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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
commit5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch)
treea94efe259b9009378be6d90eb30d2b019d95c194 /mm/percpu.c
parentInitial commit. (diff)
downloadlinux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.tar.xz
linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.zip
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'mm/percpu.c')
-rw-r--r--mm/percpu.c3181
1 files changed, 3181 insertions, 0 deletions
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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 <tj@kernel.org>
+ *
+ * Copyright (C) 2017 Facebook Inc.
+ * Copyright (C) 2017 Dennis Zhou <dennis@kernel.org>
+ *
+ * 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/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 free bytes left, 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_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++;
+ pcpu_block_update(e_block, 0, end);
+
+ /* reset md_blocks in the middle */
+ nr_empty_pages += (e_index - s_index - 1);
+ for (block = s_block + 1; block < e_block; block++) {
+ block->first_free = 0;
+ block->scan_hint = 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;
+ }
+ }
+
+ if (nr_empty_pages)
+ pcpu_update_empty_pages(chunk, nr_empty_pages);
+
+ /*
+ * Refresh chunk metadata when the free makes a block free or spans
+ * across blocks. The contig_hint may be off by up to a page, but if
+ * the contig_hint is contained in a block, it will be accurate with
+ * the else condition below.
+ */
+ if (((end - start) >= PCPU_BITMAP_BLOCK_BITS) || s_index != e_index)
+ pcpu_chunk_refresh_hint(chunk, true);
+ else
+ pcpu_block_update(&chunk->chunk_md,
+ pcpu_block_off_to_off(s_index, start),
+ end);
+}
+
+/**
+ * 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)
+{
+ unsigned 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;
+ bitmap_next_clear_region(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)
+{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
+ 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_md->contig_hint_start, align) -
+ chunk_md->contig_hint_start;
+ if (bit_off + alloc_bits > chunk_md->contig_hint)
+ return -1;
+
+ bit_off = pcpu_next_hint(chunk_md, alloc_bits);
+ 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_find_zero_area - modified from bitmap_find_next_zero_area_off()
+ * @map: the address to base the search on
+ * @size: the bitmap size in bits
+ * @start: the bitnumber to start searching at
+ * @nr: the number of zeroed bits we're looking for
+ * @align_mask: alignment mask for zero area
+ * @largest_off: offset of the largest area skipped
+ * @largest_bits: size of the largest area skipped
+ *
+ * The @align_mask should be one less than a power of 2.
+ *
+ * This is a modified version of bitmap_find_next_zero_area_off() to remember
+ * the largest area that was skipped. This is imperfect, but in general is
+ * good enough. The largest remembered region is the largest failed region
+ * seen. This does not include anything we possibly skipped due to alignment.
+ * pcpu_block_update_scan() does scan backwards to try and recover what was
+ * lost to alignment. While this can cause scanning to miss earlier possible
+ * free areas, smaller allocations will eventually fill those holes.
+ */
+static unsigned long pcpu_find_zero_area(unsigned long *map,
+ unsigned long size,
+ unsigned long start,
+ unsigned long nr,
+ unsigned long align_mask,
+ unsigned long *largest_off,
+ unsigned long *largest_bits)
+{
+ unsigned long index, end, i, area_off, area_bits;
+again:
+ index = find_next_zero_bit(map, size, start);
+
+ /* Align allocation */
+ index = __ALIGN_MASK(index, align_mask);
+ area_off = index;
+
+ end = index + nr;
+ if (end > size)
+ return end;
+ i = find_next_bit(map, end, index);
+ if (i < end) {
+ area_bits = i - area_off;
+ /* remember largest unused area with best alignment */
+ if (area_bits > *largest_bits ||
+ (area_bits == *largest_bits && *largest_off &&
+ (!area_off || __ffs(area_off) > __ffs(*largest_off)))) {
+ *largest_off = area_off;
+ *largest_bits = area_bits;
+ }
+
+ start = i + 1;
+ goto again;
+ }
+ return index;
+}
+
+/**
+ * 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)
+{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
+ size_t align_mask = (align) ? (align - 1) : 0;
+ unsigned long area_off = 0, area_bits = 0;
+ int bit_off, end, oslot;
+
+ lockdep_assert_held(&pcpu_lock);
+
+ oslot = pcpu_chunk_slot(chunk);
+
+ /*
+ * Search to find a fit.
+ */
+ end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
+ pcpu_chunk_map_bits(chunk));
+ bit_off = pcpu_find_zero_area(chunk->alloc_map, end, start, alloc_bits,
+ align_mask, &area_off, &area_bits);
+ if (bit_off >= end)
+ return -1;
+
+ if (area_bits)
+ pcpu_block_update_scan(chunk, area_off, area_bits);
+
+ /* 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_md->first_free)
+ chunk_md->first_free = 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.
+ *
+ * RETURNS:
+ * Number of freed bytes.
+ */
+static int pcpu_free_area(struct pcpu_chunk *chunk, int off)
+{
+ struct pcpu_block_md *chunk_md = &chunk->chunk_md;
+ int bit_off, bits, end, oslot, freed;
+
+ 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);
+
+ freed = bits * PCPU_MIN_ALLOC_SIZE;
+
+ /* update metadata */
+ chunk->free_bytes += freed;
+
+ /* update first free bit */
+ chunk_md->first_free = min(chunk_md->first_free, bit_off);
+
+ pcpu_block_update_hint_free(chunk, bit_off, bits);
+
+ pcpu_chunk_relocate(chunk, oslot);
+
+ return freed;
+}
+
+static void pcpu_init_md_block(struct pcpu_block_md *block, int nr_bits)
+{
+ block->scan_hint = 0;
+ block->contig_hint = nr_bits;
+ block->left_free = nr_bits;
+ block->right_free = nr_bits;
+ block->first_free = 0;
+ block->nr_bits = nr_bits;
+}
+
+static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
+{
+ struct pcpu_block_md *md_block;
+
+ /* init the chunk's block */
+ pcpu_init_md_block(&chunk->chunk_md, pcpu_chunk_map_bits(chunk));
+
+ for (md_block = chunk->md_blocks;
+ md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
+ md_block++)
+ pcpu_init_md_block(md_block, 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;
+ size_t alloc_size;
+
+ /* 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 */
+ alloc_size = struct_size(chunk, populated,
+ BITS_TO_LONGS(region_size >> PAGE_SHIFT));
+ chunk = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!chunk)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ 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);
+
+ alloc_size = BITS_TO_LONGS(region_bits) * sizeof(chunk->alloc_map[0]);
+ chunk->alloc_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!chunk->alloc_map)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ alloc_size =
+ BITS_TO_LONGS(region_bits + 1) * sizeof(chunk->bound_map[0]);
+ chunk->bound_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!chunk->bound_map)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ alloc_size = pcpu_chunk_nr_blocks(chunk) * sizeof(chunk->md_blocks[0]);
+ chunk->md_blocks = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!chunk->md_blocks)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+#ifdef CONFIG_MEMCG_KMEM
+ /* first chunk isn't memcg-aware */
+ chunk->obj_cgroups = NULL;
+#endif
+ 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 = chunk->nr_pages;
+
+ 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->chunk_md.first_free = 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(enum pcpu_chunk_type type, 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;
+
+#ifdef CONFIG_MEMCG_KMEM
+ if (pcpu_is_memcg_chunk(type)) {
+ chunk->obj_cgroups =
+ pcpu_mem_zalloc(pcpu_chunk_map_bits(chunk) *
+ sizeof(struct obj_cgroup *), gfp);
+ if (!chunk->obj_cgroups)
+ goto objcg_fail;
+ }
+#endif
+
+ pcpu_init_md_blocks(chunk);
+
+ /* init metadata */
+ chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;
+
+ return chunk;
+
+#ifdef CONFIG_MEMCG_KMEM
+objcg_fail:
+ pcpu_mem_free(chunk->md_blocks);
+#endif
+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;
+#ifdef CONFIG_MEMCG_KMEM
+ pcpu_mem_free(chunk->obj_cgroups);
+#endif
+ 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
+ *
+ * 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)
+{
+ 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;
+
+ pcpu_update_empty_pages(chunk, 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;
+ pcpu_nr_populated -= nr;
+
+ pcpu_update_empty_pages(chunk, -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(enum pcpu_chunk_type type,
+ 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));
+}
+
+#ifdef CONFIG_MEMCG_KMEM
+static enum pcpu_chunk_type pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
+ struct obj_cgroup **objcgp)
+{
+ struct obj_cgroup *objcg;
+
+ if (!memcg_kmem_enabled() || !(gfp & __GFP_ACCOUNT))
+ return PCPU_CHUNK_ROOT;
+
+ objcg = get_obj_cgroup_from_current();
+ if (!objcg)
+ return PCPU_CHUNK_ROOT;
+
+ if (obj_cgroup_charge(objcg, gfp, size * num_possible_cpus())) {
+ obj_cgroup_put(objcg);
+ return PCPU_FAIL_ALLOC;
+ }
+
+ *objcgp = objcg;
+ return PCPU_CHUNK_MEMCG;
+}
+
+static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
+ struct pcpu_chunk *chunk, int off,
+ size_t size)
+{
+ if (!objcg)
+ return;
+
+ if (chunk) {
+ chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = objcg;
+
+ rcu_read_lock();
+ mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
+ size * num_possible_cpus());
+ rcu_read_unlock();
+ } else {
+ obj_cgroup_uncharge(objcg, size * num_possible_cpus());
+ obj_cgroup_put(objcg);
+ }
+}
+
+static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
+{
+ struct obj_cgroup *objcg;
+
+ if (!pcpu_is_memcg_chunk(pcpu_chunk_type(chunk)))
+ return;
+
+ objcg = chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT];
+ chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = NULL;
+
+ obj_cgroup_uncharge(objcg, size * num_possible_cpus());
+
+ rcu_read_lock();
+ mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
+ -(size * num_possible_cpus()));
+ rcu_read_unlock();
+
+ obj_cgroup_put(objcg);
+}
+
+#else /* CONFIG_MEMCG_KMEM */
+static enum pcpu_chunk_type
+pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp, struct obj_cgroup **objcgp)
+{
+ return PCPU_CHUNK_ROOT;
+}
+
+static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
+ struct pcpu_chunk *chunk, int off,
+ size_t size)
+{
+}
+
+static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
+{
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
+/**
+ * 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)
+{
+ gfp_t pcpu_gfp;
+ bool is_atomic;
+ bool do_warn;
+ enum pcpu_chunk_type type;
+ struct list_head *pcpu_slot;
+ struct obj_cgroup *objcg = NULL;
+ static int warn_limit = 10;
+ struct pcpu_chunk *chunk, *next;
+ const char *err;
+ int slot, off, cpu, ret;
+ unsigned long flags;
+ void __percpu *ptr;
+ size_t bits, bit_align;
+
+ gfp = current_gfp_context(gfp);
+ /* whitelisted flags that can be passed to the backing allocators */
+ pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+ is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
+ do_warn = !(gfp & __GFP_NOWARN);
+
+ /*
+ * 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;
+ }
+
+ type = pcpu_memcg_pre_alloc_hook(size, gfp, &objcg);
+ if (unlikely(type == PCPU_FAIL_ALLOC))
+ return NULL;
+ pcpu_slot = pcpu_chunk_list(type);
+
+ 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)) {
+ pcpu_memcg_post_alloc_hook(objcg, NULL, 0, size);
+ 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_safe(chunk, next, &pcpu_slot[slot], list) {
+ off = pcpu_find_block_fit(chunk, bits, bit_align,
+ is_atomic);
+ if (off < 0) {
+ if (slot < PCPU_SLOT_FAIL_THRESHOLD)
+ pcpu_chunk_move(chunk, 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(type, 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) {
+ unsigned int page_start, page_end, rs, re;
+
+ page_start = PFN_DOWN(off);
+ page_end = PFN_UP(off + size);
+
+ bitmap_for_each_clear_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);
+ spin_unlock_irqrestore(&pcpu_lock, flags);
+ }
+
+ mutex_unlock(&pcpu_alloc_mutex);
+ }
+
+ if (pcpu_nr_empty_pop_pages[type] < 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);
+
+ pcpu_memcg_post_alloc_hook(objcg, chunk, off, size);
+
+ 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);
+ }
+
+ pcpu_memcg_post_alloc_hook(objcg, NULL, 0, size);
+
+ 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
+ * @type: chunk type
+ *
+ * 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(enum pcpu_chunk_type type)
+{
+ /* gfp flags passed to underlying allocators */
+ const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
+ LIST_HEAD(to_free);
+ struct list_head *pcpu_slot = pcpu_chunk_list(type);
+ 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) {
+ unsigned int rs, re;
+
+ bitmap_for_each_set_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[type],
+ 0, PCPU_EMPTY_POP_PAGES_HIGH);
+ }
+
+ for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
+ unsigned 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 */
+ bitmap_for_each_clear_region(chunk->populated, rs, re, 0,
+ chunk->nr_pages) {
+ int nr = min_t(int, 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);
+ 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(type, 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);
+}
+
+/**
+ * pcpu_balance_workfn - manage the amount of free chunks and populated pages
+ * @work: unused
+ *
+ * Call __pcpu_balance_workfn() for each chunk type.
+ */
+static void pcpu_balance_workfn(struct work_struct *work)
+{
+ enum pcpu_chunk_type type;
+
+ for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
+ __pcpu_balance_workfn(type);
+}
+
+/**
+ * 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 size, off;
+ bool need_balance = false;
+ struct list_head *pcpu_slot;
+
+ 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;
+
+ size = pcpu_free_area(chunk, off);
+
+ pcpu_slot = pcpu_chunk_list(pcpu_chunk_type(chunk));
+
+ pcpu_memcg_free_hook(chunk, off, size);
+
+ /* 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) {
+ need_balance = true;
+ break;
+ }
+ }
+
+ trace_percpu_free_percpu(chunk->base_addr, off, ptr);
+
+ spin_unlock_irqrestore(&pcpu_lock, flags);
+
+ if (need_balance)
+ pcpu_schedule_balance_work();
+}
+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(struct_size(ai, groups, nr_groups),
+ __alignof__(ai->groups[0].cpu_map[0]));
+ ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
+
+ ptr = memblock_alloc(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
+ * percpu 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.
+ */
+void __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;
+ size_t alloc_size;
+ enum pcpu_chunk_type type;
+
+#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 */
+ alloc_size = ai->nr_groups * sizeof(group_offsets[0]);
+ group_offsets = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!group_offsets)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ alloc_size = ai->nr_groups * sizeof(group_sizes[0]);
+ group_sizes = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!group_sizes)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ alloc_size = nr_cpu_ids * sizeof(unit_map[0]);
+ unit_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!unit_map)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ alloc_size = nr_cpu_ids * sizeof(unit_off[0]);
+ unit_off = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
+ if (!unit_off)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ alloc_size);
+
+ 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 = struct_size(chunk, populated,
+ BITS_TO_LONGS(pcpu_unit_pages));
+
+ 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_chunk_lists = memblock_alloc(pcpu_nr_slots *
+ sizeof(pcpu_chunk_lists[0]) *
+ PCPU_NR_CHUNK_TYPES,
+ SMP_CACHE_BYTES);
+ if (!pcpu_chunk_lists)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ pcpu_nr_slots * sizeof(pcpu_chunk_lists[0]) *
+ PCPU_NR_CHUNK_TYPES);
+
+ for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
+ for (i = 0; i < pcpu_nr_slots; i++)
+ INIT_LIST_HEAD(&pcpu_chunk_list(type)[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_CHUNK_ROOT] = 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;
+}
+
+#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, 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 < nr_groups; 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 = 0;
+
+ 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(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 s%zu r%zu d%zu u%zu\n",
+ PFN_DOWN(size_sum), ai->static_size, ai->reserved_size,
+ ai->dyn_size, ai->unit_size);
+
+ 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 = 0;
+ 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);
+ if (!pages)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ pages_size);
+
+ /* 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 s%zu r%zu d%zu\n",
+ unit_pages, psize_str, ai->static_size,
+ ai->reserved_size, ai->dyn_size);
+
+ 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(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(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;
+
+ pcpu_setup_first_chunk(ai, fc);
+ 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);