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linux/mm/percpu.c

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/*
* mm/percpu.c - percpu memory allocator
*
* Copyright (C) 2009 SUSE Linux Products GmbH
* Copyright (C) 2009 Tejun Heo <tj@kernel.org>
*
* Copyright (C) 2017 Facebook Inc.
* Copyright (C) 2017 Dennis Zhou <dennisszhou@gmail.com>
*
* This file is released under the GPLv2 license.
*
* The percpu allocator handles both static and dynamic areas. Percpu
* areas are allocated in chunks which are divided into units. There is
* a 1-to-1 mapping for units to possible cpus. These units are grouped
* based on NUMA properties of the machine.
*
* c0 c1 c2
* ------------------- ------------------- ------------
* | u0 | u1 | u2 | u3 | | u0 | u1 | u2 | u3 | | u0 | u1 | u
* ------------------- ...... ------------------- .... ------------
*
* Allocation is done by offsets into a unit's address space. Ie., an
* area of 512 bytes at 6k in c1 occupies 512 bytes at 6k in c1:u0,
* c1:u1, c1:u2, etc. On NUMA machines, the mapping may be non-linear
* and even sparse. Access is handled by configuring percpu base
* registers according to the cpu to unit mappings and offsetting the
* base address using pcpu_unit_size.
*
* There is special consideration for the first chunk which must handle
* the static percpu variables in the kernel image as allocation services
* are not online yet. In short, the first chunk is structured like so:
*
* <Static | [Reserved] | Dynamic>
*
* The static data is copied from the original section managed by the
* linker. The reserved section, if non-zero, primarily manages static
* percpu variables from kernel modules. Finally, the dynamic section
* takes care of normal allocations.
*
* The allocator organizes chunks into lists according to free size and
* tries to allocate from the fullest chunk first. Each chunk is managed
* by a bitmap with metadata blocks. The allocation map is updated on
* every allocation and free to reflect the current state while the boundary
* map is only updated on allocation. Each metadata block contains
* information to help mitigate the need to iterate over large portions
* of the bitmap. The reverse mapping from page to chunk is stored in
* the page's index. Lastly, units are lazily backed and grow in unison.
*
* There is a unique conversion that goes on here between bytes and bits.
* Each bit represents a fragment of size PCPU_MIN_ALLOC_SIZE. The chunk
* tracks the number of pages it is responsible for in nr_pages. Helper
* functions are used to convert from between the bytes, bits, and blocks.
* All hints are managed in bits unless explicitly stated.
*
* To use this allocator, arch code should do the following:
*
* - 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
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bitmap.h>
#include <linux/memblock.h>
#include <linux/err.h>
#include <linux/lcm.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/percpu.h>
#include <linux/pfn.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include <linux/kmemleak.h>
#include <linux/sched.h>
#include <asm/cacheflush.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
#define CREATE_TRACE_POINTS
#include <trace/events/percpu.h>
#include "percpu-internal.h"
/* the slots are sorted by free bytes left, 1-31 bytes share the same slot */
#define PCPU_SLOT_BASE_SHIFT 5
#define PCPU_EMPTY_POP_PAGES_LOW 2
#define PCPU_EMPTY_POP_PAGES_HIGH 4
#ifdef CONFIG_SMP
/* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
#ifndef __addr_to_pcpu_ptr
#define __addr_to_pcpu_ptr(addr) \
(void __percpu *)((unsigned long)(addr) - \
(unsigned long)pcpu_base_addr + \
(unsigned long)__per_cpu_start)
#endif
#ifndef __pcpu_ptr_to_addr
#define __pcpu_ptr_to_addr(ptr) \
(void __force *)((unsigned long)(ptr) + \
(unsigned long)pcpu_base_addr - \
(unsigned long)__per_cpu_start)
#endif
#else /* CONFIG_SMP */
/* on UP, it's always identity mapped */
#define __addr_to_pcpu_ptr(addr) (void __percpu *)(addr)
#define __pcpu_ptr_to_addr(ptr) (void __force *)(ptr)
#endif /* CONFIG_SMP */
static int pcpu_unit_pages __ro_after_init;
static int pcpu_unit_size __ro_after_init;
static int pcpu_nr_units __ro_after_init;
static int pcpu_atom_size __ro_after_init;
int pcpu_nr_slots __ro_after_init;
static size_t pcpu_chunk_struct_size __ro_after_init;
/* cpus with the lowest and highest unit addresses */
static unsigned int pcpu_low_unit_cpu __ro_after_init;
static unsigned int pcpu_high_unit_cpu __ro_after_init;
/* the address of the first chunk which starts with the kernel static area */
void *pcpu_base_addr __ro_after_init;
EXPORT_SYMBOL_GPL(pcpu_base_addr);
static const int *pcpu_unit_map __ro_after_init; /* cpu -> unit */
const unsigned long *pcpu_unit_offsets __ro_after_init; /* cpu -> unit offset */
/* group information, used for vm allocation */
static int pcpu_nr_groups __ro_after_init;
static const unsigned long *pcpu_group_offsets __ro_after_init;
static const size_t *pcpu_group_sizes __ro_after_init;
/*
* The first chunk which always exists. Note that unlike other
* chunks, this one can be allocated and mapped in several different
* ways and thus often doesn't live in the vmalloc area.
*/
struct pcpu_chunk *pcpu_first_chunk __ro_after_init;
/*
* Optional reserved chunk. This chunk reserves part of the first
* chunk and serves it for reserved allocations. When the reserved
* region doesn't exist, the following variable is NULL.
*/
struct pcpu_chunk *pcpu_reserved_chunk __ro_after_init;
DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */
static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop, map ext */
struct list_head *pcpu_slot __ro_after_init; /* chunk list slots */
/* chunks which need their map areas extended, protected by pcpu_lock */
static LIST_HEAD(pcpu_map_extend_chunks);
/*
* The number of empty populated pages, protected by pcpu_lock. The
* reserved chunk doesn't contribute to the count.
*/
int pcpu_nr_empty_pop_pages;
/*
* The number of populated pages in use by the allocator, protected by
* pcpu_lock. This number is kept per a unit per chunk (i.e. when a page gets
* allocated/deallocated, it is allocated/deallocated in all units of a chunk
* and increments/decrements this count by 1).
*/
static unsigned long pcpu_nr_populated;
/*
* Balance work is used to populate or destroy chunks asynchronously. We
* try to keep the number of populated free pages between
* PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
* empty chunk.
*/
static void pcpu_balance_workfn(struct work_struct *work);
static DECLARE_WORK(pcpu_balance_work, pcpu_balance_workfn);
static bool pcpu_async_enabled __read_mostly;
static bool pcpu_atomic_alloc_failed;
static void pcpu_schedule_balance_work(void)
{
if (pcpu_async_enabled)
schedule_work(&pcpu_balance_work);
}
/**
* pcpu_addr_in_chunk - check if the address is served from this chunk
* @chunk: chunk of interest
* @addr: percpu address
*
* RETURNS:
* True if the address is served from this chunk.
*/
static bool pcpu_addr_in_chunk(struct pcpu_chunk *chunk, void *addr)
{
void *start_addr, *end_addr;
if (!chunk)
return false;
start_addr = chunk->base_addr + chunk->start_offset;
end_addr = chunk->base_addr + chunk->nr_pages * PAGE_SIZE -
chunk->end_offset;
return addr >= start_addr && addr < end_addr;
}
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_bytes < PCPU_MIN_ALLOC_SIZE || chunk->contig_bits == 0)
return 0;
return pcpu_size_to_slot(chunk->free_bytes);
}
/* set the pointer to a chunk in a page struct */
static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
{
page->index = (unsigned long)pcpu;
}
/* obtain pointer to a chunk from a page struct */
static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
{
return (struct pcpu_chunk *)page->index;
}
static int __maybe_unused pcpu_page_idx(unsigned int cpu, int page_idx)
{
return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
}
static unsigned long pcpu_unit_page_offset(unsigned int cpu, int page_idx)
{
return pcpu_unit_offsets[cpu] + (page_idx << PAGE_SHIFT);
}
static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
unsigned int cpu, int page_idx)
{
return (unsigned long)chunk->base_addr +
pcpu_unit_page_offset(cpu, page_idx);
}
static void pcpu_next_unpop(unsigned long *bitmap, int *rs, int *re, int end)
{
*rs = find_next_zero_bit(bitmap, end, *rs);
*re = find_next_bit(bitmap, end, *rs + 1);
}
static void pcpu_next_pop(unsigned long *bitmap, int *rs, int *re, int end)
{
*rs = find_next_bit(bitmap, end, *rs);
*re = find_next_zero_bit(bitmap, end, *rs + 1);
}
/*
* Bitmap region iterators. Iterates over the bitmap between
* [@start, @end) in @chunk. @rs and @re should be integer variables
* and will be set to start and end index of the current free region.
*/
#define pcpu_for_each_unpop_region(bitmap, rs, re, start, end) \
for ((rs) = (start), pcpu_next_unpop((bitmap), &(rs), &(re), (end)); \
(rs) < (re); \
(rs) = (re) + 1, pcpu_next_unpop((bitmap), &(rs), &(re), (end)))
#define pcpu_for_each_pop_region(bitmap, rs, re, start, end) \
for ((rs) = (start), pcpu_next_pop((bitmap), &(rs), &(re), (end)); \
(rs) < (re); \
(rs) = (re) + 1, pcpu_next_pop((bitmap), &(rs), &(re), (end)))
/*
* The following are helper functions to help access bitmaps and convert
* between bitmap offsets to address offsets.
*/
static unsigned long *pcpu_index_alloc_map(struct pcpu_chunk *chunk, int index)
{
return chunk->alloc_map +
(index * PCPU_BITMAP_BLOCK_BITS / BITS_PER_LONG);
}
static unsigned long pcpu_off_to_block_index(int off)
{
return off / PCPU_BITMAP_BLOCK_BITS;
}
static unsigned long pcpu_off_to_block_off(int off)
{
return off & (PCPU_BITMAP_BLOCK_BITS - 1);
}
static unsigned long pcpu_block_off_to_off(int index, int off)
{
return index * PCPU_BITMAP_BLOCK_BITS + off;
}
/**
* pcpu_next_md_free_region - finds the next hint free area
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of free area
*
* Helper function for pcpu_for_each_md_free_region. It checks
* block->contig_hint and performs aggregation across blocks to find the
* next hint. It modifies bit_off and bits in-place to be consumed in the
* loop.
*/
static void pcpu_next_md_free_region(struct pcpu_chunk *chunk, int *bit_off,
int *bits)
{
int i = pcpu_off_to_block_index(*bit_off);
int block_off = pcpu_off_to_block_off(*bit_off);
struct pcpu_block_md *block;
*bits = 0;
for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
block++, i++) {
/* handles contig area across blocks */
if (*bits) {
*bits += block->left_free;
if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
continue;
return;
}
/*
* This checks three things. First is there a contig_hint to
* check. Second, have we checked this hint before by
* comparing the block_off. Third, is this the same as the
* right contig hint. In the last case, it spills over into
* the next block and should be handled by the contig area
* across blocks code.
*/
*bits = block->contig_hint;
if (*bits && block->contig_hint_start >= block_off &&
*bits + block->contig_hint_start < PCPU_BITMAP_BLOCK_BITS) {
*bit_off = pcpu_block_off_to_off(i,
block->contig_hint_start);
return;
}
/* reset to satisfy the second predicate above */
block_off = 0;
*bits = block->right_free;
*bit_off = (i + 1) * PCPU_BITMAP_BLOCK_BITS - block->right_free;
}
}
/**
* pcpu_next_fit_region - finds fit areas for a given allocation request
* @chunk: chunk of interest
* @alloc_bits: size of allocation
* @align: alignment of area (max PAGE_SIZE)
* @bit_off: chunk offset
* @bits: size of free area
*
* Finds the next free region that is viable for use with a given size and
* alignment. This only returns if there is a valid area to be used for this
* allocation. block->first_free is returned if the allocation request fits
* within the block to see if the request can be fulfilled prior to the contig
* hint.
*/
static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits,
int align, int *bit_off, int *bits)
{
int i = pcpu_off_to_block_index(*bit_off);
int block_off = pcpu_off_to_block_off(*bit_off);
struct pcpu_block_md *block;
*bits = 0;
for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
block++, i++) {
/* handles contig area across blocks */
if (*bits) {
*bits += block->left_free;
if (*bits >= alloc_bits)
return;
if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
continue;
}
/* check block->contig_hint */
*bits = ALIGN(block->contig_hint_start, align) -
block->contig_hint_start;
/*
* This uses the block offset to determine if this has been
* checked in the prior iteration.
*/
if (block->contig_hint &&
block->contig_hint_start >= block_off &&
block->contig_hint >= *bits + alloc_bits) {
*bits += alloc_bits + block->contig_hint_start -
block->first_free;
*bit_off = pcpu_block_off_to_off(i, block->first_free);
return;
}
/* reset to satisfy the second predicate above */
block_off = 0;
*bit_off = ALIGN(PCPU_BITMAP_BLOCK_BITS - block->right_free,
align);
*bits = PCPU_BITMAP_BLOCK_BITS - *bit_off;
*bit_off = pcpu_block_off_to_off(i, *bit_off);
if (*bits >= alloc_bits)
return;
}
/* no valid offsets were found - fail condition */
*bit_off = pcpu_chunk_map_bits(chunk);
}
/*
* Metadata free area iterators. These perform aggregation of free areas
* based on the metadata blocks and return the offset @bit_off and size in
* bits of the free area @bits. pcpu_for_each_fit_region only returns when
* a fit is found for the allocation request.
*/
#define pcpu_for_each_md_free_region(chunk, bit_off, bits) \
for (pcpu_next_md_free_region((chunk), &(bit_off), &(bits)); \
(bit_off) < pcpu_chunk_map_bits((chunk)); \
(bit_off) += (bits) + 1, \
pcpu_next_md_free_region((chunk), &(bit_off), &(bits)))
#define pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) \
for (pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
&(bits)); \
(bit_off) < pcpu_chunk_map_bits((chunk)); \
(bit_off) += (bits), \
pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
&(bits)))
/**
* pcpu_mem_zalloc - allocate memory
* @size: bytes to allocate
* @gfp: allocation flags
*
* Allocate @size bytes. If @size is smaller than PAGE_SIZE,
* kzalloc() is used; otherwise, the equivalent of vzalloc() is used.
* This is to facilitate passing through whitelisted flags. The
* returned memory is always zeroed.
*
* RETURNS:
* Pointer to the allocated area on success, NULL on failure.
*/
static void *pcpu_mem_zalloc(size_t size, gfp_t gfp)
{
if (WARN_ON_ONCE(!slab_is_available()))
return NULL;
if (size <= PAGE_SIZE)
return kzalloc(size, gfp);
else
return __vmalloc(size, gfp | __GFP_ZERO, PAGE_KERNEL);
}
/**
* pcpu_mem_free - free memory
* @ptr: memory to free
*
* Free @ptr. @ptr should have been allocated using pcpu_mem_zalloc().
*/
static void pcpu_mem_free(void *ptr)
{
kvfree(ptr);
}
/**
* pcpu_chunk_relocate - put chunk in the appropriate chunk slot
* @chunk: chunk of interest
* @oslot: the previous slot it was on
*
* This function is called after an allocation or free changed @chunk.
* New slot according to the changed state is determined and @chunk is
* moved to the slot. Note that the reserved chunk is never put on
* chunk slots.
*
* CONTEXT:
* pcpu_lock.
*/
static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
{
int nslot = pcpu_chunk_slot(chunk);
if (chunk != pcpu_reserved_chunk && oslot != nslot) {
if (oslot < nslot)
list_move(&chunk->list, &pcpu_slot[nslot]);
else
list_move_tail(&chunk->list, &pcpu_slot[nslot]);
}
}
/**
* pcpu_cnt_pop_pages- counts populated backing pages in range
* @chunk: chunk of interest
* @bit_off: start offset
* @bits: size of area to check
*
* Calculates the number of populated pages in the region
* [page_start, page_end). This keeps track of how many empty populated
* pages are available and decide if async work should be scheduled.
*
* RETURNS:
* The nr of populated pages.
*/
static inline int pcpu_cnt_pop_pages(struct pcpu_chunk *chunk, int bit_off,
int bits)
{
int page_start = PFN_UP(bit_off * PCPU_MIN_ALLOC_SIZE);
int page_end = PFN_DOWN((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
if (page_start >= page_end)
return 0;
/*
* bitmap_weight counts the number of bits set in a bitmap up to
* the specified number of bits. This is counting the populated
* pages up to page_end and then subtracting the populated pages
* up to page_start to count the populated pages in
* [page_start, page_end).
*/
return bitmap_weight(chunk->populated, page_end) -
bitmap_weight(chunk->populated, page_start);
}
/**
* pcpu_chunk_update - updates the chunk metadata given a free area
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of free area
*
* This updates the chunk's contig hint and starting offset given a free area.
* Choose the best starting offset if the contig hint is equal.
*/
static void pcpu_chunk_update(struct pcpu_chunk *chunk, int bit_off, int bits)
{
if (bits > chunk->contig_bits) {
chunk->contig_bits_start = bit_off;
chunk->contig_bits = bits;
} else if (bits == chunk->contig_bits && chunk->contig_bits_start &&
(!bit_off ||
__ffs(bit_off) > __ffs(chunk->contig_bits_start))) {
/* use the start with the best alignment */
chunk->contig_bits_start = bit_off;
}
}
/**
* pcpu_chunk_refresh_hint - updates metadata about a chunk
* @chunk: chunk of interest
*
* Iterates over the metadata blocks to find the largest contig area.
* It also counts the populated pages and uses the delta to update the
* global count.
*
* Updates:
* chunk->contig_bits
* chunk->contig_bits_start
* nr_empty_pop_pages (chunk and global)
*/
static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
{
int bit_off, bits, nr_empty_pop_pages;
/* clear metadata */
chunk->contig_bits = 0;
bit_off = chunk->first_bit;
bits = nr_empty_pop_pages = 0;
pcpu_for_each_md_free_region(chunk, bit_off, bits) {
pcpu_chunk_update(chunk, bit_off, bits);
nr_empty_pop_pages += pcpu_cnt_pop_pages(chunk, bit_off, bits);
}
/*
* Keep track of nr_empty_pop_pages.
*
* The chunk maintains the previous number of free pages it held,
* so the delta is used to update the global counter. The reserved
* chunk is not part of the free page count as they are populated
* at init and are special to serving reserved allocations.
*/
if (chunk != pcpu_reserved_chunk)
pcpu_nr_empty_pop_pages +=
(nr_empty_pop_pages - chunk->nr_empty_pop_pages);
chunk->nr_empty_pop_pages = nr_empty_pop_pages;
}
/**
* pcpu_block_update - updates a block given a free area
* @block: block of interest
* @start: start offset in block
* @end: end offset in block
*
* Updates a block given a known free area. The region [start, end) is
* expected to be the entirety of the free area within a block. Chooses
* the best starting offset if the contig hints are equal.
*/
static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
{
int contig = end - start;
block->first_free = min(block->first_free, start);
if (start == 0)
block->left_free = contig;
if (end == PCPU_BITMAP_BLOCK_BITS)
block->right_free = contig;
if (contig > block->contig_hint) {
block->contig_hint_start = start;
block->contig_hint = contig;
} else if (block->contig_hint_start && contig == block->contig_hint &&
(!start || __ffs(start) > __ffs(block->contig_hint_start))) {
/* use the start with the best alignment */
block->contig_hint_start = start;
}
}
/**
* pcpu_block_refresh_hint
* @chunk: chunk of interest
* @index: index of the metadata block
*
* Scans over the block beginning at first_free and updates the block
* metadata accordingly.
*/
static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
{
struct pcpu_block_md *block = chunk->md_blocks + index;
unsigned long *alloc_map = pcpu_index_alloc_map(chunk, index);
int rs, re; /* region start, region end */
/* clear hints */
block->contig_hint = 0;
block->left_free = block->right_free = 0;
/* iterate over free areas and update the contig hints */
pcpu_for_each_unpop_region(alloc_map, rs, re, block->first_free,
PCPU_BITMAP_BLOCK_BITS) {
pcpu_block_update(block, rs, re);
}
}
/**
* pcpu_block_update_hint_alloc - update hint on allocation path
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of request
*
* Updates metadata for the allocation path. The metadata only has to be
* refreshed by a full scan iff the chunk's contig hint is broken. Block level
* scans are required if the block's contig hint is broken.
*/
static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
int bits)
{
struct pcpu_block_md *s_block, *e_block, *block;
int s_index, e_index; /* block indexes of the freed allocation */
int s_off, e_off; /* block offsets of the freed allocation */
/*
* Calculate per block offsets.
* The calculation uses an inclusive range, but the resulting offsets
* are [start, end). e_index always points to the last block in the
* range.
*/
s_index = pcpu_off_to_block_index(bit_off);
e_index = pcpu_off_to_block_index(bit_off + bits - 1);
s_off = pcpu_off_to_block_off(bit_off);
e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
s_block = chunk->md_blocks + s_index;
e_block = chunk->md_blocks + e_index;
/*
* Update s_block.
* block->first_free must be updated if the allocation takes its place.
* If the allocation breaks the contig_hint, a scan is required to
* restore this hint.
*/
if (s_off == s_block->first_free)
s_block->first_free = find_next_zero_bit(
pcpu_index_alloc_map(chunk, s_index),
PCPU_BITMAP_BLOCK_BITS,
s_off + bits);
if (s_off >= s_block->contig_hint_start &&
s_off < s_block->contig_hint_start + s_block->contig_hint) {
/* block contig hint is broken - scan to fix it */
pcpu_block_refresh_hint(chunk, s_index);
} else {
/* update left and right contig manually */
s_block->left_free = min(s_block->left_free, s_off);
if (s_index == e_index)
s_block->right_free = min_t(int, s_block->right_free,
PCPU_BITMAP_BLOCK_BITS - e_off);
else
s_block->right_free = 0;
}
/*
* Update e_block.
*/
if (s_index != e_index) {
/*
* When the allocation is across blocks, the end is along
* the left part of the e_block.
*/
e_block->first_free = find_next_zero_bit(
pcpu_index_alloc_map(chunk, e_index),
PCPU_BITMAP_BLOCK_BITS, e_off);
if (e_off == PCPU_BITMAP_BLOCK_BITS) {
/* reset the block */
e_block++;
} else {
if (e_off > e_block->contig_hint_start) {
/* contig hint is broken - scan to fix it */
pcpu_block_refresh_hint(chunk, e_index);
} else {
e_block->left_free = 0;
e_block->right_free =
min_t(int, e_block->right_free,
PCPU_BITMAP_BLOCK_BITS - e_off);
}
}
/* update in-between md_blocks */
for (block = s_block + 1; block < e_block; block++) {
block->contig_hint = 0;
block->left_free = 0;
block->right_free = 0;
}
}
/*
* The only time a full chunk scan is required is if the chunk
* contig hint is broken. Otherwise, it means a smaller space
* was used and therefore the chunk contig hint is still correct.
*/
if (bit_off >= chunk->contig_bits_start &&
bit_off < chunk->contig_bits_start + chunk->contig_bits)
pcpu_chunk_refresh_hint(chunk);
}
/**
* pcpu_block_update_hint_free - updates the block hints on the free path
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of request
*
* Updates metadata for the allocation path. This avoids a blind block
* refresh by making use of the block contig hints. If this fails, it scans
* forward and backward to determine the extent of the free area. This is
* capped at the boundary of blocks.
*
* A chunk update is triggered if a page becomes free, a block becomes free,
* or the free spans across blocks. This tradeoff is to minimize iterating
* over the block metadata to update chunk->contig_bits. chunk->contig_bits
* may be off by up to a page, but it will never be more than the available
* space. If the contig hint is contained in one block, it will be accurate.
*/
static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
int bits)
{
struct pcpu_block_md *s_block, *e_block, *block;
int s_index, e_index; /* block indexes of the freed allocation */
int s_off, e_off; /* block offsets of the freed allocation */
int start, end; /* start and end of the whole free area */
/*
* Calculate per block offsets.
* The calculation uses an inclusive range, but the resulting offsets
* are [start, end). e_index always points to the last block in the
* range.
*/
s_index = pcpu_off_to_block_index(bit_off);
e_index = pcpu_off_to_block_index(bit_off + bits - 1);
s_off = pcpu_off_to_block_off(bit_off);
e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
s_block = chunk->md_blocks + s_index;
e_block = chunk->md_blocks + e_index;
/*
* Check if the freed area aligns with the block->contig_hint.
* If it does, then the scan to find the beginning/end of the
* larger free area can be avoided.
*
* start and end refer to beginning and end of the free area
* within each their respective blocks. This is not necessarily
* the entire free area as it may span blocks past the beginning
* or end of the block.
*/
start = s_off;
if (s_off == s_block->contig_hint + s_block->contig_hint_start) {
start = s_block->contig_hint_start;
} else {
/*
* Scan backwards to find the extent of the free area.
* find_last_bit returns the starting bit, so if the start bit
* is returned, that means there was no last bit and the
* remainder of the chunk is free.
*/
int l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index),
start);
start = (start == l_bit) ? 0 : l_bit + 1;
}
end = e_off;
if (e_off == e_block->contig_hint_start)
end = e_block->contig_hint_start + e_block->contig_hint;
else
end = find_next_bit(pcpu_index_alloc_map(chunk, e_index),
PCPU_BITMAP_BLOCK_BITS, end);
/* update s_block */
e_off = (s_index == e_index) ? end : PCPU_BITMAP_BLOCK_BITS;
pcpu_block_update(s_block, start, e_off);
/* freeing in the same block */
if (s_index != e_index) {
/* update e_block */
pcpu_block_update(e_block, 0, end);
/* reset md_blocks in the middle */
for (block = s_block + 1; block < e_block; block++) {
block->first_free = 0;
block->contig_hint_start = 0;
block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
block->left_free = PCPU_BITMAP_BLOCK_BITS;
block->right_free = PCPU_BITMAP_BLOCK_BITS;
}
}
/*
* Refresh chunk metadata when the free makes a page free, a block
* free, or spans across blocks. The contig hint may be off by up to
* a page, but if the hint is contained in a block, it will be accurate
* with the else condition below.
*/
if ((ALIGN_DOWN(end, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS)) >
ALIGN(start, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS))) ||
s_index != e_index)
pcpu_chunk_refresh_hint(chunk);
else
pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
s_block->contig_hint);
}
/**
* pcpu_is_populated - determines if the region is populated
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of area
* @next_off: return value for the next offset to start searching
*
* For atomic allocations, check if the backing pages are populated.
*
* RETURNS:
* Bool if the backing pages are populated.
* next_index is to skip over unpopulated blocks in pcpu_find_block_fit.
*/
static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
int *next_off)
{
int page_start, page_end, rs, re;
page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
rs = page_start;
pcpu_next_unpop(chunk->populated, &rs, &re, page_end);
if (rs >= page_end)
return true;
*next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
return false;
}
/**
* pcpu_find_block_fit - finds the block index to start searching
* @chunk: chunk of interest
* @alloc_bits: size of request in allocation units
* @align: alignment of area (max PAGE_SIZE bytes)
* @pop_only: use populated regions only
*
* Given a chunk and an allocation spec, find the offset to begin searching
* for a free region. This iterates over the bitmap metadata blocks to
* find an offset that will be guaranteed to fit the requirements. It is
* not quite first fit as if the allocation does not fit in the contig hint
* of a block or chunk, it is skipped. This errs on the side of caution
* to prevent excess iteration. Poor alignment can cause the allocator to
* skip over blocks and chunks that have valid free areas.
*
* RETURNS:
* The offset in the bitmap to begin searching.
* -1 if no offset is found.
*/
static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
size_t align, bool pop_only)
{
int bit_off, bits, next_off;
/*
* Check to see if the allocation can fit in the chunk's contig hint.
* This is an optimization to prevent scanning by assuming if it
* cannot fit in the global hint, there is memory pressure and creating
* a new chunk would happen soon.
*/
bit_off = ALIGN(chunk->contig_bits_start, align) -
chunk->contig_bits_start;
if (bit_off + alloc_bits > chunk->contig_bits)
return -1;
bit_off = chunk->first_bit;
bits = 0;
pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) {
if (!pop_only || pcpu_is_populated(chunk, bit_off, bits,
&next_off))
break;
bit_off = next_off;
bits = 0;
}
if (bit_off == pcpu_chunk_map_bits(chunk))
return -1;
return bit_off;
}
/**
* pcpu_alloc_area - allocates an area from a pcpu_chunk
* @chunk: chunk of interest
* @alloc_bits: size of request in allocation units
* @align: alignment of area (max PAGE_SIZE)
* @start: bit_off to start searching
*
* This function takes in a @start offset to begin searching to fit an
* allocation of @alloc_bits with alignment @align. It needs to scan
* the allocation map because if it fits within the block's contig hint,
* @start will be block->first_free. This is an attempt to fill the
* allocation prior to breaking the contig hint. The allocation and
* boundary maps are updated accordingly if it confirms a valid
* free area.
*
* RETURNS:
* Allocated addr offset in @chunk on success.
* -1 if no matching area is found.
*/
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
size_t align, int start)
{
size_t align_mask = (align) ? (align - 1) : 0;
int bit_off, end, oslot;
lockdep_assert_held(&pcpu_lock);
oslot = pcpu_chunk_slot(chunk);
/*
* Search to find a fit.
*/
end = start + alloc_bits + PCPU_BITMAP_BLOCK_BITS;
bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
alloc_bits, align_mask);
if (bit_off >= end)
return -1;
/* update alloc map */
bitmap_set(chunk->alloc_map, bit_off, alloc_bits);
/* update boundary map */
set_bit(bit_off, chunk->bound_map);
bitmap_clear(chunk->bound_map, bit_off + 1, alloc_bits - 1);
set_bit(bit_off + alloc_bits, chunk->bound_map);
chunk->free_bytes -= alloc_bits * PCPU_MIN_ALLOC_SIZE;
/* update first free bit */
if (bit_off == chunk->first_bit)
chunk->first_bit = find_next_zero_bit(
chunk->alloc_map,
pcpu_chunk_map_bits(chunk),
bit_off + alloc_bits);
pcpu_block_update_hint_alloc(chunk, bit_off, alloc_bits);
pcpu_chunk_relocate(chunk, oslot);
return bit_off * PCPU_MIN_ALLOC_SIZE;
}
/**
* pcpu_free_area - frees the corresponding offset
* @chunk: chunk of interest
* @off: addr offset into chunk
*
* This function determines the size of an allocation to free using
* the boundary bitmap and clears the allocation map.
*/
static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
{
int bit_off, bits, end, oslot;
lockdep_assert_held(&pcpu_lock);
pcpu_stats_area_dealloc(chunk);
oslot = pcpu_chunk_slot(chunk);
bit_off = off / PCPU_MIN_ALLOC_SIZE;
/* find end index */
end = find_next_bit(chunk->bound_map, pcpu_chunk_map_bits(chunk),
bit_off + 1);
bits = end - bit_off;
bitmap_clear(chunk->alloc_map, bit_off, bits);
/* update metadata */
chunk->free_bytes += bits * PCPU_MIN_ALLOC_SIZE;
/* update first free bit */
chunk->first_bit = min(chunk->first_bit, bit_off);
pcpu_block_update_hint_free(chunk, bit_off, bits);
pcpu_chunk_relocate(chunk, oslot);
}
static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
{
struct pcpu_block_md *md_block;
for (md_block = chunk->md_blocks;
md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
md_block++) {
md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
md_block->left_free = PCPU_BITMAP_BLOCK_BITS;
md_block->right_free = PCPU_BITMAP_BLOCK_BITS;
}
}
/**
* pcpu_alloc_first_chunk - creates chunks that serve the first chunk
* @tmp_addr: the start of the region served
* @map_size: size of the region served
*
* This is responsible for creating the chunks that serve the first chunk. The
* base_addr is page aligned down of @tmp_addr while the region end is page
* aligned up. Offsets are kept track of to determine the region served. All
* this is done to appease the bitmap allocator in avoiding partial blocks.
*
* RETURNS:
* Chunk serving the region at @tmp_addr of @map_size.
*/
static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
int map_size)
{
struct pcpu_chunk *chunk;
unsigned long aligned_addr, lcm_align;
int start_offset, offset_bits, region_size, region_bits;
/* region calculations */
aligned_addr = tmp_addr & PAGE_MASK;
start_offset = tmp_addr - aligned_addr;
/*
* Align the end of the region with the LCM of PAGE_SIZE and
* PCPU_BITMAP_BLOCK_SIZE. One of these constants is a multiple of
* the other.
*/
lcm_align = lcm(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE);
region_size = ALIGN(start_offset + map_size, lcm_align);
/* allocate chunk */
chunk = memblock_alloc(sizeof(struct pcpu_chunk) +
BITS_TO_LONGS(region_size >> PAGE_SHIFT),
SMP_CACHE_BYTES);
INIT_LIST_HEAD(&chunk->list);
chunk->base_addr = (void *)aligned_addr;
chunk->start_offset = start_offset;
chunk->end_offset = region_size - chunk->start_offset - map_size;
chunk->nr_pages = region_size >> PAGE_SHIFT;
region_bits = pcpu_chunk_map_bits(chunk);
chunk->alloc_map = memblock_alloc(BITS_TO_LONGS(region_bits) * sizeof(chunk->alloc_map[0]),
SMP_CACHE_BYTES);
chunk->bound_map = memblock_alloc(BITS_TO_LONGS(region_bits + 1) * sizeof(chunk->bound_map[0]),
SMP_CACHE_BYTES);
chunk->md_blocks = memblock_alloc(pcpu_chunk_nr_blocks(chunk) * sizeof(chunk->md_blocks[0]),
SMP_CACHE_BYTES);
pcpu_init_md_blocks(chunk);
/* manage populated page bitmap */
chunk->immutable = true;
bitmap_fill(chunk->populated, chunk->nr_pages);
chunk->nr_populated = chunk->nr_pages;
chunk->nr_empty_pop_pages =
pcpu_cnt_pop_pages(chunk, start_offset / PCPU_MIN_ALLOC_SIZE,
map_size / PCPU_MIN_ALLOC_SIZE);
chunk->contig_bits = map_size / PCPU_MIN_ALLOC_SIZE;
chunk->free_bytes = map_size;
if (chunk->start_offset) {
/* hide the beginning of the bitmap */
offset_bits = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
bitmap_set(chunk->alloc_map, 0, offset_bits);
set_bit(0, chunk->bound_map);
set_bit(offset_bits, chunk->bound_map);
chunk->first_bit = offset_bits;
pcpu_block_update_hint_alloc(chunk, 0, offset_bits);
}
if (chunk->end_offset) {
/* hide the end of the bitmap */
offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE;
bitmap_set(chunk->alloc_map,
pcpu_chunk_map_bits(chunk) - offset_bits,
offset_bits);
set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE,
chunk->bound_map);
set_bit(region_bits, chunk->bound_map);
pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk)
- offset_bits, offset_bits);
}
return chunk;
}
static struct pcpu_chunk *pcpu_alloc_chunk(gfp_t gfp)
{
struct pcpu_chunk *chunk;
int region_bits;
chunk = pcpu_mem_zalloc(pcpu_chunk_struct_size, gfp);
if (!chunk)
return NULL;
INIT_LIST_HEAD(&chunk->list);
chunk->nr_pages = pcpu_unit_pages;
region_bits = pcpu_chunk_map_bits(chunk);
chunk->alloc_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits) *
sizeof(chunk->alloc_map[0]), gfp);
if (!chunk->alloc_map)
goto alloc_map_fail;
chunk->bound_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits + 1) *
sizeof(chunk->bound_map[0]), gfp);
if (!chunk->bound_map)
goto bound_map_fail;
chunk->md_blocks = pcpu_mem_zalloc(pcpu_chunk_nr_blocks(chunk) *
sizeof(chunk->md_blocks[0]), gfp);
if (!chunk->md_blocks)
goto md_blocks_fail;
pcpu_init_md_blocks(chunk);
/* init metadata */
chunk->contig_bits = region_bits;
chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;
return chunk;
md_blocks_fail:
pcpu_mem_free(chunk->bound_map);
bound_map_fail:
pcpu_mem_free(chunk->alloc_map);
alloc_map_fail:
pcpu_mem_free(chunk);
return NULL;
}
static void pcpu_free_chunk(struct pcpu_chunk *chunk)
{
if (!chunk)
return;
pcpu_mem_free(chunk->md_blocks);
pcpu_mem_free(chunk->bound_map);
pcpu_mem_free(chunk->alloc_map);
pcpu_mem_free(chunk);
}
/**
* pcpu_chunk_populated - post-population bookkeeping
* @chunk: pcpu_chunk which got populated
* @page_start: the start page
* @page_end: the end page
* @for_alloc: if this is to populate for allocation
*
* Pages in [@page_start,@page_end) have been populated to @chunk. Update
* the bookkeeping information accordingly. Must be called after each
* successful population.
*
* If this is @for_alloc, do not increment pcpu_nr_empty_pop_pages because it
* is to serve an allocation in that area.
*/
static void pcpu_chunk_populated(struct pcpu_chunk *chunk, int page_start,
int page_end, bool for_alloc)
{
int nr = page_end - page_start;
lockdep_assert_held(&pcpu_lock);
bitmap_set(chunk->populated, page_start, nr);
chunk->nr_populated += nr;
pcpu_nr_populated += nr;
if (!for_alloc) {
chunk->nr_empty_pop_pages += nr;
pcpu_nr_empty_pop_pages += nr;
}
}
/**
* pcpu_chunk_depopulated - post-depopulation bookkeeping
* @chunk: pcpu_chunk which got depopulated
* @page_start: the start page
* @page_end: the end page
*
* Pages in [@page_start,@page_end) have been depopulated from @chunk.
* Update the bookkeeping information accordingly. Must be called after
* each successful depopulation.
*/
static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,
int page_start, int page_end)
{
int nr = page_end - page_start;
lockdep_assert_held(&pcpu_lock);
bitmap_clear(chunk->populated, page_start, nr);
chunk->nr_populated -= nr;
chunk->nr_empty_pop_pages -= nr;
pcpu_nr_empty_pop_pages -= nr;
pcpu_nr_populated -= nr;
}
/*
* Chunk management implementation.
*
* To allow different implementations, chunk alloc/free and
* [de]population are implemented in a separate file which is pulled
* into this file and compiled together. The following functions
* should be implemented.
*
* pcpu_populate_chunk - populate the specified range of a chunk
* pcpu_depopulate_chunk - depopulate the specified range of a chunk
* pcpu_create_chunk - create a new chunk
* pcpu_destroy_chunk - destroy a chunk, always preceded by full depop
* pcpu_addr_to_page - translate address to physical address
* pcpu_verify_alloc_info - check alloc_info is acceptable during init
*/
static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
int page_start, int page_end, gfp_t gfp);
static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
int page_start, int page_end);
static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp);
static void pcpu_destroy_chunk(struct pcpu_chunk *chunk);
static struct page *pcpu_addr_to_page(void *addr);
static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);
#ifdef CONFIG_NEED_PER_CPU_KM
#include "percpu-km.c"
#else
#include "percpu-vm.c"
#endif
/**
* pcpu_chunk_addr_search - determine chunk containing specified address
* @addr: address for which the chunk needs to be determined.
*
* This is an internal function that handles all but static allocations.
* Static percpu address values should never be passed into the allocator.
*
* RETURNS:
* The address of the found chunk.
*/
static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
{
/* is it in the dynamic region (first chunk)? */
if (pcpu_addr_in_chunk(pcpu_first_chunk, addr))
return pcpu_first_chunk;
/* is it in the reserved region? */
if (pcpu_addr_in_chunk(pcpu_reserved_chunk, addr))
return pcpu_reserved_chunk;
/*
* The address is relative to unit0 which might be unused and
* thus unmapped. Offset the address to the unit space of the
* current processor before looking it up in the vmalloc
* space. Note that any possible cpu id can be used here, so
* there's no need to worry about preemption or cpu hotplug.
*/
addr += pcpu_unit_offsets[raw_smp_processor_id()];
return pcpu_get_page_chunk(pcpu_addr_to_page(addr));
}
/**
* pcpu_alloc - the percpu allocator
* @size: size of area to allocate in bytes
* @align: alignment of area (max PAGE_SIZE)
* @reserved: allocate from the reserved chunk if available
* @gfp: allocation flags
*
* Allocate percpu area of @size bytes aligned at @align. If @gfp doesn't
* contain %GFP_KERNEL, the allocation is atomic. If @gfp has __GFP_NOWARN
* then no warning will be triggered on invalid or failed allocation
* requests.
*
* RETURNS:
* Percpu pointer to the allocated area on success, NULL on failure.
*/
static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
gfp_t gfp)
{
/* whitelisted flags that can be passed to the backing allocators */
gfp_t pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
bool is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
bool do_warn = !(gfp & __GFP_NOWARN);
static int warn_limit = 10;
struct pcpu_chunk *chunk;
const char *err;
int slot, off, cpu, ret;
unsigned long flags;
void __percpu *ptr;
size_t bits, bit_align;
/*
* There is now a minimum allocation size of PCPU_MIN_ALLOC_SIZE,
* therefore alignment must be a minimum of that many bytes.
* An allocation may have internal fragmentation from rounding up
* of up to PCPU_MIN_ALLOC_SIZE - 1 bytes.
*/
if (unlikely(align < PCPU_MIN_ALLOC_SIZE))
align = PCPU_MIN_ALLOC_SIZE;
size = ALIGN(size, PCPU_MIN_ALLOC_SIZE);
bits = size >> PCPU_MIN_ALLOC_SHIFT;
bit_align = align >> PCPU_MIN_ALLOC_SHIFT;
if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE ||
!is_power_of_2(align))) {
WARN(do_warn, "illegal size (%zu) or align (%zu) for percpu allocation\n",
size, align);
return NULL;
}
if (!is_atomic) {
/*
* pcpu_balance_workfn() allocates memory under this mutex,
* and it may wait for memory reclaim. Allow current task
* to become OOM victim, in case of memory pressure.
*/
if (gfp & __GFP_NOFAIL)
mutex_lock(&pcpu_alloc_mutex);
else if (mutex_lock_killable(&pcpu_alloc_mutex))
return NULL;
}
spin_lock_irqsave(&pcpu_lock, flags);
/* serve reserved allocations from the reserved chunk if available */
if (reserved && pcpu_reserved_chunk) {
chunk = pcpu_reserved_chunk;
off = pcpu_find_block_fit(chunk, bits, bit_align, is_atomic);
if (off < 0) {
err = "alloc from reserved chunk failed";
goto fail_unlock;
}
off = pcpu_alloc_area(chunk, bits, bit_align, off);
if (off >= 0)
goto area_found;
err = "alloc from reserved chunk failed";
goto fail_unlock;
}
restart:
/* search through normal chunks */
for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
list_for_each_entry(chunk, &pcpu_slot[slot], list) {
off = pcpu_find_block_fit(chunk, bits, bit_align,
is_atomic);
if (off < 0)
continue;
off = pcpu_alloc_area(chunk, bits, bit_align, off);
if (off >= 0)
goto area_found;
}
}
spin_unlock_irqrestore(&pcpu_lock, flags);
/*
* No space left. Create a new chunk. We don't want multiple
* tasks to create chunks simultaneously. Serialize and create iff
* there's still no empty chunk after grabbing the mutex.
*/
if (is_atomic) {
err = "atomic alloc failed, no space left";
goto fail;
}
if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
chunk = pcpu_create_chunk(pcpu_gfp);
if (!chunk) {
err = "failed to allocate new chunk";
goto fail;
}
spin_lock_irqsave(&pcpu_lock, flags);
pcpu_chunk_relocate(chunk, -1);
} else {
spin_lock_irqsave(&pcpu_lock, flags);
}
goto restart;
area_found:
pcpu_stats_area_alloc(chunk, size);
spin_unlock_irqrestore(&pcpu_lock, flags);
/* populate if not all pages are already there */
if (!is_atomic) {
int page_start, page_end, rs, re;
page_start = PFN_DOWN(off);
page_end = PFN_UP(off + size);
pcpu_for_each_unpop_region(chunk->populated, rs, re,
page_start, page_end) {
WARN_ON(chunk->immutable);
ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
spin_lock_irqsave(&pcpu_lock, flags);
if (ret) {
pcpu_free_area(chunk, off);
err = "failed to populate";
goto fail_unlock;
}
pcpu_chunk_populated(chunk, rs, re, true);
spin_unlock_irqrestore(&pcpu_lock, flags);
}
mutex_unlock(&pcpu_alloc_mutex);
}
if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
pcpu_schedule_balance_work();
/* clear the areas and return address relative to base address */
for_each_possible_cpu(cpu)
memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
kmemleak_alloc_percpu(ptr, size, gfp);
trace_percpu_alloc_percpu(reserved, is_atomic, size, align,
chunk->base_addr, off, ptr);
return ptr;
fail_unlock:
spin_unlock_irqrestore(&pcpu_lock, flags);
fail:
trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
if (!is_atomic && do_warn && warn_limit) {
pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
size, align, is_atomic, err);
dump_stack();
if (!--warn_limit)
pr_info("limit reached, disable warning\n");
}
if (is_atomic) {
/* see the flag handling in pcpu_blance_workfn() */
pcpu_atomic_alloc_failed = true;
pcpu_schedule_balance_work();
} else {
mutex_unlock(&pcpu_alloc_mutex);
}
return NULL;
}
/**
* __alloc_percpu_gfp - allocate dynamic percpu area
* @size: size of area to allocate in bytes
* @align: alignment of area (max PAGE_SIZE)
* @gfp: allocation flags
*
* Allocate zero-filled percpu area of @size bytes aligned at @align. If
* @gfp doesn't contain %GFP_KERNEL, the allocation doesn't block and can
* be called from any context but is a lot more likely to fail. If @gfp
* has __GFP_NOWARN then no warning will be triggered on invalid or failed
* allocation requests.
*
* RETURNS:
* Percpu pointer to the allocated area on success, NULL on failure.
*/
void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp)
{
return pcpu_alloc(size, align, false, gfp);
}
EXPORT_SYMBOL_GPL(__alloc_percpu_gfp);
/**
* __alloc_percpu - allocate dynamic percpu area
* @size: size of area to allocate in bytes
* @align: alignment of area (max PAGE_SIZE)
*
* Equivalent to __alloc_percpu_gfp(size, align, %GFP_KERNEL).
*/
void __percpu *__alloc_percpu(size_t size, size_t align)
{
return pcpu_alloc(size, align, false, GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(__alloc_percpu);
/**
* __alloc_reserved_percpu - allocate reserved percpu area
* @size: size of area to allocate in bytes
* @align: alignment of area (max PAGE_SIZE)
*
* Allocate zero-filled percpu area of @size bytes aligned at @align
* from reserved percpu area if arch has set it up; otherwise,
* allocation is served from the same dynamic area. Might sleep.
* Might trigger writeouts.
*
* CONTEXT:
* Does GFP_KERNEL allocation.
*
* RETURNS:
* Percpu pointer to the allocated area on success, NULL on failure.
*/
void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
{
return pcpu_alloc(size, align, true, GFP_KERNEL);
}
/**
* pcpu_balance_workfn - manage the amount of free chunks and populated pages
* @work: unused
*
* Reclaim all fully free chunks except for the first one. This is also
* responsible for maintaining the pool of empty populated pages. However,
* it is possible that this is called when physical memory is scarce causing
* OOM killer to be triggered. We should avoid doing so until an actual
* allocation causes the failure as it is possible that requests can be
* serviced from already backed regions.
*/
static void pcpu_balance_workfn(struct work_struct *work)
{
/* gfp flags passed to underlying allocators */
const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
LIST_HEAD(to_free);
struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1];
struct pcpu_chunk *chunk, *next;
int slot, nr_to_pop, ret;
/*
* There's no reason to keep around multiple unused chunks and VM
* areas can be scarce. Destroy all free chunks except for one.
*/
mutex_lock(&pcpu_alloc_mutex);
spin_lock_irq(&pcpu_lock);
list_for_each_entry_safe(chunk, next, free_head, list) {
WARN_ON(chunk->immutable);
/* spare the first one */
if (chunk == list_first_entry(free_head, struct pcpu_chunk, list))
continue;
list_move(&chunk->list, &to_free);
}
spin_unlock_irq(&pcpu_lock);
list_for_each_entry_safe(chunk, next, &to_free, list) {
int rs, re;
pcpu_for_each_pop_region(chunk->populated, rs, re, 0,
chunk->nr_pages) {
pcpu_depopulate_chunk(chunk, rs, re);
spin_lock_irq(&pcpu_lock);
pcpu_chunk_depopulated(chunk, rs, re);
spin_unlock_irq(&pcpu_lock);
}
pcpu_destroy_chunk(chunk);
cond_resched();
}
/*
* Ensure there are certain number of free populated pages for
* atomic allocs. Fill up from the most packed so that atomic
* allocs don't increase fragmentation. If atomic allocation
* failed previously, always populate the maximum amount. This
* should prevent atomic allocs larger than PAGE_SIZE from keeping
* failing indefinitely; however, large atomic allocs are not
* something we support properly and can be highly unreliable and
* inefficient.
*/
retry_pop:
if (pcpu_atomic_alloc_failed) {
nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
/* best effort anyway, don't worry about synchronization */
pcpu_atomic_alloc_failed = false;
} else {
nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
pcpu_nr_empty_pop_pages,
0, PCPU_EMPTY_POP_PAGES_HIGH);
}
for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
int nr_unpop = 0, rs, re;
if (!nr_to_pop)
break;
spin_lock_irq(&pcpu_lock);
list_for_each_entry(chunk, &pcpu_slot[slot], list) {
nr_unpop = chunk->nr_pages - chunk->nr_populated;
if (nr_unpop)
break;
}
spin_unlock_irq(&pcpu_lock);
if (!nr_unpop)
continue;
/* @chunk can't go away while pcpu_alloc_mutex is held */
pcpu_for_each_unpop_region(chunk->populated, rs, re, 0,
chunk->nr_pages) {
int nr = min(re - rs, nr_to_pop);
ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
if (!ret) {
nr_to_pop -= nr;
spin_lock_irq(&pcpu_lock);
pcpu_chunk_populated(chunk, rs, rs + nr, false);
spin_unlock_irq(&pcpu_lock);
} else {
nr_to_pop = 0;
}
if (!nr_to_pop)
break;
}
}
if (nr_to_pop) {
/* ran out of chunks to populate, create a new one and retry */
chunk = pcpu_create_chunk(gfp);
if (chunk) {
spin_lock_irq(&pcpu_lock);
pcpu_chunk_relocate(chunk, -1);
spin_unlock_irq(&pcpu_lock);
goto retry_pop;
}
}
mutex_unlock(&pcpu_alloc_mutex);
}
/**
* free_percpu - free percpu area
* @ptr: pointer to area to free
*
* Free percpu area @ptr.
*
* CONTEXT:
* Can be called from atomic context.
*/
void free_percpu(void __percpu *ptr)
{
void *addr;
struct pcpu_chunk *chunk;
unsigned long flags;
int off;
if (!ptr)
return;
kmemleak_free_percpu(ptr);
addr = __pcpu_ptr_to_addr(ptr);
spin_lock_irqsave(&pcpu_lock, flags);
chunk = pcpu_chunk_addr_search(addr);
off = addr - chunk->base_addr;
pcpu_free_area(chunk, off);
/* if there are more than one fully free chunks, wake up grim reaper */
if (chunk->free_bytes == pcpu_unit_size) {
struct pcpu_chunk *pos;
list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
if (pos != chunk) {
pcpu_schedule_balance_work();
break;
}
}
trace_percpu_free_percpu(chunk->base_addr, off, ptr);
spin_unlock_irqrestore(&pcpu_lock, flags);
}
EXPORT_SYMBOL_GPL(free_percpu);
bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
{
#ifdef CONFIG_SMP
const size_t static_size = __per_cpu_end - __per_cpu_start;
void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
unsigned int cpu;
for_each_possible_cpu(cpu) {
void *start = per_cpu_ptr(base, cpu);
void *va = (void *)addr;
if (va >= start && va < start + static_size) {
if (can_addr) {
*can_addr = (unsigned long) (va - start);
*can_addr += (unsigned long)
per_cpu_ptr(base, get_boot_cpu_id());
}
return true;
}
}
#endif
/* on UP, can't distinguish from other static vars, always false */
return false;
}
/**
* is_kernel_percpu_address - test whether address is from static percpu area
* @addr: address to test
*
* Test whether @addr belongs to in-kernel static percpu area. Module
* static percpu areas are not considered. For those, use
* is_module_percpu_address().
*
* RETURNS:
* %true if @addr is from in-kernel static percpu area, %false otherwise.
*/
bool is_kernel_percpu_address(unsigned long addr)
{
return __is_kernel_percpu_address(addr, NULL);
}
/**
* per_cpu_ptr_to_phys - convert translated percpu address to physical address
* @addr: the address to be converted to physical address
*
* Given @addr which is dereferenceable address obtained via one of
* percpu access macros, this function translates it into its physical
* address. The caller is responsible for ensuring @addr stays valid
* until this function finishes.
*
* percpu allocator has special setup for the first chunk, which currently
* supports either embedding in linear address space or vmalloc mapping,
* and, from the second one, the backing allocator (currently either vm or
* km) provides translation.
*
* The addr can be translated simply without checking if it falls into the
* first chunk. But the current code reflects better how percpu allocator
* actually works, and the verification can discover both bugs in percpu
* allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
* code.
*
* RETURNS:
* The physical address for @addr.
*/
phys_addr_t per_cpu_ptr_to_phys(void *addr)
{
void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
bool in_first_chunk = false;
unsigned long first_low, first_high;
unsigned int cpu;
/*
* The following test on unit_low/high isn't strictly
* necessary but will speed up lookups of addresses which
* aren't in the first chunk.
*
* The address check is against full chunk sizes. pcpu_base_addr
* points to the beginning of the first chunk including the
* static region. Assumes good intent as the first chunk may
* not be full (ie. < pcpu_unit_pages in size).
*/
first_low = (unsigned long)pcpu_base_addr +
pcpu_unit_page_offset(pcpu_low_unit_cpu, 0);
first_high = (unsigned long)pcpu_base_addr +
pcpu_unit_page_offset(pcpu_high_unit_cpu, pcpu_unit_pages);
if ((unsigned long)addr >= first_low &&
(unsigned long)addr < first_high) {
for_each_possible_cpu(cpu) {
void *start = per_cpu_ptr(base, cpu);
if (addr >= start && addr < start + pcpu_unit_size) {
in_first_chunk = true;
break;
}
}
}
if (in_first_chunk) {
if (!is_vmalloc_addr(addr))
return __pa(addr);
else
return page_to_phys(vmalloc_to_page(addr)) +
offset_in_page(addr);
} else
return page_to_phys(pcpu_addr_to_page(addr)) +
offset_in_page(addr);
}
/**
* pcpu_alloc_alloc_info - allocate percpu allocation info
* @nr_groups: the number of groups
* @nr_units: the number of units
*
* Allocate ai which is large enough for @nr_groups groups containing
* @nr_units units. The returned ai's groups[0].cpu_map points to the
* cpu_map array which is long enough for @nr_units and filled with
* NR_CPUS. It's the caller's responsibility to initialize cpu_map
* pointer of other groups.
*
* RETURNS:
* Pointer to the allocated pcpu_alloc_info on success, NULL on
* failure.
*/
struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
int nr_units)
{
struct pcpu_alloc_info *ai;
size_t base_size, ai_size;
void *ptr;
int unit;
base_size = ALIGN(sizeof(*ai) + nr_groups * sizeof(ai->groups[0]),
__alignof__(ai->groups[0].cpu_map[0]));
ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
ptr = memblock_alloc_nopanic(PFN_ALIGN(ai_size), PAGE_SIZE);
if (!ptr)
return NULL;
ai = ptr;
ptr += base_size;
ai->groups[0].cpu_map = ptr;
for (unit = 0; unit < nr_units; unit++)
ai->groups[0].cpu_map[unit] = NR_CPUS;
ai->nr_groups = nr_groups;
ai->__ai_size = PFN_ALIGN(ai_size);
return ai;
}
/**
* pcpu_free_alloc_info - free percpu allocation info
* @ai: pcpu_alloc_info to free
*
* Free @ai which was allocated by pcpu_alloc_alloc_info().
*/
void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
{
memblock_free_early(__pa(ai), ai->__ai_size);
}
/**
* pcpu_dump_alloc_info - print out information about pcpu_alloc_info
* @lvl: loglevel
* @ai: allocation info to dump
*
* Print out information about @ai using loglevel @lvl.
*/
static void pcpu_dump_alloc_info(const char *lvl,
const struct pcpu_alloc_info *ai)
{
int group_width = 1, cpu_width = 1, width;
char empty_str[] = "--------";
int alloc = 0, alloc_end = 0;
int group, v;
int upa, apl; /* units per alloc, allocs per line */
v = ai->nr_groups;
while (v /= 10)
group_width++;
v = num_possible_cpus();
while (v /= 10)
cpu_width++;
empty_str[min_t(int, cpu_width, sizeof(empty_str) - 1)] = '\0';
upa = ai->alloc_size / ai->unit_size;
width = upa * (cpu_width + 1) + group_width + 3;
apl = rounddown_pow_of_two(max(60 / width, 1));
printk("%spcpu-alloc: s%zu r%zu d%zu u%zu alloc=%zu*%zu",
lvl, ai->static_size, ai->reserved_size, ai->dyn_size,
ai->unit_size, ai->alloc_size / ai->atom_size, ai->atom_size);
for (group = 0; group < ai->nr_groups; group++) {
const struct pcpu_group_info *gi = &ai->groups[group];
int unit = 0, unit_end = 0;
BUG_ON(gi->nr_units % upa);
for (alloc_end += gi->nr_units / upa;
alloc < alloc_end; alloc++) {
if (!(alloc % apl)) {
pr_cont("\n");
printk("%spcpu-alloc: ", lvl);
}
pr_cont("[%0*d] ", group_width, group);
for (unit_end += upa; unit < unit_end; unit++)
if (gi->cpu_map[unit] != NR_CPUS)
pr_cont("%0*d ",
cpu_width, gi->cpu_map[unit]);
else
pr_cont("%s ", empty_str);
}
}
pr_cont("\n");
}
/**
* pcpu_setup_first_chunk - initialize the first percpu chunk
* @ai: pcpu_alloc_info describing how to percpu area is shaped
* @base_addr: mapped address
*
* Initialize the first percpu chunk which contains the kernel static
* perpcu area. This function is to be called from arch percpu area
* setup path.
*
* @ai contains all information necessary to initialize the first
* chunk and prime the dynamic percpu allocator.
*
* @ai->static_size is the size of static percpu area.
*
* @ai->reserved_size, if non-zero, specifies the amount of bytes to
* reserve after the static area in the first chunk. This reserves
* the first chunk such that it's available only through reserved
* percpu allocation. This is primarily used to serve module percpu
* static areas on architectures where the addressing model has
* limited offset range for symbol relocations to guarantee module
* percpu symbols fall inside the relocatable range.
*
* @ai->dyn_size determines the number of bytes available for dynamic
* allocation in the first chunk. The area between @ai->static_size +
* @ai->reserved_size + @ai->dyn_size and @ai->unit_size is unused.
*
* @ai->unit_size specifies unit size and must be aligned to PAGE_SIZE
* and equal to or larger than @ai->static_size + @ai->reserved_size +
* @ai->dyn_size.
*
* @ai->atom_size is the allocation atom size and used as alignment
* for vm areas.
*
* @ai->alloc_size is the allocation size and always multiple of
* @ai->atom_size. This is larger than @ai->atom_size if
* @ai->unit_size is larger than @ai->atom_size.
*
* @ai->nr_groups and @ai->groups describe virtual memory layout of
* percpu areas. Units which should be colocated are put into the
* same group. Dynamic VM areas will be allocated according to these
* groupings. If @ai->nr_groups is zero, a single group containing
* all units is assumed.
*
* The caller should have mapped the first chunk at @base_addr and
* copied static data to each unit.
*
* The first chunk will always contain a static and a dynamic region.
* However, the static region is not managed by any chunk. If the first
* chunk also contains a reserved region, it is served by two chunks -
* one for the reserved region and one for the dynamic region. They
* share the same vm, but use offset regions in the area allocation map.
* The chunk serving the dynamic region is circulated in the chunk slots
* and available for dynamic allocation like any other chunk.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
void *base_addr)
{
size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
size_t static_size, dyn_size;
struct pcpu_chunk *chunk;
unsigned long *group_offsets;
size_t *group_sizes;
unsigned long *unit_off;
unsigned int cpu;
int *unit_map;
int group, unit, i;
int map_size;
unsigned long tmp_addr;
#define PCPU_SETUP_BUG_ON(cond) do { \
if (unlikely(cond)) { \
pr_emerg("failed to initialize, %s\n", #cond); \
pr_emerg("cpu_possible_mask=%*pb\n", \
cpumask_pr_args(cpu_possible_mask)); \
pcpu_dump_alloc_info(KERN_EMERG, ai); \
BUG(); \
} \
} while (0)
/* sanity checks */
PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
#ifdef CONFIG_SMP
PCPU_SETUP_BUG_ON(!ai->static_size);
PCPU_SETUP_BUG_ON(offset_in_page(__per_cpu_start));
#endif
PCPU_SETUP_BUG_ON(!base_addr);
PCPU_SETUP_BUG_ON(offset_in_page(base_addr));
PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
PCPU_SETUP_BUG_ON(offset_in_page(ai->unit_size));
PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->unit_size, PCPU_BITMAP_BLOCK_SIZE));
PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
PCPU_SETUP_BUG_ON(!ai->dyn_size);
PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE));
PCPU_SETUP_BUG_ON(!(IS_ALIGNED(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) ||
IS_ALIGNED(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE)));
PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
/* process group information and build config tables accordingly */
group_offsets = memblock_alloc(ai->nr_groups * sizeof(group_offsets[0]),
SMP_CACHE_BYTES);
group_sizes = memblock_alloc(ai->nr_groups * sizeof(group_sizes[0]),
SMP_CACHE_BYTES);
unit_map = memblock_alloc(nr_cpu_ids * sizeof(unit_map[0]),
SMP_CACHE_BYTES);
unit_off = memblock_alloc(nr_cpu_ids * sizeof(unit_off[0]),
SMP_CACHE_BYTES);
for (cpu = 0; cpu < nr_cpu_ids; cpu++)
unit_map[cpu] = UINT_MAX;
pcpu_low_unit_cpu = NR_CPUS;
pcpu_high_unit_cpu = NR_CPUS;
for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
const struct pcpu_group_info *gi = &ai->groups[group];
group_offsets[group] = gi->base_offset;
group_sizes[group] = gi->nr_units * ai->unit_size;
for (i = 0; i < gi->nr_units; i++) {
cpu = gi->cpu_map[i];
if (cpu == NR_CPUS)
continue;
PCPU_SETUP_BUG_ON(cpu >= nr_cpu_ids);
PCPU_SETUP_BUG_ON(!cpu_possible(cpu));
PCPU_SETUP_BUG_ON(unit_map[cpu] != UINT_MAX);
unit_map[cpu] = unit + i;
unit_off[cpu] = gi->base_offset + i * ai->unit_size;
/* determine low/high unit_cpu */
if (pcpu_low_unit_cpu == NR_CPUS ||
unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
pcpu_low_unit_cpu = cpu;
if (pcpu_high_unit_cpu == NR_CPUS ||
unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
pcpu_high_unit_cpu = cpu;
}
}
pcpu_nr_units = unit;
for_each_possible_cpu(cpu)
PCPU_SETUP_BUG_ON(unit_map[cpu] == UINT_MAX);
/* we're done parsing the input, undefine BUG macro and dump config */
#undef PCPU_SETUP_BUG_ON
pcpu_dump_alloc_info(KERN_DEBUG, ai);
pcpu_nr_groups = ai->nr_groups;
pcpu_group_offsets = group_offsets;
pcpu_group_sizes = group_sizes;
pcpu_unit_map = unit_map;
pcpu_unit_offsets = unit_off;
/* determine basic parameters */
pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT;
pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
pcpu_atom_size = ai->atom_size;
pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);
pcpu_stats_save_ai(ai);
/*
* Allocate chunk slots. The additional last slot is for
* empty chunks.
*/
pcpu_nr_slots = __pcpu_size_to_slot(pcpu_unit_size) + 2;
pcpu_slot = memblock_alloc(pcpu_nr_slots * sizeof(pcpu_slot[0]),
SMP_CACHE_BYTES);
for (i = 0; i < pcpu_nr_slots; i++)
INIT_LIST_HEAD(&pcpu_slot[i]);
/*
* The end of the static region needs to be aligned with the
* minimum allocation size as this offsets the reserved and
* dynamic region. The first chunk ends page aligned by
* expanding the dynamic region, therefore the dynamic region
* can be shrunk to compensate while still staying above the
* configured sizes.
*/
static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE);
dyn_size = ai->dyn_size - (static_size - ai->static_size);
/*
* Initialize first chunk.
* If the reserved_size is non-zero, this initializes the reserved
* chunk. If the reserved_size is zero, the reserved chunk is NULL
* and the dynamic region is initialized here. The first chunk,
* pcpu_first_chunk, will always point to the chunk that serves
* the dynamic region.
*/
tmp_addr = (unsigned long)base_addr + static_size;
map_size = ai->reserved_size ?: dyn_size;
chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
/* init dynamic chunk if necessary */
if (ai->reserved_size) {
pcpu_reserved_chunk = chunk;
tmp_addr = (unsigned long)base_addr + static_size +
ai->reserved_size;
map_size = dyn_size;
chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
}
/* link the first chunk in */
pcpu_first_chunk = chunk;
pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
pcpu_chunk_relocate(pcpu_first_chunk, -1);
/* include all regions of the first chunk */
pcpu_nr_populated += PFN_DOWN(size_sum);
pcpu_stats_chunk_alloc();
trace_percpu_create_chunk(base_addr);
/* we're done */
pcpu_base_addr = base_addr;
return 0;
}
#ifdef CONFIG_SMP
const char * const pcpu_fc_names[PCPU_FC_NR] __initconst = {
[PCPU_FC_AUTO] = "auto",
[PCPU_FC_EMBED] = "embed",
[PCPU_FC_PAGE] = "page",
};
enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
static int __init percpu_alloc_setup(char *str)
{
if (!str)
return -EINVAL;
if (0)
/* nada */;
#ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
else if (!strcmp(str, "embed"))
pcpu_chosen_fc = PCPU_FC_EMBED;
#endif
#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
else if (!strcmp(str, "page"))
pcpu_chosen_fc = PCPU_FC_PAGE;
#endif
else
pr_warn("unknown allocator %s specified\n", str);
return 0;
}
early_param("percpu_alloc", percpu_alloc_setup);
/*
* pcpu_embed_first_chunk() is used by the generic percpu setup.
* Build it if needed by the arch config or the generic setup is going
* to be used.
*/
#if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
!defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
#define BUILD_EMBED_FIRST_CHUNK
#endif
/* build pcpu_page_first_chunk() iff needed by the arch config */
#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
#define BUILD_PAGE_FIRST_CHUNK
#endif
/* pcpu_build_alloc_info() is used by both embed and page first chunk */
#if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
/**
* pcpu_build_alloc_info - build alloc_info considering distances between CPUs
* @reserved_size: the size of reserved percpu area in bytes
* @dyn_size: minimum free size for dynamic allocation in bytes
* @atom_size: allocation atom size
* @cpu_distance_fn: callback to determine distance between cpus, optional
*
* This function determines grouping of units, their mappings to cpus
* and other parameters considering needed percpu size, allocation
* atom size and distances between CPUs.
*
* Groups are always multiples of atom size and CPUs which are of
* LOCAL_DISTANCE both ways are grouped together and share space for
* units in the same group. The returned configuration is guaranteed
* to have CPUs on different nodes on different groups and >=75% usage
* of allocated virtual address space.
*
* RETURNS:
* On success, pointer to the new allocation_info is returned. On
* failure, ERR_PTR value is returned.
*/
static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
size_t reserved_size, size_t dyn_size,
size_t atom_size,
pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
{
static int group_map[NR_CPUS] __initdata;
static int group_cnt[NR_CPUS] __initdata;
const size_t static_size = __per_cpu_end - __per_cpu_start;
int nr_groups = 1, nr_units = 0;
size_t size_sum, min_unit_size, alloc_size;
int upa, max_upa, uninitialized_var(best_upa); /* units_per_alloc */
int last_allocs, group, unit;
unsigned int cpu, tcpu;
struct pcpu_alloc_info *ai;
unsigned int *cpu_map;
/* this function may be called multiple times */
memset(group_map, 0, sizeof(group_map));
memset(group_cnt, 0, sizeof(group_cnt));
/* calculate size_sum and ensure dyn_size is enough for early alloc */
size_sum = PFN_ALIGN(static_size + reserved_size +
max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
dyn_size = size_sum - static_size - reserved_size;
/*
* Determine min_unit_size, alloc_size and max_upa such that
* alloc_size is multiple of atom_size and is the smallest
* which can accommodate 4k aligned segments which are equal to
* or larger than min_unit_size.
*/
min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
/* determine the maximum # of units that can fit in an allocation */
alloc_size = roundup(min_unit_size, atom_size);
upa = alloc_size / min_unit_size;
while (alloc_size % upa || (offset_in_page(alloc_size / upa)))
upa--;
max_upa = upa;
/* group cpus according to their proximity */
for_each_possible_cpu(cpu) {
group = 0;
next_group:
for_each_possible_cpu(tcpu) {
if (cpu == tcpu)
break;
if (group_map[tcpu] == group && cpu_distance_fn &&
(cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
group++;
nr_groups = max(nr_groups, group + 1);
goto next_group;
}
}
group_map[cpu] = group;
group_cnt[group]++;
}
/*
* Wasted space is caused by a ratio imbalance of upa to group_cnt.
* Expand the unit_size until we use >= 75% of the units allocated.
* Related to atom_size, which could be much larger than the unit_size.
*/
last_allocs = INT_MAX;
for (upa = max_upa; upa; upa--) {
int allocs = 0, wasted = 0;
if (alloc_size % upa || (offset_in_page(alloc_size / upa)))
continue;
for (group = 0; group < nr_groups; group++) {
int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
allocs += this_allocs;
wasted += this_allocs * upa - group_cnt[group];
}
/*
* Don't accept if wastage is over 1/3. The
* greater-than comparison ensures upa==1 always
* passes the following check.
*/
if (wasted > num_possible_cpus() / 3)
continue;
/* and then don't consume more memory */
if (allocs > last_allocs)
break;
last_allocs = allocs;
best_upa = upa;
}
upa = best_upa;
/* allocate and fill alloc_info */
for (group = 0; group < nr_groups; group++)
nr_units += roundup(group_cnt[group], upa);
ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
if (!ai)
return ERR_PTR(-ENOMEM);
cpu_map = ai->groups[0].cpu_map;
for (group = 0; group < nr_groups; group++) {
ai->groups[group].cpu_map = cpu_map;
cpu_map += roundup(group_cnt[group], upa);
}
ai->static_size = static_size;
ai->reserved_size = reserved_size;
ai->dyn_size = dyn_size;
ai->unit_size = alloc_size / upa;
ai->atom_size = atom_size;
ai->alloc_size = alloc_size;
for (group = 0, unit = 0; group_cnt[group]; group++) {
struct pcpu_group_info *gi = &ai->groups[group];
/*
* Initialize base_offset as if all groups are located
* back-to-back. The caller should update this to
* reflect actual allocation.
*/
gi->base_offset = unit * ai->unit_size;
for_each_possible_cpu(cpu)
if (group_map[cpu] == group)
gi->cpu_map[gi->nr_units++] = cpu;
gi->nr_units = roundup(gi->nr_units, upa);
unit += gi->nr_units;
}
BUG_ON(unit != nr_units);
return ai;
}
#endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
#if defined(BUILD_EMBED_FIRST_CHUNK)
/**
* pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
* @reserved_size: the size of reserved percpu area in bytes
* @dyn_size: minimum free size for dynamic allocation in bytes
* @atom_size: allocation atom size
* @cpu_distance_fn: callback to determine distance between cpus, optional
* @alloc_fn: function to allocate percpu page
* @free_fn: function to free percpu page
*
* This is a helper to ease setting up embedded first percpu chunk and
* can be called where pcpu_setup_first_chunk() is expected.
*
* If this function is used to setup the first chunk, it is allocated
* by calling @alloc_fn and used as-is without being mapped into
* vmalloc area. Allocations are always whole multiples of @atom_size
* aligned to @atom_size.
*
* This enables the first chunk to piggy back on the linear physical
* mapping which often uses larger page size. Please note that this
* can result in very sparse cpu->unit mapping on NUMA machines thus
* requiring large vmalloc address space. Don't use this allocator if
* vmalloc space is not orders of magnitude larger than distances
* between node memory addresses (ie. 32bit NUMA machines).
*
* @dyn_size specifies the minimum dynamic area size.
*
* If the needed size is smaller than the minimum or specified unit
* size, the leftover is returned using @free_fn.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
size_t atom_size,
pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
pcpu_fc_alloc_fn_t alloc_fn,
pcpu_fc_free_fn_t free_fn)
{
void *base = (void *)ULONG_MAX;
void **areas = NULL;
struct pcpu_alloc_info *ai;
size_t size_sum, areas_size;
unsigned long max_distance;
int group, i, highest_group, rc;
ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
cpu_distance_fn);
if (IS_ERR(ai))
return PTR_ERR(ai);
size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
areas_size = PFN_ALIGN(ai->nr_groups * sizeof(void *));
areas = memblock_alloc_nopanic(areas_size, SMP_CACHE_BYTES);
if (!areas) {
rc = -ENOMEM;
goto out_free;
}
/* allocate, copy and determine base address & max_distance */
highest_group = 0;
for (group = 0; group < ai->nr_groups; group++) {
struct pcpu_group_info *gi = &ai->groups[group];
unsigned int cpu = NR_CPUS;
void *ptr;
for (i = 0; i < gi->nr_units && cpu == NR_CPUS; i++)
cpu = gi->cpu_map[i];
BUG_ON(cpu == NR_CPUS);
/* allocate space for the whole group */
ptr = alloc_fn(cpu, gi->nr_units * ai->unit_size, atom_size);
if (!ptr) {
rc = -ENOMEM;
goto out_free_areas;
}
/* kmemleak tracks the percpu allocations separately */
kmemleak_free(ptr);
areas[group] = ptr;
base = min(ptr, base);
if (ptr > areas[highest_group])
highest_group = group;
}
max_distance = areas[highest_group] - base;
max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
/* warn if maximum distance is further than 75% of vmalloc space */
if (max_distance > VMALLOC_TOTAL * 3 / 4) {
pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
max_distance, VMALLOC_TOTAL);
#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
/* and fail if we have fallback */
rc = -EINVAL;
goto out_free_areas;
#endif
}
/*
* Copy data and free unused parts. This should happen after all
* allocations are complete; otherwise, we may end up with
* overlapping groups.
*/
for (group = 0; group < ai->nr_groups; group++) {
struct pcpu_group_info *gi = &ai->groups[group];
void *ptr = areas[group];
for (i = 0; i < gi->nr_units; i++, ptr += ai->unit_size) {
if (gi->cpu_map[i] == NR_CPUS) {
/* unused unit, free whole */
free_fn(ptr, ai->unit_size);
continue;
}
/* copy and return the unused part */
memcpy(ptr, __per_cpu_load, ai->static_size);
free_fn(ptr + size_sum, ai->unit_size - size_sum);
}
}
/* base address is now known, determine group base offsets */
for (group = 0; group < ai->nr_groups; group++) {
ai->groups[group].base_offset = areas[group] - base;
}
pr_info("Embedded %zu pages/cpu @%p s%zu r%zu d%zu u%zu\n",
PFN_DOWN(size_sum), base, ai->static_size, ai->reserved_size,
ai->dyn_size, ai->unit_size);
rc = pcpu_setup_first_chunk(ai, base);
goto out_free;
out_free_areas:
for (group = 0; group < ai->nr_groups; group++)
if (areas[group])
free_fn(areas[group],
ai->groups[group].nr_units * ai->unit_size);
out_free:
pcpu_free_alloc_info(ai);
if (areas)
memblock_free_early(__pa(areas), areas_size);
return rc;
}
#endif /* BUILD_EMBED_FIRST_CHUNK */
#ifdef BUILD_PAGE_FIRST_CHUNK
/**
* pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
* @reserved_size: the size of reserved percpu area in bytes
* @alloc_fn: function to allocate percpu page, always called with PAGE_SIZE
* @free_fn: function to free percpu page, always called with PAGE_SIZE
* @populate_pte_fn: function to populate pte
*
* This is a helper to ease setting up page-remapped first percpu
* chunk and can be called where pcpu_setup_first_chunk() is expected.
*
* This is the basic allocator. Static percpu area is allocated
* page-by-page into vmalloc area.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int __init pcpu_page_first_chunk(size_t reserved_size,
pcpu_fc_alloc_fn_t alloc_fn,
pcpu_fc_free_fn_t free_fn,
pcpu_fc_populate_pte_fn_t populate_pte_fn)
{
static struct vm_struct vm;
struct pcpu_alloc_info *ai;
char psize_str[16];
int unit_pages;
size_t pages_size;
struct page **pages;
int unit, i, j, rc;
int upa;
int nr_g0_units;
snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
if (IS_ERR(ai))
return PTR_ERR(ai);
BUG_ON(ai->nr_groups != 1);
upa = ai->alloc_size/ai->unit_size;
nr_g0_units = roundup(num_possible_cpus(), upa);
if (WARN_ON(ai->groups[0].nr_units != nr_g0_units)) {
pcpu_free_alloc_info(ai);
return -EINVAL;
}
unit_pages = ai->unit_size >> PAGE_SHIFT;
/* unaligned allocations can't be freed, round up to page size */
pages_size = PFN_ALIGN(unit_pages * num_possible_cpus() *
sizeof(pages[0]));
pages = memblock_alloc(pages_size, SMP_CACHE_BYTES);
/* allocate pages */
j = 0;
for (unit = 0; unit < num_possible_cpus(); unit++) {
unsigned int cpu = ai->groups[0].cpu_map[unit];
for (i = 0; i < unit_pages; i++) {
void *ptr;
ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
if (!ptr) {
pr_warn("failed to allocate %s page for cpu%u\n",
psize_str, cpu);
goto enomem;
}
/* kmemleak tracks the percpu allocations separately */
kmemleak_free(ptr);
pages[j++] = virt_to_page(ptr);
}
}
/* allocate vm area, map the pages and copy static data */
vm.flags = VM_ALLOC;
vm.size = num_possible_cpus() * ai->unit_size;
vm_area_register_early(&vm, PAGE_SIZE);
for (unit = 0; unit < num_possible_cpus(); unit++) {
unsigned long unit_addr =
(unsigned long)vm.addr + unit * ai->unit_size;
for (i = 0; i < unit_pages; i++)
populate_pte_fn(unit_addr + (i << PAGE_SHIFT));
/* pte already populated, the following shouldn't fail */
rc = __pcpu_map_pages(unit_addr, &pages[unit * unit_pages],
unit_pages);
if (rc < 0)
panic("failed to map percpu area, err=%d\n", rc);
/*
* FIXME: Archs with virtual cache should flush local
* cache for the linear mapping here - something
* equivalent to flush_cache_vmap() on the local cpu.
* flush_cache_vmap() can't be used as most supporting
* data structures are not set up yet.
*/
/* copy static data */
memcpy((void *)unit_addr, __per_cpu_load, ai->static_size);
}
/* we're ready, commit */
pr_info("%d %s pages/cpu @%p s%zu r%zu d%zu\n",
unit_pages, psize_str, vm.addr, ai->static_size,
ai->reserved_size, ai->dyn_size);
rc = pcpu_setup_first_chunk(ai, vm.addr);
goto out_free_ar;
enomem:
while (--j >= 0)
free_fn(page_address(pages[j]), PAGE_SIZE);
rc = -ENOMEM;
out_free_ar:
memblock_free_early(__pa(pages), pages_size);
pcpu_free_alloc_info(ai);
return rc;
}
#endif /* BUILD_PAGE_FIRST_CHUNK */
#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
/*
* Generic SMP percpu area setup.
*
* The embedding helper is used because its behavior closely resembles
* the original non-dynamic generic percpu area setup. This is
* important because many archs have addressing restrictions and might
* fail if the percpu area is located far away from the previous
* location. As an added bonus, in non-NUMA cases, embedding is
* generally a good idea TLB-wise because percpu area can piggy back
* on the physical linear memory mapping which uses large page
* mappings on applicable archs.
*/
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);
static void * __init pcpu_dfl_fc_alloc(unsigned int cpu, size_t size,
size_t align)
{
return memblock_alloc_from_nopanic(
size, align, __pa(MAX_DMA_ADDRESS));
}
static void __init pcpu_dfl_fc_free(void *ptr, size_t size)
{
memblock_free_early(__pa(ptr), size);
}
void __init setup_per_cpu_areas(void)
{
unsigned long delta;
unsigned int cpu;
int rc;
/*
* Always reserve area for module percpu variables. That's
* what the legacy allocator did.
*/
rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
PERCPU_DYNAMIC_RESERVE, PAGE_SIZE, NULL,
pcpu_dfl_fc_alloc, pcpu_dfl_fc_free);
if (rc < 0)
panic("Failed to initialize percpu areas.");
delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
for_each_possible_cpu(cpu)
__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
}
#endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
#else /* CONFIG_SMP */
/*
* UP percpu area setup.
*
* UP always uses km-based percpu allocator with identity mapping.
* Static percpu variables are indistinguishable from the usual static
* variables and don't require any special preparation.
*/
void __init setup_per_cpu_areas(void)
{
const size_t unit_size =
roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
PERCPU_DYNAMIC_RESERVE));
struct pcpu_alloc_info *ai;
void *fc;
ai = pcpu_alloc_alloc_info(1, 1);
fc = memblock_alloc_from_nopanic(unit_size,
PAGE_SIZE,
__pa(MAX_DMA_ADDRESS));
if (!ai || !fc)
panic("Failed to allocate memory for percpu areas.");
/* kmemleak tracks the percpu allocations separately */
kmemleak_free(fc);
ai->dyn_size = unit_size;
ai->unit_size = unit_size;
ai->atom_size = unit_size;
ai->alloc_size = unit_size;
ai->groups[0].nr_units = 1;
ai->groups[0].cpu_map[0] = 0;
if (pcpu_setup_first_chunk(ai, fc) < 0)
panic("Failed to initialize percpu areas.");
pcpu_free_alloc_info(ai);
}
#endif /* CONFIG_SMP */
/*
* pcpu_nr_pages - calculate total number of populated backing pages
*
* This reflects the number of pages populated to back chunks. Metadata is
* excluded in the number exposed in meminfo as the number of backing pages
* scales with the number of cpus and can quickly outweigh the memory used for
* metadata. It also keeps this calculation nice and simple.
*
* RETURNS:
* Total number of populated backing pages in use by the allocator.
*/
unsigned long pcpu_nr_pages(void)
{
return pcpu_nr_populated * pcpu_nr_units;
}
/*
* Percpu allocator is initialized early during boot when neither slab or
* workqueue is available. Plug async management until everything is up
* and running.
*/
static int __init percpu_enable_async(void)
{
pcpu_async_enabled = true;
return 0;
}
subsys_initcall(percpu_enable_async);
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