/*

   * 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.  Each chunk is
   * consisted of boot-time determined number of 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.

   *
   *  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.  On UMA, units corresponds directly to
   * cpus.  On NUMA, the mapping can be non-linear and even sparse.
   * Percpu access can be done by configuring percpu base registers
   * according to cpu to unit mapping and pcpu_unit_size.

   *

   * There are usually many small percpu allocations many of them being
   * 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 equal 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 can be determined from the address using the index field
   * in the page struct. The index field contains a pointer to the chunk.

   *
   * To use this allocator, arch code should do the followings.
   *

   * - 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

   */
  
  #include <linux/bitmap.h>
  #include <linux/bootmem.h>

  #include <linux/err.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 <asm/cacheflush.h>

  #include <asm/sections.h>

  #include <asm/tlbflush.h>

  #include <asm/io.h>

  #define PCPU_SLOT_BASE_SHIFT		5	/* 1-31 shares the same slot */
  #define PCPU_DFL_MAP_ALLOC		16	/* start a map with 16 ents */

  #define PCPU_ATOMIC_MAP_MARGIN_LOW	32
  #define PCPU_ATOMIC_MAP_MARGIN_HIGH	64

  #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 */

  struct pcpu_chunk {
  	struct list_head	list;		/* linked to pcpu_slot lists */

  	int			free_size;	/* free bytes in the chunk */
  	int			contig_hint;	/* max contiguous size hint */

  	void			*base_addr;	/* base address of this chunk */

  	int			map_used;	/* # of map entries used before the sentry */

  	int			map_alloc;	/* # of map entries allocated */
  	int			*map;		/* allocation map */

  	struct work_struct	map_extend_work;/* async ->map[] extension */

  	void			*data;		/* chunk data */

  	int			first_free;	/* no free below this */

  	bool			immutable;	/* no [de]population allowed */

  	int			nr_populated;	/* # of populated pages */

  	unsigned long		populated[];	/* populated bitmap */

  };

  static int pcpu_unit_pages __read_mostly;
  static int pcpu_unit_size __read_mostly;

  static int pcpu_nr_units __read_mostly;

  static int pcpu_atom_size __read_mostly;

  static int pcpu_nr_slots __read_mostly;
  static size_t pcpu_chunk_struct_size __read_mostly;

  /* cpus with the lowest and highest unit addresses */
  static unsigned int pcpu_low_unit_cpu __read_mostly;
  static unsigned int pcpu_high_unit_cpu __read_mostly;

  /* the address of the first chunk which starts with the kernel static area */

  void *pcpu_base_addr __read_mostly;

  EXPORT_SYMBOL_GPL(pcpu_base_addr);

  static const int *pcpu_unit_map __read_mostly;		/* cpu -> unit */
  const unsigned long *pcpu_unit_offsets __read_mostly;	/* cpu -> unit offset */

  /* group information, used for vm allocation */
  static int pcpu_nr_groups __read_mostly;
  static const unsigned long *pcpu_group_offsets __read_mostly;
  static const size_t *pcpu_group_sizes __read_mostly;

  /*
   * 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.
   */
  static struct pcpu_chunk *pcpu_first_chunk;
  
  /*
   * Optional reserved chunk.  This chunk reserves part of the first
   * chunk and serves it for reserved allocations.  The amount of
   * reserved offset is in pcpu_reserved_chunk_limit.  When reserved
   * area doesn't exist, the following variables contain NULL and 0
   * respectively.
   */

  static struct pcpu_chunk *pcpu_reserved_chunk;

  static int pcpu_reserved_chunk_limit;

  static DEFINE_SPINLOCK(pcpu_lock);	/* all internal data structures */
  static DEFINE_MUTEX(pcpu_alloc_mutex);	/* chunk create/destroy, [de]pop */

  static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */

  /*
   * The number of empty populated pages, protected by pcpu_lock.  The
   * reserved chunk doesn't contribute to the count.
   */
  static int pcpu_nr_empty_pop_pages;

  /*
   * 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);
  }

  static bool pcpu_addr_in_first_chunk(void *addr)
  {
  	void *first_start = pcpu_first_chunk->base_addr;
  
  	return addr >= first_start && addr < first_start + pcpu_unit_size;
  }
  
  static bool pcpu_addr_in_reserved_chunk(void *addr)
  {
  	void *first_start = pcpu_first_chunk->base_addr;
  
  	return addr >= first_start &&
  		addr < first_start + pcpu_reserved_chunk_limit;
  }

  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_size < sizeof(int) || chunk->contig_hint < sizeof(int))
  		return 0;
  
  	return pcpu_size_to_slot(chunk->free_size);
  }

  /* 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_chunk_addr(struct pcpu_chunk *chunk,
  				     unsigned int cpu, int page_idx)

  {

  	return (unsigned long)chunk->base_addr + pcpu_unit_offsets[cpu] +

  		(page_idx << PAGE_SHIFT);

  }

  static void __maybe_unused pcpu_next_unpop(struct pcpu_chunk *chunk,
  					   int *rs, int *re, int end)

  {
  	*rs = find_next_zero_bit(chunk->populated, end, *rs);
  	*re = find_next_bit(chunk->populated, end, *rs + 1);
  }

  static void __maybe_unused pcpu_next_pop(struct pcpu_chunk *chunk,
  					 int *rs, int *re, int end)

  {
  	*rs = find_next_bit(chunk->populated, end, *rs);
  	*re = find_next_zero_bit(chunk->populated, end, *rs + 1);
  }
  
  /*
   * (Un)populated page region iterators.  Iterate over (un)populated

   * page regions between @start and @end in @chunk.  @rs and @re should

   * be integer variables and will be set to start and end page index of
   * the current region.
   */
  #define pcpu_for_each_unpop_region(chunk, rs, re, start, end)		    \
  	for ((rs) = (start), pcpu_next_unpop((chunk), &(rs), &(re), (end)); \
  	     (rs) < (re);						    \
  	     (rs) = (re) + 1, pcpu_next_unpop((chunk), &(rs), &(re), (end)))
  
  #define pcpu_for_each_pop_region(chunk, rs, re, start, end)		    \
  	for ((rs) = (start), pcpu_next_pop((chunk), &(rs), &(re), (end));   \
  	     (rs) < (re);						    \
  	     (rs) = (re) + 1, pcpu_next_pop((chunk), &(rs), &(re), (end)))

  /**

   * pcpu_mem_zalloc - allocate memory

   * @size: bytes to allocate

   *

   * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,

   * kzalloc() is used; otherwise, vzalloc() is used.  The returned

   * memory is always zeroed.

   *

   * CONTEXT:
   * Does GFP_KERNEL allocation.
   *

   * RETURNS:

   * Pointer to the allocated area on success, NULL on failure.

   */

  static void *pcpu_mem_zalloc(size_t size)

  {

  	if (WARN_ON_ONCE(!slab_is_available()))
  		return NULL;

  	if (size <= PAGE_SIZE)
  		return kzalloc(size, GFP_KERNEL);

  	else
  		return vzalloc(size);

  }

  /**
   * pcpu_mem_free - free memory
   * @ptr: memory to free
   * @size: size of the area
   *

   * Free @ptr.  @ptr should have been allocated using pcpu_mem_zalloc().

   */
  static void pcpu_mem_free(void *ptr, size_t size)
  {

  	if (size <= PAGE_SIZE)

  		kfree(ptr);

  	else

  		vfree(ptr);

  }
  
  /**

   * pcpu_count_occupied_pages - count the number of pages an area occupies
   * @chunk: chunk of interest
   * @i: index of the area in question
   *
   * Count the number of pages chunk's @i'th area occupies.  When the area's
   * start and/or end address isn't aligned to page boundary, the straddled
   * page is included in the count iff the rest of the page is free.
   */
  static int pcpu_count_occupied_pages(struct pcpu_chunk *chunk, int i)
  {
  	int off = chunk->map[i] & ~1;
  	int end = chunk->map[i + 1] & ~1;
  
  	if (!PAGE_ALIGNED(off) && i > 0) {
  		int prev = chunk->map[i - 1];
  
  		if (!(prev & 1) && prev <= round_down(off, PAGE_SIZE))
  			off = round_down(off, PAGE_SIZE);
  	}
  
  	if (!PAGE_ALIGNED(end) && i + 1 < chunk->map_used) {
  		int next = chunk->map[i + 1];
  		int nend = chunk->map[i + 2] & ~1;
  
  		if (!(next & 1) && nend >= round_up(end, PAGE_SIZE))
  			end = round_up(end, PAGE_SIZE);
  	}
  
  	return max_t(int, PFN_DOWN(end) - PFN_UP(off), 0);
  }
  
  /**

   * 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_need_to_extend - determine whether chunk area map needs to be extended
   * @chunk: chunk of interest

   * @is_atomic: the allocation context

   *

   * Determine whether area map of @chunk needs to be extended.  If
   * @is_atomic, only the amount necessary for a new allocation is
   * considered; however, async extension is scheduled if the left amount is
   * low.  If !@is_atomic, it aims for more empty space.  Combined, this
   * ensures that the map is likely to have enough available space to
   * accomodate atomic allocations which can't extend maps directly.

   *

   * CONTEXT:

   * pcpu_lock.

   *

   * RETURNS:

   * New target map allocation length if extension is necessary, 0
   * otherwise.

   */

  static int pcpu_need_to_extend(struct pcpu_chunk *chunk, bool is_atomic)

  {

  	int margin, new_alloc;
  
  	if (is_atomic) {
  		margin = 3;

  		if (chunk->map_alloc <

  		    chunk->map_used + PCPU_ATOMIC_MAP_MARGIN_LOW &&
  		    pcpu_async_enabled)

  			schedule_work(&chunk->map_extend_work);
  	} else {
  		margin = PCPU_ATOMIC_MAP_MARGIN_HIGH;
  	}
  
  	if (chunk->map_alloc >= chunk->map_used + margin)

  		return 0;
  
  	new_alloc = PCPU_DFL_MAP_ALLOC;

  	while (new_alloc < chunk->map_used + margin)

  		new_alloc *= 2;

  	return new_alloc;
  }
  
  /**
   * pcpu_extend_area_map - extend area map of a chunk
   * @chunk: chunk of interest
   * @new_alloc: new target allocation length of the area map
   *
   * Extend area map of @chunk to have @new_alloc entries.
   *
   * CONTEXT:
   * Does GFP_KERNEL allocation.  Grabs and releases pcpu_lock.
   *
   * RETURNS:
   * 0 on success, -errno on failure.
   */
  static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
  {
  	int *old = NULL, *new = NULL;
  	size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
  	unsigned long flags;

  	new = pcpu_mem_zalloc(new_size);

  	if (!new)

  		return -ENOMEM;

  	/* acquire pcpu_lock and switch to new area map */
  	spin_lock_irqsave(&pcpu_lock, flags);
  
  	if (new_alloc <= chunk->map_alloc)
  		goto out_unlock;

  	old_size = chunk->map_alloc * sizeof(chunk->map[0]);

  	old = chunk->map;
  
  	memcpy(new, old, old_size);

  	chunk->map_alloc = new_alloc;
  	chunk->map = new;

  	new = NULL;
  
  out_unlock:
  	spin_unlock_irqrestore(&pcpu_lock, flags);
  
  	/*
  	 * pcpu_mem_free() might end up calling vfree() which uses
  	 * IRQ-unsafe lock and thus can't be called under pcpu_lock.
  	 */
  	pcpu_mem_free(old, old_size);
  	pcpu_mem_free(new, new_size);

  	return 0;
  }

  static void pcpu_map_extend_workfn(struct work_struct *work)
  {
  	struct pcpu_chunk *chunk = container_of(work, struct pcpu_chunk,
  						map_extend_work);
  	int new_alloc;
  
  	spin_lock_irq(&pcpu_lock);
  	new_alloc = pcpu_need_to_extend(chunk, false);
  	spin_unlock_irq(&pcpu_lock);
  
  	if (new_alloc)
  		pcpu_extend_area_map(chunk, new_alloc);
  }

  /**

   * pcpu_fit_in_area - try to fit the requested allocation in a candidate area
   * @chunk: chunk the candidate area belongs to
   * @off: the offset to the start of the candidate area
   * @this_size: the size of the candidate area
   * @size: the size of the target allocation
   * @align: the alignment of the target allocation
   * @pop_only: only allocate from already populated region
   *
   * We're trying to allocate @size bytes aligned at @align.  @chunk's area
   * at @off sized @this_size is a candidate.  This function determines
   * whether the target allocation fits in the candidate area and returns the
   * number of bytes to pad after @off.  If the target area doesn't fit, -1
   * is returned.
   *
   * If @pop_only is %true, this function only considers the already
   * populated part of the candidate area.
   */
  static int pcpu_fit_in_area(struct pcpu_chunk *chunk, int off, int this_size,
  			    int size, int align, bool pop_only)
  {
  	int cand_off = off;
  
  	while (true) {
  		int head = ALIGN(cand_off, align) - off;
  		int page_start, page_end, rs, re;
  
  		if (this_size < head + size)
  			return -1;
  
  		if (!pop_only)
  			return head;
  
  		/*
  		 * If the first unpopulated page is beyond the end of the
  		 * allocation, the whole allocation is populated;
  		 * otherwise, retry from the end of the unpopulated area.
  		 */
  		page_start = PFN_DOWN(head + off);
  		page_end = PFN_UP(head + off + size);
  
  		rs = page_start;
  		pcpu_next_unpop(chunk, &rs, &re, PFN_UP(off + this_size));
  		if (rs >= page_end)
  			return head;
  		cand_off = re * PAGE_SIZE;
  	}
  }
  
  /**

   * pcpu_alloc_area - allocate area from a pcpu_chunk
   * @chunk: chunk of interest

   * @size: wanted size in bytes

   * @align: wanted align

   * @pop_only: allocate only from the populated area

   * @occ_pages_p: out param for the number of pages the area occupies

   *
   * 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.
   *

   * @chunk->map must have at least two free slots.
   *

   * CONTEXT:
   * pcpu_lock.
   *

   * RETURNS:

   * Allocated offset in @chunk on success, -1 if no matching area is
   * found.

   */

  static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,

  			   bool pop_only, int *occ_pages_p)

  {
  	int oslot = pcpu_chunk_slot(chunk);
  	int max_contig = 0;
  	int i, off;

  	bool seen_free = false;

  	int *p;

  	for (i = chunk->first_free, p = chunk->map + i; i < chunk->map_used; i++, p++) {

  		int head, tail;

  		int this_size;
  
  		off = *p;
  		if (off & 1)
  			continue;

  		this_size = (p[1] & ~1) - off;

  
  		head = pcpu_fit_in_area(chunk, off, this_size, size, align,
  					pop_only);
  		if (head < 0) {

  			if (!seen_free) {
  				chunk->first_free = i;
  				seen_free = true;
  			}

  			max_contig = max(this_size, 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) || !(p[-1] & 1))) {

  			*p = off += head;

  			if (p[-1] & 1)

  				chunk->free_size -= head;

  			else
  				max_contig = max(*p - p[-1], max_contig);

  			this_size -= head;

  			head = 0;
  		}
  
  		/* if tail is small, just keep it around */

  		tail = this_size - head - size;
  		if (tail < sizeof(int)) {

  			tail = 0;

  			size = this_size - head;
  		}

  
  		/* split if warranted */
  		if (head || tail) {

  			int nr_extra = !!head + !!tail;
  
  			/* insert new subblocks */

  			memmove(p + nr_extra + 1, p + 1,

  				sizeof(chunk->map[0]) * (chunk->map_used - i));
  			chunk->map_used += nr_extra;

  			if (head) {

  				if (!seen_free) {
  					chunk->first_free = i;
  					seen_free = true;
  				}

  				*++p = off += head;
  				++i;

  				max_contig = max(head, max_contig);
  			}
  			if (tail) {

  				p[1] = off + size;

  				max_contig = max(tail, max_contig);

  			}

  		}

  		if (!seen_free)
  			chunk->first_free = i + 1;

  		/* update hint and mark allocated */

  		if (i + 1 == chunk->map_used)

  			chunk->contig_hint = max_contig; /* fully scanned */
  		else
  			chunk->contig_hint = max(chunk->contig_hint,
  						 max_contig);

  		chunk->free_size -= size;
  		*p |= 1;

  		*occ_pages_p = pcpu_count_occupied_pages(chunk, 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 matching area */
  	return -1;

  }
  
  /**
   * pcpu_free_area - free area to a pcpu_chunk
   * @chunk: chunk of interest
   * @freeme: offset of area to free

   * @occ_pages_p: out param for the number of pages the area occupies

   *
   * Free area starting from @freeme to @chunk.  Note that this function
   * only modifies the allocation map.  It doesn't depopulate or unmap
   * the area.

   *
   * CONTEXT:
   * pcpu_lock.

   */

  static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme,
  			   int *occ_pages_p)

  {
  	int oslot = pcpu_chunk_slot(chunk);

  	int off = 0;
  	unsigned i, j;
  	int to_free = 0;
  	int *p;
  
  	freeme |= 1;	/* we are searching for <given offset, in use> pair */
  
  	i = 0;
  	j = chunk->map_used;
  	while (i != j) {
  		unsigned k = (i + j) / 2;
  		off = chunk->map[k];
  		if (off < freeme)
  			i = k + 1;
  		else if (off > freeme)
  			j = k;
  		else
  			i = j = k;
  	}

  	BUG_ON(off != freeme);

  	if (i < chunk->first_free)
  		chunk->first_free = i;

  	p = chunk->map + i;
  	*p = off &= ~1;
  	chunk->free_size += (p[1] & ~1) - off;

  	*occ_pages_p = pcpu_count_occupied_pages(chunk, i);

  	/* merge with next? */
  	if (!(p[1] & 1))
  		to_free++;

  	/* merge with previous? */

  	if (i > 0 && !(p[-1] & 1)) {
  		to_free++;

  		i--;

  		p--;

  	}

  	if (to_free) {
  		chunk->map_used -= to_free;
  		memmove(p + 1, p + 1 + to_free,
  			(chunk->map_used - i) * sizeof(chunk->map[0]));

  	}

  	chunk->contig_hint = max(chunk->map[i + 1] - chunk->map[i] - 1, chunk->contig_hint);

  	pcpu_chunk_relocate(chunk, oslot);
  }

  static struct pcpu_chunk *pcpu_alloc_chunk(void)
  {
  	struct pcpu_chunk *chunk;

  	chunk = pcpu_mem_zalloc(pcpu_chunk_struct_size);

  	if (!chunk)
  		return NULL;

  	chunk->map = pcpu_mem_zalloc(PCPU_DFL_MAP_ALLOC *
  						sizeof(chunk->map[0]));

  	if (!chunk->map) {

  		pcpu_mem_free(chunk, pcpu_chunk_struct_size);

  		return NULL;
  	}
  
  	chunk->map_alloc = PCPU_DFL_MAP_ALLOC;

  	chunk->map[0] = 0;
  	chunk->map[1] = pcpu_unit_size | 1;
  	chunk->map_used = 1;

  
  	INIT_LIST_HEAD(&chunk->list);

  	INIT_WORK(&chunk->map_extend_work, pcpu_map_extend_workfn);

  	chunk->free_size = pcpu_unit_size;
  	chunk->contig_hint = pcpu_unit_size;
  
  	return chunk;
  }
  
  static void pcpu_free_chunk(struct pcpu_chunk *chunk)
  {
  	if (!chunk)
  		return;
  	pcpu_mem_free(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]));

  	pcpu_mem_free(chunk, pcpu_chunk_struct_size);

  }

  /**
   * pcpu_chunk_populated - post-population bookkeeping
   * @chunk: pcpu_chunk which got populated
   * @page_start: the start page
   * @page_end: the end page
   *
   * Pages in [@page_start,@page_end) have been populated to @chunk.  Update
   * the bookkeeping information accordingly.  Must be called after each
   * successful population.
   */
  static void pcpu_chunk_populated(struct pcpu_chunk *chunk,
  				 int page_start, int page_end)
  {
  	int nr = page_end - page_start;
  
  	lockdep_assert_held(&pcpu_lock);
  
  	bitmap_set(chunk->populated, page_start, nr);
  	chunk->nr_populated += 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;
  	pcpu_nr_empty_pop_pages -= 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 off, int size);
  static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size);
  static struct pcpu_chunk *pcpu_create_chunk(void);
  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.
   *
   * RETURNS:
   * The address of the found chunk.
   */
  static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
  {
  	/* is it in the first chunk? */
  	if (pcpu_addr_in_first_chunk(addr)) {
  		/* is it in the reserved area? */
  		if (pcpu_addr_in_reserved_chunk(addr))
  			return pcpu_reserved_chunk;
  		return pcpu_first_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.

   *
   * 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)

  {

  	static int warn_limit = 10;

  	struct pcpu_chunk *chunk;

  	const char *err;

  	bool is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;

  	int occ_pages = 0;

  	int slot, off, new_alloc, cpu, ret;

  	unsigned long flags;

  	void __percpu *ptr;

  	/*
  	 * We want the lowest bit of offset available for in-use/free

  	 * indicator, so force >= 16bit alignment and make size even.

  	 */
  	if (unlikely(align < 2))
  		align = 2;

  	size = ALIGN(size, 2);

  	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {

  		WARN(true, "illegal size (%zu) or align (%zu) for "
  		     "percpu allocation
  ", size, align);
  		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;

  
  		if (size > chunk->contig_hint) {
  			err = "alloc from reserved chunk failed";

  			goto fail_unlock;

  		}

  		while ((new_alloc = pcpu_need_to_extend(chunk, is_atomic))) {

  			spin_unlock_irqrestore(&pcpu_lock, flags);

  			if (is_atomic ||
  			    pcpu_extend_area_map(chunk, new_alloc) < 0) {

  				err = "failed to extend area map of reserved chunk";

  				goto fail;

  			}
  			spin_lock_irqsave(&pcpu_lock, flags);
  		}

  		off = pcpu_alloc_area(chunk, size, align, is_atomic,
  				      &occ_pages);

  		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) {
  			if (size > chunk->contig_hint)
  				continue;

  			new_alloc = pcpu_need_to_extend(chunk, is_atomic);

  			if (new_alloc) {

  				if (is_atomic)
  					continue;

  				spin_unlock_irqrestore(&pcpu_lock, flags);
  				if (pcpu_extend_area_map(chunk,
  							 new_alloc) < 0) {
  					err = "failed to extend area map";

  					goto fail;

  				}
  				spin_lock_irqsave(&pcpu_lock, flags);
  				/*
  				 * pcpu_lock has been dropped, need to
  				 * restart cpu_slot list walking.
  				 */
  				goto restart;

  			}

  			off = pcpu_alloc_area(chunk, size, align, is_atomic,
  					      &occ_pages);

  			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)
  		goto fail;

  	mutex_lock(&pcpu_alloc_mutex);
  
  	if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
  		chunk = pcpu_create_chunk();
  		if (!chunk) {

  			mutex_unlock(&pcpu_alloc_mutex);

  			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);

  	}

  	mutex_unlock(&pcpu_alloc_mutex);

  	goto restart;

  
  area_found:

  	spin_unlock_irqrestore(&pcpu_lock, flags);

  	/* populate if not all pages are already there */

  	if (!is_atomic) {

  		int page_start, page_end, rs, re;

  		mutex_lock(&pcpu_alloc_mutex);

  		page_start = PFN_DOWN(off);
  		page_end = PFN_UP(off + size);

  		pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
  			WARN_ON(chunk->immutable);
  
  			ret = pcpu_populate_chunk(chunk, rs, re);
  
  			spin_lock_irqsave(&pcpu_lock, flags);
  			if (ret) {
  				mutex_unlock(&pcpu_alloc_mutex);

  				pcpu_free_area(chunk, off, &occ_pages);

  				err = "failed to populate";
  				goto fail_unlock;
  			}

  			pcpu_chunk_populated(chunk, rs, re);

  			spin_unlock_irqrestore(&pcpu_lock, flags);

  		}

  		mutex_unlock(&pcpu_alloc_mutex);
  	}

  	if (chunk != pcpu_reserved_chunk)
  		pcpu_nr_empty_pop_pages -= occ_pages;

  	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);

  	return ptr;

  
  fail_unlock:

  	spin_unlock_irqrestore(&pcpu_lock, flags);

  fail:

  	if (!is_atomic && warn_limit) {
  		pr_warning("PERCPU: allocation failed, size=%zu align=%zu atomic=%d, %s
  ",
  			   size, align, is_atomic, err);

  		dump_stack();
  		if (!--warn_limit)
  			pr_info("PERCPU: limit reached, disable warning
  ");
  	}

  	if (is_atomic) {
  		/* see the flag handling in pcpu_blance_workfn() */
  		pcpu_atomic_alloc_failed = true;
  		pcpu_schedule_balance_work();
  	}

  	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.

   *

   * 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.
   */

  static void pcpu_balance_workfn(struct work_struct *work)

  {

  	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, rs, re, 0, pcpu_unit_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);

  	}

  	/*
  	 * 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 = pcpu_unit_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, rs, re, 0, pcpu_unit_pages) {
  			int nr = min(re - rs, nr_to_pop);
  
  			ret = pcpu_populate_chunk(chunk, rs, rs + nr);
  			if (!ret) {
  				nr_to_pop -= nr;
  				spin_lock_irq(&pcpu_lock);
  				pcpu_chunk_populated(chunk, rs, rs + nr);
  				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();
  		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, occ_pages;

  
  	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, &occ_pages);
  
  	if (chunk != pcpu_reserved_chunk)
  		pcpu_nr_empty_pop_pages += occ_pages;

  	/* if there are more than one fully free chunks, wake up grim reaper */

  	if (chunk->free_size == pcpu_unit_size) {
  		struct pcpu_chunk *pos;

  		list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)

  			if (pos != chunk) {

  				pcpu_schedule_balance_work();

  				break;
  			}
  	}

  	spin_unlock_irqrestore(&pcpu_lock, flags);

  }
  EXPORT_SYMBOL_GPL(free_percpu);

  /**

   * 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)
  {

  #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);
  
  		if ((void *)addr >= start && (void *)addr < start + static_size)
  			return true;
          }

  #endif
  	/* on UP, can't distinguish from other static vars, always false */

  	return false;
  }
  
  /**

   * 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.
  	 */

  	first_low = pcpu_chunk_addr(pcpu_first_chunk, pcpu_low_unit_cpu, 0);
  	first_high = pcpu_chunk_addr(pcpu_first_chunk, 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), 0);

  	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)) {

  				printk(KERN_CONT "
  ");

  				printk("%spcpu-alloc: ", lvl);
  			}

  			printk(KERN_CONT "[%0*d] ", group_width, group);

  
  			for (unit_end += upa; unit < unit_end; unit++)
  				if (gi->cpu_map[unit] != NR_CPUS)

  					printk(KERN_CONT "%0*d ", cpu_width,

  					       gi->cpu_map[unit]);
  				else

  					printk(KERN_CONT "%s ", empty_str);

  		}

  	}

  	printk(KERN_CONT "
  ");

  }

  /**

   * 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.

   *

   * If the first chunk ends up with both reserved and dynamic areas, it
   * is served by two chunks - one to serve the core static and reserved
   * areas and the other for the dynamic area.  They share the same vm
   * and page map but uses different area allocation map to stay away
   * from each other.  The latter chunk is circulated in the chunk slots
   * and available for dynamic allocation like any other chunks.
   *

   * RETURNS:

   * 0 on success, -errno on failure.

   */

  int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
  				  void *base_addr)

  {

  	static int smap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata;
  	static int dmap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata;

  	size_t dyn_size = ai->dyn_size;
  	size_t size_sum = ai->static_size + ai->reserved_size + dyn_size;

  	struct pcpu_chunk *schunk, *dchunk = NULL;

  	unsigned long *group_offsets;
  	size_t *group_sizes;

  	unsigned long *unit_off;

  	unsigned int cpu;

  	int *unit_map;
  	int group, unit, i;

  #define PCPU_SETUP_BUG_ON(cond)	do {					\
  	if (unlikely(cond)) {						\
  		pr_emerg("PERCPU: failed to initialize, %s", #cond);	\

  		pr_emerg("PERCPU: cpu_possible_mask=%*pb
  ",		\
  			 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((unsigned long)__per_cpu_start & ~PAGE_MASK);

  #endif

  	PCPU_SETUP_BUG_ON(!base_addr);

  	PCPU_SETUP_BUG_ON((unsigned long)base_addr & ~PAGE_MASK);

  	PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
  	PCPU_SETUP_BUG_ON(ai->unit_size & ~PAGE_MASK);
  	PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);

  	PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_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);

  	/*
  	 * 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]);

  	/*
  	 * Initialize static chunk.  If reserved_size is zero, the
  	 * static chunk covers static area + dynamic allocation area
  	 * in the first chunk.  If reserved_size is not zero, it
  	 * covers static area + reserved area (mostly used for module
  	 * static percpu allocation).
  	 */

  	schunk = memblock_virt_alloc(pcpu_chunk_struct_size, 0);

  	INIT_LIST_HEAD(&schunk->list);

  	INIT_WORK(&schunk->map_extend_work, pcpu_map_extend_workfn);

  	schunk->base_addr = base_addr;

  	schunk->map = smap;
  	schunk->map_alloc = ARRAY_SIZE(smap);

  	schunk->immutable = true;

  	bitmap_fill(schunk->populated, pcpu_unit_pages);

  	schunk->nr_populated = pcpu_unit_pages;

  	if (ai->reserved_size) {
  		schunk->free_size = ai->reserved_size;

  		pcpu_reserved_chunk = schunk;

  		pcpu_reserved_chunk_limit = ai->static_size + ai->reserved_size;

  	} else {
  		schunk->free_size = dyn_size;
  		dyn_size = 0;			/* dynamic area covered */
  	}

  	schunk->contig_hint = schunk->free_size;

  	schunk->map[0] = 1;
  	schunk->map[1] = ai->static_size;
  	schunk->map_used = 1;

  	if (schunk->free_size)

  		schunk->map[++schunk->map_used] = 1 | (ai->static_size + schunk->free_size);
  	else
  		schunk->map[1] |= 1;

  	/* init dynamic chunk if necessary */
  	if (dyn_size) {

  		dchunk = memblock_virt_alloc(pcpu_chunk_struct_size, 0);

  		INIT_LIST_HEAD(&dchunk->list);

  		INIT_WORK(&dchunk->map_extend_work, pcpu_map_extend_workfn);

  		dchunk->base_addr = base_addr;

  		dchunk->map = dmap;
  		dchunk->map_alloc = ARRAY_SIZE(dmap);

  		dchunk->immutable = true;

  		bitmap_fill(dchunk->populated, pcpu_unit_pages);

  		dchunk->nr_populated = pcpu_unit_pages;

  
  		dchunk->contig_hint = dchunk->free_size = dyn_size;

  		dchunk->map[0] = 1;
  		dchunk->map[1] = pcpu_reserved_chunk_limit;
  		dchunk->map[2] = (pcpu_reserved_chunk_limit + dchunk->free_size) | 1;
  		dchunk->map_used = 2;

  	}

  	/* link the first chunk in */

  	pcpu_first_chunk = dchunk ?: schunk;

  	pcpu_nr_empty_pop_pages +=
  		pcpu_count_occupied_pages(pcpu_first_chunk, 1);

  	pcpu_chunk_relocate(pcpu_first_chunk, -1);

  
  	/* 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_warning("PERCPU: unknown allocator %s specified
  ", str);

  	return 0;