[linux.git] / lib / percpu_ida.c

/*
 * Percpu IDA library
 *
 * Copyright (C) 2013 Datera, Inc. Kent Overstreet
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/mm.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/sched/signal.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/percpu_ida.h>

struct percpu_ida_cpu {
	/*
	 * Even though this is percpu, we need a lock for tag stealing by remote
	 * CPUs:
	 */
	spinlock_t			lock;

	/* nr_free/freelist form a stack of free IDs */
	unsigned			nr_free;
	unsigned			freelist[];
};

static inline void move_tags(unsigned *dst, unsigned *dst_nr,
			     unsigned *src, unsigned *src_nr,
			     unsigned nr)
{
	*src_nr -= nr;
	memcpy(dst + *dst_nr, src + *src_nr, sizeof(unsigned) * nr);
	*dst_nr += nr;
}

/*
 * Try to steal tags from a remote cpu's percpu freelist.
 *
 * We first check how many percpu freelists have tags
 *
 * Then we iterate through the cpus until we find some tags - we don't attempt
 * to find the "best" cpu to steal from, to keep cacheline bouncing to a
 * minimum.
 */
static inline void steal_tags(struct percpu_ida *pool,
			      struct percpu_ida_cpu *tags)
{
	unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
	struct percpu_ida_cpu *remote;

	for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
	     cpus_have_tags; cpus_have_tags--) {
		cpu = cpumask_next(cpu, &pool->cpus_have_tags);

		if (cpu >= nr_cpu_ids) {
			cpu = cpumask_first(&pool->cpus_have_tags);
			if (cpu >= nr_cpu_ids)
				BUG();
		}

		pool->cpu_last_stolen = cpu;
		remote = per_cpu_ptr(pool->tag_cpu, cpu);

		cpumask_clear_cpu(cpu, &pool->cpus_have_tags);

		if (remote == tags)
			continue;

		spin_lock(&remote->lock);

		if (remote->nr_free) {
			memcpy(tags->freelist,
			       remote->freelist,
			       sizeof(unsigned) * remote->nr_free);

			tags->nr_free = remote->nr_free;
			remote->nr_free = 0;
		}

		spin_unlock(&remote->lock);

		if (tags->nr_free)
			break;
	}
}

/*
 * Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
 * our percpu freelist:
 */
static inline void alloc_global_tags(struct percpu_ida *pool,
				     struct percpu_ida_cpu *tags)
{
	move_tags(tags->freelist, &tags->nr_free,
		  pool->freelist, &pool->nr_free,
		  min(pool->nr_free, pool->percpu_batch_size));
}

static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
{
	int tag = -ENOSPC;

	spin_lock(&tags->lock);
	if (tags->nr_free)
		tag = tags->freelist[--tags->nr_free];
	spin_unlock(&tags->lock);

	return tag;
}

/**
 * percpu_ida_alloc - allocate a tag
 * @pool: pool to allocate from
 * @state: task state for prepare_to_wait
 *
 * Returns a tag - an integer in the range [0..nr_tags) (passed to
 * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
 *
 * Safe to be called from interrupt context (assuming it isn't passed
 * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
 *
 * @gfp indicates whether or not to wait until a free id is available (it's not
 * used for internal memory allocations); thus if passed __GFP_RECLAIM we may sleep
 * however long it takes until another thread frees an id (same semantics as a
 * mempool).
 *
 * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
 */
int percpu_ida_alloc(struct percpu_ida *pool, int state)
{
	DEFINE_WAIT(wait);
	struct percpu_ida_cpu *tags;
	unsigned long flags;
	int tag;

	local_irq_save(flags);
	tags = this_cpu_ptr(pool->tag_cpu);

	/* Fastpath */
	tag = alloc_local_tag(tags);
	if (likely(tag >= 0)) {
		local_irq_restore(flags);
		return tag;
	}

	while (1) {
		spin_lock(&pool->lock);

		/*
		 * prepare_to_wait() must come before steal_tags(), in case
		 * percpu_ida_free() on another cpu flips a bit in
		 * cpus_have_tags
		 *
		 * global lock held and irqs disabled, don't need percpu lock
		 */
		if (state != TASK_RUNNING)
			prepare_to_wait(&pool->wait, &wait, state);

		if (!tags->nr_free)
			alloc_global_tags(pool, tags);
		if (!tags->nr_free)
			steal_tags(pool, tags);

		if (tags->nr_free) {
			tag = tags->freelist[--tags->nr_free];
			if (tags->nr_free)
				cpumask_set_cpu(smp_processor_id(),
						&pool->cpus_have_tags);
		}

		spin_unlock(&pool->lock);
		local_irq_restore(flags);

		if (tag >= 0 || state == TASK_RUNNING)
			break;

		if (signal_pending_state(state, current)) {
			tag = -ERESTARTSYS;
			break;
		}

		schedule();

		local_irq_save(flags);
		tags = this_cpu_ptr(pool->tag_cpu);
	}
	if (state != TASK_RUNNING)
		finish_wait(&pool->wait, &wait);

	return tag;
}
EXPORT_SYMBOL_GPL(percpu_ida_alloc);

/**
 * percpu_ida_free - free a tag
 * @pool: pool @tag was allocated from
 * @tag: a tag previously allocated with percpu_ida_alloc()
 *
 * Safe to be called from interrupt context.
 */
void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
{
	struct percpu_ida_cpu *tags;
	unsigned long flags;
	unsigned nr_free;

	BUG_ON(tag >= pool->nr_tags);

	local_irq_save(flags);
	tags = this_cpu_ptr(pool->tag_cpu);

	spin_lock(&tags->lock);
	tags->freelist[tags->nr_free++] = tag;

	nr_free = tags->nr_free;
	spin_unlock(&tags->lock);

	if (nr_free == 1) {
		cpumask_set_cpu(smp_processor_id(),
				&pool->cpus_have_tags);
		wake_up(&pool->wait);
	}

	if (nr_free == pool->percpu_max_size) {
		spin_lock(&pool->lock);

		/*
		 * Global lock held and irqs disabled, don't need percpu
		 * lock
		 */
		if (tags->nr_free == pool->percpu_max_size) {
			move_tags(pool->freelist, &pool->nr_free,
				  tags->freelist, &tags->nr_free,
				  pool->percpu_batch_size);

			wake_up(&pool->wait);
		}
		spin_unlock(&pool->lock);
	}

	local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(percpu_ida_free);

/**
 * percpu_ida_destroy - release a tag pool's resources
 * @pool: pool to free
 *
 * Frees the resources allocated by percpu_ida_init().
 */
void percpu_ida_destroy(struct percpu_ida *pool)
{
	free_percpu(pool->tag_cpu);
	free_pages((unsigned long) pool->freelist,
		   get_order(pool->nr_tags * sizeof(unsigned)));
}
EXPORT_SYMBOL_GPL(percpu_ida_destroy);

/**
 * percpu_ida_init - initialize a percpu tag pool
 * @pool: pool to initialize
 * @nr_tags: number of tags that will be available for allocation
 *
 * Initializes @pool so that it can be used to allocate tags - integers in the
 * range [0, nr_tags). Typically, they'll be used by driver code to refer to a
 * preallocated array of tag structures.
 *
 * Allocation is percpu, but sharding is limited by nr_tags - for best
 * performance, the workload should not span more cpus than nr_tags / 128.
 */
int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
	unsigned long max_size, unsigned long batch_size)
{
	unsigned i, cpu, order;

	memset(pool, 0, sizeof(*pool));

	init_waitqueue_head(&pool->wait);
	spin_lock_init(&pool->lock);
	pool->nr_tags = nr_tags;
	pool->percpu_max_size = max_size;
	pool->percpu_batch_size = batch_size;

	/* Guard against overflow */
	if (nr_tags > (unsigned) INT_MAX + 1) {
		pr_err("percpu_ida_init(): nr_tags too large\n");
		return -EINVAL;
	}

	order = get_order(nr_tags * sizeof(unsigned));
	pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
	if (!pool->freelist)
		return -ENOMEM;

	for (i = 0; i < nr_tags; i++)
		pool->freelist[i] = i;

	pool->nr_free = nr_tags;

	pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
				       pool->percpu_max_size * sizeof(unsigned),
				       sizeof(unsigned));
	if (!pool->tag_cpu)
		goto err;

	for_each_possible_cpu(cpu)
		spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);

	return 0;
err:
	percpu_ida_destroy(pool);
	return -ENOMEM;
}
EXPORT_SYMBOL_GPL(__percpu_ida_init);

/**
 * percpu_ida_for_each_free - iterate free ids of a pool
 * @pool: pool to iterate
 * @fn: interate callback function
 * @data: parameter for @fn
 *
 * Note, this doesn't guarantee to iterate all free ids restrictly. Some free
 * ids might be missed, some might be iterated duplicated, and some might
 * be iterated and not free soon.
 */
int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
	void *data)
{
	unsigned long flags;
	struct percpu_ida_cpu *remote;
	unsigned cpu, i, err = 0;

	local_irq_save(flags);
	for_each_possible_cpu(cpu) {
		remote = per_cpu_ptr(pool->tag_cpu, cpu);
		spin_lock(&remote->lock);
		for (i = 0; i < remote->nr_free; i++) {
			err = fn(remote->freelist[i], data);
			if (err)
				break;
		}
		spin_unlock(&remote->lock);
		if (err)
			goto out;
	}

	spin_lock(&pool->lock);
	for (i = 0; i < pool->nr_free; i++) {
		err = fn(pool->freelist[i], data);
		if (err)
			break;
	}
	spin_unlock(&pool->lock);
out:
	local_irq_restore(flags);
	return err;
}
EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);

/**
 * percpu_ida_free_tags - return free tags number of a specific cpu or global pool
 * @pool: pool related
 * @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
 *
 * Note: this just returns a snapshot of free tags number.
 */
unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
{
	struct percpu_ida_cpu *remote;
	if (cpu == nr_cpu_ids)
		return pool->nr_free;
	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	return remote->nr_free;
}
EXPORT_SYMBOL_GPL(percpu_ida_free_tags);
Commit	Line	Data
798ab48e KO	1	/*
	2	* Percpu IDA library
	3	*
	4	* Copyright (C) 2013 Datera, Inc. Kent Overstreet
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License as
	8	* published by the Free Software Foundation; either version 2, or (at
	9	* your option) any later version.
	10	*
	11	* This program is distributed in the hope that it will be useful, but
	12	* WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	14	* General Public License for more details.
	15	*/
	16
fd771233	17	#include <linux/mm.h>
798ab48e KO	18	#include <linux/bitmap.h>
	19	#include <linux/bitops.h>
	20	#include <linux/bug.h>
	21	#include <linux/err.h>
	22	#include <linux/export.h>
798ab48e KO	23	#include <linux/init.h>
	24	#include <linux/kernel.h>
	25	#include <linux/percpu.h>
174cd4b1	26	#include <linux/sched/signal.h>
798ab48e KO	27	#include <linux/string.h>
	28	#include <linux/spinlock.h>
	29	#include <linux/percpu_ida.h>
	30
798ab48e KO	31	struct percpu_ida_cpu {
	32	/*
	33	* Even though this is percpu, we need a lock for tag stealing by remote
	34	* CPUs:
	35	*/
	36	spinlock_t lock;
	37
	38	/* nr_free/freelist form a stack of free IDs */
	39	unsigned nr_free;
	40	unsigned freelist[];
	41	};
	42
	43	static inline void move_tags(unsigned dst, unsigned dst_nr,
	44	unsigned src, unsigned src_nr,
	45	unsigned nr)
	46	{
	47	*src_nr -= nr;
	48	memcpy(dst + dst_nr, src + src_nr, sizeof(unsigned) * nr);
	49	*dst_nr += nr;
	50	}
	51
	52	/*
	53	* Try to steal tags from a remote cpu's percpu freelist.
	54	*
d835502f	55	* We first check how many percpu freelists have tags
798ab48e KO	56	*
	57	* Then we iterate through the cpus until we find some tags - we don't attempt
	58	* to find the "best" cpu to steal from, to keep cacheline bouncing to a
	59	* minimum.
	60	*/
	61	static inline void steal_tags(struct percpu_ida *pool,
	62	struct percpu_ida_cpu *tags)
	63	{
	64	unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
	65	struct percpu_ida_cpu *remote;
	66
	67	for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
d835502f	68	cpus_have_tags; cpus_have_tags--) {
798ab48e KO	69	cpu = cpumask_next(cpu, &pool->cpus_have_tags);
	70
	71	if (cpu >= nr_cpu_ids) {
	72	cpu = cpumask_first(&pool->cpus_have_tags);
	73	if (cpu >= nr_cpu_ids)
	74	BUG();
	75	}
	76
	77	pool->cpu_last_stolen = cpu;
	78	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	79
	80	cpumask_clear_cpu(cpu, &pool->cpus_have_tags);
	81
	82	if (remote == tags)
	83	continue;
	84
	85	spin_lock(&remote->lock);
	86
	87	if (remote->nr_free) {
	88	memcpy(tags->freelist,
	89	remote->freelist,
	90	sizeof(unsigned) * remote->nr_free);
	91
	92	tags->nr_free = remote->nr_free;
	93	remote->nr_free = 0;
	94	}
	95
	96	spin_unlock(&remote->lock);
	97
	98	if (tags->nr_free)
	99	break;
	100	}
	101	}
	102
	103	/*
	104	* Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
	105	* our percpu freelist:
	106	*/
	107	static inline void alloc_global_tags(struct percpu_ida *pool,
	108	struct percpu_ida_cpu *tags)
	109	{
	110	move_tags(tags->freelist, &tags->nr_free,
	111	pool->freelist, &pool->nr_free,
e26b53d0	112	min(pool->nr_free, pool->percpu_batch_size));
798ab48e KO	113	}
798ab48e KO	114
6b378382	115	static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
798ab48e KO	116	{
	117	int tag = -ENOSPC;
	118
	119	spin_lock(&tags->lock);
	120	if (tags->nr_free)
	121	tag = tags->freelist[--tags->nr_free];
	122	spin_unlock(&tags->lock);
	123
	124	return tag;
	125	}
	126
	127	/**
	128	* percpu_ida_alloc - allocate a tag
	129	* @pool: pool to allocate from
6f6b5d1e	130	* @state: task state for prepare_to_wait
798ab48e KO	131	*
	132	* Returns a tag - an integer in the range [0..nr_tags) (passed to
	133	* tag_pool_init()), or otherwise -ENOSPC on allocation failure.
	134	*
	135	* Safe to be called from interrupt context (assuming it isn't passed
555b270e	136	* TASK_UNINTERRUPTIBLE \| TASK_INTERRUPTIBLE, of course).
798ab48e KO	137	*
798ab48e KO	138	* @gfp indicates whether or not to wait until a free id is available (it's not
71baba4b	139	* used for internal memory allocations); thus if passed __GFP_RECLAIM we may sleep
798ab48e KO	140	* however long it takes until another thread frees an id (same semantics as a
	141	* mempool).
	142	*
555b270e	143	* Will not fail if passed TASK_UNINTERRUPTIBLE \| TASK_INTERRUPTIBLE.
798ab48e	144	*/
6f6b5d1e	145	int percpu_ida_alloc(struct percpu_ida *pool, int state)
798ab48e KO	146	{
	147	DEFINE_WAIT(wait);
	148	struct percpu_ida_cpu *tags;
	149	unsigned long flags;
	150	int tag;
	151
	152	local_irq_save(flags);
	153	tags = this_cpu_ptr(pool->tag_cpu);
	154
	155	/* Fastpath */
6b378382	156	tag = alloc_local_tag(tags);
798ab48e KO	157	if (likely(tag >= 0)) {
	158	local_irq_restore(flags);
	159	return tag;
	160	}
	161
	162	while (1) {
	163	spin_lock(&pool->lock);
	164
	165	/*
	166	* prepare_to_wait() must come before steal_tags(), in case
	167	* percpu_ida_free() on another cpu flips a bit in
	168	* cpus_have_tags
	169	*
	170	* global lock held and irqs disabled, don't need percpu lock
	171	*/
6f6b5d1e KO	172	if (state != TASK_RUNNING)
6f6b5d1e KO	173	prepare_to_wait(&pool->wait, &wait, state);
798ab48e KO	174
	175	if (!tags->nr_free)
	176	alloc_global_tags(pool, tags);
	177	if (!tags->nr_free)
	178	steal_tags(pool, tags);
	179
	180	if (tags->nr_free) {
	181	tag = tags->freelist[--tags->nr_free];
	182	if (tags->nr_free)
	183	cpumask_set_cpu(smp_processor_id(),
	184	&pool->cpus_have_tags);
	185	}
	186
	187	spin_unlock(&pool->lock);
	188	local_irq_restore(flags);
	189
6f6b5d1e	190	if (tag >= 0 \|\| state == TASK_RUNNING)
798ab48e KO	191	break;
798ab48e KO	192
555b270e NB	193	if (signal_pending_state(state, current)) {
	194	tag = -ERESTARTSYS;
	195	break;
	196	}
	197
798ab48e KO	198	schedule();
	199
	200	local_irq_save(flags);
	201	tags = this_cpu_ptr(pool->tag_cpu);
	202	}
6f6b5d1e KO	203	if (state != TASK_RUNNING)
6f6b5d1e KO	204	finish_wait(&pool->wait, &wait);
798ab48e	205
798ab48e KO	206	return tag;
	207	}
	208	EXPORT_SYMBOL_GPL(percpu_ida_alloc);
	209
	210	/**
	211	* percpu_ida_free - free a tag
	212	* @pool: pool @tag was allocated from
	213	* @tag: a tag previously allocated with percpu_ida_alloc()
	214	*
	215	* Safe to be called from interrupt context.
	216	*/
	217	void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
	218	{
	219	struct percpu_ida_cpu *tags;
	220	unsigned long flags;
	221	unsigned nr_free;
	222
	223	BUG_ON(tag >= pool->nr_tags);
	224
	225	local_irq_save(flags);
	226	tags = this_cpu_ptr(pool->tag_cpu);
	227
	228	spin_lock(&tags->lock);
	229	tags->freelist[tags->nr_free++] = tag;
	230
	231	nr_free = tags->nr_free;
	232	spin_unlock(&tags->lock);
	233
	234	if (nr_free == 1) {
	235	cpumask_set_cpu(smp_processor_id(),
	236	&pool->cpus_have_tags);
	237	wake_up(&pool->wait);
	238	}
	239
e26b53d0	240	if (nr_free == pool->percpu_max_size) {
798ab48e KO	241	spin_lock(&pool->lock);
	242
	243	/*
	244	* Global lock held and irqs disabled, don't need percpu
	245	* lock
	246	*/
e26b53d0	247	if (tags->nr_free == pool->percpu_max_size) {
798ab48e KO	248	move_tags(pool->freelist, &pool->nr_free,
798ab48e KO	249	tags->freelist, &tags->nr_free,
e26b53d0	250	pool->percpu_batch_size);
798ab48e KO	251
	252	wake_up(&pool->wait);
	253	}
	254	spin_unlock(&pool->lock);
	255	}
	256
	257	local_irq_restore(flags);
	258	}
	259	EXPORT_SYMBOL_GPL(percpu_ida_free);
	260
	261	/**
	262	* percpu_ida_destroy - release a tag pool's resources
	263	* @pool: pool to free
	264	*
	265	* Frees the resources allocated by percpu_ida_init().
	266	*/
	267	void percpu_ida_destroy(struct percpu_ida *pool)
	268	{
	269	free_percpu(pool->tag_cpu);
	270	free_pages((unsigned long) pool->freelist,
	271	get_order(pool->nr_tags * sizeof(unsigned)));
	272	}
	273	EXPORT_SYMBOL_GPL(percpu_ida_destroy);
	274
	275	/**
	276	* percpu_ida_init - initialize a percpu tag pool
	277	* @pool: pool to initialize
	278	* @nr_tags: number of tags that will be available for allocation
	279	*
	280	* Initializes @pool so that it can be used to allocate tags - integers in the
	281	* range [0, nr_tags). Typically, they'll be used by driver code to refer to a
	282	* preallocated array of tag structures.
	283	*
	284	* Allocation is percpu, but sharding is limited by nr_tags - for best
	285	* performance, the workload should not span more cpus than nr_tags / 128.
	286	*/
e26b53d0 SL	287	int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
e26b53d0 SL	288	unsigned long max_size, unsigned long batch_size)
798ab48e KO	289	{
	290	unsigned i, cpu, order;
	291
	292	memset(pool, 0, sizeof(*pool));
	293
	294	init_waitqueue_head(&pool->wait);
	295	spin_lock_init(&pool->lock);
	296	pool->nr_tags = nr_tags;
e26b53d0 SL	297	pool->percpu_max_size = max_size;
e26b53d0 SL	298	pool->percpu_batch_size = batch_size;
798ab48e KO	299
	300	/* Guard against overflow */
	301	if (nr_tags > (unsigned) INT_MAX + 1) {
	302	pr_err("percpu_ida_init(): nr_tags too large\n");
	303	return -EINVAL;
	304	}
	305
	306	order = get_order(nr_tags * sizeof(unsigned));
	307	pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
	308	if (!pool->freelist)
	309	return -ENOMEM;
	310
	311	for (i = 0; i < nr_tags; i++)
	312	pool->freelist[i] = i;
	313
	314	pool->nr_free = nr_tags;
	315
	316	pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
e26b53d0	317	pool->percpu_max_size * sizeof(unsigned),
798ab48e KO	318	sizeof(unsigned));
	319	if (!pool->tag_cpu)
	320	goto err;
	321
	322	for_each_possible_cpu(cpu)
	323	spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);
	324
	325	return 0;
	326	err:
	327	percpu_ida_destroy(pool);
	328	return -ENOMEM;
	329	}
e26b53d0	330	EXPORT_SYMBOL_GPL(__percpu_ida_init);
7fc2ba17 SL	331
	332	/**
	333	* percpu_ida_for_each_free - iterate free ids of a pool
	334	* @pool: pool to iterate
	335	* @fn: interate callback function
	336	* @data: parameter for @fn
	337	*
	338	* Note, this doesn't guarantee to iterate all free ids restrictly. Some free
	339	* ids might be missed, some might be iterated duplicated, and some might
	340	* be iterated and not free soon.
	341	*/
	342	int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
	343	void *data)
	344	{
	345	unsigned long flags;
	346	struct percpu_ida_cpu *remote;
	347	unsigned cpu, i, err = 0;
	348
	349	local_irq_save(flags);
	350	for_each_possible_cpu(cpu) {
	351	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	352	spin_lock(&remote->lock);
	353	for (i = 0; i < remote->nr_free; i++) {
	354	err = fn(remote->freelist[i], data);
	355	if (err)
	356	break;
	357	}
	358	spin_unlock(&remote->lock);
	359	if (err)
	360	goto out;
	361	}
	362
	363	spin_lock(&pool->lock);
	364	for (i = 0; i < pool->nr_free; i++) {
	365	err = fn(pool->freelist[i], data);
	366	if (err)
	367	break;
	368	}
	369	spin_unlock(&pool->lock);
	370	out:
	371	local_irq_restore(flags);
	372	return err;
	373	}
	374	EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
1dddc01a SL	375
	376	/**
	377	* percpu_ida_free_tags - return free tags number of a specific cpu or global pool
	378	* @pool: pool related
	379	* @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
	380	*
	381	* Note: this just returns a snapshot of free tags number.
	382	*/
	383	unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
	384	{
	385	struct percpu_ida_cpu *remote;
	386	if (cpu == nr_cpu_ids)
	387	return pool->nr_free;
	388	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	389	return remote->nr_free;
	390	}
	391	EXPORT_SYMBOL_GPL(percpu_ida_free_tags);