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percpu.c
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percpu.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/percpu.c - percpu memory allocator
*
* Copyright (C) 2009 SUSE Linux Products GmbH
* Copyright (C) 2009 Tejun Heo <[email protected]>
*
* Copyright (C) 2017 Facebook Inc.
* Copyright (C) 2017 Dennis Zhou <[email protected]>
*
* 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
* memcg-awareness. To make a percpu allocation memcg-aware the __GFP_ACCOUNT
* flag should be passed. All memcg-aware allocations are sharing one set
* of chunks and all unaccounted allocations and allocations performed
* by processes belonging to the root memory cgroup are using the second set.
*
* The allocator 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/cpumask.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 <linux/sched/mm.h>
#include <linux/memcontrol.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 the size of the biggest continuous free area.
* 1-31 bytes share the same slot.
*/
#define PCPU_SLOT_BASE_SHIFT 5
/* chunks in slots below this are subject to being sidelined on failed alloc */
#define PCPU_SLOT_FAIL_THRESHOLD 3
#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_chunk_lists __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 by chunk type, protected by pcpu_lock.
* The reserved chunk doesn't contribute to the count.
*/
int pcpu_nr_empty_pop_pages[PCPU_NR_CHUNK_TYPES];
/*
* 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)
{
const struct pcpu_block_md *chunk_md = &chunk->chunk_md;
if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE ||
chunk_md->contig_hint == 0)
return 0;
return pcpu_size_to_slot(chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
}
/* 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);
}
/*
* 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_check_block_hint - check against the contig hint
* @block: block of interest
* @bits: size of allocation
* @align: alignment of area (max PAGE_SIZE)
*
* Check to see if the allocation can fit in the block's contig hint.
* Note, a chunk uses the same hints as a block so this can also check against
* the chunk's contig hint.
*/
static bool pcpu_check_block_hint(struct pcpu_block_md *block, int bits,
size_t align)
{
int bit_off = ALIGN(block->contig_hint_start, align) -
block->contig_hint_start;
return bit_off + bits <= block->contig_hint;
}
/*
* pcpu_next_hint - determine which hint to use
* @block: block of interest
* @alloc_bits: size of allocation
*
* This determines if we should scan based on the scan_hint or first_free.
* In general, we want to scan from first_free to fulfill allocations by
* first fit. However, if we know a scan_hint at position scan_hint_start
* cannot fulfill an allocation, we can begin scanning from there knowing
* the contig_hint will be our fallback.
*/
static int pcpu_next_hint(struct pcpu_block_md *block, int alloc_bits)
{
/*
* The three conditions below determine if we can skip past the
* scan_hint. First, does the scan hint exist. Second, is the
* contig_hint after the scan_hint (possibly not true iff
* contig_hint == scan_hint). Third, is the allocation request
* larger than the scan_hint.
*/
if (block->scan_hint &&
block->contig_hint_start > block->scan_hint_start &&
alloc_bits > block->scan_hint)
return block->scan_hint_start + block->scan_hint;
return block->first_free;
}
/**
* 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) {
int start = pcpu_next_hint(block, alloc_bits);
*bits += alloc_bits + block->contig_hint_start -
start;
*bit_off = pcpu_block_off_to_off(i, start);
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);
}
/**
* 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);
}
static void __pcpu_chunk_move(struct pcpu_chunk *chunk, int slot,
bool move_front)
{
if (chunk != pcpu_reserved_chunk) {
struct list_head *pcpu_slot;
pcpu_slot = pcpu_chunk_list(pcpu_chunk_type(chunk));
if (move_front)
list_move(&chunk->list, &pcpu_slot[slot]);
else
list_move_tail(&chunk->list, &pcpu_slot[slot]);
}
}
static void pcpu_chunk_move(struct pcpu_chunk *chunk, int slot)
{
__pcpu_chunk_move(chunk, slot, true);
}
/**
* 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 (oslot != nslot)
__pcpu_chunk_move(chunk, nslot, oslot < nslot);
}
/*
* pcpu_update_empty_pages - update empty page counters
* @chunk: chunk of interest
* @nr: nr of empty pages
*
* This is used to keep track of the empty pages now based on the premise
* a md_block covers a page. The hint update functions recognize if a block
* is made full or broken to calculate deltas for keeping track of free pages.
*/
static inline void pcpu_update_empty_pages(struct pcpu_chunk *chunk, int nr)
{
chunk->nr_empty_pop_pages += nr;
if (chunk != pcpu_reserved_chunk)
pcpu_nr_empty_pop_pages[pcpu_chunk_type(chunk)] += nr;
}
/*
* pcpu_region_overlap - determines if two regions overlap
* @a: start of first region, inclusive
* @b: end of first region, exclusive
* @x: start of second region, inclusive
* @y: end of second region, exclusive
*
* This is used to determine if the hint region [a, b) overlaps with the
* allocated region [x, y).
*/
static inline bool pcpu_region_overlap(int a, int b, int x, int y)
{
return (a < y) && (x < b);
}
/**
* 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 == block->nr_bits)
block->right_free = contig;
if (contig > block->contig_hint) {
/* promote the old contig_hint to be the new scan_hint */
if (start > block->contig_hint_start) {
if (block->contig_hint > block->scan_hint) {
block->scan_hint_start =
block->contig_hint_start;
block->scan_hint = block->contig_hint;
} else if (start < block->scan_hint_start) {
/*
* The old contig_hint == scan_hint. But, the
* new contig is larger so hold the invariant
* scan_hint_start < contig_hint_start.
*/
block->scan_hint = 0;
}
} else {
block->scan_hint = 0;
}
block->contig_hint_start = start;
block->contig_hint = contig;
} else if (contig == block->contig_hint) {
if (block->contig_hint_start &&
(!start ||
__ffs(start) > __ffs(block->contig_hint_start))) {
/* start has a better alignment so use it */
block->contig_hint_start = start;
if (start < block->scan_hint_start &&
block->contig_hint > block->scan_hint)
block->scan_hint = 0;
} else if (start > block->scan_hint_start ||
block->contig_hint > block->scan_hint) {
/*
* Knowing contig == contig_hint, update the scan_hint
* if it is farther than or larger than the current
* scan_hint.
*/
block->scan_hint_start = start;
block->scan_hint = contig;
}
} else {
/*
* The region is smaller than the contig_hint. So only update
* the scan_hint if it is larger than or equal and farther than
* the current scan_hint.
*/
if ((start < block->contig_hint_start &&
(contig > block->scan_hint ||
(contig == block->scan_hint &&
start > block->scan_hint_start)))) {
block->scan_hint_start = start;
block->scan_hint = contig;
}
}
}
/*
* pcpu_block_update_scan - update a block given a free area from a scan
* @chunk: chunk of interest
* @bit_off: chunk offset
* @bits: size of free area
*
* Finding the final allocation spot first goes through pcpu_find_block_fit()
* to find a block that can hold the allocation and then pcpu_alloc_area()
* where a scan is used. When allocations require specific alignments,
* we can inadvertently create holes which will not be seen in the alloc
* or free paths.
*
* This takes a given free area hole and updates a block as it may change the
* scan_hint. We need to scan backwards to ensure we don't miss free bits
* from alignment.
*/
static void pcpu_block_update_scan(struct pcpu_chunk *chunk, int bit_off,
int bits)
{
int s_off = pcpu_off_to_block_off(bit_off);
int e_off = s_off + bits;
int s_index, l_bit;
struct pcpu_block_md *block;
if (e_off > PCPU_BITMAP_BLOCK_BITS)
return;
s_index = pcpu_off_to_block_index(bit_off);
block = chunk->md_blocks + s_index;
/* scan backwards in case of alignment skipping free bits */
l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index), s_off);
s_off = (s_off == l_bit) ? 0 : l_bit + 1;
pcpu_block_update(block, s_off, e_off);
}
/**
* pcpu_chunk_refresh_hint - updates metadata about a chunk
* @chunk: chunk of interest
* @full_scan: if we should scan from the beginning
*
* Iterates over the metadata blocks to find the largest contig area.
* A full scan can be avoided on the allocation path as this is triggered
* if we broke the contig_hint. In doing so, the scan_hint will be before
* the contig_hint or after if the scan_hint == contig_hint. This cannot
* be prevented on freeing as we want to find the largest area possibly
* spanning blocks.
*/
static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk, bool full_scan)
{
struct pcpu_block_md *chunk_md = &chunk->chunk_md;
int bit_off, bits;
/* promote scan_hint to contig_hint */
if (!full_scan && chunk_md->scan_hint) {
bit_off = chunk_md->scan_hint_start + chunk_md->scan_hint;
chunk_md->contig_hint_start = chunk_md->scan_hint_start;
chunk_md->contig_hint = chunk_md->scan_hint;
chunk_md->scan_hint = 0;
} else {
bit_off = chunk_md->first_free;
chunk_md->contig_hint = 0;
}
bits = 0;
pcpu_for_each_md_free_region(chunk, bit_off, bits)
pcpu_block_update(chunk_md, bit_off, bit_off + bits);
}
/**
* 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);
unsigned int rs, re, start; /* region start, region end */
/* promote scan_hint to contig_hint */
if (block->scan_hint) {
start = block->scan_hint_start + block->scan_hint;
block->contig_hint_start = block->scan_hint_start;
block->contig_hint = block->scan_hint;
block->scan_hint = 0;
} else {
start = block->first_free;
block->contig_hint = 0;
}
block->right_free = 0;
/* iterate over free areas and update the contig hints */
bitmap_for_each_clear_region(alloc_map, rs, re, start,
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 *chunk_md = &chunk->chunk_md;
int nr_empty_pages = 0;
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_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
nr_empty_pages++;
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 (pcpu_region_overlap(s_block->scan_hint_start,
s_block->scan_hint_start + s_block->scan_hint,
s_off,
s_off + bits))
s_block->scan_hint = 0;
if (pcpu_region_overlap(s_block->contig_hint_start,
s_block->contig_hint_start +
s_block->contig_hint,
s_off,
s_off + bits)) {
/* block contig hint is broken - scan to fix it */
if (!s_off)
s_block->left_free = 0;
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) {
if (e_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
nr_empty_pages++;
/*
* 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->scan_hint_start)
e_block->scan_hint = 0;
e_block->left_free = 0;
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->right_free =
min_t(int, e_block->right_free,
PCPU_BITMAP_BLOCK_BITS - e_off);
}
}
/* update in-between md_blocks */
nr_empty_pages += (e_index - s_index - 1);
for (block = s_block + 1; block < e_block; block++) {
block->scan_hint = 0;
block->contig_hint = 0;
block->left_free = 0;
block->right_free = 0;
}
}
if (nr_empty_pages)
pcpu_update_empty_pages(chunk, -nr_empty_pages);
if (pcpu_region_overlap(chunk_md->scan_hint_start,
chunk_md->scan_hint_start +
chunk_md->scan_hint,
bit_off,
bit_off + bits))
chunk_md->scan_hint = 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 (pcpu_region_overlap(chunk_md->contig_hint_start,
chunk_md->contig_hint_start +
chunk_md->contig_hint,
bit_off,
bit_off + bits))
pcpu_chunk_refresh_hint(chunk, false);
}
/**
* 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_md->contig_hint.
* chunk_md->contig_hint 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)
{
int nr_empty_pages = 0;
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;
if (!start && e_off == PCPU_BITMAP_BLOCK_BITS)
nr_empty_pages++;
pcpu_block_update(s_block, start, e_off);
/* freeing in the same block */
if (s_index != e_index) {
/* update e_block */
if (end == PCPU_BITMAP_BLOCK_BITS)
nr_empty_pages++;