1 files changed, 1226 insertions, 0 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
new file mode 100644
index 000000000000..bfe6a3afaf45
--- /dev/null
+++ b/mm/percpu.c
@@ -0,0 +1,1226 @@
+/*
+ * linux/mm/percpu.c - percpu memory allocator
+ *
+ * Copyright (C) 2009           SUSE Linux Products GmbH
+ * Copyright (C) 2009           Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ * This is percpu allocator which can handle both static and dynamic
+ * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
+ * chunk is consisted of num_possible_cpus() units and the first chunk
+ * is used for static percpu variables in the kernel image (special
+ * boot time alloc/init handling necessary as these areas need to be
+ * brought up before allocation services are running).  Unit grows as
+ * necessary and all units grow or shrink in unison.  When a chunk is
+ * filled up, another chunk is allocated.  ie. in vmalloc area
+ *
+ *  c0                           c1                         c2
+ *  -------------------          -------------------        ------------
+ * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
+ *  -------------------  ......  -------------------  ....  ------------
+ *
+ * Allocation is done in offset-size areas of single unit space.  Ie,
+ * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
+ * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring
+ * percpu base registers UNIT_SIZE apart.
+ *
+ * There are usually many small percpu allocations many of them as
+ * small as 4 bytes.  The allocator organizes chunks into lists
+ * according to free size and tries to allocate from the fullest one.
+ * Each chunk keeps the maximum contiguous area size hint which is
+ * guaranteed to be eqaul to or larger than the maximum contiguous
+ * area in the chunk.  This helps the allocator not to iterate the
+ * chunk maps unnecessarily.
+ *
+ * Allocation state in each chunk is kept using an array of integers
+ * on chunk->map.  A positive value in the map represents a free
+ * region and negative allocated.  Allocation inside a chunk is done
+ * by scanning this map sequentially and serving the first matching
+ * entry.  This is mostly copied from the percpu_modalloc() allocator.
+ * Chunks are also linked into a rb tree to ease address to chunk
+ * mapping during free.
+ *
+ * To use this allocator, arch code should do the followings.
+ *
+ * - define CONFIG_HAVE_DYNAMIC_PER_CPU_AREA
+ *
+ * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
+ *   regular address to percpu pointer and back
+ *
+ * - use pcpu_setup_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/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/pfn.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+#define PCPU_SLOT_BASE_SHIFT            5       /* 1-31 shares the same slot */
+#define PCPU_DFL_MAP_ALLOC              16      /* start a map with 16 ents */
+
+struct pcpu_chunk {
+        struct list_head        list;           /* linked to pcpu_slot lists */
+        struct rb_node          rb_node;        /* key is chunk->vm->addr */
+        int                     free_size;      /* free bytes in the chunk */
+        int                     contig_hint;    /* max contiguous size hint */
+        struct vm_struct        *vm;            /* mapped vmalloc region */
+        int                     map_used;       /* # of map entries used */
+        int                     map_alloc;      /* # of map entries allocated */
+        int                     *map;           /* allocation map */
+        bool                    immutable;      /* no [de]population allowed */
+        struct page             **page;         /* points to page array */
+        struct page             *page_ar[];     /* #cpus * UNIT_PAGES */
+};
+
+static int pcpu_unit_pages __read_mostly;
+static int pcpu_unit_size __read_mostly;
+static int pcpu_chunk_size __read_mostly;
+static int pcpu_nr_slots __read_mostly;
+static size_t pcpu_chunk_struct_size __read_mostly;
+
+/* the address of the first chunk which starts with the kernel static area */
+void *pcpu_base_addr __read_mostly;
+EXPORT_SYMBOL_GPL(pcpu_base_addr);
+
+/* optional reserved chunk, only accessible for reserved allocations */
+static struct pcpu_chunk *pcpu_reserved_chunk;
+/* offset limit of the reserved chunk */
+static int pcpu_reserved_chunk_limit;
+
+/*
+ * Synchronization rules.
+ *
+ * There are two locks - pcpu_alloc_mutex and pcpu_lock.  The former
+ * protects allocation/reclaim paths, chunks and chunk->page arrays.
+ * The latter is a spinlock and protects the index data structures -
+ * chunk slots, rbtree, chunks and area maps in chunks.
+ *
+ * During allocation, pcpu_alloc_mutex is kept locked all the time and
+ * pcpu_lock is grabbed and released as necessary.  All actual memory
+ * allocations are done using GFP_KERNEL with pcpu_lock released.
+ *
+ * Free path accesses and alters only the index data structures, so it
+ * can be safely called from atomic context.  When memory needs to be
+ * returned to the system, free path schedules reclaim_work which
+ * grabs both pcpu_alloc_mutex and pcpu_lock, unlinks chunks to be
+ * reclaimed, release both locks and frees the chunks.  Note that it's
+ * necessary to grab both locks to remove a chunk from circulation as
+ * allocation path might be referencing the chunk with only
+ * pcpu_alloc_mutex locked.
+ */
+static DEFINE_MUTEX(pcpu_alloc_mutex);  /* protects whole alloc and reclaim */
+static DEFINE_SPINLOCK(pcpu_lock);      /* protects index data structures */
+
+static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
+static struct rb_root pcpu_addr_root = RB_ROOT; /* chunks by address */
+
+/* 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))
+                return 0;
+
+        return pcpu_size_to_slot(chunk->free_size);
+}
+
+static int pcpu_page_idx(unsigned int cpu, int page_idx)
+{
+        return cpu * pcpu_unit_pages + page_idx;
+}
+
+static struct page **pcpu_chunk_pagep(struct pcpu_chunk *chunk,
+                                      unsigned int cpu, int page_idx)
+{
+        return &chunk->page[pcpu_page_idx(cpu, page_idx)];
+}
+
+static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
+                                     unsigned int cpu, int page_idx)
+{
+        return (unsigned long)chunk->vm->addr +
+                (pcpu_page_idx(cpu, page_idx) << PAGE_SHIFT);
+}
+
+static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
+                                     int page_idx)
+{
+        return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
+}
+
+/**
+ * pcpu_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.
+ *
+ * CONTEXT:
+ * Does GFP_KERNEL allocation.
+ *
+ * RETURNS:
+ * Pointer to the allocated area on success, NULL on failure.
+ */
+static void *pcpu_mem_alloc(size_t 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(ptr);
+        else
+                vfree(ptr);
+}
+
+/**
+ * pcpu_chunk_relocate - put chunk in the appropriate chunk slot
+ * @chunk: chunk of interest
+ * @oslot: the previous slot it was on
+ *
+ * This function is called after an allocation or free changed @chunk.
+ * New slot according to the changed state is determined and @chunk is
+ * moved to the slot.  Note that the reserved chunk is never put on
+ * chunk slots.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ */
+static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
+{
+        int nslot = pcpu_chunk_slot(chunk);
+
+        if (chunk != pcpu_reserved_chunk && oslot != nslot) {
+                if (oslot < nslot)
+                        list_move(&chunk->list, &pcpu_slot[nslot]);
+                else
+                        list_move_tail(&chunk->list, &pcpu_slot[nslot]);
+        }
+}
+
+static struct rb_node **pcpu_chunk_rb_search(void *addr,
+                                             struct rb_node **parentp)
+{
+        struct rb_node **p = &pcpu_addr_root.rb_node;
+        struct rb_node *parent = NULL;
+        struct pcpu_chunk *chunk;
+
+        while (*p) {
+                parent = *p;
+                chunk = rb_entry(parent, struct pcpu_chunk, rb_node);
+
+                if (addr < chunk->vm->addr)
+                        p = &(*p)->rb_left;
+                else if (addr > chunk->vm->addr)
+                        p = &(*p)->rb_right;
+                else
+                        break;
+        }
+
+        if (parentp)
+                *parentp = parent;
+        return p;
+}
+
+/**
+ * pcpu_chunk_addr_search - search for chunk containing specified address
+ * @addr: address to search for
+ *
+ * Look for chunk which might contain @addr.  More specifically, it
+ * searchs for the chunk with the highest start address which isn't
+ * beyond @addr.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ *
+ * RETURNS:
+ * The address of the found chunk.
+ */
+static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
+{
+        struct rb_node *n, *parent;
+        struct pcpu_chunk *chunk;
+
+        /* is it in the reserved chunk? */
+        if (pcpu_reserved_chunk) {
+                void *start = pcpu_reserved_chunk->vm->addr;
+
+                if (addr >= start && addr < start + pcpu_reserved_chunk_limit)
+                        return pcpu_reserved_chunk;
+        }
+
+        /* nah... search the regular ones */
+        n = *pcpu_chunk_rb_search(addr, &parent);
+        if (!n) {
+                /* no exactly matching chunk, the parent is the closest */
+                n = parent;
+                BUG_ON(!n);
+        }
+        chunk = rb_entry(n, struct pcpu_chunk, rb_node);
+
+        if (addr < chunk->vm->addr) {
+                /* the parent was the next one, look for the previous one */
+                n = rb_prev(n);
+                BUG_ON(!n);
+                chunk = rb_entry(n, struct pcpu_chunk, rb_node);
+        }
+
+        return chunk;
+}
+
+/**
+ * pcpu_chunk_addr_insert - insert chunk into address rb tree
+ * @new: chunk to insert
+ *
+ * Insert @new into address rb tree.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ */
+static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
+{
+        struct rb_node **p, *parent;
+
+        p = pcpu_chunk_rb_search(new->vm->addr, &parent);
+        BUG_ON(*p);
+        rb_link_node(&new->rb_node, parent, p);
+        rb_insert_color(&new->rb_node, &pcpu_addr_root);
+}
+
+/**
+ * pcpu_extend_area_map - extend area map for allocation
+ * @chunk: target chunk
+ *
+ * Extend area map of @chunk so that it can accomodate an allocation.
+ * A single allocation can split an area into three areas, so this
+ * function makes sure that @chunk->map has at least two extra slots.
+ *
+ * CONTEXT:
+ * pcpu_alloc_mutex, pcpu_lock.  pcpu_lock is released and reacquired
+ * if area map is extended.
+ *
+ * RETURNS:
+ * 0 if noop, 1 if successfully extended, -errno on failure.
+ */
+static int pcpu_extend_area_map(struct pcpu_chunk *chunk)
+{
+        int new_alloc;
+        int *new;
+        size_t size;
+
+        /* has enough? */
+        if (chunk->map_alloc >= chunk->map_used + 2)
+                return 0;
+
+        spin_unlock_irq(&pcpu_lock);
+
+        new_alloc = PCPU_DFL_MAP_ALLOC;
+        while (new_alloc < chunk->map_used + 2)
+                new_alloc *= 2;
+
+        new = pcpu_mem_alloc(new_alloc * sizeof(new[0]));
+        if (!new) {
+                spin_lock_irq(&pcpu_lock);
+                return -ENOMEM;
+        }
+
+        /*
+         * Acquire pcpu_lock and switch to new area map.  Only free
+         * could have happened inbetween, so map_used couldn't have
+         * grown.
+         */
+        spin_lock_irq(&pcpu_lock);
+        BUG_ON(new_alloc < chunk->map_used + 2);
+
+        size = chunk->map_alloc * sizeof(chunk->map[0]);
+        memcpy(new, chunk->map, 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)
+                pcpu_mem_free(chunk->map, size);
+
+        chunk->map_alloc = new_alloc;
+        chunk->map = new;
+        return 0;
+}
+
+/**
+ * pcpu_split_block - split a map block
+ * @chunk: chunk of interest
+ * @i: index of map block to split
+ * @head: head size in bytes (can be 0)
+ * @tail: tail size in bytes (can be 0)
+ *
+ * Split the @i'th map block into two or three blocks.  If @head is
+ * non-zero, @head bytes block is inserted before block @i moving it
+ * to @i+1 and reducing its size by @head bytes.
+ *
+ * If @tail is non-zero, the target block, which can be @i or @i+1
+ * depending on @head, is reduced by @tail bytes and @tail byte block
+ * is inserted after the target block.
+ *
+ * @chunk->map must have enough free slots to accomodate the split.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ */
+static void pcpu_split_block(struct pcpu_chunk *chunk, int i,
+                             int head, int tail)
+{
+        int nr_extra = !!head + !!tail;
+
+        BUG_ON(chunk->map_alloc < chunk->map_used + nr_extra);
+
+        /* insert new subblocks */
+        memmove(&chunk->map[i + nr_extra], &chunk->map[i],
+                sizeof(chunk->map[0]) * (chunk->map_used - i));
+        chunk->map_used += nr_extra;
+
+        if (head) {
+                chunk->map[i + 1] = chunk->map[i] - head;
+                chunk->map[i++] = head;
+        }
+        if (tail) {
+                chunk->map[i++] -= tail;
+                chunk->map[i] = tail;
+        }
+}
+
+/**
+ * pcpu_alloc_area - allocate area from a pcpu_chunk
+ * @chunk: chunk of interest
+ * @size: wanted size in bytes
+ * @align: wanted align
+ *
+ * Try to allocate @size bytes area aligned at @align from @chunk.
+ * Note that this function only allocates the offset.  It doesn't
+ * populate or map the area.
+ *
+ * @chunk->map must have at least two free slots.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ *
+ * RETURNS:
+ * Allocated offset in @chunk on success, -1 if no matching area is
+ * found.
+ */
+static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
+{
+        int oslot = pcpu_chunk_slot(chunk);
+        int max_contig = 0;
+        int i, off;
+
+        for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
+                bool is_last = i + 1 == chunk->map_used;
+                int head, tail;
+
+                /* extra for alignment requirement */
+                head = ALIGN(off, align) - off;
+                BUG_ON(i == 0 && head != 0);
+
+                if (chunk->map[i] < 0)
+                        continue;
+                if (chunk->map[i] < head + size) {
+                        max_contig = max(chunk->map[i], max_contig);
+                        continue;
+                }
+
+                /*
+                 * If head is small or the previous block is free,
+                 * merge'em.  Note that 'small' is defined as smaller
+                 * than sizeof(int), which is very small but isn't too
+                 * uncommon for percpu allocations.
+                 */
+                if (head && (head < sizeof(int) || chunk->map[i - 1] > 0)) {
+                        if (chunk->map[i - 1] > 0)
+                                chunk->map[i - 1] += head;
+                        else {
+                                chunk->map[i - 1] -= head;
+                                chunk->free_size -= head;
+                        }
+                        chunk->map[i] -= head;
+                        off += head;
+                        head = 0;
+                }
+
+                /* if tail is small, just keep it around */
+                tail = chunk->map[i] - head - size;
+                if (tail < sizeof(int))
+                        tail = 0;
+
+                /* split if warranted */
+                if (head || tail) {
+                        pcpu_split_block(chunk, i, head, tail);
+                        if (head) {
+                                i++;
+                                off += head;
+                                max_contig = max(chunk->map[i - 1], max_contig);
+                        }
+                        if (tail)
+                                max_contig = max(chunk->map[i + 1], max_contig);
+                }
+
+                /* update hint and mark allocated */
+                if (is_last)
+                        chunk->contig_hint = max_contig; /* fully scanned */
+                else
+                        chunk->contig_hint = max(chunk->contig_hint,
+                                                 max_contig);
+
+                chunk->free_size -= chunk->map[i];
+                chunk->map[i] = -chunk->map[i];
+
+                pcpu_chunk_relocate(chunk, oslot);
+                return off;
+        }
+
+        chunk->contig_hint = max_contig;        /* fully scanned */
+        pcpu_chunk_relocate(chunk, oslot);
+
+        /* tell the upper layer that this chunk has no matching area */
+        return -1;
+}
+
+/**
+ * pcpu_free_area - free area to a pcpu_chunk
+ * @chunk: chunk of interest
+ * @freeme: offset of area to free
+ *
+ * Free area starting from @freeme to @chunk.  Note that this function
+ * only modifies the allocation map.  It doesn't depopulate or unmap
+ * the area.
+ *
+ * CONTEXT:
+ * pcpu_lock.
+ */
+static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
+{
+        int oslot = pcpu_chunk_slot(chunk);
+        int i, off;
+
+        for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++]))
+                if (off == freeme)
+                        break;
+        BUG_ON(off != freeme);
+        BUG_ON(chunk->map[i] > 0);
+
+        chunk->map[i] = -chunk->map[i];
+        chunk->free_size += chunk->map[i];
+
+        /* merge with previous? */
+        if (i > 0 && chunk->map[i - 1] >= 0) {
+                chunk->map[i - 1] += chunk->map[i];
+                chunk->map_used--;
+                memmove(&chunk->map[i], &chunk->map[i + 1],
+                        (chunk->map_used - i) * sizeof(chunk->map[0]));
+                i--;
+        }
+        /* merge with next? */
+        if (i + 1 < chunk->map_used && chunk->map[i + 1] >= 0) {
+                chunk->map[i] += chunk->map[i + 1];
+                chunk->map_used--;
+                memmove(&chunk->map[i + 1], &chunk->map[i + 2],
+                        (chunk->map_used - (i + 1)) * sizeof(chunk->map[0]));
+        }
+
+        chunk->contig_hint = max(chunk->map[i], chunk->contig_hint);
+        pcpu_chunk_relocate(chunk, oslot);
+}
+
+/**
+ * pcpu_unmap - unmap pages out of a pcpu_chunk
+ * @chunk: chunk of interest
+ * @page_start: page index of the first page to unmap
+ * @page_end: page index of the last page to unmap + 1
+ * @flush: whether to flush cache and tlb or not
+ *
+ * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
+ * If @flush is true, vcache is flushed before unmapping and tlb
+ * after.
+ */
+static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
+                       bool flush)
+{
+        unsigned int last = num_possible_cpus() - 1;
+        unsigned int cpu;
+
+        /* unmap must not be done on immutable chunk */
+        WARN_ON(chunk->immutable);
+
+        /*
+         * Each flushing trial can be very expensive, issue flush on
+         * the whole region at once rather than doing it for each cpu.
+         * This could be an overkill but is more scalable.
+         */
+        if (flush)
+                flush_cache_vunmap(pcpu_chunk_addr(chunk, 0, page_start),
+                                   pcpu_chunk_addr(chunk, last, page_end));
+
+        for_each_possible_cpu(cpu)
+                unmap_kernel_range_noflush(
+                                pcpu_chunk_addr(chunk, cpu, page_start),
+                                (page_end - page_start) << PAGE_SHIFT);
+
+        /* ditto as flush_cache_vunmap() */
+        if (flush)
+                flush_tlb_kernel_range(pcpu_chunk_addr(chunk, 0, page_start),
+                                       pcpu_chunk_addr(chunk, last, page_end));
+}
+
+/**
+ * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
+ * @chunk: chunk to depopulate
+ * @off: offset to the area to depopulate
+ * @size: size of the area to depopulate 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,
+                                  bool flush)
+{
+        int page_start = PFN_DOWN(off);
+        int page_end = PFN_UP(off + size);
+        int unmap_start = -1;
+        int uninitialized_var(unmap_end);
+        unsigned int cpu;
+        int i;
+
+        for (i = page_start; i < page_end; i++) {
+                for_each_possible_cpu(cpu) {
+                        struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+
+                        if (!*pagep)
+                                continue;
+
+                        __free_page(*pagep);
+
+                        /*
+                         * If it's partial depopulation, it might get
+                         * populated or depopulated again.  Mark the
+                         * page gone.
+                         */
+                        *pagep = NULL;
+
+                        unmap_start = unmap_start < 0 ? i : unmap_start;
+                        unmap_end = i + 1;
+                }
+        }
+
+        if (unmap_start >= 0)
+                pcpu_unmap(chunk, unmap_start, unmap_end, flush);
+}
+
+/**
+ * pcpu_map - map pages into a pcpu_chunk
+ * @chunk: chunk of interest
+ * @page_start: page index of the first page to map
+ * @page_end: page index of the last page to map + 1
+ *
+ * For each cpu, map pages [@page_start,@page_end) into @chunk.
+ * vcache is flushed afterwards.
+ */
+static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
+{
+        unsigned int last = num_possible_cpus() - 1;
+        unsigned int cpu;
+        int err;
+
+        /* map must not be done on immutable chunk */
+        WARN_ON(chunk->immutable);
+
+        for_each_possible_cpu(cpu) {
+                err = map_kernel_range_noflush(
+                                pcpu_chunk_addr(chunk, cpu, page_start),
+                                (page_end - page_start) << PAGE_SHIFT,
+                                PAGE_KERNEL,
+                                pcpu_chunk_pagep(chunk, cpu, page_start));
+                if (err < 0)
+                        return err;
+        }
+
+        /* flush at once, please read comments in pcpu_unmap() */
+        flush_cache_vmap(pcpu_chunk_addr(chunk, 0, page_start),
+                         pcpu_chunk_addr(chunk, last, page_end));
+        return 0;
+}
+
+/**
+ * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
+ * @chunk: chunk of interest
+ * @off: offset to the area to populate
+ * @size: size of the area to populate in bytes
+ *
+ * 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 uninitialized_var(map_end);
+        unsigned int cpu;
+        int i;
+
+        for (i = page_start; i < page_end; i++) {
+                if (pcpu_chunk_page_occupied(chunk, i)) {
+                        if (map_start >= 0) {
+                                if (pcpu_map(chunk, map_start, map_end))
+                                        goto err;
+                                map_start = -1;
+                        }
+                        continue;
+                }
+
+                map_start = map_start < 0 ? i : map_start;
+                map_end = i + 1;
+
+                for_each_possible_cpu(cpu) {
+                        struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);
+
+                        *pagep = alloc_pages_node(cpu_to_node(cpu),
+                                                  alloc_mask, 0);
+                        if (!*pagep)
+                                goto err;
+                }
+        }
+
+        if (map_start >= 0 && pcpu_map(chunk, map_start, map_end))
+                goto err;
+
+        for_each_possible_cpu(cpu)
+                memset(chunk->vm->addr + cpu * pcpu_unit_size + off, 0,
+                       size);
+
+        return 0;
+err:
+        /* likely under heavy memory pressure, give memory back */
+        pcpu_depopulate_chunk(chunk, off, size, true);
+        return -ENOMEM;
+}
+
+static void free_pcpu_chunk(struct pcpu_chunk *chunk)
+{
+        if (!chunk)
+                return;
+        if (chunk->vm)
+                free_vm_area(chunk->vm);
+        pcpu_mem_free(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]));
+        kfree(chunk);
+}
+
+static struct pcpu_chunk *alloc_pcpu_chunk(void)
+{
+        struct pcpu_chunk *chunk;
+
+        chunk = kzalloc(pcpu_chunk_struct_size, GFP_KERNEL);
+        if (!chunk)
+                return NULL;
+
+        chunk->map = pcpu_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->page = chunk->page_ar;
+
+        chunk->vm = get_vm_area(pcpu_chunk_size, GFP_KERNEL);
+        if (!chunk->vm) {
+                free_pcpu_chunk(chunk);
+                return NULL;
+        }
+
+        INIT_LIST_HEAD(&chunk->list);
+        chunk->free_size = pcpu_unit_size;
+        chunk->contig_hint = pcpu_unit_size;
+
+        return chunk;
+}
+
+/**
+ * pcpu_alloc - the percpu allocator
+ * @size: size of area to allocate in bytes
+ * @align: alignment of area (max PAGE_SIZE)
+ * @reserved: allocate from the reserved chunk if available
+ *
+ * Allocate percpu area of @size bytes aligned at @align.
+ *
+ * CONTEXT:
+ * Does GFP_KERNEL allocation.
+ *
+ * RETURNS:
+ * Percpu pointer to the allocated area on success, NULL on failure.
+ */
+static void *pcpu_alloc(size_t size, size_t align, bool reserved)
+{
+        struct pcpu_chunk *chunk;
+        int slot, off;
+
+        if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
+                WARN(true, "illegal size (%zu) or align (%zu) for "
+                     "percpu allocation\n", size, align);
+                return NULL;
+        }
+
+        mutex_lock(&pcpu_alloc_mutex);
+        spin_lock_irq(&pcpu_lock);
+
+        /* serve reserved allocations from the reserved chunk if available */
+        if (reserved && pcpu_reserved_chunk) {
+                chunk = pcpu_reserved_chunk;
+                if (size > chunk->contig_hint ||
+                    pcpu_extend_area_map(chunk) < 0)
+                        goto fail_unlock;
+                off = pcpu_alloc_area(chunk, size, align);
+                if (off >= 0)
+                        goto area_found;
+                goto fail_unlock;
+        }
+
+restart:
+        /* search through normal chunks */
+        for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
+                list_for_each_entry(chunk, &pcpu_slot[slot], list) {
+                        if (size > chunk->contig_hint)
+                                continue;
+
+                        switch (pcpu_extend_area_map(chunk)) {
+                        case 0:
+                                break;
+                        case 1:
+                                goto restart;   /* pcpu_lock dropped, restart */
+                        default:
+                                goto fail_unlock;
+                        }
+
+                        off = pcpu_alloc_area(chunk, size, align);
+                        if (off >= 0)
+                                goto area_found;
+                }
+        }
+
+        /* hmmm... no space left, create a new chunk */
+        spin_unlock_irq(&pcpu_lock);
+
+        chunk = alloc_pcpu_chunk();
+        if (!chunk)
+                goto fail_unlock_mutex;
+
+        spin_lock_irq(&pcpu_lock);
+        pcpu_chunk_relocate(chunk, -1);
+        pcpu_chunk_addr_insert(chunk);
+        goto restart;
+
+area_found:
+        spin_unlock_irq(&pcpu_lock);
+
+        /* populate, map and clear the area */
+        if (pcpu_populate_chunk(chunk, off, size)) {
+                spin_lock_irq(&pcpu_lock);
+                pcpu_free_area(chunk, off);
+                goto fail_unlock;
+        }
+
+        mutex_unlock(&pcpu_alloc_mutex);
+
+        return __addr_to_pcpu_ptr(chunk->vm->addr + off);
+
+fail_unlock:
+        spin_unlock_irq(&pcpu_lock);
+fail_unlock_mutex:
+        mutex_unlock(&pcpu_alloc_mutex);
+        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);
+
+/**
+ * __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)
+{
+        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;
+
+                rb_erase(&chunk->rb_node, &pcpu_addr_root);
+                list_move(&chunk->list, &todo);
+        }
+
+        spin_unlock_irq(&pcpu_lock);
+        mutex_unlock(&pcpu_alloc_mutex);
+
+        list_for_each_entry_safe(chunk, next, &todo, list) {
+                pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size, false);
+                free_pcpu_chunk(chunk);
+        }
+}
+
+/**
+ * free_percpu - free percpu area
+ * @ptr: pointer to area to free
+ *
+ * Free percpu area @ptr.
+ *
+ * CONTEXT:
+ * Can be called from atomic context.
+ */
+void free_percpu(void *ptr)
+{
+        void *addr = __pcpu_ptr_to_addr(ptr);
+        struct pcpu_chunk *chunk;
+        unsigned long flags;
+        int off;
+
+        if (!ptr)
+                return;
+
+        spin_lock_irqsave(&pcpu_lock, flags);
+
+        chunk = pcpu_chunk_addr_search(addr);
+        off = addr - chunk->vm->addr;
+
+        pcpu_free_area(chunk, off);
+
+        /* if there are more than one fully free chunks, wake up grim reaper */
+        if (chunk->free_size == pcpu_unit_size) {
+                struct pcpu_chunk *pos;
+
+                list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
+                        if (pos != chunk) {
+                                schedule_work(&pcpu_reclaim_work);
+                                break;
+                        }
+        }
+
+        spin_unlock_irqrestore(&pcpu_lock, flags);
+}
+EXPORT_SYMBOL_GPL(free_percpu);
+
+/**
+ * pcpu_setup_first_chunk - initialize the first percpu chunk
+ * @get_page_fn: callback to fetch page pointer
+ * @static_size: the size of static percpu area in bytes
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
+ * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @base_addr: mapped address, NULL for auto
+ * @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
+ *
+ * Initialize the first percpu chunk which contains the kernel static
+ * perpcu area.  This function is to be called from arch percpu area
+ * setup path.  The first two parameters are mandatory.  The rest are
+ * optional.
+ *
+ * @get_page_fn() should return pointer to percpu page given cpu
+ * number and page number.  It should at least return enough pages to
+ * cover the static area.  The returned pages for static area should
+ * have been initialized with valid data.  If @unit_size is specified,
+ * it can also return pages after the static area.  NULL return
+ * indicates end of pages for the cpu.  Note that @get_page_fn() must
+ * return the same number of pages for all cpus.
+ *
+ * @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.
+ *
+ * @unit_size, if non-negative, specifies unit size and must be
+ * aligned to PAGE_SIZE and equal to or larger than @static_size +
+ * @reserved_size + @dyn_size.
+ *
+ * @dyn_size, if non-negative, limits the number of bytes available
+ * for dynamic allocation in the first chunk.  Specifying non-negative
+ * value make percpu leave alone the area beyond @static_size +
+ * @reserved_size + @dyn_size.
+ *
+ * Non-null @base_addr means that the caller already allocated virtual
+ * region for the first chunk and mapped it.  percpu must not mess
+ * with the chunk.  Note that @base_addr with 0 @unit_size or non-NULL
+ * @populate_pte_fn doesn't make any sense.
+ *
+ * @populate_pte_fn is used to populate the pagetable.  NULL means the
+ * caller already populated the pagetable.
+ *
+ * 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.
+ */
+size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
+                                     size_t static_size, size_t reserved_size,
+                                     ssize_t unit_size, ssize_t dyn_size,
+                                     void *base_addr,
+                                     pcpu_populate_pte_fn_t populate_pte_fn)
+{
+        static struct vm_struct first_vm;
+        static int smap[2], dmap[2];
+        struct pcpu_chunk *schunk, *dchunk = NULL;
+        unsigned int cpu;
+        int nr_pages;
+        int err, i;
+
+        /* santiy checks */
+        BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
+                     ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
+        BUG_ON(!static_size);
+        if (unit_size >= 0) {
+                BUG_ON(unit_size < static_size + reserved_size +
+                                   (dyn_size >= 0 ? dyn_size : 0));
+                BUG_ON(unit_size & ~PAGE_MASK);
+        } else {
+                BUG_ON(dyn_size >= 0);
+                BUG_ON(base_addr);
+        }
+        BUG_ON(base_addr && populate_pte_fn);
+
+        if (unit_size >= 0)
+                pcpu_unit_pages = unit_size >> PAGE_SHIFT;
+        else
+                pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
+                                        PFN_UP(static_size + reserved_size));
+
+        pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
+        pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
+        pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
+                + num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);
+
+        if (dyn_size < 0)
+                dyn_size = pcpu_unit_size - static_size - reserved_size;
+
+        /*
+         * Allocate chunk slots.  The additional last slot is for
+         * empty chunks.
+         */
+        pcpu_nr_slots = __pcpu_size_to_slot(pcpu_unit_size) + 2;
+        pcpu_slot = alloc_bootmem(pcpu_nr_slots * sizeof(pcpu_slot[0]));
+        for (i = 0; i < pcpu_nr_slots; i++)
+                INIT_LIST_HEAD(&pcpu_slot[i]);
+
+        /*
+         * Initialize static chunk.  If reserved_size is zero, the
+         * static chunk covers static area + dynamic allocation area
+         * in the first chunk.  If reserved_size is not zero, it
+         * covers static area + reserved area (mostly used for module
+         * static percpu allocation).
+         */
+        schunk = alloc_bootmem(pcpu_chunk_struct_size);
+        INIT_LIST_HEAD(&schunk->list);
+        schunk->vm = &first_vm;
+        schunk->map = smap;
+        schunk->map_alloc = ARRAY_SIZE(smap);
+        schunk->page = schunk->page_ar;
+
+        if (reserved_size) {
+                schunk->free_size = reserved_size;
+                pcpu_reserved_chunk = schunk;   /* not for dynamic alloc */
+        } else {
+                schunk->free_size = dyn_size;
+                dyn_size = 0;                   /* dynamic area covered */
+        }
+        schunk->contig_hint = schunk->free_size;
+
+        schunk->map[schunk->map_used++] = -static_size;
+        if (schunk->free_size)
+                schunk->map[schunk->map_used++] = schunk->free_size;
+
+        pcpu_reserved_chunk_limit = static_size + schunk->free_size;
+
+        /* init dynamic chunk if necessary */
+        if (dyn_size) {
+                dchunk = alloc_bootmem(sizeof(struct pcpu_chunk));
+                INIT_LIST_HEAD(&dchunk->list);
+                dchunk->vm = &first_vm;
+                dchunk->map = dmap;
+                dchunk->map_alloc = ARRAY_SIZE(dmap);
+                dchunk->page = schunk->page_ar; /* share page map with schunk */
+
+                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;
+        }
+
+        /* allocate vm address */
+        first_vm.flags = VM_ALLOC;
+        first_vm.size = pcpu_chunk_size;
+
+        if (!base_addr)
+                vm_area_register_early(&first_vm, PAGE_SIZE);
+        else {
+                /*
+                 * Pages already mapped.  No need to remap into
+                 * vmalloc area.  In this case the first chunks can't
+                 * be mapped or unmapped by percpu and are marked
+                 * immutable.
+                 */
+                first_vm.addr = base_addr;
+                schunk->immutable = true;
+                if (dchunk)
+                        dchunk->immutable = true;
+        }
+
+        /* assign pages */
+        nr_pages = -1;
+        for_each_possible_cpu(cpu) {
+                for (i = 0; i < pcpu_unit_pages; i++) {
+                        struct page *page = get_page_fn(cpu, i);
+
+                        if (!page)
+                                break;
+                        *pcpu_chunk_pagep(schunk, cpu, i) = page;
+                }
+
+                BUG_ON(i < PFN_UP(static_size));
+
+                if (nr_pages < 0)
+                        nr_pages = i;
+                else
+                        BUG_ON(nr_pages != i);
+        }
+
+        /* map them */
+        if (populate_pte_fn) {
+                for_each_possible_cpu(cpu)
+                        for (i = 0; i < nr_pages; i++)
+                                populate_pte_fn(pcpu_chunk_addr(schunk,
+                                                                cpu, i));
+
+                err = pcpu_map(schunk, 0, nr_pages);
+                if (err)
+                        panic("failed to setup static percpu area, err=%d\n",
+                              err);
+        }
+
+        /* link the first chunk in */
+        if (!dchunk) {
+                pcpu_chunk_relocate(schunk, -1);
+                pcpu_chunk_addr_insert(schunk);
+        } else {
+                pcpu_chunk_relocate(dchunk, -1);
+                pcpu_chunk_addr_insert(dchunk);
+        }
+
+        /* we're done */
+        pcpu_base_addr = (void *)pcpu_chunk_addr(schunk, 0, 0);
+        return pcpu_unit_size;
+}