percpu.c 31.2 KB
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/*
 * linux/mm/percpu.c - percpu memory allocator
 *
 * Copyright (C) 2009		SUSE Linux Products GmbH
 * Copyright (C) 2009		Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 *
 * This is percpu allocator which can handle both static and dynamic
 * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
 * chunk is consisted of num_possible_cpus() units and the first chunk
 * is used for static percpu variables in the kernel image (special
 * boot time alloc/init handling necessary as these areas need to be
 * brought up before allocation services are running).  Unit grows as
 * necessary and all units grow or shrink in unison.  When a chunk is
 * filled up, another chunk is allocated.  ie. in vmalloc area
 *
 *  c0                           c1                         c2
 *  -------------------          -------------------        ------------
 * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
 *  -------------------  ......  -------------------  ....  ------------
 *
 * Allocation is done in offset-size areas of single unit space.  Ie,
 * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
 * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring
 * percpu base registers UNIT_SIZE apart.
 *
 * There are usually many small percpu allocations many of them as
 * small as 4 bytes.  The allocator organizes chunks into lists
 * according to free size and tries to allocate from the fullest one.
 * Each chunk keeps the maximum contiguous area size hint which is
 * guaranteed to be eqaul to or larger than the maximum contiguous
 * area in the chunk.  This helps the allocator not to iterate the
 * chunk maps unnecessarily.
 *
 * Allocation state in each chunk is kept using an array of integers
 * on chunk->map.  A positive value in the map represents a free
 * region and negative allocated.  Allocation inside a chunk is done
 * by scanning this map sequentially and serving the first matching
 * entry.  This is mostly copied from the percpu_modalloc() allocator.
 * Chunks are also linked into a rb tree to ease address to chunk
 * mapping during free.
 *
 * To use this allocator, arch code should do the followings.
 *
 * - define CONFIG_HAVE_DYNAMIC_PER_CPU_AREA
 *
 * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
 *   regular address to percpu pointer and back
 *
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 * - use pcpu_setup_first_chunk() during percpu area initialization to
 *   setup the first chunk containing the kernel static percpu area
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 */

#include <linux/bitmap.h>
#include <linux/bootmem.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/percpu.h>
#include <linux/pfn.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

#define PCPU_SLOT_BASE_SHIFT		5	/* 1-31 shares the same slot */
#define PCPU_DFL_MAP_ALLOC		16	/* start a map with 16 ents */

struct pcpu_chunk {
	struct list_head	list;		/* linked to pcpu_slot lists */
	struct rb_node		rb_node;	/* key is chunk->vm->addr */
	int			free_size;	/* free bytes in the chunk */
	int			contig_hint;	/* max contiguous size hint */
	struct vm_struct	*vm;		/* mapped vmalloc region */
	int			map_used;	/* # of map entries used */
	int			map_alloc;	/* # of map entries allocated */
	int			*map;		/* allocation map */
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	bool			immutable;	/* no [de]population allowed */
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	struct page		**page;		/* points to page array */
	struct page		*page_ar[];	/* #cpus * UNIT_PAGES */
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};

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static int pcpu_unit_pages __read_mostly;
static int pcpu_unit_size __read_mostly;
static int pcpu_chunk_size __read_mostly;
static int pcpu_nr_slots __read_mostly;
static size_t pcpu_chunk_struct_size __read_mostly;
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/* the address of the first chunk which starts with the kernel static area */
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void *pcpu_base_addr __read_mostly;
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EXPORT_SYMBOL_GPL(pcpu_base_addr);

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/* optional reserved chunk, only accessible for reserved allocations */
static struct pcpu_chunk *pcpu_reserved_chunk;
/* offset limit of the reserved chunk */
static int pcpu_reserved_chunk_limit;

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/*
 * One mutex to rule them all.
 *
 * The following mutex is grabbed in the outermost public alloc/free
 * interface functions and released only when the operation is
 * complete.  As such, every function in this file other than the
 * outermost functions are called under pcpu_mutex.
 *
 * It can easily be switched to use spinlock such that only the area
 * allocation and page population commit are protected with it doing
 * actual [de]allocation without holding any lock.  However, given
 * what this allocator does, I think it's better to let them run
 * sequentially.
 */
static DEFINE_MUTEX(pcpu_mutex);

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static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
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static struct rb_root pcpu_addr_root = RB_ROOT;	/* chunks by address */

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static int __pcpu_size_to_slot(int size)
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{
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	int highbit = fls(size);	/* size is in bytes */
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	return max(highbit - PCPU_SLOT_BASE_SHIFT + 2, 1);
}

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static int pcpu_size_to_slot(int size)
{
	if (size == pcpu_unit_size)
		return pcpu_nr_slots - 1;
	return __pcpu_size_to_slot(size);
}

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static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
{
	if (chunk->free_size < sizeof(int) || chunk->contig_hint < sizeof(int))
		return 0;

	return pcpu_size_to_slot(chunk->free_size);
}

static int pcpu_page_idx(unsigned int cpu, int page_idx)
{
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	return cpu * pcpu_unit_pages + page_idx;
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}

static struct page **pcpu_chunk_pagep(struct pcpu_chunk *chunk,
				      unsigned int cpu, int page_idx)
{
	return &chunk->page[pcpu_page_idx(cpu, page_idx)];
}

static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
				     unsigned int cpu, int page_idx)
{
	return (unsigned long)chunk->vm->addr +
		(pcpu_page_idx(cpu, page_idx) << PAGE_SHIFT);
}

static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
				     int page_idx)
{
	return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
}

/**
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 * pcpu_mem_alloc - allocate memory
 * @size: bytes to allocate
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 *
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 * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,
 * kzalloc() is used; otherwise, vmalloc() is used.  The returned
 * memory is always zeroed.
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 *
 * RETURNS:
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 * Pointer to the allocated area on success, NULL on failure.
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 */
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static void *pcpu_mem_alloc(size_t size)
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{
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	if (size <= PAGE_SIZE)
		return kzalloc(size, GFP_KERNEL);
	else {
		void *ptr = vmalloc(size);
		if (ptr)
			memset(ptr, 0, size);
		return ptr;
	}
}
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/**
 * pcpu_mem_free - free memory
 * @ptr: memory to free
 * @size: size of the area
 *
 * Free @ptr.  @ptr should have been allocated using pcpu_mem_alloc().
 */
static void pcpu_mem_free(void *ptr, size_t size)
{
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	if (size <= PAGE_SIZE)
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		kfree(ptr);
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	else
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		vfree(ptr);
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}

/**
 * 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
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 * moved to the slot.  Note that the reserved chunk is never put on
 * chunk slots.
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 */
static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
{
	int nslot = pcpu_chunk_slot(chunk);

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	if (chunk != pcpu_reserved_chunk && oslot != nslot) {
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		if (oslot < nslot)
			list_move(&chunk->list, &pcpu_slot[nslot]);
		else
			list_move_tail(&chunk->list, &pcpu_slot[nslot]);
	}
}

static struct rb_node **pcpu_chunk_rb_search(void *addr,
					     struct rb_node **parentp)
{
	struct rb_node **p = &pcpu_addr_root.rb_node;
	struct rb_node *parent = NULL;
	struct pcpu_chunk *chunk;

	while (*p) {
		parent = *p;
		chunk = rb_entry(parent, struct pcpu_chunk, rb_node);

		if (addr < chunk->vm->addr)
			p = &(*p)->rb_left;
		else if (addr > chunk->vm->addr)
			p = &(*p)->rb_right;
		else
			break;
	}

	if (parentp)
		*parentp = parent;
	return p;
}

/**
 * pcpu_chunk_addr_search - search for chunk containing specified address
 * @addr: address to search for
 *
 * Look for chunk which might contain @addr.  More specifically, it
 * searchs for the chunk with the highest start address which isn't
 * beyond @addr.
 *
 * RETURNS:
 * The address of the found chunk.
 */
static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
{
	struct rb_node *n, *parent;
	struct pcpu_chunk *chunk;

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	/* is it in the reserved chunk? */
	if (pcpu_reserved_chunk) {
		void *start = pcpu_reserved_chunk->vm->addr;

		if (addr >= start && addr < start + pcpu_reserved_chunk_limit)
			return pcpu_reserved_chunk;
	}

	/* nah... search the regular ones */
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	n = *pcpu_chunk_rb_search(addr, &parent);
	if (!n) {
		/* no exactly matching chunk, the parent is the closest */
		n = parent;
		BUG_ON(!n);
	}
	chunk = rb_entry(n, struct pcpu_chunk, rb_node);

	if (addr < chunk->vm->addr) {
		/* the parent was the next one, look for the previous one */
		n = rb_prev(n);
		BUG_ON(!n);
		chunk = rb_entry(n, struct pcpu_chunk, rb_node);
	}

	return chunk;
}

/**
 * pcpu_chunk_addr_insert - insert chunk into address rb tree
 * @new: chunk to insert
 *
 * Insert @new into address rb tree.
 */
static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
{
	struct rb_node **p, *parent;

	p = pcpu_chunk_rb_search(new->vm->addr, &parent);
	BUG_ON(*p);
	rb_link_node(&new->rb_node, parent, p);
	rb_insert_color(&new->rb_node, &pcpu_addr_root);
}

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/**
 * pcpu_extend_area_map - extend area map for allocation
 * @chunk: target chunk
 *
 * Extend area map of @chunk so that it can accomodate an allocation.
 * A single allocation can split an area into three areas, so this
 * function makes sure that @chunk->map has at least two extra slots.
 *
 * RETURNS:
 * 0 if noop, 1 if successfully extended, -errno on failure.
 */
static int pcpu_extend_area_map(struct pcpu_chunk *chunk)
{
	int new_alloc;
	int *new;
	size_t size;

	/* has enough? */
	if (chunk->map_alloc >= chunk->map_used + 2)
		return 0;

	new_alloc = PCPU_DFL_MAP_ALLOC;
	while (new_alloc < chunk->map_used + 2)
		new_alloc *= 2;

	new = pcpu_mem_alloc(new_alloc * sizeof(new[0]));
	if (!new)
		return -ENOMEM;

	size = chunk->map_alloc * sizeof(chunk->map[0]);
	memcpy(new, chunk->map, size);

	/*
	 * map_alloc < PCPU_DFL_MAP_ALLOC indicates that the chunk is
	 * one of the first chunks and still using static map.
	 */
	if (chunk->map_alloc >= PCPU_DFL_MAP_ALLOC)
		pcpu_mem_free(chunk->map, size);

	chunk->map_alloc = new_alloc;
	chunk->map = new;
	return 0;
}

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/**
 * pcpu_split_block - split a map block
 * @chunk: chunk of interest
 * @i: index of map block to split
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 * @head: head size in bytes (can be 0)
 * @tail: tail size in bytes (can be 0)
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 *
 * Split the @i'th map block into two or three blocks.  If @head is
 * non-zero, @head bytes block is inserted before block @i moving it
 * to @i+1 and reducing its size by @head bytes.
 *
 * If @tail is non-zero, the target block, which can be @i or @i+1
 * depending on @head, is reduced by @tail bytes and @tail byte block
 * is inserted after the target block.
 *
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 * @chunk->map must have enough free slots to accomodate the split.
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 */
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static void pcpu_split_block(struct pcpu_chunk *chunk, int i,
			     int head, int tail)
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{
	int nr_extra = !!head + !!tail;
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	BUG_ON(chunk->map_alloc < chunk->map_used + nr_extra);
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	/* insert new subblocks */
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	memmove(&chunk->map[i + nr_extra], &chunk->map[i],
		sizeof(chunk->map[0]) * (chunk->map_used - i));
	chunk->map_used += nr_extra;

	if (head) {
		chunk->map[i + 1] = chunk->map[i] - head;
		chunk->map[i++] = head;
	}
	if (tail) {
		chunk->map[i++] -= tail;
		chunk->map[i] = tail;
	}
}

/**
 * pcpu_alloc_area - allocate area from a pcpu_chunk
 * @chunk: chunk of interest
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 * @size: wanted size in bytes
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 * @align: wanted align
 *
 * Try to allocate @size bytes area aligned at @align from @chunk.
 * Note that this function only allocates the offset.  It doesn't
 * populate or map the area.
 *
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 * @chunk->map must have at least two free slots.
 *
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 * RETURNS:
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 * Allocated offset in @chunk on success, -1 if no matching area is
 * found.
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 */
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
{
	int oslot = pcpu_chunk_slot(chunk);
	int max_contig = 0;
	int i, off;

	for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++])) {
		bool is_last = i + 1 == chunk->map_used;
		int head, tail;

		/* extra for alignment requirement */
		head = ALIGN(off, align) - off;
		BUG_ON(i == 0 && head != 0);

		if (chunk->map[i] < 0)
			continue;
		if (chunk->map[i] < head + size) {
			max_contig = max(chunk->map[i], max_contig);
			continue;
		}

		/*
		 * If head is small or the previous block is free,
		 * merge'em.  Note that 'small' is defined as smaller
		 * than sizeof(int), which is very small but isn't too
		 * uncommon for percpu allocations.
		 */
		if (head && (head < sizeof(int) || chunk->map[i - 1] > 0)) {
			if (chunk->map[i - 1] > 0)
				chunk->map[i - 1] += head;
			else {
				chunk->map[i - 1] -= head;
				chunk->free_size -= head;
			}
			chunk->map[i] -= head;
			off += head;
			head = 0;
		}

		/* if tail is small, just keep it around */
		tail = chunk->map[i] - head - size;
		if (tail < sizeof(int))
			tail = 0;

		/* split if warranted */
		if (head || tail) {
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			pcpu_split_block(chunk, i, head, tail);
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			if (head) {
				i++;
				off += head;
				max_contig = max(chunk->map[i - 1], max_contig);
			}
			if (tail)
				max_contig = max(chunk->map[i + 1], max_contig);
		}

		/* update hint and mark allocated */
		if (is_last)
			chunk->contig_hint = max_contig; /* fully scanned */
		else
			chunk->contig_hint = max(chunk->contig_hint,
						 max_contig);

		chunk->free_size -= chunk->map[i];
		chunk->map[i] = -chunk->map[i];

		pcpu_chunk_relocate(chunk, oslot);
		return off;
	}

	chunk->contig_hint = max_contig;	/* fully scanned */
	pcpu_chunk_relocate(chunk, oslot);

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	/* tell the upper layer that this chunk has no matching area */
	return -1;
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}

/**
 * pcpu_free_area - free area to a pcpu_chunk
 * @chunk: chunk of interest
 * @freeme: offset of area to free
 *
 * Free area starting from @freeme to @chunk.  Note that this function
 * only modifies the allocation map.  It doesn't depopulate or unmap
 * the area.
 */
static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
{
	int oslot = pcpu_chunk_slot(chunk);
	int i, off;

	for (i = 0, off = 0; i < chunk->map_used; off += abs(chunk->map[i++]))
		if (off == freeme)
			break;
	BUG_ON(off != freeme);
	BUG_ON(chunk->map[i] > 0);

	chunk->map[i] = -chunk->map[i];
	chunk->free_size += chunk->map[i];

	/* merge with previous? */
	if (i > 0 && chunk->map[i - 1] >= 0) {
		chunk->map[i - 1] += chunk->map[i];
		chunk->map_used--;
		memmove(&chunk->map[i], &chunk->map[i + 1],
			(chunk->map_used - i) * sizeof(chunk->map[0]));
		i--;
	}
	/* merge with next? */
	if (i + 1 < chunk->map_used && chunk->map[i + 1] >= 0) {
		chunk->map[i] += chunk->map[i + 1];
		chunk->map_used--;
		memmove(&chunk->map[i + 1], &chunk->map[i + 2],
			(chunk->map_used - (i + 1)) * sizeof(chunk->map[0]));
	}

	chunk->contig_hint = max(chunk->map[i], chunk->contig_hint);
	pcpu_chunk_relocate(chunk, oslot);
}

/**
 * pcpu_unmap - unmap pages out of a pcpu_chunk
 * @chunk: chunk of interest
 * @page_start: page index of the first page to unmap
 * @page_end: page index of the last page to unmap + 1
 * @flush: whether to flush cache and tlb or not
 *
 * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
 * If @flush is true, vcache is flushed before unmapping and tlb
 * after.
 */
static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
		       bool flush)
{
	unsigned int last = num_possible_cpus() - 1;
	unsigned int cpu;

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	/* unmap must not be done on immutable chunk */
	WARN_ON(chunk->immutable);

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	/*
	 * Each flushing trial can be very expensive, issue flush on
	 * the whole region at once rather than doing it for each cpu.
	 * This could be an overkill but is more scalable.
	 */
	if (flush)
		flush_cache_vunmap(pcpu_chunk_addr(chunk, 0, page_start),
				   pcpu_chunk_addr(chunk, last, page_end));

	for_each_possible_cpu(cpu)
		unmap_kernel_range_noflush(
				pcpu_chunk_addr(chunk, cpu, page_start),
				(page_end - page_start) << PAGE_SHIFT);

	/* ditto as flush_cache_vunmap() */
	if (flush)
		flush_tlb_kernel_range(pcpu_chunk_addr(chunk, 0, page_start),
				       pcpu_chunk_addr(chunk, last, page_end));
}

/**
 * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
 * @chunk: chunk to depopulate
 * @off: offset to the area to depopulate
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 * @size: size of the area to depopulate in bytes
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 * @flush: whether to flush cache and tlb or not
 *
 * For each cpu, depopulate and unmap pages [@page_start,@page_end)
 * from @chunk.  If @flush is true, vcache is flushed before unmapping
 * and tlb after.
 */
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static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size,
				  bool flush)
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{
	int page_start = PFN_DOWN(off);
	int page_end = PFN_UP(off + size);
	int unmap_start = -1;
	int uninitialized_var(unmap_end);
	unsigned int cpu;
	int i;

	for (i = page_start; i < page_end; i++) {
		for_each_possible_cpu(cpu) {
			struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);

			if (!*pagep)
				continue;

			__free_page(*pagep);

			/*
			 * If it's partial depopulation, it might get
			 * populated or depopulated again.  Mark the
			 * page gone.
			 */
			*pagep = NULL;

			unmap_start = unmap_start < 0 ? i : unmap_start;
			unmap_end = i + 1;
		}
	}

	if (unmap_start >= 0)
		pcpu_unmap(chunk, unmap_start, unmap_end, flush);
}

/**
 * pcpu_map - map pages into a pcpu_chunk
 * @chunk: chunk of interest
 * @page_start: page index of the first page to map
 * @page_end: page index of the last page to map + 1
 *
 * For each cpu, map pages [@page_start,@page_end) into @chunk.
 * vcache is flushed afterwards.
 */
static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
{
	unsigned int last = num_possible_cpus() - 1;
	unsigned int cpu;
	int err;

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	/* map must not be done on immutable chunk */
	WARN_ON(chunk->immutable);

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	for_each_possible_cpu(cpu) {
		err = map_kernel_range_noflush(
				pcpu_chunk_addr(chunk, cpu, page_start),
				(page_end - page_start) << PAGE_SHIFT,
				PAGE_KERNEL,
				pcpu_chunk_pagep(chunk, cpu, page_start));
		if (err < 0)
			return err;
	}

	/* flush at once, please read comments in pcpu_unmap() */
	flush_cache_vmap(pcpu_chunk_addr(chunk, 0, page_start),
			 pcpu_chunk_addr(chunk, last, page_end));
	return 0;
}

/**
 * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
 * @chunk: chunk of interest
 * @off: offset to the area to populate
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 * @size: size of the area to populate in bytes
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 *
 * For each cpu, populate and map pages [@page_start,@page_end) into
 * @chunk.  The area is cleared on return.
 */
static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
{
	const gfp_t alloc_mask = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
	int page_start = PFN_DOWN(off);
	int page_end = PFN_UP(off + size);
	int map_start = -1;
663
	int uninitialized_var(map_end);
664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693
	unsigned int cpu;
	int i;

	for (i = page_start; i < page_end; i++) {
		if (pcpu_chunk_page_occupied(chunk, i)) {
			if (map_start >= 0) {
				if (pcpu_map(chunk, map_start, map_end))
					goto err;
				map_start = -1;
			}
			continue;
		}

		map_start = map_start < 0 ? i : map_start;
		map_end = i + 1;

		for_each_possible_cpu(cpu) {
			struct page **pagep = pcpu_chunk_pagep(chunk, cpu, i);

			*pagep = alloc_pages_node(cpu_to_node(cpu),
						  alloc_mask, 0);
			if (!*pagep)
				goto err;
		}
	}

	if (map_start >= 0 && pcpu_map(chunk, map_start, map_end))
		goto err;

	for_each_possible_cpu(cpu)
694
		memset(chunk->vm->addr + cpu * pcpu_unit_size + off, 0,
695 696 697 698 699 700 701 702 703 704 705 706 707 708 709
		       size);

	return 0;
err:
	/* likely under heavy memory pressure, give memory back */
	pcpu_depopulate_chunk(chunk, off, size, true);
	return -ENOMEM;
}

static void free_pcpu_chunk(struct pcpu_chunk *chunk)
{
	if (!chunk)
		return;
	if (chunk->vm)
		free_vm_area(chunk->vm);
710
	pcpu_mem_free(chunk->map, chunk->map_alloc * sizeof(chunk->map[0]));
711 712 713 714 715 716 717 718 719 720 721
	kfree(chunk);
}

static struct pcpu_chunk *alloc_pcpu_chunk(void)
{
	struct pcpu_chunk *chunk;

	chunk = kzalloc(pcpu_chunk_struct_size, GFP_KERNEL);
	if (!chunk)
		return NULL;

722
	chunk->map = pcpu_mem_alloc(PCPU_DFL_MAP_ALLOC * sizeof(chunk->map[0]));
723 724
	chunk->map_alloc = PCPU_DFL_MAP_ALLOC;
	chunk->map[chunk->map_used++] = pcpu_unit_size;
725
	chunk->page = chunk->page_ar;
726 727 728 729 730 731 732 733 734 735 736 737 738 739 740

	chunk->vm = get_vm_area(pcpu_chunk_size, GFP_KERNEL);
	if (!chunk->vm) {
		free_pcpu_chunk(chunk);
		return NULL;
	}

	INIT_LIST_HEAD(&chunk->list);
	chunk->free_size = pcpu_unit_size;
	chunk->contig_hint = pcpu_unit_size;

	return chunk;
}

/**
741
 * pcpu_alloc - the percpu allocator
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742
 * @size: size of area to allocate in bytes
743
 * @align: alignment of area (max PAGE_SIZE)
744
 * @reserved: allocate from the reserved chunk if available
745 746 747 748 749 750 751
 *
 * Allocate percpu area of @size bytes aligned at @align.  Might
 * sleep.  Might trigger writeouts.
 *
 * RETURNS:
 * Percpu pointer to the allocated area on success, NULL on failure.
 */
752
static void *pcpu_alloc(size_t size, size_t align, bool reserved)
753 754 755 756 757
{
	void *ptr = NULL;
	struct pcpu_chunk *chunk;
	int slot, off;

758
	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
759 760 761 762 763 764 765
		WARN(true, "illegal size (%zu) or align (%zu) for "
		     "percpu allocation\n", size, align);
		return NULL;
	}

	mutex_lock(&pcpu_mutex);

766 767 768
	/* serve reserved allocations from the reserved chunk if available */
	if (reserved && pcpu_reserved_chunk) {
		chunk = pcpu_reserved_chunk;
769 770
		if (size > chunk->contig_hint ||
		    pcpu_extend_area_map(chunk) < 0)
771 772 773 774 775 776 777 778
			goto out_unlock;
		off = pcpu_alloc_area(chunk, size, align);
		if (off >= 0)
			goto area_found;
		goto out_unlock;
	}

	/* search through normal chunks */
779 780 781 782
	for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
		list_for_each_entry(chunk, &pcpu_slot[slot], list) {
			if (size > chunk->contig_hint)
				continue;
783 784
			if (pcpu_extend_area_map(chunk) < 0)
				goto out_unlock;
785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813
			off = pcpu_alloc_area(chunk, size, align);
			if (off >= 0)
				goto area_found;
		}
	}

	/* hmmm... no space left, create a new chunk */
	chunk = alloc_pcpu_chunk();
	if (!chunk)
		goto out_unlock;
	pcpu_chunk_relocate(chunk, -1);
	pcpu_chunk_addr_insert(chunk);

	off = pcpu_alloc_area(chunk, size, align);
	if (off < 0)
		goto out_unlock;

area_found:
	/* populate, map and clear the area */
	if (pcpu_populate_chunk(chunk, off, size)) {
		pcpu_free_area(chunk, off);
		goto out_unlock;
	}

	ptr = __addr_to_pcpu_ptr(chunk->vm->addr + off);
out_unlock:
	mutex_unlock(&pcpu_mutex);
	return ptr;
}
814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829

/**
 * __alloc_percpu - allocate dynamic percpu area
 * @size: size of area to allocate in bytes
 * @align: alignment of area (max PAGE_SIZE)
 *
 * Allocate percpu area of @size bytes aligned at @align.  Might
 * sleep.  Might trigger writeouts.
 *
 * RETURNS:
 * Percpu pointer to the allocated area on success, NULL on failure.
 */
void *__alloc_percpu(size_t size, size_t align)
{
	return pcpu_alloc(size, align, false);
}
830 831
EXPORT_SYMBOL_GPL(__alloc_percpu);

832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848
/**
 * __alloc_reserved_percpu - allocate reserved percpu area
 * @size: size of area to allocate in bytes
 * @align: alignment of area (max PAGE_SIZE)
 *
 * Allocate percpu area of @size bytes aligned at @align from reserved
 * percpu area if arch has set it up; otherwise, allocation is served
 * from the same dynamic area.  Might sleep.  Might trigger writeouts.
 *
 * RETURNS:
 * Percpu pointer to the allocated area on success, NULL on failure.
 */
void *__alloc_reserved_percpu(size_t size, size_t align)
{
	return pcpu_alloc(size, align, true);
}

849 850
static void pcpu_kill_chunk(struct pcpu_chunk *chunk)
{
851
	WARN_ON(chunk->immutable);
852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896
	pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size, false);
	list_del(&chunk->list);
	rb_erase(&chunk->rb_node, &pcpu_addr_root);
	free_pcpu_chunk(chunk);
}

/**
 * free_percpu - free percpu area
 * @ptr: pointer to area to free
 *
 * Free percpu area @ptr.  Might sleep.
 */
void free_percpu(void *ptr)
{
	void *addr = __pcpu_ptr_to_addr(ptr);
	struct pcpu_chunk *chunk;
	int off;

	if (!ptr)
		return;

	mutex_lock(&pcpu_mutex);

	chunk = pcpu_chunk_addr_search(addr);
	off = addr - chunk->vm->addr;

	pcpu_free_area(chunk, off);

	/* the chunk became fully free, kill one if there are other free ones */
	if (chunk->free_size == pcpu_unit_size) {
		struct pcpu_chunk *pos;

		list_for_each_entry(pos,
				    &pcpu_slot[pcpu_chunk_slot(chunk)], list)
			if (pos != chunk) {
				pcpu_kill_chunk(pos);
				break;
			}
	}

	mutex_unlock(&pcpu_mutex);
}
EXPORT_SYMBOL_GPL(free_percpu);

/**
897 898 899
 * pcpu_setup_first_chunk - initialize the first percpu chunk
 * @get_page_fn: callback to fetch page pointer
 * @static_size: the size of static percpu area in bytes
900
 * @reserved_size: the size of reserved percpu area in bytes
901 902
 * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
 * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918
 * @base_addr: mapped address, NULL for auto
 * @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
 *
 * Initialize the first percpu chunk which contains the kernel static
 * perpcu area.  This function is to be called from arch percpu area
 * setup path.  The first two parameters are mandatory.  The rest are
 * optional.
 *
 * @get_page_fn() should return pointer to percpu page given cpu
 * number and page number.  It should at least return enough pages to
 * cover the static area.  The returned pages for static area should
 * have been initialized with valid data.  If @unit_size is specified,
 * it can also return pages after the static area.  NULL return
 * indicates end of pages for the cpu.  Note that @get_page_fn() must
 * return the same number of pages for all cpus.
 *
919 920 921 922 923 924 925 926
 * @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.
 *
927 928
 * @unit_size, if non-negative, specifies unit size and must be
 * aligned to PAGE_SIZE and equal to or larger than @static_size +
929
 * @reserved_size + @dyn_size.
930
 *
931 932 933
 * @dyn_size, if non-negative, limits the number of bytes available
 * for dynamic allocation in the first chunk.  Specifying non-negative
 * value make percpu leave alone the area beyond @static_size +
934
 * @reserved_size + @dyn_size.
935 936 937 938 939 940 941 942
 *
 * Non-null @base_addr means that the caller already allocated virtual
 * region for the first chunk and mapped it.  percpu must not mess
 * with the chunk.  Note that @base_addr with 0 @unit_size or non-NULL
 * @populate_pte_fn doesn't make any sense.
 *
 * @populate_pte_fn is used to populate the pagetable.  NULL means the
 * caller already populated the pagetable.
943
 *
944 945 946 947 948 949 950
 * If the first chunk ends up with both reserved and dynamic areas, it
 * is served by two chunks - one to serve the core static and reserved
 * areas and the other for the dynamic area.  They share the same vm
 * and page map but uses different area allocation map to stay away
 * from each other.  The latter chunk is circulated in the chunk slots
 * and available for dynamic allocation like any other chunks.
 *
951 952 953 954
 * RETURNS:
 * The determined pcpu_unit_size which can be used to initialize
 * percpu access.
 */
955
size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
956
				     size_t static_size, size_t reserved_size,
957 958
				     ssize_t unit_size, ssize_t dyn_size,
				     void *base_addr,
959
				     pcpu_populate_pte_fn_t populate_pte_fn)
960
{
961
	static struct vm_struct first_vm;
962 963
	static int smap[2], dmap[2];
	struct pcpu_chunk *schunk, *dchunk = NULL;
964
	unsigned int cpu;
965
	int nr_pages;
966 967
	int err, i;

968
	/* santiy checks */
969 970
	BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
		     ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
971
	BUG_ON(!static_size);
972
	if (unit_size >= 0) {
973
		BUG_ON(unit_size < static_size + reserved_size +
974 975 976 977 978 979
				   (dyn_size >= 0 ? dyn_size : 0));
		BUG_ON(unit_size & ~PAGE_MASK);
	} else {
		BUG_ON(dyn_size >= 0);
		BUG_ON(base_addr);
	}
980
	BUG_ON(base_addr && populate_pte_fn);
981

982
	if (unit_size >= 0)
983 984 985
		pcpu_unit_pages = unit_size >> PAGE_SHIFT;
	else
		pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
986
					PFN_UP(static_size + reserved_size));
987

988
	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
989 990
	pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
T
Tejun Heo 已提交
991
		+ num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);
992

993
	if (dyn_size < 0)
994
		dyn_size = pcpu_unit_size - static_size - reserved_size;
995

996 997 998 999 1000
	/*
	 * Allocate chunk slots.  The additional last slot is for
	 * empty chunks.
	 */
	pcpu_nr_slots = __pcpu_size_to_slot(pcpu_unit_size) + 2;
1001 1002 1003 1004
	pcpu_slot = alloc_bootmem(pcpu_nr_slots * sizeof(pcpu_slot[0]));
	for (i = 0; i < pcpu_nr_slots; i++)
		INIT_LIST_HEAD(&pcpu_slot[i]);

1005 1006 1007 1008 1009 1010 1011
	/*
	 * Initialize static chunk.  If reserved_size is zero, the
	 * static chunk covers static area + dynamic allocation area
	 * in the first chunk.  If reserved_size is not zero, it
	 * covers static area + reserved area (mostly used for module
	 * static percpu allocation).
	 */
1012 1013 1014
	schunk = alloc_bootmem(pcpu_chunk_struct_size);
	INIT_LIST_HEAD(&schunk->list);
	schunk->vm = &first_vm;
1015 1016
	schunk->map = smap;
	schunk->map_alloc = ARRAY_SIZE(smap);
1017
	schunk->page = schunk->page_ar;
1018 1019 1020 1021 1022 1023 1024 1025

	if (reserved_size) {
		schunk->free_size = reserved_size;
		pcpu_reserved_chunk = schunk;	/* not for dynamic alloc */
	} else {
		schunk->free_size = dyn_size;
		dyn_size = 0;			/* dynamic area covered */
	}
1026
	schunk->contig_hint = schunk->free_size;
1027

1028 1029 1030 1031
	schunk->map[schunk->map_used++] = -static_size;
	if (schunk->free_size)
		schunk->map[schunk->map_used++] = schunk->free_size;

1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047
	pcpu_reserved_chunk_limit = static_size + schunk->free_size;

	/* init dynamic chunk if necessary */
	if (dyn_size) {
		dchunk = alloc_bootmem(sizeof(struct pcpu_chunk));
		INIT_LIST_HEAD(&dchunk->list);
		dchunk->vm = &first_vm;
		dchunk->map = dmap;
		dchunk->map_alloc = ARRAY_SIZE(dmap);
		dchunk->page = schunk->page_ar;	/* share page map with schunk */

		dchunk->contig_hint = dchunk->free_size = dyn_size;
		dchunk->map[dchunk->map_used++] = -pcpu_reserved_chunk_limit;
		dchunk->map[dchunk->map_used++] = dchunk->free_size;
	}

1048
	/* allocate vm address */
1049 1050
	first_vm.flags = VM_ALLOC;
	first_vm.size = pcpu_chunk_size;
1051 1052

	if (!base_addr)
1053
		vm_area_register_early(&first_vm, PAGE_SIZE);
1054 1055 1056
	else {
		/*
		 * Pages already mapped.  No need to remap into
1057 1058
		 * vmalloc area.  In this case the first chunks can't
		 * be mapped or unmapped by percpu and are marked
1059 1060
		 * immutable.
		 */
1061 1062
		first_vm.addr = base_addr;
		schunk->immutable = true;
1063 1064
		if (dchunk)
			dchunk->immutable = true;
1065 1066 1067 1068
	}

	/* assign pages */
	nr_pages = -1;
1069
	for_each_possible_cpu(cpu) {
1070 1071 1072 1073 1074
		for (i = 0; i < pcpu_unit_pages; i++) {
			struct page *page = get_page_fn(cpu, i);

			if (!page)
				break;
1075
			*pcpu_chunk_pagep(schunk, cpu, i) = page;
1076
		}
1077

1078
		BUG_ON(i < PFN_UP(static_size));
1079 1080 1081 1082 1083

		if (nr_pages < 0)
			nr_pages = i;
		else
			BUG_ON(nr_pages != i);
1084 1085
	}

1086 1087 1088 1089
	/* map them */
	if (populate_pte_fn) {
		for_each_possible_cpu(cpu)
			for (i = 0; i < nr_pages; i++)
1090
				populate_pte_fn(pcpu_chunk_addr(schunk,
1091 1092
								cpu, i));

1093
		err = pcpu_map(schunk, 0, nr_pages);
1094 1095 1096 1097
		if (err)
			panic("failed to setup static percpu area, err=%d\n",
			      err);
	}
1098

1099
	/* link the first chunk in */
1100 1101 1102 1103 1104 1105 1106
	if (!dchunk) {
		pcpu_chunk_relocate(schunk, -1);
		pcpu_chunk_addr_insert(schunk);
	} else {
		pcpu_chunk_relocate(dchunk, -1);
		pcpu_chunk_addr_insert(dchunk);
	}
1107 1108

	/* we're done */
1109
	pcpu_base_addr = (void *)pcpu_chunk_addr(schunk, 0, 0);
1110 1111
	return pcpu_unit_size;
}