Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 2793 insertions, 0 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
new file mode 100644
index 000000000..0151f276a
--- /dev/null
+++ b/mm/percpu.c
@@ -0,0 +1,2793 @@
+/*
+ * mm/percpu.c - percpu memory allocator
+ *
+ * Copyright (C) 2009		SUSE Linux Products GmbH
+ * Copyright (C) 2009		Tejun Heo <tj@kernel.org>
+ *
+ * Copyright (C) 2017		Facebook Inc.
+ * Copyright (C) 2017		Dennis Zhou <dennisszhou@gmail.com>
+ *
+ * This file is released under the GPLv2 license.
+ *
+ * The percpu allocator handles both static and dynamic areas.  Percpu
+ * areas are allocated in chunks which are divided into units.  There is
+ * a 1-to-1 mapping for units to possible cpus.  These units are grouped
+ * based on NUMA properties of the machine.
+ *
+ *  c0                           c1                         c2
+ *  -------------------          -------------------        ------------
+ * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
+ *  -------------------  ......  -------------------  ....  ------------
+ *
+ * Allocation is done by offsets into a unit's address space.  Ie., an
+ * area of 512 bytes at 6k in c1 occupies 512 bytes at 6k in c1:u0,
+ * c1:u1, c1:u2, etc.  On NUMA machines, the mapping may be non-linear
+ * and even sparse.  Access is handled by configuring percpu base
+ * registers according to the cpu to unit mappings and offsetting the
+ * base address using pcpu_unit_size.
+ *
+ * There is special consideration for the first chunk which must handle
+ * the static percpu variables in the kernel image as allocation services
+ * are not online yet.  In short, the first chunk is structured like so:
+ *
+ *                  <Static | [Reserved] | Dynamic>
+ *
+ * The static data is copied from the original section managed by the
+ * linker.  The reserved section, if non-zero, primarily manages static
+ * percpu variables from kernel modules.  Finally, the dynamic section
+ * takes care of normal allocations.
+ *
+ * The allocator organizes chunks into lists according to free size and
+ * tries to allocate from the fullest chunk first.  Each chunk is managed
+ * by a bitmap with metadata blocks.  The allocation map is updated on
+ * every allocation and free to reflect the current state while the boundary
+ * map is only updated on allocation.  Each metadata block contains
+ * information to help mitigate the need to iterate over large portions
+ * of the bitmap.  The reverse mapping from page to chunk is stored in
+ * the page's index.  Lastly, units are lazily backed and grow in unison.
+ *
+ * There is a unique conversion that goes on here between bytes and bits.
+ * Each bit represents a fragment of size PCPU_MIN_ALLOC_SIZE.  The chunk
+ * tracks the number of pages it is responsible for in nr_pages.  Helper
+ * functions are used to convert from between the bytes, bits, and blocks.
+ * All hints are managed in bits unless explicitly stated.
+ *
+ * To use this allocator, arch code should do the following:
+ *
+ * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
+ *   regular address to percpu pointer and back if they need to be
+ *   different from the default
+ *
+ * - use pcpu_setup_first_chunk() during percpu area initialization to
+ *   setup the first chunk containing the kernel static percpu area
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/bootmem.h>
+#include <linux/err.h>
+#include <linux/lcm.h>
+#include <linux/list.h>
+#include <linux/log2.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/pfn.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+#include <linux/kmemleak.h>
+#include <linux/sched.h>
+
+#include <asm/cacheflush.h>
+#include <asm/sections.h>
+#include <asm/tlbflush.h>
+#include <asm/io.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/percpu.h>
+
+#include "percpu-internal.h"
+
+/* the slots are sorted by free bytes left, 1-31 bytes share the same slot */
+#define PCPU_SLOT_BASE_SHIFT		5
+
+#define PCPU_EMPTY_POP_PAGES_LOW	2
+#define PCPU_EMPTY_POP_PAGES_HIGH	4
+
+#ifdef CONFIG_SMP
+/* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
+#ifndef __addr_to_pcpu_ptr
+#define __addr_to_pcpu_ptr(addr)					\
+	(void __percpu *)((unsigned long)(addr) -			\
+			  (unsigned long)pcpu_base_addr	+		\
+			  (unsigned long)__per_cpu_start)
+#endif
+#ifndef __pcpu_ptr_to_addr
+#define __pcpu_ptr_to_addr(ptr)						\
+	(void __force *)((unsigned long)(ptr) +				\
+			 (unsigned long)pcpu_base_addr -		\
+			 (unsigned long)__per_cpu_start)
+#endif
+#else	/* CONFIG_SMP */
+/* on UP, it's always identity mapped */
+#define __addr_to_pcpu_ptr(addr)	(void __percpu *)(addr)
+#define __pcpu_ptr_to_addr(ptr)		(void __force *)(ptr)
+#endif	/* CONFIG_SMP */
+
+static int pcpu_unit_pages __ro_after_init;
+static int pcpu_unit_size __ro_after_init;
+static int pcpu_nr_units __ro_after_init;
+static int pcpu_atom_size __ro_after_init;
+int pcpu_nr_slots __ro_after_init;
+static size_t pcpu_chunk_struct_size __ro_after_init;
+
+/* cpus with the lowest and highest unit addresses */
+static unsigned int pcpu_low_unit_cpu __ro_after_init;
+static unsigned int pcpu_high_unit_cpu __ro_after_init;
+
+/* the address of the first chunk which starts with the kernel static area */
+void *pcpu_base_addr __ro_after_init;
+EXPORT_SYMBOL_GPL(pcpu_base_addr);
+
+static const int *pcpu_unit_map __ro_after_init;		/* cpu -> unit */
+const unsigned long *pcpu_unit_offsets __ro_after_init;	/* cpu -> unit offset */
+
+/* group information, used for vm allocation */
+static int pcpu_nr_groups __ro_after_init;
+static const unsigned long *pcpu_group_offsets __ro_after_init;
+static const size_t *pcpu_group_sizes __ro_after_init;
+
+/*
+ * The first chunk which always exists.  Note that unlike other
+ * chunks, this one can be allocated and mapped in several different
+ * ways and thus often doesn't live in the vmalloc area.
+ */
+struct pcpu_chunk *pcpu_first_chunk __ro_after_init;
+
+/*
+ * Optional reserved chunk.  This chunk reserves part of the first
+ * chunk and serves it for reserved allocations.  When the reserved
+ * region doesn't exist, the following variable is NULL.
+ */
+struct pcpu_chunk *pcpu_reserved_chunk __ro_after_init;
+
+DEFINE_SPINLOCK(pcpu_lock);	/* all internal data structures */
+static DEFINE_MUTEX(pcpu_alloc_mutex);	/* chunk create/destroy, [de]pop, map ext */
+
+struct list_head *pcpu_slot __ro_after_init; /* chunk list slots */
+
+/* chunks which need their map areas extended, protected by pcpu_lock */
+static LIST_HEAD(pcpu_map_extend_chunks);
+
+/*
+ * The number of empty populated pages, protected by pcpu_lock.  The
+ * reserved chunk doesn't contribute to the count.
+ */
+int pcpu_nr_empty_pop_pages;
+
+/*
+ * The number of populated pages in use by the allocator, protected by
+ * pcpu_lock.  This number is kept per a unit per chunk (i.e. when a page gets
+ * allocated/deallocated, it is allocated/deallocated in all units of a chunk
+ * and increments/decrements this count by 1).
+ */
+static unsigned long pcpu_nr_populated;
+
+/*
+ * Balance work is used to populate or destroy chunks asynchronously.  We
+ * try to keep the number of populated free pages between
+ * PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
+ * empty chunk.
+ */
+static void pcpu_balance_workfn(struct work_struct *work);
+static DECLARE_WORK(pcpu_balance_work, pcpu_balance_workfn);
+static bool pcpu_async_enabled __read_mostly;
+static bool pcpu_atomic_alloc_failed;
+
+static void pcpu_schedule_balance_work(void)
+{
+	if (pcpu_async_enabled)
+		schedule_work(&pcpu_balance_work);
+}
+
+/**
+ * pcpu_addr_in_chunk - check if the address is served from this chunk
+ * @chunk: chunk of interest
+ * @addr: percpu address
+ *
+ * RETURNS:
+ * True if the address is served from this chunk.
+ */
+static bool pcpu_addr_in_chunk(struct pcpu_chunk *chunk, void *addr)
+{
+	void *start_addr, *end_addr;
+
+	if (!chunk)
+		return false;
+
+	start_addr = chunk->base_addr + chunk->start_offset;
+	end_addr = chunk->base_addr + chunk->nr_pages * PAGE_SIZE -
+		   chunk->end_offset;
+
+	return addr >= start_addr && addr < end_addr;
+}
+
+static int __pcpu_size_to_slot(int size)
+{
+	int highbit = fls(size);	/* size is in bytes */
+	return max(highbit - PCPU_SLOT_BASE_SHIFT + 2, 1);
+}
+
+static int pcpu_size_to_slot(int size)
+{
+	if (size == pcpu_unit_size)
+		return pcpu_nr_slots - 1;
+	return __pcpu_size_to_slot(size);
+}
+
+static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
+{
+	if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE || chunk->contig_bits == 0)
+		return 0;
+
+	return pcpu_size_to_slot(chunk->free_bytes);
+}
+
+/* set the pointer to a chunk in a page struct */
+static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
+{
+	page->index = (unsigned long)pcpu;
+}
+
+/* obtain pointer to a chunk from a page struct */
+static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
+{
+	return (struct pcpu_chunk *)page->index;
+}
+
+static int __maybe_unused pcpu_page_idx(unsigned int cpu, int page_idx)
+{
+	return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
+}
+
+static unsigned long pcpu_unit_page_offset(unsigned int cpu, int page_idx)
+{
+	return pcpu_unit_offsets[cpu] + (page_idx << PAGE_SHIFT);
+}
+
+static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
+				     unsigned int cpu, int page_idx)
+{
+	return (unsigned long)chunk->base_addr +
+	       pcpu_unit_page_offset(cpu, page_idx);
+}
+
+static void pcpu_next_unpop(unsigned long *bitmap, int *rs, int *re, int end)
+{
+	*rs = find_next_zero_bit(bitmap, end, *rs);
+	*re = find_next_bit(bitmap, end, *rs + 1);
+}
+
+static void pcpu_next_pop(unsigned long *bitmap, int *rs, int *re, int end)
+{
+	*rs = find_next_bit(bitmap, end, *rs);
+	*re = find_next_zero_bit(bitmap, end, *rs + 1);
+}
+
+/*
+ * Bitmap region iterators.  Iterates over the bitmap between
+ * [@start, @end) in @chunk.  @rs and @re should be integer variables
+ * and will be set to start and end index of the current free region.
+ */
+#define pcpu_for_each_unpop_region(bitmap, rs, re, start, end)		     \
+	for ((rs) = (start), pcpu_next_unpop((bitmap), &(rs), &(re), (end)); \
+	     (rs) < (re);						     \
+	     (rs) = (re) + 1, pcpu_next_unpop((bitmap), &(rs), &(re), (end)))
+
+#define pcpu_for_each_pop_region(bitmap, rs, re, start, end)		     \
+	for ((rs) = (start), pcpu_next_pop((bitmap), &(rs), &(re), (end));   \
+	     (rs) < (re);						     \
+	     (rs) = (re) + 1, pcpu_next_pop((bitmap), &(rs), &(re), (end)))
+
+/*
+ * The following are helper functions to help access bitmaps and convert
+ * between bitmap offsets to address offsets.
+ */
+static unsigned long *pcpu_index_alloc_map(struct pcpu_chunk *chunk, int index)
+{
+	return chunk->alloc_map +
+	       (index * PCPU_BITMAP_BLOCK_BITS / BITS_PER_LONG);
+}
+
+static unsigned long pcpu_off_to_block_index(int off)
+{
+	return off / PCPU_BITMAP_BLOCK_BITS;
+}
+
+static unsigned long pcpu_off_to_block_off(int off)
+{
+	return off & (PCPU_BITMAP_BLOCK_BITS - 1);
+}
+
+static unsigned long pcpu_block_off_to_off(int index, int off)
+{
+	return index * PCPU_BITMAP_BLOCK_BITS + off;
+}
+
+/**
+ * pcpu_next_md_free_region - finds the next hint free area
+ * @chunk: chunk of interest
+ * @bit_off: chunk offset
+ * @bits: size of free area
+ *
+ * Helper function for pcpu_for_each_md_free_region.  It checks
+ * block->contig_hint and performs aggregation across blocks to find the
+ * next hint.  It modifies bit_off and bits in-place to be consumed in the
+ * loop.
+ */
+static void pcpu_next_md_free_region(struct pcpu_chunk *chunk, int *bit_off,
+				     int *bits)
+{
+	int i = pcpu_off_to_block_index(*bit_off);
+	int block_off = pcpu_off_to_block_off(*bit_off);
+	struct pcpu_block_md *block;
+
+	*bits = 0;
+	for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
+	     block++, i++) {
+		/* handles contig area across blocks */
+		if (*bits) {
+			*bits += block->left_free;
+			if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
+				continue;
+			return;
+		}
+
+		/*
+		 * This checks three things.  First is there a contig_hint to
+		 * check.  Second, have we checked this hint before by
+		 * comparing the block_off.  Third, is this the same as the
+		 * right contig hint.  In the last case, it spills over into
+		 * the next block and should be handled by the contig area
+		 * across blocks code.
+		 */
+		*bits = block->contig_hint;
+		if (*bits && block->contig_hint_start >= block_off &&
+		    *bits + block->contig_hint_start < PCPU_BITMAP_BLOCK_BITS) {
+			*bit_off = pcpu_block_off_to_off(i,
+					block->contig_hint_start);
+			return;
+		}
+		/* reset to satisfy the second predicate above */
+		block_off = 0;
+
+		*bits = block->right_free;
+		*bit_off = (i + 1) * PCPU_BITMAP_BLOCK_BITS - block->right_free;
+	}
+}
+
+/**
+ * pcpu_next_fit_region - finds fit areas for a given allocation request
+ * @chunk: chunk of interest
+ * @alloc_bits: size of allocation
+ * @align: alignment of area (max PAGE_SIZE)
+ * @bit_off: chunk offset
+ * @bits: size of free area
+ *
+ * Finds the next free region that is viable for use with a given size and
+ * alignment.  This only returns if there is a valid area to be used for this
+ * allocation.  block->first_free is returned if the allocation request fits
+ * within the block to see if the request can be fulfilled prior to the contig
+ * hint.
+ */
+static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits,
+				 int align, int *bit_off, int *bits)
+{
+	int i = pcpu_off_to_block_index(*bit_off);
+	int block_off = pcpu_off_to_block_off(*bit_off);
+	struct pcpu_block_md *block;
+
+	*bits = 0;
+	for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
+	     block++, i++) {
+		/* handles contig area across blocks */
+		if (*bits) {
+			*bits += block->left_free;
+			if (*bits >= alloc_bits)
+				return;
+			if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
+				continue;
+		}
+
+		/* check block->contig_hint */
+		*bits = ALIGN(block->contig_hint_start, align) -
+			block->contig_hint_start;
+		/*
+		 * This uses the block offset to determine if this has been
+		 * checked in the prior iteration.
+		 */
+		if (block->contig_hint &&
+		    block->contig_hint_start >= block_off &&
+		    block->contig_hint >= *bits + alloc_bits) {
+			*bits += alloc_bits + block->contig_hint_start -
+				 block->first_free;
+			*bit_off = pcpu_block_off_to_off(i, block->first_free);
+			return;
+		}
+		/* reset to satisfy the second predicate above */
+		block_off = 0;
+
+		*bit_off = ALIGN(PCPU_BITMAP_BLOCK_BITS - block->right_free,
+				 align);
+		*bits = PCPU_BITMAP_BLOCK_BITS - *bit_off;
+		*bit_off = pcpu_block_off_to_off(i, *bit_off);
+		if (*bits >= alloc_bits)
+			return;
+	}
+
+	/* no valid offsets were found - fail condition */
+	*bit_off = pcpu_chunk_map_bits(chunk);
+}
+
+/*
+ * Metadata free area iterators.  These perform aggregation of free areas
+ * based on the metadata blocks and return the offset @bit_off and size in
+ * bits of the free area @bits.  pcpu_for_each_fit_region only returns when
+ * a fit is found for the allocation request.
+ */
+#define pcpu_for_each_md_free_region(chunk, bit_off, bits)		\
+	for (pcpu_next_md_free_region((chunk), &(bit_off), &(bits));	\
+	     (bit_off) < pcpu_chunk_map_bits((chunk));			\
+	     (bit_off) += (bits) + 1,					\
+	     pcpu_next_md_free_region((chunk), &(bit_off), &(bits)))
+
+#define pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits)     \
+	for (pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
+				  &(bits));				      \
+	     (bit_off) < pcpu_chunk_map_bits((chunk));			      \
+	     (bit_off) += (bits),					      \
+	     pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
+				  &(bits)))
+
+/**
+ * pcpu_mem_zalloc - allocate memory
+ * @size: bytes to allocate
+ * @gfp: allocation flags
+ *
+ * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,
+ * kzalloc() is used; otherwise, the equivalent of vzalloc() is used.
+ * This is to facilitate passing through whitelisted flags.  The
+ * returned memory is always zeroed.
+ *
+ * RETURNS:
+ * Pointer to the allocated area on success, NULL on failure.
+ */
+static void *pcpu_mem_zalloc(size_t size, gfp_t gfp)
+{
+	if (WARN_ON_ONCE(!slab_is_available()))
+		return NULL;
+
+	if (size <= PAGE_SIZE)
+		return kzalloc(size, gfp);
+	else
+		return __vmalloc(size, gfp | __GFP_ZERO, PAGE_KERNEL);
+}
+
+/**
+ * pcpu_mem_free - free memory
+ * @ptr: memory to free
+ *
+ * Free @ptr.  @ptr should have been allocated using pcpu_mem_zalloc().
+ */
+static void pcpu_mem_free(void *ptr)
+{
+	kvfree(ptr);
+}
+
+/**
+ * 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.  Note that the reserved chunk is never put on
+ * chunk slots.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ */
+static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
+{
+	int nslot = pcpu_chunk_slot(chunk);
+
+	if (chunk != pcpu_reserved_chunk && oslot != nslot) {
+		if (oslot < nslot)
+			list_move(&chunk->list, &pcpu_slot[nslot]);
+		else
+			list_move_tail(&chunk->list, &pcpu_slot[nslot]);
+	}
+}
+
+/**
+ * pcpu_cnt_pop_pages- counts populated backing pages in range
+ * @chunk: chunk of interest
+ * @bit_off: start offset
+ * @bits: size of area to check
+ *
+ * Calculates the number of populated pages in the region
+ * [page_start, page_end).  This keeps track of how many empty populated
+ * pages are available and decide if async work should be scheduled.
+ *
+ * RETURNS:
+ * The nr of populated pages.
+ */
+static inline int pcpu_cnt_pop_pages(struct pcpu_chunk *chunk, int bit_off,
+				     int bits)
+{
+	int page_start = PFN_UP(bit_off * PCPU_MIN_ALLOC_SIZE);
+	int page_end = PFN_DOWN((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
+
+	if (page_start >= page_end)
+		return 0;
+
+	/*
+	 * bitmap_weight counts the number of bits set in a bitmap up to
+	 * the specified number of bits.  This is counting the populated
+	 * pages up to page_end and then subtracting the populated pages
+	 * up to page_start to count the populated pages in
+	 * [page_start, page_end).
+	 */
+	return bitmap_weight(chunk->populated, page_end) -
+	       bitmap_weight(chunk->populated, page_start);
+}
+
+/**
+ * pcpu_chunk_update - updates the chunk metadata given a free area
+ * @chunk: chunk of interest
+ * @bit_off: chunk offset
+ * @bits: size of free area
+ *
+ * This updates the chunk's contig hint and starting offset given a free area.
+ * Choose the best starting offset if the contig hint is equal.
+ */
+static void pcpu_chunk_update(struct pcpu_chunk *chunk, int bit_off, int bits)
+{
+	if (bits > chunk->contig_bits) {
+		chunk->contig_bits_start = bit_off;
+		chunk->contig_bits = bits;
+	} else if (bits == chunk->contig_bits && chunk->contig_bits_start &&
+		   (!bit_off ||
+		    __ffs(bit_off) > __ffs(chunk->contig_bits_start))) {
+		/* use the start with the best alignment */
+		chunk->contig_bits_start = bit_off;
+	}
+}
+
+/**
+ * pcpu_chunk_refresh_hint - updates metadata about a chunk
+ * @chunk: chunk of interest
+ *
+ * Iterates over the metadata blocks to find the largest contig area.
+ * It also counts the populated pages and uses the delta to update the
+ * global count.
+ *
+ * Updates:
+ *      chunk->contig_bits
+ *      chunk->contig_bits_start
+ *      nr_empty_pop_pages (chunk and global)
+ */
+static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
+{
+	int bit_off, bits, nr_empty_pop_pages;
+
+	/* clear metadata */
+	chunk->contig_bits = 0;
+
+	bit_off = chunk->first_bit;
+	bits = nr_empty_pop_pages = 0;
+	pcpu_for_each_md_free_region(chunk, bit_off, bits) {
+		pcpu_chunk_update(chunk, bit_off, bits);
+
+		nr_empty_pop_pages += pcpu_cnt_pop_pages(chunk, bit_off, bits);
+	}
+
+	/*
+	 * Keep track of nr_empty_pop_pages.
+	 *
+	 * The chunk maintains the previous number of free pages it held,
+	 * so the delta is used to update the global counter.  The reserved
+	 * chunk is not part of the free page count as they are populated
+	 * at init and are special to serving reserved allocations.
+	 */
+	if (chunk != pcpu_reserved_chunk)
+		pcpu_nr_empty_pop_pages +=
+			(nr_empty_pop_pages - chunk->nr_empty_pop_pages);
+
+	chunk->nr_empty_pop_pages = nr_empty_pop_pages;
+}
+
+/**
+ * pcpu_block_update - updates a block given a free area
+ * @block: block of interest
+ * @start: start offset in block
+ * @end: end offset in block
+ *
+ * Updates a block given a known free area.  The region [start, end) is
+ * expected to be the entirety of the free area within a block.  Chooses
+ * the best starting offset if the contig hints are equal.
+ */
+static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
+{
+	int contig = end - start;
+
+	block->first_free = min(block->first_free, start);
+	if (start == 0)
+		block->left_free = contig;
+
+	if (end == PCPU_BITMAP_BLOCK_BITS)
+		block->right_free = contig;
+
+	if (contig > block->contig_hint) {
+		block->contig_hint_start = start;
+		block->contig_hint = contig;
+	} else if (block->contig_hint_start && contig == block->contig_hint &&
+		   (!start || __ffs(start) > __ffs(block->contig_hint_start))) {
+		/* use the start with the best alignment */
+		block->contig_hint_start = start;
+	}
+}
+
+/**
+ * pcpu_block_refresh_hint
+ * @chunk: chunk of interest
+ * @index: index of the metadata block
+ *
+ * Scans over the block beginning at first_free and updates the block
+ * metadata accordingly.
+ */
+static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
+{
+	struct pcpu_block_md *block = chunk->md_blocks + index;
+	unsigned long *alloc_map = pcpu_index_alloc_map(chunk, index);
+	int rs, re;	/* region start, region end */
+
+	/* clear hints */
+	block->contig_hint = 0;
+	block->left_free = block->right_free = 0;
+
+	/* iterate over free areas and update the contig hints */
+	pcpu_for_each_unpop_region(alloc_map, rs, re, block->first_free,
+				   PCPU_BITMAP_BLOCK_BITS) {
+		pcpu_block_update(block, rs, re);
+	}
+}
+
+/**
+ * pcpu_block_update_hint_alloc - update hint on allocation path
+ * @chunk: chunk of interest
+ * @bit_off: chunk offset
+ * @bits: size of request
+ *
+ * Updates metadata for the allocation path.  The metadata only has to be
+ * refreshed by a full scan iff the chunk's contig hint is broken.  Block level
+ * scans are required if the block's contig hint is broken.
+ */
+static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
+					 int bits)
+{
+	struct pcpu_block_md *s_block, *e_block, *block;
+	int s_index, e_index;	/* block indexes of the freed allocation */
+	int s_off, e_off;	/* block offsets of the freed allocation */
+
+	/*
+	 * Calculate per block offsets.
+	 * The calculation uses an inclusive range, but the resulting offsets
+	 * are [start, end).  e_index always points to the last block in the
+	 * range.
+	 */
+	s_index = pcpu_off_to_block_index(bit_off);
+	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
+	s_off = pcpu_off_to_block_off(bit_off);
+	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
+
+	s_block = chunk->md_blocks + s_index;
+	e_block = chunk->md_blocks + e_index;
+
+	/*
+	 * Update s_block.
+	 * block->first_free must be updated if the allocation takes its place.
+	 * If the allocation breaks the contig_hint, a scan is required to
+	 * restore this hint.
+	 */
+	if (s_off == s_block->first_free)
+		s_block->first_free = find_next_zero_bit(
+					pcpu_index_alloc_map(chunk, s_index),
+					PCPU_BITMAP_BLOCK_BITS,
+					s_off + bits);
+
+	if (s_off >= s_block->contig_hint_start &&
+	    s_off < s_block->contig_hint_start + s_block->contig_hint) {
+		/* block contig hint is broken - scan to fix it */
+		pcpu_block_refresh_hint(chunk, s_index);
+	} else {
+		/* update left and right contig manually */
+		s_block->left_free = min(s_block->left_free, s_off);
+		if (s_index == e_index)
+			s_block->right_free = min_t(int, s_block->right_free,
+					PCPU_BITMAP_BLOCK_BITS - e_off);
+		else
+			s_block->right_free = 0;
+	}
+
+	/*
+	 * Update e_block.
+	 */
+	if (s_index != e_index) {
+		/*
+		 * When the allocation is across blocks, the end is along
+		 * the left part of the e_block.
+		 */
+		e_block->first_free = find_next_zero_bit(
+				pcpu_index_alloc_map(chunk, e_index),
+				PCPU_BITMAP_BLOCK_BITS, e_off);
+
+		if (e_off == PCPU_BITMAP_BLOCK_BITS) {
+			/* reset the block */
+			e_block++;
+		} else {
+			if (e_off > e_block->contig_hint_start) {
+				/* contig hint is broken - scan to fix it */
+				pcpu_block_refresh_hint(chunk, e_index);
+			} else {
+				e_block->left_free = 0;
+				e_block->right_free =
+					min_t(int, e_block->right_free,
+					      PCPU_BITMAP_BLOCK_BITS - e_off);
+			}
+		}
+
+		/* update in-between md_blocks */
+		for (block = s_block + 1; block < e_block; block++) {
+			block->contig_hint = 0;
+			block->left_free = 0;
+			block->right_free = 0;
+		}
+	}
+
+	/*
+	 * The only time a full chunk scan is required is if the chunk
+	 * contig hint is broken.  Otherwise, it means a smaller space
+	 * was used and therefore the chunk contig hint is still correct.
+	 */
+	if (bit_off >= chunk->contig_bits_start  &&
+	    bit_off < chunk->contig_bits_start + chunk->contig_bits)
+		pcpu_chunk_refresh_hint(chunk);
+}
+
+/**
+ * pcpu_block_update_hint_free - updates the block hints on the free path
+ * @chunk: chunk of interest
+ * @bit_off: chunk offset
+ * @bits: size of request
+ *
+ * Updates metadata for the allocation path.  This avoids a blind block
+ * refresh by making use of the block contig hints.  If this fails, it scans
+ * forward and backward to determine the extent of the free area.  This is
+ * capped at the boundary of blocks.
+ *
+ * A chunk update is triggered if a page becomes free, a block becomes free,
+ * or the free spans across blocks.  This tradeoff is to minimize iterating
+ * over the block metadata to update chunk->contig_bits.  chunk->contig_bits
+ * may be off by up to a page, but it will never be more than the available
+ * space.  If the contig hint is contained in one block, it will be accurate.
+ */
+static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
+					int bits)
+{
+	struct pcpu_block_md *s_block, *e_block, *block;
+	int s_index, e_index;	/* block indexes of the freed allocation */
+	int s_off, e_off;	/* block offsets of the freed allocation */
+	int start, end;		/* start and end of the whole free area */
+
+	/*
+	 * Calculate per block offsets.
+	 * The calculation uses an inclusive range, but the resulting offsets
+	 * are [start, end).  e_index always points to the last block in the
+	 * range.
+	 */
+	s_index = pcpu_off_to_block_index(bit_off);
+	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
+	s_off = pcpu_off_to_block_off(bit_off);
+	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
+
+	s_block = chunk->md_blocks + s_index;
+	e_block = chunk->md_blocks + e_index;
+
+	/*
+	 * Check if the freed area aligns with the block->contig_hint.
+	 * If it does, then the scan to find the beginning/end of the
+	 * larger free area can be avoided.
+	 *
+	 * start and end refer to beginning and end of the free area
+	 * within each their respective blocks.  This is not necessarily
+	 * the entire free area as it may span blocks past the beginning
+	 * or end of the block.
+	 */
+	start = s_off;
+	if (s_off == s_block->contig_hint + s_block->contig_hint_start) {
+		start = s_block->contig_hint_start;
+	} else {
+		/*
+		 * Scan backwards to find the extent of the free area.
+		 * find_last_bit returns the starting bit, so if the start bit
+		 * is returned, that means there was no last bit and the
+		 * remainder of the chunk is free.
+		 */
+		int l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index),
+					  start);
+		start = (start == l_bit) ? 0 : l_bit + 1;
+	}
+
+	end = e_off;
+	if (e_off == e_block->contig_hint_start)
+		end = e_block->contig_hint_start + e_block->contig_hint;
+	else
+		end = find_next_bit(pcpu_index_alloc_map(chunk, e_index),
+				    PCPU_BITMAP_BLOCK_BITS, end);
+
+	/* update s_block */
+	e_off = (s_index == e_index) ? end : PCPU_BITMAP_BLOCK_BITS;
+	pcpu_block_update(s_block, start, e_off);
+
+	/* freeing in the same block */
+	if (s_index != e_index) {
+		/* update e_block */
+		pcpu_block_update(e_block, 0, end);
+
+		/* reset md_blocks in the middle */
+		for (block = s_block + 1; block < e_block; block++) {
+			block->first_free = 0;
+			block->contig_hint_start = 0;
+			block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
+			block->left_free = PCPU_BITMAP_BLOCK_BITS;
+			block->right_free = PCPU_BITMAP_BLOCK_BITS;
+		}
+	}
+
+	/*
+	 * Refresh chunk metadata when the free makes a page free, a block
+	 * free, or spans across blocks.  The contig hint may be off by up to
+	 * a page, but if the hint is contained in a block, it will be accurate
+	 * with the else condition below.
+	 */
+	if ((ALIGN_DOWN(end, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS)) >
+	     ALIGN(start, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS))) ||
+	    s_index != e_index)
+		pcpu_chunk_refresh_hint(chunk);
+	else
+		pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
+				  s_block->contig_hint);
+}
+
+/**
+ * pcpu_is_populated - determines if the region is populated
+ * @chunk: chunk of interest
+ * @bit_off: chunk offset
+ * @bits: size of area
+ * @next_off: return value for the next offset to start searching
+ *
+ * For atomic allocations, check if the backing pages are populated.
+ *
+ * RETURNS:
+ * Bool if the backing pages are populated.
+ * next_index is to skip over unpopulated blocks in pcpu_find_block_fit.
+ */
+static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
+			      int *next_off)
+{
+	int page_start, page_end, rs, re;
+
+	page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
+	page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
+
+	rs = page_start;
+	pcpu_next_unpop(chunk->populated, &rs, &re, page_end);
+	if (rs >= page_end)
+		return true;
+
+	*next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
+	return false;
+}
+
+/**
+ * pcpu_find_block_fit - finds the block index to start searching
+ * @chunk: chunk of interest
+ * @alloc_bits: size of request in allocation units
+ * @align: alignment of area (max PAGE_SIZE bytes)
+ * @pop_only: use populated regions only
+ *
+ * Given a chunk and an allocation spec, find the offset to begin searching
+ * for a free region.  This iterates over the bitmap metadata blocks to
+ * find an offset that will be guaranteed to fit the requirements.  It is
+ * not quite first fit as if the allocation does not fit in the contig hint
+ * of a block or chunk, it is skipped.  This errs on the side of caution
+ * to prevent excess iteration.  Poor alignment can cause the allocator to
+ * skip over blocks and chunks that have valid free areas.
+ *
+ * RETURNS:
+ * The offset in the bitmap to begin searching.
+ * -1 if no offset is found.
+ */
+static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
+			       size_t align, bool pop_only)
+{
+	int bit_off, bits, next_off;
+
+	/*
+	 * Check to see if the allocation can fit in the chunk's contig hint.
+	 * This is an optimization to prevent scanning by assuming if it
+	 * cannot fit in the global hint, there is memory pressure and creating
+	 * a new chunk would happen soon.
+	 */
+	bit_off = ALIGN(chunk->contig_bits_start, align) -
+		  chunk->contig_bits_start;
+	if (bit_off + alloc_bits > chunk->contig_bits)
+		return -1;
+
+	bit_off = chunk->first_bit;
+	bits = 0;
+	pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) {
+		if (!pop_only || pcpu_is_populated(chunk, bit_off, bits,
+						   &next_off))
+			break;
+
+		bit_off = next_off;
+		bits = 0;
+	}
+
+	if (bit_off == pcpu_chunk_map_bits(chunk))
+		return -1;
+
+	return bit_off;
+}
+
+/**
+ * pcpu_alloc_area - allocates an area from a pcpu_chunk
+ * @chunk: chunk of interest
+ * @alloc_bits: size of request in allocation units
+ * @align: alignment of area (max PAGE_SIZE)
+ * @start: bit_off to start searching
+ *
+ * This function takes in a @start offset to begin searching to fit an
+ * allocation of @alloc_bits with alignment @align.  It needs to scan
+ * the allocation map because if it fits within the block's contig hint,
+ * @start will be block->first_free. This is an attempt to fill the
+ * allocation prior to breaking the contig hint.  The allocation and
+ * boundary maps are updated accordingly if it confirms a valid
+ * free area.
+ *
+ * RETURNS:
+ * Allocated addr offset in @chunk on success.
+ * -1 if no matching area is found.
+ */
+static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
+			   size_t align, int start)
+{
+	size_t align_mask = (align) ? (align - 1) : 0;
+	int bit_off, end, oslot;
+
+	lockdep_assert_held(&pcpu_lock);
+
+	oslot = pcpu_chunk_slot(chunk);
+
+	/*
+	 * Search to find a fit.
+	 */
+	end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
+		    pcpu_chunk_map_bits(chunk));
+	bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
+					     alloc_bits, align_mask);
+	if (bit_off >= end)
+		return -1;
+
+	/* update alloc map */
+	bitmap_set(chunk->alloc_map, bit_off, alloc_bits);
+
+	/* update boundary map */
+	set_bit(bit_off, chunk->bound_map);
+	bitmap_clear(chunk->bound_map, bit_off + 1, alloc_bits - 1);
+	set_bit(bit_off + alloc_bits, chunk->bound_map);
+
+	chunk->free_bytes -= alloc_bits * PCPU_MIN_ALLOC_SIZE;
+
+	/* update first free bit */
+	if (bit_off == chunk->first_bit)
+		chunk->first_bit = find_next_zero_bit(
+					chunk->alloc_map,
+					pcpu_chunk_map_bits(chunk),
+					bit_off + alloc_bits);
+
+	pcpu_block_update_hint_alloc(chunk, bit_off, alloc_bits);
+
+	pcpu_chunk_relocate(chunk, oslot);
+
+	return bit_off * PCPU_MIN_ALLOC_SIZE;
+}
+
+/**
+ * pcpu_free_area - frees the corresponding offset
+ * @chunk: chunk of interest
+ * @off: addr offset into chunk
+ *
+ * This function determines the size of an allocation to free using
+ * the boundary bitmap and clears the allocation map.
+ */
+static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
+{
+	int bit_off, bits, end, oslot;
+
+	lockdep_assert_held(&pcpu_lock);
+	pcpu_stats_area_dealloc(chunk);
+
+	oslot = pcpu_chunk_slot(chunk);
+
+	bit_off = off / PCPU_MIN_ALLOC_SIZE;
+
+	/* find end index */
+	end = find_next_bit(chunk->bound_map, pcpu_chunk_map_bits(chunk),
+			    bit_off + 1);
+	bits = end - bit_off;
+	bitmap_clear(chunk->alloc_map, bit_off, bits);
+
+	/* update metadata */
+	chunk->free_bytes += bits * PCPU_MIN_ALLOC_SIZE;
+
+	/* update first free bit */
+	chunk->first_bit = min(chunk->first_bit, bit_off);
+
+	pcpu_block_update_hint_free(chunk, bit_off, bits);
+
+	pcpu_chunk_relocate(chunk, oslot);
+}
+
+static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
+{
+	struct pcpu_block_md *md_block;
+
+	for (md_block = chunk->md_blocks;
+	     md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
+	     md_block++) {
+		md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
+		md_block->left_free = PCPU_BITMAP_BLOCK_BITS;
+		md_block->right_free = PCPU_BITMAP_BLOCK_BITS;
+	}
+}
+
+/**
+ * pcpu_alloc_first_chunk - creates chunks that serve the first chunk
+ * @tmp_addr: the start of the region served
+ * @map_size: size of the region served
+ *
+ * This is responsible for creating the chunks that serve the first chunk.  The
+ * base_addr is page aligned down of @tmp_addr while the region end is page
+ * aligned up.  Offsets are kept track of to determine the region served. All
+ * this is done to appease the bitmap allocator in avoiding partial blocks.
+ *
+ * RETURNS:
+ * Chunk serving the region at @tmp_addr of @map_size.
+ */
+static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
+							 int map_size)
+{
+	struct pcpu_chunk *chunk;
+	unsigned long aligned_addr, lcm_align;
+	int start_offset, offset_bits, region_size, region_bits;
+
+	/* region calculations */
+	aligned_addr = tmp_addr & PAGE_MASK;
+
+	start_offset = tmp_addr - aligned_addr;
+
+	/*
+	 * Align the end of the region with the LCM of PAGE_SIZE and
+	 * PCPU_BITMAP_BLOCK_SIZE.  One of these constants is a multiple of
+	 * the other.
+	 */
+	lcm_align = lcm(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE);
+	region_size = ALIGN(start_offset + map_size, lcm_align);
+
+	/* allocate chunk */
+	chunk = memblock_virt_alloc(sizeof(struct pcpu_chunk) +
+				    BITS_TO_LONGS(region_size >> PAGE_SHIFT) * sizeof(unsigned long),
+				    0);
+
+	INIT_LIST_HEAD(&chunk->list);
+
+	chunk->base_addr = (void *)aligned_addr;
+	chunk->start_offset = start_offset;
+	chunk->end_offset = region_size - chunk->start_offset - map_size;
+
+	chunk->nr_pages = region_size >> PAGE_SHIFT;
+	region_bits = pcpu_chunk_map_bits(chunk);
+
+	chunk->alloc_map = memblock_virt_alloc(BITS_TO_LONGS(region_bits) *
+					       sizeof(chunk->alloc_map[0]), 0);
+	chunk->bound_map = memblock_virt_alloc(BITS_TO_LONGS(region_bits + 1) *
+					       sizeof(chunk->bound_map[0]), 0);
+	chunk->md_blocks = memblock_virt_alloc(pcpu_chunk_nr_blocks(chunk) *
+					       sizeof(chunk->md_blocks[0]), 0);
+	pcpu_init_md_blocks(chunk);
+
+	/* manage populated page bitmap */
+	chunk->immutable = true;
+	bitmap_fill(chunk->populated, chunk->nr_pages);
+	chunk->nr_populated = chunk->nr_pages;
+	chunk->nr_empty_pop_pages =
+		pcpu_cnt_pop_pages(chunk, start_offset / PCPU_MIN_ALLOC_SIZE,
+				   map_size / PCPU_MIN_ALLOC_SIZE);
+
+	chunk->contig_bits = map_size / PCPU_MIN_ALLOC_SIZE;
+	chunk->free_bytes = map_size;
+
+	if (chunk->start_offset) {
+		/* hide the beginning of the bitmap */
+		offset_bits = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
+		bitmap_set(chunk->alloc_map, 0, offset_bits);
+		set_bit(0, chunk->bound_map);
+		set_bit(offset_bits, chunk->bound_map);
+
+		chunk->first_bit = offset_bits;
+
+		pcpu_block_update_hint_alloc(chunk, 0, offset_bits);
+	}
+
+	if (chunk->end_offset) {
+		/* hide the end of the bitmap */
+		offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE;
+		bitmap_set(chunk->alloc_map,
+			   pcpu_chunk_map_bits(chunk) - offset_bits,
+			   offset_bits);
+		set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE,
+			chunk->bound_map);
+		set_bit(region_bits, chunk->bound_map);
+
+		pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk)
+					     - offset_bits, offset_bits);
+	}
+
+	return chunk;
+}
+
+static struct pcpu_chunk *pcpu_alloc_chunk(gfp_t gfp)
+{
+	struct pcpu_chunk *chunk;
+	int region_bits;
+
+	chunk = pcpu_mem_zalloc(pcpu_chunk_struct_size, gfp);
+	if (!chunk)
+		return NULL;
+
+	INIT_LIST_HEAD(&chunk->list);
+	chunk->nr_pages = pcpu_unit_pages;
+	region_bits = pcpu_chunk_map_bits(chunk);
+
+	chunk->alloc_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits) *
+					   sizeof(chunk->alloc_map[0]), gfp);
+	if (!chunk->alloc_map)
+		goto alloc_map_fail;
+
+	chunk->bound_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits + 1) *
+					   sizeof(chunk->bound_map[0]), gfp);
+	if (!chunk->bound_map)
+		goto bound_map_fail;
+
+	chunk->md_blocks = pcpu_mem_zalloc(pcpu_chunk_nr_blocks(chunk) *
+					   sizeof(chunk->md_blocks[0]), gfp);
+	if (!chunk->md_blocks)
+		goto md_blocks_fail;
+
+	pcpu_init_md_blocks(chunk);
+
+	/* init metadata */
+	chunk->contig_bits = region_bits;
+	chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;
+
+	return chunk;
+
+md_blocks_fail:
+	pcpu_mem_free(chunk->bound_map);
+bound_map_fail:
+	pcpu_mem_free(chunk->alloc_map);
+alloc_map_fail:
+	pcpu_mem_free(chunk);
+
+	return NULL;
+}
+
+static void pcpu_free_chunk(struct pcpu_chunk *chunk)
+{
+	if (!chunk)
+		return;
+	pcpu_mem_free(chunk->md_blocks);
+	pcpu_mem_free(chunk->bound_map);
+	pcpu_mem_free(chunk->alloc_map);
+	pcpu_mem_free(chunk);
+}
+
+/**
+ * pcpu_chunk_populated - post-population bookkeeping
+ * @chunk: pcpu_chunk which got populated
+ * @page_start: the start page
+ * @page_end: the end page
+ * @for_alloc: if this is to populate for allocation
+ *
+ * Pages in [@page_start,@page_end) have been populated to @chunk.  Update
+ * the bookkeeping information accordingly.  Must be called after each
+ * successful population.
+ *
+ * If this is @for_alloc, do not increment pcpu_nr_empty_pop_pages because it
+ * is to serve an allocation in that area.
+ */
+static void pcpu_chunk_populated(struct pcpu_chunk *chunk, int page_start,
+				 int page_end, bool for_alloc)
+{
+	int nr = page_end - page_start;
+
+	lockdep_assert_held(&pcpu_lock);
+
+	bitmap_set(chunk->populated, page_start, nr);
+	chunk->nr_populated += nr;
+	pcpu_nr_populated += nr;
+
+	if (!for_alloc) {
+		chunk->nr_empty_pop_pages += nr;
+		pcpu_nr_empty_pop_pages += nr;
+	}
+}
+
+/**
+ * pcpu_chunk_depopulated - post-depopulation bookkeeping
+ * @chunk: pcpu_chunk which got depopulated
+ * @page_start: the start page
+ * @page_end: the end page
+ *
+ * Pages in [@page_start,@page_end) have been depopulated from @chunk.
+ * Update the bookkeeping information accordingly.  Must be called after
+ * each successful depopulation.
+ */
+static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,
+				   int page_start, int page_end)
+{
+	int nr = page_end - page_start;
+
+	lockdep_assert_held(&pcpu_lock);
+
+	bitmap_clear(chunk->populated, page_start, nr);
+	chunk->nr_populated -= nr;
+	chunk->nr_empty_pop_pages -= nr;
+	pcpu_nr_empty_pop_pages -= nr;
+	pcpu_nr_populated -= nr;
+}
+
+/*
+ * Chunk management implementation.
+ *
+ * To allow different implementations, chunk alloc/free and
+ * [de]population are implemented in a separate file which is pulled
+ * into this file and compiled together.  The following functions
+ * should be implemented.
+ *
+ * pcpu_populate_chunk		- populate the specified range of a chunk
+ * pcpu_depopulate_chunk	- depopulate the specified range of a chunk
+ * pcpu_create_chunk		- create a new chunk
+ * pcpu_destroy_chunk		- destroy a chunk, always preceded by full depop
+ * pcpu_addr_to_page		- translate address to physical address
+ * pcpu_verify_alloc_info	- check alloc_info is acceptable during init
+ */
+static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
+			       int page_start, int page_end, gfp_t gfp);
+static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
+				  int page_start, int page_end);
+static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp);
+static void pcpu_destroy_chunk(struct pcpu_chunk *chunk);
+static struct page *pcpu_addr_to_page(void *addr);
+static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);
+
+#ifdef CONFIG_NEED_PER_CPU_KM
+#include "percpu-km.c"
+#else
+#include "percpu-vm.c"
+#endif
+
+/**
+ * pcpu_chunk_addr_search - determine chunk containing specified address
+ * @addr: address for which the chunk needs to be determined.
+ *
+ * This is an internal function that handles all but static allocations.
+ * Static percpu address values should never be passed into the allocator.
+ *
+ * RETURNS:
+ * The address of the found chunk.
+ */
+static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
+{
+	/* is it in the dynamic region (first chunk)? */
+	if (pcpu_addr_in_chunk(pcpu_first_chunk, addr))
+		return pcpu_first_chunk;
+
+	/* is it in the reserved region? */
+	if (pcpu_addr_in_chunk(pcpu_reserved_chunk, addr))
+		return pcpu_reserved_chunk;
+
+	/*
+	 * The address is relative to unit0 which might be unused and
+	 * thus unmapped.  Offset the address to the unit space of the
+	 * current processor before looking it up in the vmalloc
+	 * space.  Note that any possible cpu id can be used here, so
+	 * there's no need to worry about preemption or cpu hotplug.
+	 */
+	addr += pcpu_unit_offsets[raw_smp_processor_id()];
+	return pcpu_get_page_chunk(pcpu_addr_to_page(addr));
+}
+
+/**
+ * pcpu_alloc - the percpu allocator
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ * @reserved: allocate from the reserved chunk if available
+ * @gfp: allocation flags
+ *
+ * Allocate percpu area of @size bytes aligned at @align.  If @gfp doesn't
+ * contain %GFP_KERNEL, the allocation is atomic. If @gfp has __GFP_NOWARN
+ * then no warning will be triggered on invalid or failed allocation
+ * requests.
+ *
+ * RETURNS:
+ * Percpu pointer to the allocated area on success, NULL on failure.
+ */
+static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
+				 gfp_t gfp)
+{
+	/* whitelisted flags that can be passed to the backing allocators */
+	gfp_t pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+	bool is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
+	bool do_warn = !(gfp & __GFP_NOWARN);
+	static int warn_limit = 10;
+	struct pcpu_chunk *chunk;
+	const char *err;
+	int slot, off, cpu, ret;
+	unsigned long flags;
+	void __percpu *ptr;
+	size_t bits, bit_align;
+
+	/*
+	 * There is now a minimum allocation size of PCPU_MIN_ALLOC_SIZE,
+	 * therefore alignment must be a minimum of that many bytes.
+	 * An allocation may have internal fragmentation from rounding up
+	 * of up to PCPU_MIN_ALLOC_SIZE - 1 bytes.
+	 */
+	if (unlikely(align < PCPU_MIN_ALLOC_SIZE))
+		align = PCPU_MIN_ALLOC_SIZE;
+
+	size = ALIGN(size, PCPU_MIN_ALLOC_SIZE);
+	bits = size >> PCPU_MIN_ALLOC_SHIFT;
+	bit_align = align >> PCPU_MIN_ALLOC_SHIFT;
+
+	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE ||
+		     !is_power_of_2(align))) {
+		WARN(do_warn, "illegal size (%zu) or align (%zu) for percpu allocation\n",
+		     size, align);
+		return NULL;
+	}
+
+	if (!is_atomic) {
+		/*
+		 * pcpu_balance_workfn() allocates memory under this mutex,
+		 * and it may wait for memory reclaim. Allow current task
+		 * to become OOM victim, in case of memory pressure.
+		 */
+		if (gfp & __GFP_NOFAIL)
+			mutex_lock(&pcpu_alloc_mutex);
+		else if (mutex_lock_killable(&pcpu_alloc_mutex))
+			return NULL;
+	}
+
+	spin_lock_irqsave(&pcpu_lock, flags);
+
+	/* serve reserved allocations from the reserved chunk if available */
+	if (reserved && pcpu_reserved_chunk) {
+		chunk = pcpu_reserved_chunk;
+
+		off = pcpu_find_block_fit(chunk, bits, bit_align, is_atomic);
+		if (off < 0) {
+			err = "alloc from reserved chunk failed";
+			goto fail_unlock;
+		}
+
+		off = pcpu_alloc_area(chunk, bits, bit_align, off);
+		if (off >= 0)
+			goto area_found;
+
+		err = "alloc from reserved chunk failed";
+		goto fail_unlock;
+	}
+
+restart:
+	/* search through normal chunks */
+	for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
+		list_for_each_entry(chunk, &pcpu_slot[slot], list) {
+			off = pcpu_find_block_fit(chunk, bits, bit_align,
+						  is_atomic);
+			if (off < 0)
+				continue;
+
+			off = pcpu_alloc_area(chunk, bits, bit_align, off);
+			if (off >= 0)
+				goto area_found;
+
+		}
+	}
+
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+
+	/*
+	 * No space left.  Create a new chunk.  We don't want multiple
+	 * tasks to create chunks simultaneously.  Serialize and create iff
+	 * there's still no empty chunk after grabbing the mutex.
+	 */
+	if (is_atomic) {
+		err = "atomic alloc failed, no space left";
+		goto fail;
+	}
+
+	if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
+		chunk = pcpu_create_chunk(pcpu_gfp);
+		if (!chunk) {
+			err = "failed to allocate new chunk";
+			goto fail;
+		}
+
+		spin_lock_irqsave(&pcpu_lock, flags);
+		pcpu_chunk_relocate(chunk, -1);
+	} else {
+		spin_lock_irqsave(&pcpu_lock, flags);
+	}
+
+	goto restart;
+
+area_found:
+	pcpu_stats_area_alloc(chunk, size);
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+
+	/* populate if not all pages are already there */
+	if (!is_atomic) {
+		int page_start, page_end, rs, re;
+
+		page_start = PFN_DOWN(off);
+		page_end = PFN_UP(off + size);
+
+		pcpu_for_each_unpop_region(chunk->populated, rs, re,
+					   page_start, page_end) {
+			WARN_ON(chunk->immutable);
+
+			ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
+
+			spin_lock_irqsave(&pcpu_lock, flags);
+			if (ret) {
+				pcpu_free_area(chunk, off);
+				err = "failed to populate";
+				goto fail_unlock;
+			}
+			pcpu_chunk_populated(chunk, rs, re, true);
+			spin_unlock_irqrestore(&pcpu_lock, flags);
+		}
+
+		mutex_unlock(&pcpu_alloc_mutex);
+	}
+
+	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
+		pcpu_schedule_balance_work();
+
+	/* clear the areas and return address relative to base address */
+	for_each_possible_cpu(cpu)
+		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
+
+	ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
+	kmemleak_alloc_percpu(ptr, size, gfp);
+
+	trace_percpu_alloc_percpu(reserved, is_atomic, size, align,
+			chunk->base_addr, off, ptr);
+
+	return ptr;
+
+fail_unlock:
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+fail:
+	trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
+
+	if (!is_atomic && do_warn && warn_limit) {
+		pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
+			size, align, is_atomic, err);
+		dump_stack();
+		if (!--warn_limit)
+			pr_info("limit reached, disable warning\n");
+	}
+	if (is_atomic) {
+		/* see the flag handling in pcpu_blance_workfn() */
+		pcpu_atomic_alloc_failed = true;
+		pcpu_schedule_balance_work();
+	} else {
+		mutex_unlock(&pcpu_alloc_mutex);
+	}
+	return NULL;
+}
+
+/**
+ * __alloc_percpu_gfp - allocate dynamic percpu area
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ * @gfp: allocation flags
+ *
+ * Allocate zero-filled percpu area of @size bytes aligned at @align.  If
+ * @gfp doesn't contain %GFP_KERNEL, the allocation doesn't block and can
+ * be called from any context but is a lot more likely to fail. If @gfp
+ * has __GFP_NOWARN then no warning will be triggered on invalid or failed
+ * allocation requests.
+ *
+ * RETURNS:
+ * Percpu pointer to the allocated area on success, NULL on failure.
+ */
+void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp)
+{
+	return pcpu_alloc(size, align, false, gfp);
+}
+EXPORT_SYMBOL_GPL(__alloc_percpu_gfp);
+
+/**
+ * __alloc_percpu - allocate dynamic percpu area
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ *
+ * Equivalent to __alloc_percpu_gfp(size, align, %GFP_KERNEL).
+ */
+void __percpu *__alloc_percpu(size_t size, size_t align)
+{
+	return pcpu_alloc(size, align, false, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(__alloc_percpu);
+
+/**
+ * __alloc_reserved_percpu - allocate reserved percpu area
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ *
+ * Allocate zero-filled percpu area of @size bytes aligned at @align
+ * from reserved percpu area if arch has set it up; otherwise,
+ * allocation is served from the same dynamic area.  Might sleep.
+ * Might trigger writeouts.
+ *
+ * CONTEXT:
+ * Does GFP_KERNEL allocation.
+ *
+ * RETURNS:
+ * Percpu pointer to the allocated area on success, NULL on failure.
+ */
+void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
+{
+	return pcpu_alloc(size, align, true, GFP_KERNEL);
+}
+
+/**
+ * pcpu_balance_workfn - manage the amount of free chunks and populated pages
+ * @work: unused
+ *
+ * Reclaim all fully free chunks except for the first one.  This is also
+ * responsible for maintaining the pool of empty populated pages.  However,
+ * it is possible that this is called when physical memory is scarce causing
+ * OOM killer to be triggered.  We should avoid doing so until an actual
+ * allocation causes the failure as it is possible that requests can be
+ * serviced from already backed regions.
+ */
+static void pcpu_balance_workfn(struct work_struct *work)
+{
+	/* gfp flags passed to underlying allocators */
+	const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
+	LIST_HEAD(to_free);
+	struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1];
+	struct pcpu_chunk *chunk, *next;
+	int slot, nr_to_pop, ret;
+
+	/*
+	 * There's no reason to keep around multiple unused chunks and VM
+	 * areas can be scarce.  Destroy all free chunks except for one.
+	 */
+	mutex_lock(&pcpu_alloc_mutex);
+	spin_lock_irq(&pcpu_lock);
+
+	list_for_each_entry_safe(chunk, next, free_head, list) {
+		WARN_ON(chunk->immutable);
+
+		/* spare the first one */
+		if (chunk == list_first_entry(free_head, struct pcpu_chunk, list))
+			continue;
+
+		list_move(&chunk->list, &to_free);
+	}
+
+	spin_unlock_irq(&pcpu_lock);
+
+	list_for_each_entry_safe(chunk, next, &to_free, list) {
+		int rs, re;
+
+		pcpu_for_each_pop_region(chunk->populated, rs, re, 0,
+					 chunk->nr_pages) {
+			pcpu_depopulate_chunk(chunk, rs, re);
+			spin_lock_irq(&pcpu_lock);
+			pcpu_chunk_depopulated(chunk, rs, re);
+			spin_unlock_irq(&pcpu_lock);
+		}
+		pcpu_destroy_chunk(chunk);
+		cond_resched();
+	}
+
+	/*
+	 * Ensure there are certain number of free populated pages for
+	 * atomic allocs.  Fill up from the most packed so that atomic
+	 * allocs don't increase fragmentation.  If atomic allocation
+	 * failed previously, always populate the maximum amount.  This
+	 * should prevent atomic allocs larger than PAGE_SIZE from keeping
+	 * failing indefinitely; however, large atomic allocs are not
+	 * something we support properly and can be highly unreliable and
+	 * inefficient.
+	 */
+retry_pop:
+	if (pcpu_atomic_alloc_failed) {
+		nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
+		/* best effort anyway, don't worry about synchronization */
+		pcpu_atomic_alloc_failed = false;
+	} else {
+		nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
+				  pcpu_nr_empty_pop_pages,
+				  0, PCPU_EMPTY_POP_PAGES_HIGH);
+	}
+
+	for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
+		int nr_unpop = 0, rs, re;
+
+		if (!nr_to_pop)
+			break;
+
+		spin_lock_irq(&pcpu_lock);
+		list_for_each_entry(chunk, &pcpu_slot[slot], list) {
+			nr_unpop = chunk->nr_pages - chunk->nr_populated;
+			if (nr_unpop)
+				break;
+		}
+		spin_unlock_irq(&pcpu_lock);
+
+		if (!nr_unpop)
+			continue;
+
+		/* @chunk can't go away while pcpu_alloc_mutex is held */
+		pcpu_for_each_unpop_region(chunk->populated, rs, re, 0,
+					   chunk->nr_pages) {
+			int nr = min(re - rs, nr_to_pop);
+
+			ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
+			if (!ret) {
+				nr_to_pop -= nr;
+				spin_lock_irq(&pcpu_lock);
+				pcpu_chunk_populated(chunk, rs, rs + nr, false);
+				spin_unlock_irq(&pcpu_lock);
+			} else {
+				nr_to_pop = 0;
+			}
+
+			if (!nr_to_pop)
+				break;
+		}
+	}
+
+	if (nr_to_pop) {
+		/* ran out of chunks to populate, create a new one and retry */
+		chunk = pcpu_create_chunk(gfp);
+		if (chunk) {
+			spin_lock_irq(&pcpu_lock);
+			pcpu_chunk_relocate(chunk, -1);
+			spin_unlock_irq(&pcpu_lock);
+			goto retry_pop;
+		}
+	}
+
+	mutex_unlock(&pcpu_alloc_mutex);
+}
+
+/**
+ * free_percpu - free percpu area
+ * @ptr: pointer to area to free
+ *
+ * Free percpu area @ptr.
+ *
+ * CONTEXT:
+ * Can be called from atomic context.
+ */
+void free_percpu(void __percpu *ptr)
+{
+	void *addr;
+	struct pcpu_chunk *chunk;
+	unsigned long flags;
+	int off;
+	bool need_balance = false;
+
+	if (!ptr)
+		return;
+
+	kmemleak_free_percpu(ptr);
+
+	addr = __pcpu_ptr_to_addr(ptr);
+
+	spin_lock_irqsave(&pcpu_lock, flags);
+
+	chunk = pcpu_chunk_addr_search(addr);
+	off = addr - chunk->base_addr;
+
+	pcpu_free_area(chunk, off);
+
+	/* if there are more than one fully free chunks, wake up grim reaper */
+	if (chunk->free_bytes == pcpu_unit_size) {
+		struct pcpu_chunk *pos;
+
+		list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
+			if (pos != chunk) {
+				need_balance = true;
+				break;
+			}
+	}
+
+	trace_percpu_free_percpu(chunk->base_addr, off, ptr);
+
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+
+	if (need_balance)
+		pcpu_schedule_balance_work();
+}
+EXPORT_SYMBOL_GPL(free_percpu);
+
+bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
+{
+#ifdef CONFIG_SMP
+	const size_t static_size = __per_cpu_end - __per_cpu_start;
+	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu) {
+		void *start = per_cpu_ptr(base, cpu);
+		void *va = (void *)addr;
+
+		if (va >= start && va < start + static_size) {
+			if (can_addr) {
+				*can_addr = (unsigned long) (va - start);
+				*can_addr += (unsigned long)
+					per_cpu_ptr(base, get_boot_cpu_id());
+			}
+			return true;
+		}
+	}
+#endif
+	/* on UP, can't distinguish from other static vars, always false */
+	return false;
+}
+
+/**
+ * is_kernel_percpu_address - test whether address is from static percpu area
+ * @addr: address to test
+ *
+ * Test whether @addr belongs to in-kernel static percpu area.  Module
+ * static percpu areas are not considered.  For those, use
+ * is_module_percpu_address().
+ *
+ * RETURNS:
+ * %true if @addr is from in-kernel static percpu area, %false otherwise.
+ */
+bool is_kernel_percpu_address(unsigned long addr)
+{
+	return __is_kernel_percpu_address(addr, NULL);
+}
+
+/**
+ * per_cpu_ptr_to_phys - convert translated percpu address to physical address
+ * @addr: the address to be converted to physical address
+ *
+ * Given @addr which is dereferenceable address obtained via one of
+ * percpu access macros, this function translates it into its physical
+ * address.  The caller is responsible for ensuring @addr stays valid
+ * until this function finishes.
+ *
+ * percpu allocator has special setup for the first chunk, which currently
+ * supports either embedding in linear address space or vmalloc mapping,
+ * and, from the second one, the backing allocator (currently either vm or
+ * km) provides translation.
+ *
+ * The addr can be translated simply without checking if it falls into the
+ * first chunk. But the current code reflects better how percpu allocator
+ * actually works, and the verification can discover both bugs in percpu
+ * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
+ * code.
+ *
+ * RETURNS:
+ * The physical address for @addr.
+ */
+phys_addr_t per_cpu_ptr_to_phys(void *addr)
+{
+	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
+	bool in_first_chunk = false;
+	unsigned long first_low, first_high;
+	unsigned int cpu;
+
+	/*
+	 * The following test on unit_low/high isn't strictly
+	 * necessary but will speed up lookups of addresses which
+	 * aren't in the first chunk.
+	 *
+	 * The address check is against full chunk sizes.  pcpu_base_addr
+	 * points to the beginning of the first chunk including the
+	 * static region.  Assumes good intent as the first chunk may
+	 * not be full (ie. < pcpu_unit_pages in size).
+	 */
+	first_low = (unsigned long)pcpu_base_addr +
+		    pcpu_unit_page_offset(pcpu_low_unit_cpu, 0);
+	first_high = (unsigned long)pcpu_base_addr +
+		     pcpu_unit_page_offset(pcpu_high_unit_cpu, pcpu_unit_pages);
+	if ((unsigned long)addr >= first_low &&
+	    (unsigned long)addr < first_high) {
+		for_each_possible_cpu(cpu) {
+			void *start = per_cpu_ptr(base, cpu);
+
+			if (addr >= start && addr < start + pcpu_unit_size) {
+				in_first_chunk = true;
+				break;
+			}
+		}
+	}
+
+	if (in_first_chunk) {
+		if (!is_vmalloc_addr(addr))
+			return __pa(addr);
+		else
+			return page_to_phys(vmalloc_to_page(addr)) +
+			       offset_in_page(addr);
+	} else
+		return page_to_phys(pcpu_addr_to_page(addr)) +
+		       offset_in_page(addr);
+}
+
+/**
+ * pcpu_alloc_alloc_info - allocate percpu allocation info
+ * @nr_groups: the number of groups
+ * @nr_units: the number of units
+ *
+ * Allocate ai which is large enough for @nr_groups groups containing
+ * @nr_units units.  The returned ai's groups[0].cpu_map points to the
+ * cpu_map array which is long enough for @nr_units and filled with
+ * NR_CPUS.  It's the caller's responsibility to initialize cpu_map
+ * pointer of other groups.
+ *
+ * RETURNS:
+ * Pointer to the allocated pcpu_alloc_info on success, NULL on
+ * failure.
+ */
+struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
+						      int nr_units)
+{
+	struct pcpu_alloc_info *ai;
+	size_t base_size, ai_size;
+	void *ptr;
+	int unit;
+
+	base_size = ALIGN(sizeof(*ai) + nr_groups * sizeof(ai->groups[0]),
+			  __alignof__(ai->groups[0].cpu_map[0]));
+	ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
+
+	ptr = memblock_virt_alloc_nopanic(PFN_ALIGN(ai_size), PAGE_SIZE);
+	if (!ptr)
+		return NULL;
+	ai = ptr;
+	ptr += base_size;
+
+	ai->groups[0].cpu_map = ptr;
+
+	for (unit = 0; unit < nr_units; unit++)
+		ai->groups[0].cpu_map[unit] = NR_CPUS;
+
+	ai->nr_groups = nr_groups;
+	ai->__ai_size = PFN_ALIGN(ai_size);
+
+	return ai;
+}
+
+/**
+ * pcpu_free_alloc_info - free percpu allocation info
+ * @ai: pcpu_alloc_info to free
+ *
+ * Free @ai which was allocated by pcpu_alloc_alloc_info().
+ */
+void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
+{
+	memblock_free_early(__pa(ai), ai->__ai_size);
+}
+
+/**
+ * pcpu_dump_alloc_info - print out information about pcpu_alloc_info
+ * @lvl: loglevel
+ * @ai: allocation info to dump
+ *
+ * Print out information about @ai using loglevel @lvl.
+ */
+static void pcpu_dump_alloc_info(const char *lvl,
+				 const struct pcpu_alloc_info *ai)
+{
+	int group_width = 1, cpu_width = 1, width;
+	char empty_str[] = "--------";
+	int alloc = 0, alloc_end = 0;
+	int group, v;
+	int upa, apl;	/* units per alloc, allocs per line */
+
+	v = ai->nr_groups;
+	while (v /= 10)
+		group_width++;
+
+	v = num_possible_cpus();
+	while (v /= 10)
+		cpu_width++;
+	empty_str[min_t(int, cpu_width, sizeof(empty_str) - 1)] = '\0';
+
+	upa = ai->alloc_size / ai->unit_size;
+	width = upa * (cpu_width + 1) + group_width + 3;
+	apl = rounddown_pow_of_two(max(60 / width, 1));
+
+	printk("%spcpu-alloc: s%zu r%zu d%zu u%zu alloc=%zu*%zu",
+	       lvl, ai->static_size, ai->reserved_size, ai->dyn_size,
+	       ai->unit_size, ai->alloc_size / ai->atom_size, ai->atom_size);
+
+	for (group = 0; group < ai->nr_groups; group++) {
+		const struct pcpu_group_info *gi = &ai->groups[group];
+		int unit = 0, unit_end = 0;
+
+		BUG_ON(gi->nr_units % upa);
+		for (alloc_end += gi->nr_units / upa;
+		     alloc < alloc_end; alloc++) {
+			if (!(alloc % apl)) {
+				pr_cont("\n");
+				printk("%spcpu-alloc: ", lvl);
+			}
+			pr_cont("[%0*d] ", group_width, group);
+
+			for (unit_end += upa; unit < unit_end; unit++)
+				if (gi->cpu_map[unit] != NR_CPUS)
+					pr_cont("%0*d ",
+						cpu_width, gi->cpu_map[unit]);
+				else
+					pr_cont("%s ", empty_str);
+		}
+	}
+	pr_cont("\n");
+}
+
+/**
+ * pcpu_setup_first_chunk - initialize the first percpu chunk
+ * @ai: pcpu_alloc_info describing how to percpu area is shaped
+ * @base_addr: mapped address
+ *
+ * Initialize the first percpu chunk which contains the kernel static
+ * perpcu area.  This function is to be called from arch percpu area
+ * setup path.
+ *
+ * @ai contains all information necessary to initialize the first
+ * chunk and prime the dynamic percpu allocator.
+ *
+ * @ai->static_size is the size of static percpu area.
+ *
+ * @ai->reserved_size, if non-zero, specifies the amount of bytes to
+ * reserve after the static area in the first chunk.  This reserves
+ * the first chunk such that it's available only through reserved
+ * percpu allocation.  This is primarily used to serve module percpu
+ * static areas on architectures where the addressing model has
+ * limited offset range for symbol relocations to guarantee module
+ * percpu symbols fall inside the relocatable range.
+ *
+ * @ai->dyn_size determines the number of bytes available for dynamic
+ * allocation in the first chunk.  The area between @ai->static_size +
+ * @ai->reserved_size + @ai->dyn_size and @ai->unit_size is unused.
+ *
+ * @ai->unit_size specifies unit size and must be aligned to PAGE_SIZE
+ * and equal to or larger than @ai->static_size + @ai->reserved_size +
+ * @ai->dyn_size.
+ *
+ * @ai->atom_size is the allocation atom size and used as alignment
+ * for vm areas.
+ *
+ * @ai->alloc_size is the allocation size and always multiple of
+ * @ai->atom_size.  This is larger than @ai->atom_size if
+ * @ai->unit_size is larger than @ai->atom_size.
+ *
+ * @ai->nr_groups and @ai->groups describe virtual memory layout of
+ * percpu areas.  Units which should be colocated are put into the
+ * same group.  Dynamic VM areas will be allocated according to these
+ * groupings.  If @ai->nr_groups is zero, a single group containing
+ * all units is assumed.
+ *
+ * The caller should have mapped the first chunk at @base_addr and
+ * copied static data to each unit.
+ *
+ * The first chunk will always contain a static and a dynamic region.
+ * However, the static region is not managed by any chunk.  If the first
+ * chunk also contains a reserved region, it is served by two chunks -
+ * one for the reserved region and one for the dynamic region.  They
+ * share the same vm, but use offset regions in the area allocation map.
+ * The chunk serving the dynamic region is circulated in the chunk slots
+ * and available for dynamic allocation like any other chunk.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
+				  void *base_addr)
+{
+	size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
+	size_t static_size, dyn_size;
+	struct pcpu_chunk *chunk;
+	unsigned long *group_offsets;
+	size_t *group_sizes;
+	unsigned long *unit_off;
+	unsigned int cpu;
+	int *unit_map;
+	int group, unit, i;
+	int map_size;
+	unsigned long tmp_addr;
+
+#define PCPU_SETUP_BUG_ON(cond)	do {					\
+	if (unlikely(cond)) {						\
+		pr_emerg("failed to initialize, %s\n", #cond);		\
+		pr_emerg("cpu_possible_mask=%*pb\n",			\
+			 cpumask_pr_args(cpu_possible_mask));		\
+		pcpu_dump_alloc_info(KERN_EMERG, ai);			\
+		BUG();							\
+	}								\
+} while (0)
+
+	/* sanity checks */
+	PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
+#ifdef CONFIG_SMP
+	PCPU_SETUP_BUG_ON(!ai->static_size);
+	PCPU_SETUP_BUG_ON(offset_in_page(__per_cpu_start));
+#endif
+	PCPU_SETUP_BUG_ON(!base_addr);
+	PCPU_SETUP_BUG_ON(offset_in_page(base_addr));
+	PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
+	PCPU_SETUP_BUG_ON(offset_in_page(ai->unit_size));
+	PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
+	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->unit_size, PCPU_BITMAP_BLOCK_SIZE));
+	PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
+	PCPU_SETUP_BUG_ON(!ai->dyn_size);
+	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE));
+	PCPU_SETUP_BUG_ON(!(IS_ALIGNED(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) ||
+			    IS_ALIGNED(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE)));
+	PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
+
+	/* process group information and build config tables accordingly */
+	group_offsets = memblock_virt_alloc(ai->nr_groups *
+					     sizeof(group_offsets[0]), 0);
+	group_sizes = memblock_virt_alloc(ai->nr_groups *
+					   sizeof(group_sizes[0]), 0);
+	unit_map = memblock_virt_alloc(nr_cpu_ids * sizeof(unit_map[0]), 0);
+	unit_off = memblock_virt_alloc(nr_cpu_ids * sizeof(unit_off[0]), 0);
+
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
+		unit_map[cpu] = UINT_MAX;
+
+	pcpu_low_unit_cpu = NR_CPUS;
+	pcpu_high_unit_cpu = NR_CPUS;
+
+	for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
+		const struct pcpu_group_info *gi = &ai->groups[group];
+
+		group_offsets[group] = gi->base_offset;
+		group_sizes[group] = gi->nr_units * ai->unit_size;
+
+		for (i = 0; i < gi->nr_units; i++) {
+			cpu = gi->cpu_map[i];
+			if (cpu == NR_CPUS)
+				continue;
+
+			PCPU_SETUP_BUG_ON(cpu >= nr_cpu_ids);
+			PCPU_SETUP_BUG_ON(!cpu_possible(cpu));
+			PCPU_SETUP_BUG_ON(unit_map[cpu] != UINT_MAX);
+
+			unit_map[cpu] = unit + i;
+			unit_off[cpu] = gi->base_offset + i * ai->unit_size;
+
+			/* determine low/high unit_cpu */
+			if (pcpu_low_unit_cpu == NR_CPUS ||
+			    unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
+				pcpu_low_unit_cpu = cpu;
+			if (pcpu_high_unit_cpu == NR_CPUS ||
+			    unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
+				pcpu_high_unit_cpu = cpu;
+		}
+	}
+	pcpu_nr_units = unit;
+
+	for_each_possible_cpu(cpu)
+		PCPU_SETUP_BUG_ON(unit_map[cpu] == UINT_MAX);
+
+	/* we're done parsing the input, undefine BUG macro and dump config */
+#undef PCPU_SETUP_BUG_ON
+	pcpu_dump_alloc_info(KERN_DEBUG, ai);
+
+	pcpu_nr_groups = ai->nr_groups;
+	pcpu_group_offsets = group_offsets;
+	pcpu_group_sizes = group_sizes;
+	pcpu_unit_map = unit_map;
+	pcpu_unit_offsets = unit_off;
+
+	/* determine basic parameters */
+	pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT;
+	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
+	pcpu_atom_size = ai->atom_size;
+	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
+		BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);
+
+	pcpu_stats_save_ai(ai);
+
+	/*
+	 * Allocate chunk slots.  The additional last slot is for
+	 * empty chunks.
+	 */
+	pcpu_nr_slots = __pcpu_size_to_slot(pcpu_unit_size) + 2;
+	pcpu_slot = memblock_virt_alloc(
+			pcpu_nr_slots * sizeof(pcpu_slot[0]), 0);
+	for (i = 0; i < pcpu_nr_slots; i++)
+		INIT_LIST_HEAD(&pcpu_slot[i]);
+
+	/*
+	 * The end of the static region needs to be aligned with the
+	 * minimum allocation size as this offsets the reserved and
+	 * dynamic region.  The first chunk ends page aligned by
+	 * expanding the dynamic region, therefore the dynamic region
+	 * can be shrunk to compensate while still staying above the
+	 * configured sizes.
+	 */
+	static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE);
+	dyn_size = ai->dyn_size - (static_size - ai->static_size);
+
+	/*
+	 * Initialize first chunk.
+	 * If the reserved_size is non-zero, this initializes the reserved
+	 * chunk.  If the reserved_size is zero, the reserved chunk is NULL
+	 * and the dynamic region is initialized here.  The first chunk,
+	 * pcpu_first_chunk, will always point to the chunk that serves
+	 * the dynamic region.
+	 */
+	tmp_addr = (unsigned long)base_addr + static_size;
+	map_size = ai->reserved_size ?: dyn_size;
+	chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
+
+	/* init dynamic chunk if necessary */
+	if (ai->reserved_size) {
+		pcpu_reserved_chunk = chunk;
+
+		tmp_addr = (unsigned long)base_addr + static_size +
+			   ai->reserved_size;
+		map_size = dyn_size;
+		chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
+	}
+
+	/* link the first chunk in */
+	pcpu_first_chunk = chunk;
+	pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
+	pcpu_chunk_relocate(pcpu_first_chunk, -1);
+
+	/* include all regions of the first chunk */
+	pcpu_nr_populated += PFN_DOWN(size_sum);
+
+	pcpu_stats_chunk_alloc();
+	trace_percpu_create_chunk(base_addr);
+
+	/* we're done */
+	pcpu_base_addr = base_addr;
+	return 0;
+}
+
+#ifdef CONFIG_SMP
+
+const char * const pcpu_fc_names[PCPU_FC_NR] __initconst = {
+	[PCPU_FC_AUTO]	= "auto",
+	[PCPU_FC_EMBED]	= "embed",
+	[PCPU_FC_PAGE]	= "page",
+};
+
+enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
+
+static int __init percpu_alloc_setup(char *str)
+{
+	if (!str)
+		return -EINVAL;
+
+	if (0)
+		/* nada */;
+#ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
+	else if (!strcmp(str, "embed"))
+		pcpu_chosen_fc = PCPU_FC_EMBED;
+#endif
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+	else if (!strcmp(str, "page"))
+		pcpu_chosen_fc = PCPU_FC_PAGE;
+#endif
+	else
+		pr_warn("unknown allocator %s specified\n", str);
+
+	return 0;
+}
+early_param("percpu_alloc", percpu_alloc_setup);
+
+/*
+ * pcpu_embed_first_chunk() is used by the generic percpu setup.
+ * Build it if needed by the arch config or the generic setup is going
+ * to be used.
+ */
+#if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
+	!defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
+#define BUILD_EMBED_FIRST_CHUNK
+#endif
+
+/* build pcpu_page_first_chunk() iff needed by the arch config */
+#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
+#define BUILD_PAGE_FIRST_CHUNK
+#endif
+
+/* pcpu_build_alloc_info() is used by both embed and page first chunk */
+#if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
+/**
+ * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: minimum free size for dynamic allocation in bytes
+ * @atom_size: allocation atom size
+ * @cpu_distance_fn: callback to determine distance between cpus, optional
+ *
+ * This function determines grouping of units, their mappings to cpus
+ * and other parameters considering needed percpu size, allocation
+ * atom size and distances between CPUs.
+ *
+ * Groups are always multiples of atom size and CPUs which are of
+ * LOCAL_DISTANCE both ways are grouped together and share space for
+ * units in the same group.  The returned configuration is guaranteed
+ * to have CPUs on different nodes on different groups and >=75% usage
+ * of allocated virtual address space.
+ *
+ * RETURNS:
+ * On success, pointer to the new allocation_info is returned.  On
+ * failure, ERR_PTR value is returned.
+ */
+static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
+				size_t reserved_size, size_t dyn_size,
+				size_t atom_size,
+				pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
+{
+	static int group_map[NR_CPUS] __initdata;
+	static int group_cnt[NR_CPUS] __initdata;
+	const size_t static_size = __per_cpu_end - __per_cpu_start;
+	int nr_groups = 1, nr_units = 0;
+	size_t size_sum, min_unit_size, alloc_size;
+	int upa, max_upa, uninitialized_var(best_upa);	/* units_per_alloc */
+	int last_allocs, group, unit;
+	unsigned int cpu, tcpu;
+	struct pcpu_alloc_info *ai;
+	unsigned int *cpu_map;
+
+	/* this function may be called multiple times */
+	memset(group_map, 0, sizeof(group_map));
+	memset(group_cnt, 0, sizeof(group_cnt));
+
+	/* calculate size_sum and ensure dyn_size is enough for early alloc */
+	size_sum = PFN_ALIGN(static_size + reserved_size +
+			    max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
+	dyn_size = size_sum - static_size - reserved_size;
+
+	/*
+	 * Determine min_unit_size, alloc_size and max_upa such that
+	 * alloc_size is multiple of atom_size and is the smallest
+	 * which can accommodate 4k aligned segments which are equal to
+	 * or larger than min_unit_size.
+	 */
+	min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
+
+	/* determine the maximum # of units that can fit in an allocation */
+	alloc_size = roundup(min_unit_size, atom_size);
+	upa = alloc_size / min_unit_size;
+	while (alloc_size % upa || (offset_in_page(alloc_size / upa)))
+		upa--;
+	max_upa = upa;
+
+	/* group cpus according to their proximity */
+	for_each_possible_cpu(cpu) {
+		group = 0;
+	next_group:
+		for_each_possible_cpu(tcpu) {
+			if (cpu == tcpu)
+				break;
+			if (group_map[tcpu] == group && cpu_distance_fn &&
+			    (cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
+			     cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
+				group++;
+				nr_groups = max(nr_groups, group + 1);
+				goto next_group;
+			}
+		}
+		group_map[cpu] = group;
+		group_cnt[group]++;
+	}
+
+	/*
+	 * Wasted space is caused by a ratio imbalance of upa to group_cnt.
+	 * Expand the unit_size until we use >= 75% of the units allocated.
+	 * Related to atom_size, which could be much larger than the unit_size.
+	 */
+	last_allocs = INT_MAX;
+	for (upa = max_upa; upa; upa--) {
+		int allocs = 0, wasted = 0;
+
+		if (alloc_size % upa || (offset_in_page(alloc_size / upa)))
+			continue;
+
+		for (group = 0; group < nr_groups; group++) {
+			int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
+			allocs += this_allocs;
+			wasted += this_allocs * upa - group_cnt[group];
+		}
+
+		/*
+		 * Don't accept if wastage is over 1/3.  The
+		 * greater-than comparison ensures upa==1 always
+		 * passes the following check.
+		 */
+		if (wasted > num_possible_cpus() / 3)
+			continue;
+
+		/* and then don't consume more memory */
+		if (allocs > last_allocs)
+			break;
+		last_allocs = allocs;
+		best_upa = upa;
+	}
+	upa = best_upa;
+
+	/* allocate and fill alloc_info */
+	for (group = 0; group < nr_groups; group++)
+		nr_units += roundup(group_cnt[group], upa);
+
+	ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
+	if (!ai)
+		return ERR_PTR(-ENOMEM);
+	cpu_map = ai->groups[0].cpu_map;
+
+	for (group = 0; group < nr_groups; group++) {
+		ai->groups[group].cpu_map = cpu_map;
+		cpu_map += roundup(group_cnt[group], upa);
+	}
+
+	ai->static_size = static_size;
+	ai->reserved_size = reserved_size;
+	ai->dyn_size = dyn_size;
+	ai->unit_size = alloc_size / upa;
+	ai->atom_size = atom_size;
+	ai->alloc_size = alloc_size;
+
+	for (group = 0, unit = 0; group_cnt[group]; group++) {
+		struct pcpu_group_info *gi = &ai->groups[group];
+
+		/*
+		 * Initialize base_offset as if all groups are located
+		 * back-to-back.  The caller should update this to
+		 * reflect actual allocation.
+		 */
+		gi->base_offset = unit * ai->unit_size;
+
+		for_each_possible_cpu(cpu)
+			if (group_map[cpu] == group)
+				gi->cpu_map[gi->nr_units++] = cpu;
+		gi->nr_units = roundup(gi->nr_units, upa);
+		unit += gi->nr_units;
+	}
+	BUG_ON(unit != nr_units);
+
+	return ai;
+}
+#endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
+
+#if defined(BUILD_EMBED_FIRST_CHUNK)
+/**
+ * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: minimum free size for dynamic allocation in bytes
+ * @atom_size: allocation atom size
+ * @cpu_distance_fn: callback to determine distance between cpus, optional
+ * @alloc_fn: function to allocate percpu page
+ * @free_fn: function to free percpu page
+ *
+ * This is a helper to ease setting up embedded first percpu chunk and
+ * can be called where pcpu_setup_first_chunk() is expected.
+ *
+ * If this function is used to setup the first chunk, it is allocated
+ * by calling @alloc_fn and used as-is without being mapped into
+ * vmalloc area.  Allocations are always whole multiples of @atom_size
+ * aligned to @atom_size.
+ *
+ * This enables the first chunk to piggy back on the linear physical
+ * mapping which often uses larger page size.  Please note that this
+ * can result in very sparse cpu->unit mapping on NUMA machines thus
+ * requiring large vmalloc address space.  Don't use this allocator if
+ * vmalloc space is not orders of magnitude larger than distances
+ * between node memory addresses (ie. 32bit NUMA machines).
+ *
+ * @dyn_size specifies the minimum dynamic area size.
+ *
+ * If the needed size is smaller than the minimum or specified unit
+ * size, the leftover is returned using @free_fn.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
+				  size_t atom_size,
+				  pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
+				  pcpu_fc_alloc_fn_t alloc_fn,
+				  pcpu_fc_free_fn_t free_fn)
+{
+	void *base = (void *)ULONG_MAX;
+	void **areas = NULL;
+	struct pcpu_alloc_info *ai;
+	size_t size_sum, areas_size;
+	unsigned long max_distance;
+	int group, i, highest_group, rc;
+
+	ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
+				   cpu_distance_fn);
+	if (IS_ERR(ai))
+		return PTR_ERR(ai);
+
+	size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
+	areas_size = PFN_ALIGN(ai->nr_groups * sizeof(void *));
+
+	areas = memblock_virt_alloc_nopanic(areas_size, 0);
+	if (!areas) {
+		rc = -ENOMEM;
+		goto out_free;
+	}
+
+	/* allocate, copy and determine base address & max_distance */
+	highest_group = 0;
+	for (group = 0; group < ai->nr_groups; group++) {
+		struct pcpu_group_info *gi = &ai->groups[group];
+		unsigned int cpu = NR_CPUS;
+		void *ptr;
+
+		for (i = 0; i < gi->nr_units && cpu == NR_CPUS; i++)
+			cpu = gi->cpu_map[i];
+		BUG_ON(cpu == NR_CPUS);
+
+		/* allocate space for the whole group */
+		ptr = alloc_fn(cpu, gi->nr_units * ai->unit_size, atom_size);
+		if (!ptr) {
+			rc = -ENOMEM;
+			goto out_free_areas;
+		}
+		/* kmemleak tracks the percpu allocations separately */
+		kmemleak_free(ptr);
+		areas[group] = ptr;
+
+		base = min(ptr, base);
+		if (ptr > areas[highest_group])
+			highest_group = group;
+	}
+	max_distance = areas[highest_group] - base;
+	max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
+
+	/* warn if maximum distance is further than 75% of vmalloc space */
+	if (max_distance > VMALLOC_TOTAL * 3 / 4) {
+		pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
+				max_distance, VMALLOC_TOTAL);
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+		/* and fail if we have fallback */
+		rc = -EINVAL;
+		goto out_free_areas;
+#endif
+	}
+
+	/*
+	 * Copy data and free unused parts.  This should happen after all
+	 * allocations are complete; otherwise, we may end up with
+	 * overlapping groups.
+	 */
+	for (group = 0; group < ai->nr_groups; group++) {
+		struct pcpu_group_info *gi = &ai->groups[group];
+		void *ptr = areas[group];
+
+		for (i = 0; i < gi->nr_units; i++, ptr += ai->unit_size) {
+			if (gi->cpu_map[i] == NR_CPUS) {
+				/* unused unit, free whole */
+				free_fn(ptr, ai->unit_size);
+				continue;
+			}
+			/* copy and return the unused part */
+			memcpy(ptr, __per_cpu_load, ai->static_size);
+			free_fn(ptr + size_sum, ai->unit_size - size_sum);
+		}
+	}
+
+	/* base address is now known, determine group base offsets */
+	for (group = 0; group < ai->nr_groups; group++) {
+		ai->groups[group].base_offset = areas[group] - base;
+	}
+
+	pr_info("Embedded %zu pages/cpu s%zu r%zu d%zu u%zu\n",
+		PFN_DOWN(size_sum), ai->static_size, ai->reserved_size,
+		ai->dyn_size, ai->unit_size);
+
+	rc = pcpu_setup_first_chunk(ai, base);
+	goto out_free;
+
+out_free_areas:
+	for (group = 0; group < ai->nr_groups; group++)
+		if (areas[group])
+			free_fn(areas[group],
+				ai->groups[group].nr_units * ai->unit_size);
+out_free:
+	pcpu_free_alloc_info(ai);
+	if (areas)
+		memblock_free_early(__pa(areas), areas_size);
+	return rc;
+}
+#endif /* BUILD_EMBED_FIRST_CHUNK */
+
+#ifdef BUILD_PAGE_FIRST_CHUNK
+/**
+ * pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @alloc_fn: function to allocate percpu page, always called with PAGE_SIZE
+ * @free_fn: function to free percpu page, always called with PAGE_SIZE
+ * @populate_pte_fn: function to populate pte
+ *
+ * This is a helper to ease setting up page-remapped first percpu
+ * chunk and can be called where pcpu_setup_first_chunk() is expected.
+ *
+ * This is the basic allocator.  Static percpu area is allocated
+ * page-by-page into vmalloc area.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int __init pcpu_page_first_chunk(size_t reserved_size,
+				 pcpu_fc_alloc_fn_t alloc_fn,
+				 pcpu_fc_free_fn_t free_fn,
+				 pcpu_fc_populate_pte_fn_t populate_pte_fn)
+{
+	static struct vm_struct vm;
+	struct pcpu_alloc_info *ai;
+	char psize_str[16];
+	int unit_pages;
+	size_t pages_size;
+	struct page **pages;
+	int unit, i, j, rc;
+	int upa;
+	int nr_g0_units;
+
+	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
+
+	ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
+	if (IS_ERR(ai))
+		return PTR_ERR(ai);
+	BUG_ON(ai->nr_groups != 1);
+	upa = ai->alloc_size/ai->unit_size;
+	nr_g0_units = roundup(num_possible_cpus(), upa);
+	if (unlikely(WARN_ON(ai->groups[0].nr_units != nr_g0_units))) {
+		pcpu_free_alloc_info(ai);
+		return -EINVAL;
+	}
+
+	unit_pages = ai->unit_size >> PAGE_SHIFT;
+
+	/* unaligned allocations can't be freed, round up to page size */
+	pages_size = PFN_ALIGN(unit_pages * num_possible_cpus() *
+			       sizeof(pages[0]));
+	pages = memblock_virt_alloc(pages_size, 0);
+
+	/* allocate pages */
+	j = 0;
+	for (unit = 0; unit < num_possible_cpus(); unit++) {
+		unsigned int cpu = ai->groups[0].cpu_map[unit];
+		for (i = 0; i < unit_pages; i++) {
+			void *ptr;
+
+			ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
+			if (!ptr) {
+				pr_warn("failed to allocate %s page for cpu%u\n",
+						psize_str, cpu);
+				goto enomem;
+			}
+			/* kmemleak tracks the percpu allocations separately */
+			kmemleak_free(ptr);
+			pages[j++] = virt_to_page(ptr);
+		}
+	}
+
+	/* allocate vm area, map the pages and copy static data */
+	vm.flags = VM_ALLOC;
+	vm.size = num_possible_cpus() * ai->unit_size;
+	vm_area_register_early(&vm, PAGE_SIZE);
+
+	for (unit = 0; unit < num_possible_cpus(); unit++) {
+		unsigned long unit_addr =
+			(unsigned long)vm.addr + unit * ai->unit_size;
+
+		for (i = 0; i < unit_pages; i++)
+			populate_pte_fn(unit_addr + (i << PAGE_SHIFT));
+
+		/* pte already populated, the following shouldn't fail */
+		rc = __pcpu_map_pages(unit_addr, &pages[unit * unit_pages],
+				      unit_pages);
+		if (rc < 0)
+			panic("failed to map percpu area, err=%d\n", rc);
+
+		/*
+		 * FIXME: Archs with virtual cache should flush local
+		 * cache for the linear mapping here - something
+		 * equivalent to flush_cache_vmap() on the local cpu.
+		 * flush_cache_vmap() can't be used as most supporting
+		 * data structures are not set up yet.
+		 */
+
+		/* copy static data */
+		memcpy((void *)unit_addr, __per_cpu_load, ai->static_size);
+	}
+
+	/* we're ready, commit */
+	pr_info("%d %s pages/cpu s%zu r%zu d%zu\n",
+		unit_pages, psize_str, ai->static_size,
+		ai->reserved_size, ai->dyn_size);
+
+	rc = pcpu_setup_first_chunk(ai, vm.addr);
+	goto out_free_ar;
+
+enomem:
+	while (--j >= 0)
+		free_fn(page_address(pages[j]), PAGE_SIZE);
+	rc = -ENOMEM;
+out_free_ar:
+	memblock_free_early(__pa(pages), pages_size);
+	pcpu_free_alloc_info(ai);
+	return rc;
+}
+#endif /* BUILD_PAGE_FIRST_CHUNK */
+
+#ifndef	CONFIG_HAVE_SETUP_PER_CPU_AREA
+/*
+ * Generic SMP percpu area setup.
+ *
+ * The embedding helper is used because its behavior closely resembles
+ * the original non-dynamic generic percpu area setup.  This is
+ * important because many archs have addressing restrictions and might
+ * fail if the percpu area is located far away from the previous
+ * location.  As an added bonus, in non-NUMA cases, embedding is
+ * generally a good idea TLB-wise because percpu area can piggy back
+ * on the physical linear memory mapping which uses large page
+ * mappings on applicable archs.
+ */
+unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
+EXPORT_SYMBOL(__per_cpu_offset);
+
+static void * __init pcpu_dfl_fc_alloc(unsigned int cpu, size_t size,
+				       size_t align)
+{
+	return  memblock_virt_alloc_from_nopanic(
+			size, align, __pa(MAX_DMA_ADDRESS));
+}
+
+static void __init pcpu_dfl_fc_free(void *ptr, size_t size)
+{
+	memblock_free_early(__pa(ptr), size);
+}
+
+void __init setup_per_cpu_areas(void)
+{
+	unsigned long delta;
+	unsigned int cpu;
+	int rc;
+
+	/*
+	 * Always reserve area for module percpu variables.  That's
+	 * what the legacy allocator did.
+	 */
+	rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
+				    PERCPU_DYNAMIC_RESERVE, PAGE_SIZE, NULL,
+				    pcpu_dfl_fc_alloc, pcpu_dfl_fc_free);
+	if (rc < 0)
+		panic("Failed to initialize percpu areas.");
+
+	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
+	for_each_possible_cpu(cpu)
+		__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
+}
+#endif	/* CONFIG_HAVE_SETUP_PER_CPU_AREA */
+
+#else	/* CONFIG_SMP */
+
+/*
+ * UP percpu area setup.
+ *
+ * UP always uses km-based percpu allocator with identity mapping.
+ * Static percpu variables are indistinguishable from the usual static
+ * variables and don't require any special preparation.
+ */
+void __init setup_per_cpu_areas(void)
+{
+	const size_t unit_size =
+		roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
+					 PERCPU_DYNAMIC_RESERVE));
+	struct pcpu_alloc_info *ai;
+	void *fc;
+
+	ai = pcpu_alloc_alloc_info(1, 1);
+	fc = memblock_virt_alloc_from_nopanic(unit_size,
+					      PAGE_SIZE,
+					      __pa(MAX_DMA_ADDRESS));
+	if (!ai || !fc)
+		panic("Failed to allocate memory for percpu areas.");
+	/* kmemleak tracks the percpu allocations separately */
+	kmemleak_free(fc);
+
+	ai->dyn_size = unit_size;
+	ai->unit_size = unit_size;
+	ai->atom_size = unit_size;
+	ai->alloc_size = unit_size;
+	ai->groups[0].nr_units = 1;
+	ai->groups[0].cpu_map[0] = 0;
+
+	if (pcpu_setup_first_chunk(ai, fc) < 0)
+		panic("Failed to initialize percpu areas.");
+	pcpu_free_alloc_info(ai);
+}
+
+#endif	/* CONFIG_SMP */
+
+/*
+ * pcpu_nr_pages - calculate total number of populated backing pages
+ *
+ * This reflects the number of pages populated to back chunks.  Metadata is
+ * excluded in the number exposed in meminfo as the number of backing pages
+ * scales with the number of cpus and can quickly outweigh the memory used for
+ * metadata.  It also keeps this calculation nice and simple.
+ *
+ * RETURNS:
+ * Total number of populated backing pages in use by the allocator.
+ */
+unsigned long pcpu_nr_pages(void)
+{
+	return pcpu_nr_populated * pcpu_nr_units;
+}
+
+/*
+ * Percpu allocator is initialized early during boot when neither slab or
+ * workqueue is available.  Plug async management until everything is up
+ * and running.
+ */
+static int __init percpu_enable_async(void)
+{
+	pcpu_async_enabled = true;
+	return 0;
+}
+subsys_initcall(percpu_enable_async);