}
+
+		/* if tail is small, just keep it around */
+		tail = chunk->map[i] - head - size;
+		if (tail < sizeof(int))
+			tail = 0;
+
+		/* split if warranted */
+		if (head || tail) {
+			if (pcpu_split_block(chunk, i, head, tail))
+				return -ENOMEM;
+			if (head) {
+				i++;
+				off += head;
+				max_contig = max(chunk->map[i - 1], max_contig);
+			}
+			if (tail)
+				max_contig = max(chunk->map[i + 1], max_contig);
+		}
+
+		/* update hint and mark allocated */
+		if (is_last)
+			chunk->contig_hint = max_contig; /* fully scanned */
+		else
+			chunk->contig_hint = max(chunk->contig_hint,
+						 max_contig);
+
+		chunk->free_size -= chunk->map[i];
+		chunk->map[i] = -chunk->map[i];
+
+		pcpu_chunk_relocate(chunk, oslot);
+		return off;
+	}
+
+	chunk->contig_hint = max_contig;	/* fully scanned */
+	pcpu_chunk_relocate(chunk, oslot);
+
+	/*
+	 * Tell the upper layer that this chunk has no area left.
+	 * Note that this is not an error condition but a notification
+	 * to upper layer that it needs to look at other chunks.
+	 * -ENOSPC is chosen as it isn't used in memory subsystem and
+	 * matches the meaning in a way.
+	 */
+	return -ENOSPC;
+}
+
+/**
+ * pcpu_free_area - free area to a pcpu_chunk
+ * @chunk: chunk of interest
+ * @freeme: offset of area to free
+ *
+ * Free area starting from @freeme to @chunk.  Note that this function
+ * only modifies the allocation map.  It doesn't depopulate or unmap
+ * the area.
+ */
+static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
+{
+	int oslot = pcpu_chunk_slot(chunk);
+	int i, off;
+
+	for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++]))
+		if (off == freeme)
+			break;
+	BUG_ON(off != freeme);
+	BUG_ON(chunk->map[i] > 0);
+
+	chunk->map[i] = -chunk->map[i];
+	chunk->free_size += chunk->map[i];
+
+	/* merge with previous? */
+	if (i > 0 && chunk->map[i - 1] >= 0) {
+		chunk->map[i - 1] += chunk->map[i];
+		chunk->map_used--;
+		memmove(&chunk->map[i], &chunk->map[i + 1],
+			(chunk->map_used - i) * sizeof(chunk->map[0]));
+		i--;
+	}
+	/* merge with next? */
+	if (i + 1 < chunk->map_used && chunk->map[i + 1] >= 0) {
+		chunk->map[i] += chunk->map[i + 1];
+		chunk->map_used--;
+		memmove(&chunk->map[i + 1], &chunk->map[i + 2],
+			(chunk->map_used - (i + 1)) * sizeof(chunk->map[0]));
+	}
+
+	chunk->contig_hint = max(chunk->map[i], chunk->contig_hint);
+	pcpu_chunk_relocate(chunk, oslot);
+}
+
+/**
+ * pcpu_unmap - unmap pages out of a pcpu_chunk
+ * @chunk: chunk of interest
+ * @page_start: page index of the first page to unmap
+ * @page_end: page index of the last page to unmap + 1
+ * @flush: whether to flush cache and tlb or not
+ *
+ * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
+ * If @flush is true, vcache is flushed before unmapping and tlb
+ * after.
+ */
+static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
+		       bool flush)
+{
+	unsigned int last = num_possible_cpus() - 1;
+	unsigned int cpu;
+
+	/*
+	 * Each flushing trial can be very expensive, issue flush on
+	 * the whole region at once rather than doing it for each cpu.
+	 * This could be an overkill but is more scalable.
+	 */
+	if (flush)
+		flush_cache_vunmap(pcpu_chunk_addr(chunk, 0, page_start),
+				   pcpu_chunk_addr(chunk, last, page_end));
+
+	for_each_possible_cpu(cpu)
+		unmap_kernel_range_noflush(
+				pcpu_chunk_addr(chunk, cpu, page_start),
+				(page_end - page_start) << PAGE_SHIFT);
+
+	/* ditto as flush_cache_vunmap() */
+	if (flush)
+		flush_tlb_kernel_range(pcpu_chunk_addr(chunk, 0, page_start),
+				       pcpu_chunk_addr(chunk, last, page_end));
+}
+
+/**
+ * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
+ * @chunk: chunk to depopulate
+ * @off: offset to the area to depopulate
+ * @size: size of the area to depopulate
+ * @flush: whether to flush cache and tlb or not
+ *
+ * For each cpu, depopulate and unmap pages [@page_start,@page_end)
+ * from @chunk.  If @flush is true, vcache is flushed before unmapping
+ * and tlb after.
+ */
+static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, size_t off,
+				  size_t size, bool flush)
+{
+	int page_start = PFN_DOWN(off);
+	int page_end = PFN_UP(off + size);
+	int unmap_start = -1;
+	int uninitialized_var(unmap_end);
+	unsigned int cpu;
+	int i;
+
+	for (i = page_start; i < page_end; i++) {
+		for_each_possible_cpu(cpu) {
+			struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+
+			if (!*pagep)
+				continue;
+
+			__free_page(*pagep);
+
+			/*
+			 * If it's partial depopulation, it might get
+			 * populated or depopulated again.  Mark the
+			 * page gone.
+			 */
+			*pagep = NULL;
+
+			unmap_start = unmap_start < 0 ? i : unmap_start;
+			unmap_end = i + 1;
+		}
+	}
+
+	if (unmap_start >= 0)
+		pcpu_unmap(chunk, unmap_start, unmap_end, flush);
+}
+
+/**
+ * pcpu_map - map pages into a pcpu_chunk
+ * @chunk: chunk of interest
+ * @page_start: page index of the first page to map
+ * @page_end: page index of the last page to map + 1
+ *
+ * For each cpu, map pages [@page_start,@page_end) into @chunk.
+ * vcache is flushed afterwards.
+ */
+static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
+{
+	unsigned int last = num_possible_cpus() - 1;
+	unsigned int cpu;
+	int err;
+
+	for_each_possible_cpu(cpu) {
+		err = map_kernel_range_noflush(
+				pcpu_chunk_addr(chunk, cpu, page_start),
+				(page_end - page_start) << PAGE_SHIFT,
+				PAGE_KERNEL,
+				pcpu_chunk_pagep(chunk, cpu, page_start));
+		if (err < 0)
+			return err;
+	}
+
+	/* flush at once, please read comments in pcpu_unmap() */
+	flush_cache_vmap(pcpu_chunk_addr(chunk, 0, page_start),
+			 pcpu_chunk_addr(chunk, last, page_end));
+	return 0;
+}
+
+/**
+ * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
+ * @chunk: chunk of interest
+ * @off: offset to the area to populate
+ * @size: size of the area to populate
+ *
+ * For each cpu, populate and map pages [@page_start,@page_end) into
+ * @chunk.  The area is cleared on return.
+ */
+static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
+{
+	const gfp_t alloc_mask = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
+	int page_start = PFN_DOWN(off);
+	int page_end = PFN_UP(off + size);
+	int map_start = -1;
+	int map_end;
+	unsigned int cpu;
+	int i;
+
+	for (i = page_start; i < page_end; i++) {
+		if (pcpu_chunk_page_occupied(chunk, i)) {
+			if (map_start >= 0) {
+				if (pcpu_map(chunk, map_start, map_end))
+					goto err;
+				map_start = -1;
+			}
+			continue;
+		}
+
+		map_start = map_start < 0 ? i : map_start;
+		map_end = i + 1;
+
+		for_each_possible_cpu(cpu) {
+			struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+
+			*pagep = alloc_pages_node(cpu_to_node(cpu),
+						  alloc_mask, 0);
+			if (!*pagep)
+				goto err;
+		}
+	}
+
+	if (map_start >= 0 && pcpu_map(chunk, map_start, map_end))
+		goto err;
+
+	for_each_possible_cpu(cpu)
+		memset(chunk->vm->addr + (cpu << pcpu_unit_shift) + off, 0,
+		       size);
+
+	return 0;
+err:
+	/* likely under heavy memory pressure, give memory back */
+	pcpu_depopulate_chunk(chunk, off, size, true);
+	return -ENOMEM;
+}
+
+static void free_pcpu_chunk(struct pcpu_chunk *chunk)
+{
+	if (!chunk)
+		return;
+	if (chunk->vm)
+		free_vm_area(chunk->vm);
+	pcpu_realloc(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]), 0);
+	kfree(chunk);
+}
+
+static struct pcpu_chunk *alloc_pcpu_chunk(void)
+{
+	struct pcpu_chunk *chunk;
+
+	chunk = kzalloc(pcpu_chunk_struct_size, GFP_KERNEL);
+	if (!chunk)
+		return NULL;
+
+	chunk->map = pcpu_realloc(NULL, 0,
+				  PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
+	chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
+	chunk->map[chunk->map_used++] = pcpu_unit_size;
+
+	chunk->vm = get_vm_area(pcpu_chunk_size, GFP_KERNEL);
+	if (!chunk->vm) {
+		free_pcpu_chunk(chunk);
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&chunk->list);
+	chunk->free_size = pcpu_unit_size;
+	chunk->contig_hint = pcpu_unit_size;
+
+	return chunk;
+}
+
+/**
+ * __alloc_percpu - allocate percpu area
+ * @size: size of area to allocate
+ * @align: alignment of area (max PAGE_SIZE)
+ *
+ * Allocate percpu area of @size bytes aligned at @align.  Might
+ * sleep.  Might trigger writeouts.
+ *
+ * RETURNS:
+ * Percpu pointer to the allocated area on success, NULL on failure.
+ */
+void *__alloc_percpu(size_t size, size_t align)
+{
+	void *ptr = NULL;
+	struct pcpu_chunk *chunk;
+	int slot, off;
+
+	if (unlikely(!size || size > PAGE_SIZE << PCPU_MIN_UNIT_PAGES_SHIFT ||
+		     align > PAGE_SIZE)) {
+		WARN(true, "illegal size (%zu) or align (%zu) for "
+		     "percpu allocation\n", size, align);
+		return NULL;
+	}
+
+	mutex_lock(&pcpu_mutex);
+
+	/* allocate area */
+	for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
+		list_for_each_entry(chunk, &pcpu_slot[slot], list) {
+			if (size > chunk->contig_hint)
+				continue;
+			off = pcpu_alloc_area(chunk, size, align);
+			if (off >= 0)
+				goto area_found;
+			if (off != -ENOSPC)
+				goto out_unlock;
+		}
+	}
+
+	/* hmmm... no space left, create a new chunk */
+	chunk = alloc_pcpu_chunk();
+	if (!chunk)
+		goto out_unlock;
+	pcpu_chunk_relocate(chunk, -1);
+	pcpu_chunk_addr_insert(chunk);
+
+	off = pcpu_alloc_area(chunk, size, align);
+	if (off < 0)
+		goto out_unlock;
+
+area_found:
+	/* populate, map and clear the area */
+	if (pcpu_populate_chunk(chunk, off, size)) {
+		pcpu_free_area(chunk, off);
+		goto out_unlock;
+	}
+
+	ptr = __addr_to_pcpu_ptr(chunk->vm->addr + off);
+out_unlock:
+	mutex_unlock(&pcpu_mutex);
+	return ptr;
+}
+EXPORT_SYMBOL_GPL(__alloc_percpu);
+
+static void pcpu_kill_chunk(struct pcpu_chunk *chunk)
+{
+	pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size, false);
+	list_del(&chunk->list);
+	rb_erase(&chunk->rb_node, &pcpu_addr_root);
+	free_pcpu_chunk(chunk);
+}
+
+/**
+ * free_percpu - free percpu area
+ * @ptr: pointer to area to free
+ *
+ * Free percpu area @ptr.  Might sleep.
+ */
+void free_percpu(void *ptr)
+{
+	void *addr = __pcpu_ptr_to_addr(ptr);
+	struct pcpu_chunk *chunk;
+	int off;
+
+	if (!ptr)
+		return;
+
+	mutex_lock(&pcpu_mutex);
+
+	chunk = pcpu_chunk_addr_search(addr);
+	off = addr - chunk->vm->addr;
+
+	pcpu_free_area(chunk, off);
+
+	/* the chunk became fully free, kill one if there are other free ones */
+	if (chunk->free_size == pcpu_unit_size) {
+		struct pcpu_chunk *pos;
+
+		list_for_each_entry(pos,
+				    &pcpu_slot[pcpu_chunk_slot(chunk)], list)
+			if (pos != chunk) {
+				pcpu_kill_chunk(pos);
+				break;
+			}
+	}
+
+	mutex_unlock(&pcpu_mutex);
+}
+EXPORT_SYMBOL_GPL(free_percpu);
+
+/**
+ * pcpu_setup_static - initialize kernel static percpu area
+ * @populate_pte_fn: callback to allocate pagetable
+ * @pages: num_possible_cpus() * PFN_UP(cpu_size) pages
+ *
+ * Initialize kernel static percpu area.  The caller should allocate
+ * all the necessary pages and pass them in @pages.
+ * @populate_pte_fn() is called on each page to be used for percpu
+ * mapping and is responsible for making sure all the necessary page
+ * tables for the page is allocated.
+ *
+ * RETURNS:
+ * The determined pcpu_unit_size which can be used to initialize
+ * percpu access.
+ */
+size_t __init pcpu_setup_static(pcpu_populate_pte_fn_t populate_pte_fn,
+				struct page **pages, size_t cpu_size)
+{
+	static struct vm_struct static_vm;
+	struct pcpu_chunk *static_chunk;
+	int nr_cpu_pages = DIV_ROUND_UP(cpu_size, PAGE_SIZE);
+	unsigned int cpu;
+	int err, i;
+
+	pcpu_unit_pages_shift = max_t(int, PCPU_MIN_UNIT_PAGES_SHIFT,
+				      order_base_2(cpu_size) - PAGE_SHIFT);
+
+	pcpu_static_size = cpu_size;
+	pcpu_unit_pages = 1 << pcpu_unit_pages_shift;
+	pcpu_unit_shift = PAGE_SHIFT + pcpu_unit_pages_shift;
+	pcpu_unit_size = 1 << pcpu_unit_shift;
+	pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
+	pcpu_nr_slots = pcpu_size_to_slot(pcpu_unit_size) + 1;
+	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
+		+ (1 << pcpu_unit_pages_shift) * sizeof(struct page *);
+
+	/* allocate chunk slots */
+	pcpu_slot = alloc_bootmem(pcpu_nr_slots * sizeof(pcpu_slot[0]));
+	for (i = 0; i < pcpu_nr_slots; i++)
+		INIT_LIST_HEAD(&pcpu_slot[i]);
+
+	/* init and register vm area */
+	static_vm.flags = VM_ALLOC;
+	static_vm.size = pcpu_chunk_size;
+	vm_area_register_early(&static_vm);
+
+	/* init static_chunk */
+	static_chunk = alloc_bootmem(pcpu_chunk_struct_size);
+	INIT_LIST_HEAD(&static_chunk->list);
+	static_chunk->vm = &static_vm;
+	static_chunk->free_size = pcpu_unit_size - pcpu_static_size;
+	static_chunk->contig_hint = static_chunk->free_size;
+
+	/* assign pages and map them */
+	for_each_possible_cpu(cpu) {
+		for (i = 0; i < nr_cpu_pages; i++) {
+			*pcpu_chunk_pagep(static_chunk, cpu, i) = *pages++;
+			populate_pte_fn(pcpu_chunk_addr(static_chunk, cpu, i));
+		}
+	}
+
+	err = pcpu_map(static_chunk, 0, nr_cpu_pages);
+	if (err)
+		panic("failed to setup static percpu area, err=%d\n", err);
+
+	/* link static_chunk in */
+	pcpu_chunk_relocate(static_chunk, -1);
+	pcpu_chunk_addr_insert(static_chunk);
+
+	/* we're done */
+	pcpu_base_addr = (void *)pcpu_chunk_addr(static_chunk, 0, 0);
+	return pcpu_unit_size;
+}