linux/mm/percpu.c
Tejun Heo ccea34b5d0 percpu: finer grained locking to break deadlock and allow atomic free
Impact: fix deadlock and allow atomic free

Percpu allocation always uses GFP_KERNEL and whole alloc/free paths
were protected by single mutex.  All percpu allocations have been from
GFP_KERNEL-safe context and the original allocator had this assumption
too.  However, by protecting both alloc and free paths with the same
mutex, the new allocator creates free -> alloc -> GFP_KERNEL
dependency which the original allocator didn't have.  This can lead to
deadlock if free is called from FS or IO paths.  Also, in general,
allocators are expected to allow free to be called from atomic
context.

This patch implements finer grained locking to break the deadlock and
allow atomic free.  For details, please read the "Synchronization
rules" comment.

While at it, also add CONTEXT: to function comments to describe which
context they expect to be called from and what they do to it.

This problem was reported by Thomas Gleixner and Peter Zijlstra.

  http://thread.gmane.org/gmane.linux.kernel/802384

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Peter Zijlstra <peterz@infradead.org>
2009-03-07 14:46:35 +09:00

1227 lines
34 KiB
C

/*
* 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;
}