/*
* 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 if they need to be
* different from the default
*
* - use pcpu_setup_first_chunk() during percpu area initialization to
* setup the first chunk containing the kernel static percpu area
*/
#include <linux/bitmap.h>
#include <linux/bootmem.h>
#include <linux/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/sections.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 */
/* 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 */
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
* @dyn_size: free size for dynamic allocation in bytes, -1 for auto
* @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -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.
*
* @dyn_size, if non-negative, determines the number of bytes
* available for dynamic allocation in the first chunk. Specifying
* non-negative value makes percpu leave alone the area beyond
* @static_size + @reserved_size + @dyn_size.
*
* @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 + if non-negative, @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 dyn_size, ssize_t unit_size,
void *base_addr,
pcpu_populate_pte_fn_t populate_pte_fn)
{
static struct vm_struct first_vm;
static int smap[2], dmap[2];
size_t size_sum = static_size + reserved_size +
(dyn_size >= 0 ? dyn_size : 0);
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 < size_sum);
BUG_ON(unit_size & ~PAGE_MASK);
BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);
} else
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(size_sum));
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;
}
/*
* Embedding first chunk setup helper.
*/
static void *pcpue_ptr __initdata;
static size_t pcpue_size __initdata;
static size_t pcpue_unit_size __initdata;
static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
{
size_t off = (size_t)pageno << PAGE_SHIFT;
if (off >= pcpue_size)
return NULL;
return virt_to_page(pcpue_ptr + cpu * pcpue_unit_size + off);
}
/**
* pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
* @static_size: the size of static percpu area in bytes
* @reserved_size: the size of reserved percpu area in bytes
* @dyn_size: free size for dynamic allocation in bytes, -1 for auto
* @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
*
* 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
* as a contiguous area using bootmem allocator and used as-is without
* being mapped into vmalloc area. This enables the first chunk to
* piggy back on the linear physical mapping which often uses larger
* page size.
*
* When @dyn_size is positive, dynamic area might be larger than
* specified to fill page alignment. Also, when @dyn_size is auto,
* @dyn_size does not fill the whole first chunk but only what's
* necessary for page alignment after static and reserved areas.
*
* If the needed size is smaller than the minimum or specified unit
* size, the leftover is returned to the bootmem allocator.
*
* RETURNS:
* The determined pcpu_unit_size which can be used to initialize
* percpu access on success, -errno on failure.
*/
ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
ssize_t dyn_size, ssize_t unit_size)
{
unsigned int cpu;
/* determine parameters and allocate */
pcpue_size = PFN_ALIGN(static_size + reserved_size +
(dyn_size >= 0 ? dyn_size : 0));
if (dyn_size != 0)
dyn_size = pcpue_size - static_size - reserved_size;
if (unit_size >= 0) {
BUG_ON(unit_size < pcpue_size);
pcpue_unit_size = unit_size;
} else
pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
pcpue_ptr = __alloc_bootmem_nopanic(
num_possible_cpus() * pcpue_unit_size,
PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
if (!pcpue_ptr)
return -ENOMEM;
/* return the leftover and copy */
for_each_possible_cpu(cpu) {
void *ptr = pcpue_ptr + cpu * pcpue_unit_size;
free_bootmem(__pa(ptr + pcpue_size),
pcpue_unit_size - pcpue_size);
memcpy(ptr, __per_cpu_load, static_size);
}
/* we're ready, commit */
pr_info("PERCPU: Embedded %zu pages at %p, static data %zu bytes\n",
pcpue_size >> PAGE_SHIFT, pcpue_ptr, static_size);
return pcpu_setup_first_chunk(pcpue_get_page, static_size,
reserved_size, dyn_size,
pcpue_unit_size, pcpue_ptr, NULL);
}
