FreeBSD/Linux Kernel Cross Reference
sys/mm/percpu.c

     /*
      * 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 */
    
    #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 */
           int                     map_alloc;      /* # of map entries allocated */
           int                     *map;           /* allocation map */
           void                    *data;          /* chunk data */
           bool                    immutable;      /* no [de]population allowed */
           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;
   
   /*
    * Synchronization rules.
    *
    * There are two locks - pcpu_alloc_mutex and pcpu_lock.  The former
    * protects allocation/reclaim paths, chunks, populated bitmap and
    * vmalloc mapping.  The latter is a spinlock and protects the index
    * data structures - chunk slots, chunks and area maps in chunks.
    *
    * During allocation, pcpu_alloc_mutex is kept locked all the time and
    * pcpu_lock is grabbed and released as necessary.  All actual memory
    * allocations are done using GFP_KERNEL with pcpu_lock released.  In
    * general, percpu memory can't be allocated with irq off but
    * irqsave/restore are still used in alloc path so that it can be used
    * from early init path - sched_init() specifically.
    *
    * Free path accesses and alters only the index data structures, so it
    * can be safely called from atomic context.  When memory needs to be
    * returned to the system, free path schedules reclaim_work which
    * grabs both pcpu_alloc_mutex and pcpu_lock, unlinks chunks to be
    * reclaimed, release both locks and frees the chunks.  Note that it's
    * necessary to grab both locks to remove a chunk from circulation as
    * allocation path might be referencing the chunk with only
    * pcpu_alloc_mutex locked.
    */
   static DEFINE_MUTEX(pcpu_alloc_mutex);  /* protects whole alloc and reclaim */
   static DEFINE_SPINLOCK(pcpu_lock);      /* protects index data structures */
   
   static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
   
   /* reclaim work to release fully free chunks, scheduled from free path */
   static void pcpu_reclaim(struct work_struct *work);
   static DECLARE_WORK(pcpu_reclaim_work, pcpu_reclaim);
   
   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_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
    *
    * Determine whether area map of @chunk needs to be extended to
    * accommodate a new allocation.
    *
    * 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)
   {
           int new_alloc;
   
           if (chunk->map_alloc >= chunk->map_used + 2)
                   return 0;
   
           new_alloc = PCPU_DFL_MAP_ALLOC;
           while (new_alloc < chunk->map_used + 2)
                   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;
   }
   
   /**
    * pcpu_split_block - split a map block
    * @chunk: chunk of interest
    * @i: index of map block to split
    * @head: head size in bytes (can be 0)
    * @tail: tail size in bytes (can be 0)
    *
    * Split the @i'th map block into two or three blocks.  If @head is
    * non-zero, @head bytes block is inserted before block @i moving it
    * to @i+1 and reducing its size by @head bytes.
    *
    * If @tail is non-zero, the target block, which can be @i or @i+1
    * depending on @head, is reduced by @tail bytes and @tail byte block
    * is inserted after the target block.
    *
    * @chunk->map must have enough free slots to accommodate the split.
    *
    * CONTEXT:
    * pcpu_lock.
    */
   static void pcpu_split_block(struct pcpu_chunk *chunk, int i,
                                int head, int tail)
   {
           int nr_extra = !!head + !!tail;
   
           BUG_ON(chunk->map_alloc < chunk->map_used + nr_extra);
   
           /* insert new subblocks */
           memmove(&chunk->map[i + nr_extra], &chunk->map[i],
                   sizeof(chunk->map[0]) * (chunk->map_used - i));
           chunk->map_used += nr_extra;
   
           if (head) {
                   chunk->map[i + 1] = chunk->map[i] - head;
                   chunk->map[i++] = head;
           }
           if (tail) {
                   chunk->map[i++] -= tail;
                   chunk->map[i] = tail;
           }
   }
   
   /**
    * pcpu_alloc_area - allocate area from a pcpu_chunk
    * @chunk: chunk of interest
    * @size: wanted size in bytes
    * @align: wanted align
    *
    * Try to allocate @size bytes area aligned at @align from @chunk.
    * Note that this function only allocates the offset.  It doesn't
    * populate or map the area.
    *
    * @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)
   {
           int oslot = pcpu_chunk_slot(chunk);
           int max_contig = 0;
           int i, off;
   
           for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
                   bool is_last = i + 1 == chunk->map_used;
                   int head, tail;
   
                   /* extra for alignment requirement */
                   head = ALIGN(off, align) - off;
                   BUG_ON(i == 0 && head != 0);
   
                   if (chunk->map[i] < 0)
                           continue;
                   if (chunk->map[i] < head + size) {
                           max_contig = max(chunk->map[i], max_contig);
                           continue;
                   }
   
                   /*
                    * If head is small or the previous block is free,
                    * merge'em.  Note that 'small' is defined as smaller
                    * than sizeof(int), which is very small but isn't too
                    * uncommon for percpu allocations.
                    */
                   if (head && (head < sizeof(int) || chunk->map[i - 1] > 0)) {
                           if (chunk->map[i - 1] > 0)
                                   chunk->map[i - 1] += head;
                           else {
                                   chunk->map[i - 1] -= head;
                                   chunk->free_size -= head;
                           }
                           chunk->map[i] -= head;
                           off += head;
                           head = 0;
                   }
   
                   /* if tail is small, just keep it around */
                   tail = chunk->map[i] - head - size;
                   if (tail < sizeof(int))
                           tail = 0;
   
                   /* split if warranted */
                   if (head || tail) {
                           pcpu_split_block(chunk, i, head, tail);
                           if (head) {
                                   i++;
                                   off += head;
                                   max_contig = max(chunk->map[i - 1], max_contig);
                           }
                           if (tail)
                                   max_contig = max(chunk->map[i + 1], max_contig);
                   }
   
                   /* update hint and mark allocated */
                   if (is_last)
                           chunk->contig_hint = max_contig; /* fully scanned */
                   else
                           chunk->contig_hint = max(chunk->contig_hint,
                                                    max_contig);
   
                   chunk->free_size -= chunk->map[i];
                   chunk->map[i] = -chunk->map[i];
   
                   pcpu_chunk_relocate(chunk, oslot);
                   return off;
           }
   
           chunk->contig_hint = max_contig;        /* fully scanned */
           pcpu_chunk_relocate(chunk, oslot);
   
           /* tell the upper layer that this chunk has no matching area */
           return -1;
   }
   
   /**
    * pcpu_free_area - free area to a pcpu_chunk
    * @chunk: chunk of interest
    * @freeme: offset of area to free
    *
    * Free area starting from @freeme to @chunk.  Note that this function
    * only modifies the allocation map.  It doesn't depopulate or unmap
    * the area.
    *
    * CONTEXT:
    * pcpu_lock.
    */
   static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
   {
           int oslot = pcpu_chunk_slot(chunk);
           int i, off;
   
           for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++]))
                   if (off == freeme)
                           break;
           BUG_ON(off != freeme);
           BUG_ON(chunk->map[i] > 0);
   
           chunk->map[i] = -chunk->map[i];
           chunk->free_size += chunk->map[i];
   
           /* merge with previous? */
           if (i > 0 && chunk->map[i - 1] >= 0) {
                   chunk->map[i - 1] += chunk->map[i];
                   chunk->map_used--;
                   memmove(&chunk->map[i], &chunk->map[i + 1],
                           (chunk->map_used - i) * sizeof(chunk->map[0]));
                   i--;
           }
           /* merge with next? */
           if (i + 1 < chunk->map_used && chunk->map[i + 1] >= 0) {
                   chunk->map[i] += chunk->map[i + 1];
                   chunk->map_used--;
                   memmove(&chunk->map[i + 1], &chunk->map[i + 2],
                           (chunk->map_used - (i + 1)) * sizeof(chunk->map[0]));
           }
   
           chunk->contig_hint = max(chunk->map[i], chunk->contig_hint);
           pcpu_chunk_relocate(chunk, oslot);
   }
   
   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) {
                   kfree(chunk);
                   return NULL;
           }
   
           chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
           chunk->map[chunk->map_used++] = pcpu_unit_size;
   
           INIT_LIST_HEAD(&chunk->list);
           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);
   }
   
   /*
    * 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
    *
    * Allocate percpu area of @size bytes aligned at @align.
    *
    * CONTEXT:
    * Does GFP_KERNEL allocation.
    *
    * 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)
   {
           static int warn_limit = 10;
           struct pcpu_chunk *chunk;
           const char *err;
           int slot, off, new_alloc;
           unsigned long flags;
           void __percpu *ptr;
   
           if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
                   WARN(true, "illegal size (%zu) or align (%zu) for "
                        "percpu allocation\n", size, align);
                   return NULL;
           }
   
           mutex_lock(&pcpu_alloc_mutex);
           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))) {
                           spin_unlock_irqrestore(&pcpu_lock, flags);
                           if (pcpu_extend_area_map(chunk, new_alloc) < 0) {
                                   err = "failed to extend area map of reserved chunk";
                                   goto fail_unlock_mutex;
                           }
                           spin_lock_irqsave(&pcpu_lock, flags);
                   }
   
                   off = pcpu_alloc_area(chunk, size, align);
                   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);
                           if (new_alloc) {
                                   spin_unlock_irqrestore(&pcpu_lock, flags);
                                   if (pcpu_extend_area_map(chunk,
                                                            new_alloc) < 0) {
                                           err = "failed to extend area map";
                                           goto fail_unlock_mutex;
                                   }
                                   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);
                           if (off >= 0)
                                   goto area_found;
                   }
           }
   
           /* hmmm... no space left, create a new chunk */
           spin_unlock_irqrestore(&pcpu_lock, flags);
   
           chunk = pcpu_create_chunk();
           if (!chunk) {
                   err = "failed to allocate new chunk";
                   goto fail_unlock_mutex;
           }
   
           spin_lock_irqsave(&pcpu_lock, flags);
           pcpu_chunk_relocate(chunk, -1);
           goto restart;
   
   area_found:
           spin_unlock_irqrestore(&pcpu_lock, flags);
   
           /* populate, map and clear the area */
           if (pcpu_populate_chunk(chunk, off, size)) {
                   spin_lock_irqsave(&pcpu_lock, flags);
                   pcpu_free_area(chunk, off);
                   err = "failed to populate";
                   goto fail_unlock;
           }
   
           mutex_unlock(&pcpu_alloc_mutex);
   
           /* return address relative to base address */
           ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
           kmemleak_alloc_percpu(ptr, size);
           return ptr;
   
   fail_unlock:
           spin_unlock_irqrestore(&pcpu_lock, flags);
   fail_unlock_mutex:
           mutex_unlock(&pcpu_alloc_mutex);
           if (warn_limit) {
                   pr_warning("PERCPU: allocation failed, size=%zu align=%zu, "
                              "%s\n", size, align, err);
                   dump_stack();
                   if (!--warn_limit)
                           pr_info("PERCPU: limit reached, disable warning\n");
           }
           return NULL;
   }
   
   /**
    * __alloc_percpu - allocate dynamic 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.
    * 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_percpu(size_t size, size_t align)
   {
           return pcpu_alloc(size, align, false);
   }
   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);
   }
   
   /**
    * pcpu_reclaim - reclaim fully free chunks, workqueue function
    * @work: unused
    *
    * Reclaim all fully free chunks except for the first one.
    *
    * CONTEXT:
    * workqueue context.
    */
   static void pcpu_reclaim(struct work_struct *work)
   {
           LIST_HEAD(todo);
           struct list_head *head = &pcpu_slot[pcpu_nr_slots - 1];
           struct pcpu_chunk *chunk, *next;
   
           mutex_lock(&pcpu_alloc_mutex);
           spin_lock_irq(&pcpu_lock);
   
           list_for_each_entry_safe(chunk, next, head, list) {
                   WARN_ON(chunk->immutable);
   
                   /* spare the first one */
                   if (chunk == list_first_entry(head, struct pcpu_chunk, list))
                           continue;
   
                   list_move(&chunk->list, &todo);
           }
   
           spin_unlock_irq(&pcpu_lock);
   
           list_for_each_entry_safe(chunk, next, &todo, list) {
                   pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size);
                   pcpu_destroy_chunk(chunk);
           }
   
           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;
   
           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_size == pcpu_unit_size) {
                   struct pcpu_chunk *pos;
   
                   list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
                           if (pos != chunk) {
                                   schedule_work(&pcpu_reclaim_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 tranlated 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 = alloc_bootmem_nopanic(PFN_ALIGN(ai_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)
  {
          free_bootmem(__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 "\n");
                                  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 "\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.
   *
   * 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 char cpus_buf[4096] __initdata;
          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;
  
          cpumask_scnprintf(cpus_buf, sizeof(cpus_buf), cpu_possible_mask);
  
  #define PCPU_SETUP_BUG_ON(cond) do {                                    \
          if (unlikely(cond)) {                                           \
                  pr_emerg("PERCPU: failed to initialize, %s", #cond);    \
                  pr_emerg("PERCPU: cpu_possible_mask=%s\n", cpus_buf);   \
                  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 = alloc_bootmem(ai->nr_groups * sizeof(group_offsets[0]));
          group_sizes = alloc_bootmem(ai->nr_groups * sizeof(group_sizes[0]));
          unit_map = alloc_bootmem(nr_cpu_ids * sizeof(unit_map[0]));
          unit_off = alloc_bootmem(nr_cpu_ids * sizeof(unit_off[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 = alloc_bootmem(pcpu_nr_slots * sizeof(pcpu_slot[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 = alloc_bootmem(pcpu_chunk_struct_size);
          INIT_LIST_HEAD(&schunk->list);
          schunk->base_addr = base_addr;
          schunk->map = smap;
          schunk->map_alloc = ARRAY_SIZE(smap);
          schunk->immutable = true;
          bitmap_fill(schunk->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[schunk->map_used++] = -ai->static_size;
          if (schunk->free_size)
                  schunk->map[schunk->map_used++] = schunk->free_size;
  
          /* init dynamic chunk if necessary */
          if (dyn_size) {
                  dchunk = alloc_bootmem(pcpu_chunk_struct_size);
                  INIT_LIST_HEAD(&dchunk->list);
                  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->contig_hint = dchunk->free_size = dyn_size;
                  dchunk->map[dchunk->map_used++] = -pcpu_reserved_chunk_limit;
                  dchunk->map[dchunk->map_used++] = dchunk->free_size;
          }
  
          /* link the first chunk in */
          pcpu_first_chunk = dchunk ?: schunk;
          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\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 mutliples 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);
  
          alloc_size = roundup(min_unit_size, atom_size);
          upa = alloc_size / min_unit_size;
          while (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
                  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]++;
          }
  
          /*
           * Expand unit size until address space usage goes over 75%
           * and then as much as possible without using more address
           * space.
           */
          last_allocs = INT_MAX;
          for (upa = max_upa; upa; upa--) {
                  int allocs = 0, wasted = 0;
  
                  if (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
                          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, max_distance;
          int group, i, 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 = alloc_bootmem_nopanic(areas_size);
          if (!areas) {
                  rc = -ENOMEM;
                  goto out_free;
          }
  
          /* allocate, copy and determine base address */
          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);
          }
  
          /*
           * 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 */
          max_distance = 0;
          for (group = 0; group < ai->nr_groups; group++) {
                  ai->groups[group].base_offset = areas[group] - base;
                  max_distance = max_t(size_t, max_distance,
                                       ai->groups[group].base_offset);
          }
          max_distance += ai->unit_size;
  
          /* warn if maximum distance is further than 75% of vmalloc space */
          if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) {
                  pr_warning("PERCPU: max_distance=0x%zx too large for vmalloc "
                             "space 0x%lx\n", max_distance,
                             (unsigned long)(VMALLOC_END - VMALLOC_START));
  #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
                  /* and fail if we have fallback */
                  rc = -EINVAL;
                  goto out_free;
  #endif
          }
  
          pr_info("PERCPU: Embedded %zu pages/cpu @%p s%zu r%zu d%zu u%zu\n",
                  PFN_DOWN(size_sum), base, 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++)
                  free_fn(areas[group],
                          ai->groups[group].nr_units * ai->unit_size);
  out_free:
          pcpu_free_alloc_info(ai);
          if (areas)
                  free_bootmem(__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;
  
          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);
          BUG_ON(ai->groups[0].nr_units != num_possible_cpus());
  
          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 = alloc_bootmem(pages_size);
  
          /* allocate pages */
          j = 0;
          for (unit = 0; unit < num_possible_cpus(); unit++)
                  for (i = 0; i < unit_pages; i++) {
                          unsigned int cpu = ai->groups[0].cpu_map[unit];
                          void *ptr;
  
                          ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
                          if (!ptr) {
                                  pr_warning("PERCPU: 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("PERCPU: %d %s pages/cpu @%p s%zu r%zu d%zu\n",
                  unit_pages, psize_str, vm.addr, 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:
          free_bootmem(__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 __alloc_bootmem_nopanic(size, align, __pa(MAX_DMA_ADDRESS));
  }
  
  static void __init pcpu_dfl_fc_free(void *ptr, size_t size)
  {
          free_bootmem(__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 = __alloc_bootmem(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.");
  }
  
  #endif  /* CONFIG_SMP */
  
  /*
   * First and reserved chunks are initialized with temporary allocation
   * map in initdata so that they can be used before slab is online.
   * This function is called after slab is brought up and replaces those
   * with properly allocated maps.
   */
  void __init percpu_init_late(void)
  {
          struct pcpu_chunk *target_chunks[] =
                  { pcpu_first_chunk, pcpu_reserved_chunk, NULL };
          struct pcpu_chunk *chunk;
          unsigned long flags;
          int i;
  
          for (i = 0; (chunk = target_chunks[i]); i++) {
                  int *map;
                  const size_t size = PERCPU_DYNAMIC_EARLY_SLOTS * sizeof(map[0]);
  
                  BUILD_BUG_ON(size > PAGE_SIZE);
  
                  map = pcpu_mem_zalloc(size);
                  BUG_ON(!map);
  
                  spin_lock_irqsave(&pcpu_lock, flags);
                  memcpy(map, chunk->map, size);
                  chunk->map = map;
                  spin_unlock_irqrestore(&pcpu_lock, flags);
          }
  }

Cache object: 331a47752037d2c298c24fd25ce6885b