sparsemem: Fix compilation on PowerPC
[linux-2.6.git] / mm / percpu.c
index 41e7a5f..083e7c9 100644 (file)
@@ -8,12 +8,13 @@
  *
  * This is percpu allocator which can handle both static and dynamic
  * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
- * chunk is consisted of num_possible_cpus() units and the first chunk
- * is used for static percpu variables in the kernel image (special
- * boot time alloc/init handling necessary as these areas need to be
- * brought up before allocation services are running).  Unit grows as
- * necessary and all units grow or shrink in unison.  When a chunk is
- * filled up, another chunk is allocated.  ie. in vmalloc area
+ * 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.  ie. in
+ * vmalloc area
  *
  *  c0                           c1                         c2
  *  -------------------          -------------------        ------------
  *
  * Allocation is done in offset-size areas of single unit space.  Ie,
  * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
- * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring
- * percpu base registers UNIT_SIZE apart.
+ * 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 as
- * small as 4 bytes.  The allocator organizes chunks into lists
+ * 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 eqaul to or larger than the maximum contiguous
  * region and negative allocated.  Allocation inside a chunk is done
  * by scanning this map sequentially and serving the first matching
  * entry.  This is mostly copied from the percpu_modalloc() allocator.
- * Chunks are also linked into a rb tree to ease address to chunk
- * mapping during free.
+ * 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 CONFIG_HAVE_DYNAMIC_PER_CPU_AREA
- *
  * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
- *   regular address to percpu pointer and back
+ *   regular address to percpu pointer and back if they need to be
+ *   different from the default
  *
- * - use pcpu_setup_static() during percpu area initialization to
- *   setup kernel static percpu area
+ * - 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/rbtree.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 #include <linux/vmalloc.h>
+#include <linux/workqueue.h>
 
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 #include <asm/tlbflush.h>
+#include <asm/io.h>
 
-#define PCPU_MIN_UNIT_PAGES_SHIFT      4       /* also max alloc size */
 #define PCPU_SLOT_BASE_SHIFT           5       /* 1-31 shares the same slot */
 #define PCPU_DFL_MAP_ALLOC             16      /* start a map with 16 ents */
 
+/* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
+#ifndef __addr_to_pcpu_ptr
+#define __addr_to_pcpu_ptr(addr)                                       \
+       (void *)((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 *)((unsigned long)(ptr) + (unsigned long)pcpu_base_addr   \
+                - (unsigned long)__per_cpu_start)
+#endif
+
 struct pcpu_chunk {
        struct list_head        list;           /* linked to pcpu_slot lists */
-       struct rb_node          rb_node;        /* key is chunk->vm->addr */
        int                     free_size;      /* free bytes in the chunk */
        int                     contig_hint;    /* max contiguous size hint */
-       struct vm_struct        *vm;            /* mapped vmalloc region */
+       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 */
-       struct page             *page[];        /* #cpus * UNIT_PAGES */
+       struct vm_struct        **vms;          /* mapped vmalloc regions */
+       bool                    immutable;      /* no [de]population allowed */
+       unsigned long           populated[];    /* populated bitmap */
 };
 
-static int pcpu_unit_pages_shift;
-static int pcpu_unit_pages;
-static int pcpu_unit_shift;
-static int pcpu_unit_size;
-static int pcpu_chunk_size;
-static int pcpu_nr_slots;
-static size_t pcpu_chunk_struct_size;
+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 numbers */
+static unsigned int pcpu_first_unit_cpu __read_mostly;
+static unsigned int pcpu_last_unit_cpu __read_mostly;
 
 /* the address of the first chunk which starts with the kernel static area */
-void *pcpu_base_addr;
+void *pcpu_base_addr __read_mostly;
 EXPORT_SYMBOL_GPL(pcpu_base_addr);
 
-/* the size of kernel static area */
-static int pcpu_static_size;
+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;
 
 /*
- * One mutex to rule them all.
+ * Synchronization rules.
  *
- * The following mutex is grabbed in the outermost public alloc/free
- * interface functions and released only when the operation is
- * complete.  As such, every function in this file other than the
- * outermost functions are called under pcpu_mutex.
+ * 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.
  *
- * It can easily be switched to use spinlock such that only the area
- * allocation and page population commit are protected with it doing
- * actual [de]allocation without holding any lock.  However, given
- * what this allocator does, I think it's better to let them run
- * sequentially.
+ * 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_mutex);
+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;            /* chunk list slots */
-static struct rb_root pcpu_addr_root = RB_ROOT;        /* chunks by address */
+static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
 
-static int pcpu_size_to_slot(int size)
+/* 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 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))
@@ -133,62 +198,104 @@ static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
 
 static int pcpu_page_idx(unsigned int cpu, int page_idx)
 {
-       return (cpu << pcpu_unit_pages_shift) + page_idx;
+       return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
 }
 
-static struct page **pcpu_chunk_pagep(struct pcpu_chunk *chunk,
-                                     unsigned int cpu, int page_idx)
+static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
+                                    unsigned int cpu, int page_idx)
 {
-       return &chunk->page[pcpu_page_idx(cpu, page_idx)];
+       return (unsigned long)chunk->base_addr + pcpu_unit_offsets[cpu] +
+               (page_idx << PAGE_SHIFT);
 }
 
-static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
-                                    unsigned int cpu, int page_idx)
+static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
+                                   unsigned int cpu, int page_idx)
+{
+       /* must not be used on pre-mapped chunk */
+       WARN_ON(chunk->immutable);
+
+       return vmalloc_to_page((void *)pcpu_chunk_addr(chunk, cpu, page_idx));
+}
+
+/* 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 (unsigned long)chunk->vm->addr +
-               (pcpu_page_idx(cpu, page_idx) << PAGE_SHIFT);
+       return (struct pcpu_chunk *)page->index;
 }
 
-static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
-                                    int page_idx)
+static void pcpu_next_unpop(struct pcpu_chunk *chunk, int *rs, int *re, int end)
 {
-       return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
+       *rs = find_next_zero_bit(chunk->populated, end, *rs);
+       *re = find_next_bit(chunk->populated, end, *rs + 1);
 }
 
+static void 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 betwen @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_realloc - versatile realloc
- * @p: the current pointer (can be NULL for new allocations)
- * @size: the current size in bytes (can be 0 for new allocations)
- * @new_size: the wanted new size in bytes (can be 0 for free)
+ * pcpu_mem_alloc - allocate memory
+ * @size: bytes to allocate
+ *
+ * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,
+ * kzalloc() is used; otherwise, vmalloc() is used.  The returned
+ * memory is always zeroed.
  *
- * More robust realloc which can be used to allocate, resize or free a
- * memory area of arbitrary size.  If the needed size goes over
- * PAGE_SIZE, kernel VM is used.
+ * CONTEXT:
+ * Does GFP_KERNEL allocation.
  *
  * RETURNS:
- * The new pointer on success, NULL on failure.
+ * Pointer to the allocated area on success, NULL on failure.
  */
-static void *pcpu_realloc(void *p, size_t size, size_t new_size)
+static void *pcpu_mem_alloc(size_t size)
 {
-       void *new;
-
-       if (new_size <= PAGE_SIZE)
-               new = kmalloc(new_size, GFP_KERNEL);
-       else
-               new = vmalloc(new_size);
-       if (new_size && !new)
-               return NULL;
-
-       memcpy(new, p, min(size, new_size));
-       if (new_size > size)
-               memset(new + size, 0, new_size - size);
+       if (size <= PAGE_SIZE)
+               return kzalloc(size, GFP_KERNEL);
+       else {
+               void *ptr = vmalloc(size);
+               if (ptr)
+                       memset(ptr, 0, size);
+               return ptr;
+       }
+}
 
+/**
+ * pcpu_mem_free - free memory
+ * @ptr: memory to free
+ * @size: size of the area
+ *
+ * Free @ptr.  @ptr should have been allocated using pcpu_mem_alloc().
+ */
+static void pcpu_mem_free(void *ptr, size_t size)
+{
        if (size <= PAGE_SIZE)
-               kfree(p);
+               kfree(ptr);
        else
-               vfree(p);
-
-       return new;
+               vfree(ptr);
 }
 
 /**
@@ -198,13 +305,17 @@ static void *pcpu_realloc(void *p, size_t size, size_t new_size)
  *
  * 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.
+ * 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 (oslot != nslot) {
+       if (chunk != pcpu_reserved_chunk && oslot != nslot) {
                if (oslot < nslot)
                        list_move(&chunk->list, &pcpu_slot[nslot]);
                else
@@ -212,78 +323,118 @@ static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
        }
 }
 
-static struct rb_node **pcpu_chunk_rb_search(void *addr,
-                                            struct rb_node **parentp)
+/**
+ * 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)
 {
-       struct rb_node **p = &pcpu_addr_root.rb_node;
-       struct rb_node *parent = NULL;
-       struct pcpu_chunk *chunk;
-
-       while (*p) {
-               parent = *p;
-               chunk = rb_entry(parent, struct pcpu_chunk, rb_node);
-
-               if (addr < chunk->vm->addr)
-                       p = &(*p)->rb_left;
-               else if (addr > chunk->vm->addr)
-                       p = &(*p)->rb_right;
-               else
-                       break;
+       void *first_start = pcpu_first_chunk->base_addr;
+
+       /* is it in the first chunk? */
+       if (addr >= first_start && addr < first_start + pcpu_unit_size) {
+               /* is it in the reserved area? */
+               if (addr < first_start + pcpu_reserved_chunk_limit)
+                       return pcpu_reserved_chunk;
+               return pcpu_first_chunk;
        }
 
-       if (parentp)
-               *parentp = parent;
-       return p;
+       /*
+        * 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(vmalloc_to_page(addr));
 }
 
 /**
- * pcpu_chunk_addr_search - search for chunk containing specified address
- * @addr: address to search for
+ * pcpu_need_to_extend - determine whether chunk area map needs to be extended
+ * @chunk: chunk of interest
  *
- * Look for chunk which might contain @addr.  More specifically, it
- * searchs for the chunk with the highest start address which isn't
- * beyond @addr.
+ * Determine whether area map of @chunk needs to be extended to
+ * accomodate a new allocation.
+ *
+ * CONTEXT:
+ * pcpu_lock.
  *
  * RETURNS:
- * The address of the found chunk.
+ * New target map allocation length if extension is necessary, 0
+ * otherwise.
  */
-static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
+static int pcpu_need_to_extend(struct pcpu_chunk *chunk)
 {
-       struct rb_node *n, *parent;
-       struct pcpu_chunk *chunk;
+       int new_alloc;
 
-       n = *pcpu_chunk_rb_search(addr, &parent);
-       if (!n) {
-               /* no exactly matching chunk, the parent is the closest */
-               n = parent;
-               BUG_ON(!n);
-       }
-       chunk = rb_entry(n, struct pcpu_chunk, rb_node);
+       if (chunk->map_alloc >= chunk->map_used + 2)
+               return 0;
 
-       if (addr < chunk->vm->addr) {
-               /* the parent was the next one, look for the previous one */
-               n = rb_prev(n);
-               BUG_ON(!n);
-               chunk = rb_entry(n, struct pcpu_chunk, rb_node);
-       }
+       new_alloc = PCPU_DFL_MAP_ALLOC;
+       while (new_alloc < chunk->map_used + 2)
+               new_alloc *= 2;
 
-       return chunk;
+       return new_alloc;
 }
 
 /**
- * pcpu_chunk_addr_insert - insert chunk into address rb tree
- * @new: chunk to insert
+ * 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.
  *
- * Insert @new into address rb tree.
+ * CONTEXT:
+ * Does GFP_KERNEL allocation.  Grabs and releases pcpu_lock.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
  */
-static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
+static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
 {
-       struct rb_node **p, *parent;
+       int *old = NULL, *new = NULL;
+       size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
+       unsigned long flags;
+
+       new = pcpu_mem_alloc(new_size);
+       if (!new)
+               return -ENOMEM;
 
-       p = pcpu_chunk_rb_search(new->vm->addr, &parent);
-       BUG_ON(*p);
-       rb_link_node(&new->rb_node, parent, p);
-       rb_insert_color(&new->rb_node, &pcpu_addr_root);
+       /* 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]);
+       memcpy(new, chunk->map, old_size);
+
+       /*
+        * map_alloc < PCPU_DFL_MAP_ALLOC indicates that the chunk is
+        * one of the first chunks and still using static map.
+        */
+       if (chunk->map_alloc >= PCPU_DFL_MAP_ALLOC)
+               old = chunk->map;
+
+       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;
 }
 
 /**
@@ -301,33 +452,19 @@ static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
  * depending on @head, is reduced by @tail bytes and @tail byte block
  * is inserted after the target block.
  *
- * RETURNS:
- * 0 on success, -errno on failure.
+ * @chunk->map must have enough free slots to accomodate the split.
+ *
+ * CONTEXT:
+ * pcpu_lock.
  */
-static int pcpu_split_block(struct pcpu_chunk *chunk, int i, int head, int tail)
+static void pcpu_split_block(struct pcpu_chunk *chunk, int i,
+                            int head, int tail)
 {
        int nr_extra = !!head + !!tail;
-       int target = chunk->map_used + nr_extra;
 
-       /* reallocation required? */
-       if (chunk->map_alloc < target) {
-               int new_alloc = chunk->map_alloc;
-               int *new;
+       BUG_ON(chunk->map_alloc < chunk->map_used + nr_extra);
 
-               while (new_alloc < target)
-                       new_alloc *= 2;
-
-               new = pcpu_realloc(chunk->map,
-                                  chunk->map_alloc * sizeof(new[0]),
-                                  new_alloc * sizeof(new[0]));
-               if (!new)
-                       return -ENOMEM;
-
-               chunk->map_alloc = new_alloc;
-               chunk->map = new;
-       }
-
-       /* insert a new subblock */
+       /* 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;
@@ -340,7 +477,6 @@ static int pcpu_split_block(struct pcpu_chunk *chunk, int i, int head, int tail)
                chunk->map[i++] -= tail;
                chunk->map[i] = tail;
        }
-       return 0;
 }
 
 /**
@@ -353,8 +489,14 @@ static int pcpu_split_block(struct pcpu_chunk *chunk, int i, int head, int tail)
  * 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, -errno on failure.
+ * 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)
 {
@@ -362,22 +504,6 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
        int max_contig = 0;
        int i, off;
 
-       /*
-        * The static chunk initially doesn't have map attached
-        * because kmalloc wasn't available during init.  Give it one.
-        */
-       if (unlikely(!chunk->map)) {
-               chunk->map = pcpu_realloc(NULL, 0,
-                               PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
-               if (!chunk->map)
-                       return -ENOMEM;
-
-               chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
-               chunk->map[chunk->map_used++] = -pcpu_static_size;
-               if (chunk->free_size)
-                       chunk->map[chunk->map_used++] = chunk->free_size;
-       }
-
        for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
                bool is_last = i + 1 == chunk->map_used;
                int head, tail;
@@ -418,8 +544,7 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
 
                /* split if warranted */
                if (head || tail) {
-                       if (pcpu_split_block(chunk, i, head, tail))
-                               return -ENOMEM;
+                       pcpu_split_block(chunk, i, head, tail);
                        if (head) {
                                i++;
                                off += head;
@@ -446,14 +571,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
        chunk->contig_hint = max_contig;        /* fully scanned */
        pcpu_chunk_relocate(chunk, oslot);
 
-       /*
-        * Tell the upper layer that this chunk has no area left.
-        * Note that this is not an error condition but a notification
-        * to upper layer that it needs to look at other chunks.
-        * -ENOSPC is chosen as it isn't used in memory subsystem and
-        * matches the meaning in a way.
-        */
-       return -ENOSPC;
+       /* tell the upper layer that this chunk has no matching area */
+       return -1;
 }
 
 /**
@@ -464,6 +583,9 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
  * 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)
 {
@@ -500,117 +622,327 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
 }
 
 /**
- * pcpu_unmap - unmap pages out of a pcpu_chunk
+ * pcpu_get_pages_and_bitmap - get temp pages array and bitmap
  * @chunk: chunk of interest
- * @page_start: page index of the first page to unmap
- * @page_end: page index of the last page to unmap + 1
- * @flush: whether to flush cache and tlb or not
+ * @bitmapp: output parameter for bitmap
+ * @may_alloc: may allocate the array
  *
- * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
- * If @flush is true, vcache is flushed before unmapping and tlb
- * after.
+ * Returns pointer to array of pointers to struct page and bitmap,
+ * both of which can be indexed with pcpu_page_idx().  The returned
+ * array is cleared to zero and *@bitmapp is copied from
+ * @chunk->populated.  Note that there is only one array and bitmap
+ * and access exclusion is the caller's responsibility.
+ *
+ * CONTEXT:
+ * pcpu_alloc_mutex and does GFP_KERNEL allocation if @may_alloc.
+ * Otherwise, don't care.
+ *
+ * RETURNS:
+ * Pointer to temp pages array on success, NULL on failure.
  */
-static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
-                      bool flush)
+static struct page **pcpu_get_pages_and_bitmap(struct pcpu_chunk *chunk,
+                                              unsigned long **bitmapp,
+                                              bool may_alloc)
 {
-       unsigned int last = num_possible_cpus() - 1;
-       unsigned int cpu;
+       static struct page **pages;
+       static unsigned long *bitmap;
+       size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
+       size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
+                            sizeof(unsigned long);
+
+       if (!pages || !bitmap) {
+               if (may_alloc && !pages)
+                       pages = pcpu_mem_alloc(pages_size);
+               if (may_alloc && !bitmap)
+                       bitmap = pcpu_mem_alloc(bitmap_size);
+               if (!pages || !bitmap)
+                       return NULL;
+       }
 
-       /*
-        * Each flushing trial can be very expensive, issue flush on
-        * the whole region at once rather than doing it for each cpu.
-        * This could be an overkill but is more scalable.
-        */
-       if (flush)
-               flush_cache_vunmap(pcpu_chunk_addr(chunk, 0, page_start),
-                                  pcpu_chunk_addr(chunk, last, page_end));
+       memset(pages, 0, pages_size);
+       bitmap_copy(bitmap, chunk->populated, pcpu_unit_pages);
 
-       for_each_possible_cpu(cpu)
-               unmap_kernel_range_noflush(
-                               pcpu_chunk_addr(chunk, cpu, page_start),
-                               (page_end - page_start) << PAGE_SHIFT);
+       *bitmapp = bitmap;
+       return pages;
+}
+
+/**
+ * pcpu_free_pages - free pages which were allocated for @chunk
+ * @chunk: chunk pages were allocated for
+ * @pages: array of pages to be freed, indexed by pcpu_page_idx()
+ * @populated: populated bitmap
+ * @page_start: page index of the first page to be freed
+ * @page_end: page index of the last page to be freed + 1
+ *
+ * Free pages [@page_start and @page_end) in @pages for all units.
+ * The pages were allocated for @chunk.
+ */
+static void pcpu_free_pages(struct pcpu_chunk *chunk,
+                           struct page **pages, unsigned long *populated,
+                           int page_start, int page_end)
+{
+       unsigned int cpu;
+       int i;
+
+       for_each_possible_cpu(cpu) {
+               for (i = page_start; i < page_end; i++) {
+                       struct page *page = pages[pcpu_page_idx(cpu, i)];
 
-       /* ditto as flush_cache_vunmap() */
-       if (flush)
-               flush_tlb_kernel_range(pcpu_chunk_addr(chunk, 0, page_start),
-                                      pcpu_chunk_addr(chunk, last, page_end));
+                       if (page)
+                               __free_page(page);
+               }
+       }
 }
 
 /**
- * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
- * @chunk: chunk to depopulate
- * @off: offset to the area to depopulate
- * @size: size of the area to depopulate in bytes
- * @flush: whether to flush cache and tlb or not
+ * pcpu_alloc_pages - allocates pages for @chunk
+ * @chunk: target chunk
+ * @pages: array to put the allocated pages into, indexed by pcpu_page_idx()
+ * @populated: populated bitmap
+ * @page_start: page index of the first page to be allocated
+ * @page_end: page index of the last page to be allocated + 1
  *
- * For each cpu, depopulate and unmap pages [@page_start,@page_end)
- * from @chunk.  If @flush is true, vcache is flushed before unmapping
- * and tlb after.
+ * Allocate pages [@page_start,@page_end) into @pages for all units.
+ * The allocation is for @chunk.  Percpu core doesn't care about the
+ * content of @pages and will pass it verbatim to pcpu_map_pages().
  */
-static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size,
-                                 bool flush)
+static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
+                           struct page **pages, unsigned long *populated,
+                           int page_start, int page_end)
 {
-       int page_start = PFN_DOWN(off);
-       int page_end = PFN_UP(off + size);
-       int unmap_start = -1;
-       int uninitialized_var(unmap_end);
+       const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
        unsigned int cpu;
        int i;
 
-       for (i = page_start; i < page_end; i++) {
-               for_each_possible_cpu(cpu) {
-                       struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+       for_each_possible_cpu(cpu) {
+               for (i = page_start; i < page_end; i++) {
+                       struct page **pagep = &pages[pcpu_page_idx(cpu, i)];
 
-                       if (!*pagep)
-                               continue;
+                       *pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
+                       if (!*pagep) {
+                               pcpu_free_pages(chunk, pages, populated,
+                                               page_start, page_end);
+                               return -ENOMEM;
+                       }
+               }
+       }
+       return 0;
+}
 
-                       __free_page(*pagep);
+/**
+ * pcpu_pre_unmap_flush - flush cache prior to unmapping
+ * @chunk: chunk the regions to be flushed belongs to
+ * @page_start: page index of the first page to be flushed
+ * @page_end: page index of the last page to be flushed + 1
+ *
+ * Pages in [@page_start,@page_end) of @chunk are about to be
+ * unmapped.  Flush cache.  As each flushing trial can be very
+ * expensive, issue flush on the whole region at once rather than
+ * doing it for each cpu.  This could be an overkill but is more
+ * scalable.
+ */
+static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
+                                int page_start, int page_end)
+{
+       flush_cache_vunmap(
+               pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
+               pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
+}
+
+static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
+{
+       unmap_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT);
+}
+
+/**
+ * pcpu_unmap_pages - unmap pages out of a pcpu_chunk
+ * @chunk: chunk of interest
+ * @pages: pages array which can be used to pass information to free
+ * @populated: populated bitmap
+ * @page_start: page index of the first page to unmap
+ * @page_end: page index of the last page to unmap + 1
+ *
+ * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
+ * Corresponding elements in @pages were cleared by the caller and can
+ * be used to carry information to pcpu_free_pages() which will be
+ * called after all unmaps are finished.  The caller should call
+ * proper pre/post flush functions.
+ */
+static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
+                            struct page **pages, unsigned long *populated,
+                            int page_start, int page_end)
+{
+       unsigned int cpu;
+       int i;
 
-                       /*
-                        * If it's partial depopulation, it might get
-                        * populated or depopulated again.  Mark the
-                        * page gone.
-                        */
-                       *pagep = NULL;
+       for_each_possible_cpu(cpu) {
+               for (i = page_start; i < page_end; i++) {
+                       struct page *page;
 
-                       unmap_start = unmap_start < 0 ? i : unmap_start;
-                       unmap_end = i + 1;
+                       page = pcpu_chunk_page(chunk, cpu, i);
+                       WARN_ON(!page);
+                       pages[pcpu_page_idx(cpu, i)] = page;
                }
+               __pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
+                                  page_end - page_start);
        }
 
-       if (unmap_start >= 0)
-               pcpu_unmap(chunk, unmap_start, unmap_end, flush);
+       for (i = page_start; i < page_end; i++)
+               __clear_bit(i, populated);
 }
 
 /**
- * pcpu_map - map pages into a pcpu_chunk
+ * pcpu_post_unmap_tlb_flush - flush TLB after unmapping
+ * @chunk: pcpu_chunk the regions to be flushed belong to
+ * @page_start: page index of the first page to be flushed
+ * @page_end: page index of the last page to be flushed + 1
+ *
+ * Pages [@page_start,@page_end) of @chunk have been unmapped.  Flush
+ * TLB for the regions.  This can be skipped if the area is to be
+ * returned to vmalloc as vmalloc will handle TLB flushing lazily.
+ *
+ * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
+ * for the whole region.
+ */
+static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
+                                     int page_start, int page_end)
+{
+       flush_tlb_kernel_range(
+               pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
+               pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
+}
+
+static int __pcpu_map_pages(unsigned long addr, struct page **pages,
+                           int nr_pages)
+{
+       return map_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT,
+                                       PAGE_KERNEL, pages);
+}
+
+/**
+ * pcpu_map_pages - map pages into a pcpu_chunk
  * @chunk: chunk of interest
+ * @pages: pages array containing pages to be mapped
+ * @populated: populated bitmap
  * @page_start: page index of the first page to map
  * @page_end: page index of the last page to map + 1
  *
- * For each cpu, map pages [@page_start,@page_end) into @chunk.
- * vcache is flushed afterwards.
+ * For each cpu, map pages [@page_start,@page_end) into @chunk.  The
+ * caller is responsible for calling pcpu_post_map_flush() after all
+ * mappings are complete.
+ *
+ * This function is responsible for setting corresponding bits in
+ * @chunk->populated bitmap and whatever is necessary for reverse
+ * lookup (addr -> chunk).
  */
-static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
+static int pcpu_map_pages(struct pcpu_chunk *chunk,
+                         struct page **pages, unsigned long *populated,
+                         int page_start, int page_end)
 {
-       unsigned int last = num_possible_cpus() - 1;
-       unsigned int cpu;
-       int err;
+       unsigned int cpu, tcpu;
+       int i, err;
 
        for_each_possible_cpu(cpu) {
-               err = map_kernel_range_noflush(
-                               pcpu_chunk_addr(chunk, cpu, page_start),
-                               (page_end - page_start) << PAGE_SHIFT,
-                               PAGE_KERNEL,
-                               pcpu_chunk_pagep(chunk, cpu, page_start));
+               err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
+                                      &pages[pcpu_page_idx(cpu, page_start)],
+                                      page_end - page_start);
                if (err < 0)
-                       return err;
+                       goto err;
+       }
+
+       /* mapping successful, link chunk and mark populated */
+       for (i = page_start; i < page_end; i++) {
+               for_each_possible_cpu(cpu)
+                       pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
+                                           chunk);
+               __set_bit(i, populated);
        }
 
-       /* flush at once, please read comments in pcpu_unmap() */
-       flush_cache_vmap(pcpu_chunk_addr(chunk, 0, page_start),
-                        pcpu_chunk_addr(chunk, last, page_end));
        return 0;
+
+err:
+       for_each_possible_cpu(tcpu) {
+               if (tcpu == cpu)
+                       break;
+               __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
+                                  page_end - page_start);
+       }
+       return err;
+}
+
+/**
+ * pcpu_post_map_flush - flush cache after mapping
+ * @chunk: pcpu_chunk the regions to be flushed belong to
+ * @page_start: page index of the first page to be flushed
+ * @page_end: page index of the last page to be flushed + 1
+ *
+ * Pages [@page_start,@page_end) of @chunk have been mapped.  Flush
+ * cache.
+ *
+ * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
+ * for the whole region.
+ */
+static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
+                               int page_start, int page_end)
+{
+       flush_cache_vmap(
+               pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
+               pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
+}
+
+/**
+ * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
+ * @chunk: chunk to depopulate
+ * @off: offset to the area to depopulate
+ * @size: size of the area to depopulate in bytes
+ * @flush: whether to flush cache and tlb or not
+ *
+ * For each cpu, depopulate and unmap pages [@page_start,@page_end)
+ * from @chunk.  If @flush is true, vcache is flushed before unmapping
+ * and tlb after.
+ *
+ * CONTEXT:
+ * pcpu_alloc_mutex.
+ */
+static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
+{
+       int page_start = PFN_DOWN(off);
+       int page_end = PFN_UP(off + size);
+       struct page **pages;
+       unsigned long *populated;
+       int rs, re;
+
+       /* quick path, check whether it's empty already */
+       pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
+               if (rs == page_start && re == page_end)
+                       return;
+               break;
+       }
+
+       /* immutable chunks can't be depopulated */
+       WARN_ON(chunk->immutable);
+
+       /*
+        * If control reaches here, there must have been at least one
+        * successful population attempt so the temp pages array must
+        * be available now.
+        */
+       pages = pcpu_get_pages_and_bitmap(chunk, &populated, false);
+       BUG_ON(!pages);
+
+       /* unmap and free */
+       pcpu_pre_unmap_flush(chunk, page_start, page_end);
+
+       pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
+               pcpu_unmap_pages(chunk, pages, populated, rs, re);
+
+       /* no need to flush tlb, vmalloc will handle it lazily */
+
+       pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
+               pcpu_free_pages(chunk, pages, populated, rs, re);
+
+       /* commit new bitmap */
+       bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
 }
 
 /**
@@ -621,61 +953,75 @@ static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
  *
  * For each cpu, populate and map pages [@page_start,@page_end) into
  * @chunk.  The area is cleared on return.
+ *
+ * CONTEXT:
+ * pcpu_alloc_mutex, does GFP_KERNEL allocation.
  */
 static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
 {
-       const gfp_t alloc_mask = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
        int page_start = PFN_DOWN(off);
        int page_end = PFN_UP(off + size);
-       int map_start = -1;
-       int map_end;
+       int free_end = page_start, unmap_end = page_start;
+       struct page **pages;
+       unsigned long *populated;
        unsigned int cpu;
-       int i;
+       int rs, re, rc;
 
-       for (i = page_start; i < page_end; i++) {
-               if (pcpu_chunk_page_occupied(chunk, i)) {
-                       if (map_start >= 0) {
-                               if (pcpu_map(chunk, map_start, map_end))
-                                       goto err;
-                               map_start = -1;
-                       }
-                       continue;
-               }
+       /* quick path, check whether all pages are already there */
+       pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end) {
+               if (rs == page_start && re == page_end)
+                       goto clear;
+               break;
+       }
 
-               map_start = map_start < 0 ? i : map_start;
-               map_end = i + 1;
+       /* need to allocate and map pages, this chunk can't be immutable */
+       WARN_ON(chunk->immutable);
 
-               for_each_possible_cpu(cpu) {
-                       struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+       pages = pcpu_get_pages_and_bitmap(chunk, &populated, true);
+       if (!pages)
+               return -ENOMEM;
 
-                       *pagep = alloc_pages_node(cpu_to_node(cpu),
-                                                 alloc_mask, 0);
-                       if (!*pagep)
-                               goto err;
-               }
+       /* alloc and map */
+       pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
+               rc = pcpu_alloc_pages(chunk, pages, populated, rs, re);
+               if (rc)
+                       goto err_free;
+               free_end = re;
        }
 
-       if (map_start >= 0 && pcpu_map(chunk, map_start, map_end))
-               goto err;
+       pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
+               rc = pcpu_map_pages(chunk, pages, populated, rs, re);
+               if (rc)
+                       goto err_unmap;
+               unmap_end = re;
+       }
+       pcpu_post_map_flush(chunk, page_start, page_end);
 
+       /* commit new bitmap */
+       bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
+clear:
        for_each_possible_cpu(cpu)
-               memset(chunk->vm->addr + (cpu << pcpu_unit_shift) + off, 0,
-                      size);
-
+               memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
        return 0;
-err:
-       /* likely under heavy memory pressure, give memory back */
-       pcpu_depopulate_chunk(chunk, off, size, true);
-       return -ENOMEM;
+
+err_unmap:
+       pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
+       pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
+               pcpu_unmap_pages(chunk, pages, populated, rs, re);
+       pcpu_post_unmap_tlb_flush(chunk, page_start, unmap_end);
+err_free:
+       pcpu_for_each_unpop_region(chunk, rs, re, page_start, free_end)
+               pcpu_free_pages(chunk, pages, populated, rs, re);
+       return rc;
 }
 
 static void free_pcpu_chunk(struct pcpu_chunk *chunk)
 {
        if (!chunk)
                return;
-       if (chunk->vm)
-               free_vm_area(chunk->vm);
-       pcpu_realloc(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]), 0);
+       if (chunk->vms)
+               pcpu_free_vm_areas(chunk->vms, pcpu_nr_groups);
+       pcpu_mem_free(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]));
        kfree(chunk);
 }
 
@@ -687,13 +1033,14 @@ static struct pcpu_chunk *alloc_pcpu_chunk(void)
        if (!chunk)
                return NULL;
 
-       chunk->map = pcpu_realloc(NULL, 0,
-                                 PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
+       chunk->map = pcpu_mem_alloc(PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
        chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
        chunk->map[chunk->map_used++] = pcpu_unit_size;
 
-       chunk->vm = get_vm_area(pcpu_chunk_size, GFP_KERNEL);
-       if (!chunk->vm) {
+       chunk->vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,
+                                      pcpu_nr_groups, pcpu_atom_size,
+                                      GFP_KERNEL);
+       if (!chunk->vms) {
                free_pcpu_chunk(chunk);
                return NULL;
        }
@@ -701,191 +1048,1087 @@ static struct pcpu_chunk *alloc_pcpu_chunk(void)
        INIT_LIST_HEAD(&chunk->list);
        chunk->free_size = pcpu_unit_size;
        chunk->contig_hint = pcpu_unit_size;
+       chunk->base_addr = chunk->vms[0]->addr - pcpu_group_offsets[0];
 
        return chunk;
 }
 
 /**
- * __alloc_percpu - allocate percpu area
+ * 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.  Might
- * sleep.  Might trigger writeouts.
+ * 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.
  */
-void *__alloc_percpu(size_t size, size_t align)
+static void *pcpu_alloc(size_t size, size_t align, bool reserved)
 {
-       void *ptr = NULL;
+       static int warn_limit = 10;
        struct pcpu_chunk *chunk;
-       int slot, off;
+       const char *err;
+       int slot, off, new_alloc;
+       unsigned long flags;
 
-       if (unlikely(!size || size > PAGE_SIZE << PCPU_MIN_UNIT_PAGES_SHIFT ||
-                    align > PAGE_SIZE)) {
+       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_mutex);
+       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;
+       }
 
-       /* allocate area */
+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;
-                       if (off != -ENOSPC)
-                               goto out_unlock;
                }
        }
 
        /* hmmm... no space left, create a new chunk */
+       spin_unlock_irqrestore(&pcpu_lock, flags);
+
        chunk = alloc_pcpu_chunk();
-       if (!chunk)
-               goto out_unlock;
-       pcpu_chunk_relocate(chunk, -1);
-       pcpu_chunk_addr_insert(chunk);
+       if (!chunk) {
+               err = "failed to allocate new chunk";
+               goto fail_unlock_mutex;
+       }
 
-       off = pcpu_alloc_area(chunk, size, align);
-       if (off < 0)
-               goto out_unlock;
+       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);
-               goto out_unlock;
+               err = "failed to populate";
+               goto fail_unlock;
        }
 
-       ptr = __addr_to_pcpu_ptr(chunk->vm->addr + off);
-out_unlock:
-       mutex_unlock(&pcpu_mutex);
-       return ptr;
+       mutex_unlock(&pcpu_alloc_mutex);
+
+       /* return address relative to base address */
+       return __addr_to_pcpu_ptr(chunk->base_addr + off);
+
+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 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 *__alloc_percpu(size_t size, size_t align)
+{
+       return pcpu_alloc(size, align, false);
 }
 EXPORT_SYMBOL_GPL(__alloc_percpu);
 
-static void pcpu_kill_chunk(struct pcpu_chunk *chunk)
+/**
+ * __alloc_reserved_percpu - allocate reserved percpu area
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ *
+ * Allocate 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 *__alloc_reserved_percpu(size_t size, size_t align)
 {
-       pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size, false);
-       list_del(&chunk->list);
-       rb_erase(&chunk->rb_node, &pcpu_addr_root);
-       free_pcpu_chunk(chunk);
+       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);
+               free_pcpu_chunk(chunk);
+       }
+
+       mutex_unlock(&pcpu_alloc_mutex);
 }
 
 /**
  * free_percpu - free percpu area
  * @ptr: pointer to area to free
  *
- * Free percpu area @ptr.  Might sleep.
+ * Free percpu area @ptr.
+ *
+ * CONTEXT:
+ * Can be called from atomic context.
  */
 void free_percpu(void *ptr)
 {
-       void *addr = __pcpu_ptr_to_addr(ptr);
+       void *addr;
        struct pcpu_chunk *chunk;
+       unsigned long flags;
        int off;
 
        if (!ptr)
                return;
 
-       mutex_lock(&pcpu_mutex);
+       addr = __pcpu_ptr_to_addr(ptr);
+
+       spin_lock_irqsave(&pcpu_lock, flags);
 
        chunk = pcpu_chunk_addr_search(addr);
-       off = addr - chunk->vm->addr;
+       off = addr - chunk->base_addr;
 
        pcpu_free_area(chunk, off);
 
-       /* the chunk became fully free, kill one if there are other free ones */
+       /* 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_chunk_slot(chunk)], list)
+               list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
                        if (pos != chunk) {
-                               pcpu_kill_chunk(pos);
+                               schedule_work(&pcpu_reclaim_work);
                                break;
                        }
        }
 
-       mutex_unlock(&pcpu_mutex);
+       spin_unlock_irqrestore(&pcpu_lock, flags);
 }
 EXPORT_SYMBOL_GPL(free_percpu);
 
 /**
- * pcpu_setup_static - initialize kernel static percpu area
- * @populate_pte_fn: callback to allocate pagetable
- * @pages: num_possible_cpus() * PFN_UP(cpu_size) pages
- * @cpu_size: the size of static percpu area in bytes
+ * 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.
+ *
+ * RETURNS:
+ * The physical address for @addr.
+ */
+phys_addr_t per_cpu_ptr_to_phys(void *addr)
+{
+       if ((unsigned long)addr < VMALLOC_START ||
+                       (unsigned long)addr >= VMALLOC_END)
+               return __pa(addr);
+       else
+               return page_to_phys(vmalloc_to_page(addr));
+}
+
+static inline size_t pcpu_calc_fc_sizes(size_t static_size,
+                                       size_t reserved_size,
+                                       ssize_t *dyn_sizep)
+{
+       size_t size_sum;
+
+       size_sum = PFN_ALIGN(static_size + reserved_size +
+                            (*dyn_sizep >= 0 ? *dyn_sizep : 0));
+       if (*dyn_sizep != 0)
+               *dyn_sizep = size_sum - static_size - reserved_size;
+
+       return size_sum;
+}
+
+/**
+ * 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_build_alloc_info - build alloc_info considering distances between CPUs
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @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.
+ */
+struct pcpu_alloc_info * __init pcpu_build_alloc_info(
+                               size_t reserved_size, ssize_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 group_cnt_max = 0, 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_map));
+
+       /*
+        * Determine min_unit_size, alloc_size and max_upa such that
+        * alloc_size is multiple of atom_size and is the smallest
+        * which can accomodate 4k aligned segments which are equal to
+        * or larger than min_unit_size.
+        */
+       size_sum = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_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]++;
+               group_cnt_max = max(group_cnt_max, 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 25%.  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;
+}
+
+/**
+ * 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("\n");
+                               printk("%spcpu-alloc: ", lvl);
+                       }
+                       printk("[%0*d] ", group_width, group);
+
+                       for (unit_end += upa; unit < unit_end; unit++)
+                               if (gi->cpu_map[unit] != NR_CPUS)
+                                       printk("%0*d ", cpu_width,
+                                              gi->cpu_map[unit]);
+                               else
+                                       printk("%s ", empty_str);
+               }
+       }
+       printk("\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.
  *
- * Initialize kernel static percpu area.  The caller should allocate
- * all the necessary pages and pass them in @pages.
- * @populate_pte_fn() is called on each page to be used for percpu
- * mapping and is responsible for making sure all the necessary page
- * tables for the page is allocated.
+ * @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:
- * The determined pcpu_unit_size which can be used to initialize
- * percpu access.
+ * 0 on success, -errno on failure.
  */
-size_t __init pcpu_setup_static(pcpu_populate_pte_fn_t populate_pte_fn,
-                               struct page **pages, size_t cpu_size)
+int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
+                                 void *base_addr)
 {
-       static struct vm_struct static_vm;
-       struct pcpu_chunk *static_chunk;
-       int nr_cpu_pages = DIV_ROUND_UP(cpu_size, PAGE_SIZE);
+       static char cpus_buf[4096] __initdata;
+       static int smap[2], dmap[2];
+       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 err, i;
+       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 */
+       BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
+                    ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
+       PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
+       PCPU_SETUP_BUG_ON(!ai->static_size);
+       PCPU_SETUP_BUG_ON(!base_addr);
+       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);
+
+       /* 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_first_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;
+
+                       if (pcpu_first_unit_cpu == NR_CPUS)
+                               pcpu_first_unit_cpu = cpu;
+               }
+       }
+       pcpu_last_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_INFO, ai);
 
-       pcpu_unit_pages_shift = max_t(int, PCPU_MIN_UNIT_PAGES_SHIFT,
-                                     order_base_2(cpu_size) - PAGE_SHIFT);
+       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;
 
-       pcpu_static_size = cpu_size;
-       pcpu_unit_pages = 1 << pcpu_unit_pages_shift;
-       pcpu_unit_shift = PAGE_SHIFT + pcpu_unit_pages_shift;
-       pcpu_unit_size = 1 << pcpu_unit_shift;
-       pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
-       pcpu_nr_slots = pcpu_size_to_slot(pcpu_unit_size) + 1;
-       pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
-               + num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);
+       /* 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 */
+       /*
+        * 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]);
 
-       /* init and register vm area */
-       static_vm.flags = VM_ALLOC;
-       static_vm.size = pcpu_chunk_size;
-       vm_area_register_early(&static_vm, PAGE_SIZE);
+       /*
+        * 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;
+       }
 
-       /* init static_chunk */
-       static_chunk = alloc_bootmem(pcpu_chunk_struct_size);
-       INIT_LIST_HEAD(&static_chunk->list);
-       static_chunk->vm = &static_vm;
-       static_chunk->free_size = pcpu_unit_size - pcpu_static_size;
-       static_chunk->contig_hint = static_chunk->free_size;
+       /* link the first chunk in */
+       pcpu_first_chunk = dchunk ?: schunk;
+       pcpu_chunk_relocate(pcpu_first_chunk, -1);
 
-       /* assign pages and map them */
-       for_each_possible_cpu(cpu) {
-               for (i = 0; i < nr_cpu_pages; i++) {
-                       *pcpu_chunk_pagep(static_chunk, cpu, i) = *pages++;
-                       populate_pte_fn(pcpu_chunk_addr(static_chunk, cpu, i));
+       /* we're done */
+       pcpu_base_addr = base_addr;
+       return 0;
+}
+
+const char *pcpu_fc_names[PCPU_FC_NR] __initdata = {
+       [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 (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);
+
+#if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
+       !defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
+/**
+ * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @atom_size: allocation atom size
+ * @cpu_distance_fn: callback to determine distance between cpus, optional
+ * @alloc_fn: function to allocate percpu page
+ * @free_fn: funtion 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).
+ *
+ * When @dyn_size is positive, dynamic area might be larger than
+ * specified to fill page alignment.  When @dyn_size is auto,
+ * @dyn_size is just big enough to fill page alignment after static
+ * and reserved areas.
+ *
+ * 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, ssize_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;
+               }
+               areas[group] = ptr;
+
+               base = min(ptr, base);
+
+               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);
                }
        }
 
-       err = pcpu_map(static_chunk, 0, nr_cpu_pages);
-       if (err)
-               panic("failed to setup static percpu area, err=%d\n", err);
+       /* 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, VMALLOC_END - VMALLOC_START);
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+               /* and fail if we have fallback */
+               rc = -EINVAL;
+               goto out_free;
+#endif
+       }
 
-       /* link static_chunk in */
-       pcpu_chunk_relocate(static_chunk, -1);
-       pcpu_chunk_addr_insert(static_chunk);
+       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 /* CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK ||
+         !CONFIG_HAVE_SETUP_PER_CPU_AREA */
 
-       /* we're done */
-       pcpu_base_addr = (void *)pcpu_chunk_addr(static_chunk, 0, 0);
-       return pcpu_unit_size;
+#ifdef CONFIG_NEED_PER_CPU_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: funtion 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, -1, 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;
+                       }
+                       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 /* CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK */
+
+/*
+ * Generic 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.
+ */
+#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
+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 initialized 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 */