[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/bitmap.h>
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/hardirq.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.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_WAIT 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
	17	#include <linux/bitmap.h>
	18	#include <linux/bitops.h>
	19	#include <linux/bug.h>
	20	#include <linux/err.h>
	21	#include <linux/export.h>
	22	#include <linux/hardirq.h>
	23	#include <linux/idr.h>
	24	#include <linux/init.h>
	25	#include <linux/kernel.h>
	26	#include <linux/percpu.h>
	27	#include <linux/sched.h>
	28	#include <linux/slab.h>
	29	#include <linux/string.h>
	30	#include <linux/spinlock.h>
	31	#include <linux/percpu_ida.h>
	32
798ab48e KO	33	struct percpu_ida_cpu {
	34	/*
	35	* Even though this is percpu, we need a lock for tag stealing by remote
	36	* CPUs:
	37	*/
	38	spinlock_t lock;
	39
	40	/* nr_free/freelist form a stack of free IDs */
	41	unsigned nr_free;
	42	unsigned freelist[];
	43	};
	44
	45	static inline void move_tags(unsigned dst, unsigned dst_nr,
	46	unsigned src, unsigned src_nr,
	47	unsigned nr)
	48	{
	49	*src_nr -= nr;
	50	memcpy(dst + dst_nr, src + src_nr, sizeof(unsigned) * nr);
	51	*dst_nr += nr;
	52	}
	53
	54	/*
	55	* Try to steal tags from a remote cpu's percpu freelist.
	56	*
d835502f	57	* We first check how many percpu freelists have tags
798ab48e KO	58	*
	59	* Then we iterate through the cpus until we find some tags - we don't attempt
	60	* to find the "best" cpu to steal from, to keep cacheline bouncing to a
	61	* minimum.
	62	*/
	63	static inline void steal_tags(struct percpu_ida *pool,
	64	struct percpu_ida_cpu *tags)
	65	{
	66	unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
	67	struct percpu_ida_cpu *remote;
	68
	69	for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
d835502f	70	cpus_have_tags; cpus_have_tags--) {
798ab48e KO	71	cpu = cpumask_next(cpu, &pool->cpus_have_tags);
	72
	73	if (cpu >= nr_cpu_ids) {
	74	cpu = cpumask_first(&pool->cpus_have_tags);
	75	if (cpu >= nr_cpu_ids)
	76	BUG();
	77	}
	78
	79	pool->cpu_last_stolen = cpu;
	80	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	81
	82	cpumask_clear_cpu(cpu, &pool->cpus_have_tags);
	83
	84	if (remote == tags)
	85	continue;
	86
	87	spin_lock(&remote->lock);
	88
	89	if (remote->nr_free) {
	90	memcpy(tags->freelist,
	91	remote->freelist,
	92	sizeof(unsigned) * remote->nr_free);
	93
	94	tags->nr_free = remote->nr_free;
	95	remote->nr_free = 0;
	96	}
	97
	98	spin_unlock(&remote->lock);
	99
	100	if (tags->nr_free)
	101	break;
	102	}
	103	}
	104
	105	/*
	106	* Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
	107	* our percpu freelist:
	108	*/
	109	static inline void alloc_global_tags(struct percpu_ida *pool,
	110	struct percpu_ida_cpu *tags)
	111	{
	112	move_tags(tags->freelist, &tags->nr_free,
	113	pool->freelist, &pool->nr_free,
e26b53d0	114	min(pool->nr_free, pool->percpu_batch_size));
798ab48e KO	115	}
798ab48e KO	116
6b378382	117	static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
798ab48e KO	118	{
	119	int tag = -ENOSPC;
	120
	121	spin_lock(&tags->lock);
	122	if (tags->nr_free)
	123	tag = tags->freelist[--tags->nr_free];
	124	spin_unlock(&tags->lock);
	125
	126	return tag;
	127	}
	128
	129	/**
	130	* percpu_ida_alloc - allocate a tag
	131	* @pool: pool to allocate from
6f6b5d1e	132	* @state: task state for prepare_to_wait
798ab48e KO	133	*
	134	* Returns a tag - an integer in the range [0..nr_tags) (passed to
	135	* tag_pool_init()), or otherwise -ENOSPC on allocation failure.
	136	*
	137	* Safe to be called from interrupt context (assuming it isn't passed
555b270e	138	* TASK_UNINTERRUPTIBLE \| TASK_INTERRUPTIBLE, of course).
798ab48e KO	139	*
	140	* @gfp indicates whether or not to wait until a free id is available (it's not
	141	* used for internal memory allocations); thus if passed __GFP_WAIT we may sleep
	142	* however long it takes until another thread frees an id (same semantics as a
	143	* mempool).
	144	*
555b270e	145	* Will not fail if passed TASK_UNINTERRUPTIBLE \| TASK_INTERRUPTIBLE.
798ab48e	146	*/
6f6b5d1e	147	int percpu_ida_alloc(struct percpu_ida *pool, int state)
798ab48e KO	148	{
	149	DEFINE_WAIT(wait);
	150	struct percpu_ida_cpu *tags;
	151	unsigned long flags;
	152	int tag;
	153
	154	local_irq_save(flags);
	155	tags = this_cpu_ptr(pool->tag_cpu);
	156
	157	/* Fastpath */
6b378382	158	tag = alloc_local_tag(tags);
798ab48e KO	159	if (likely(tag >= 0)) {
	160	local_irq_restore(flags);
	161	return tag;
	162	}
	163
	164	while (1) {
	165	spin_lock(&pool->lock);
	166
	167	/*
	168	* prepare_to_wait() must come before steal_tags(), in case
	169	* percpu_ida_free() on another cpu flips a bit in
	170	* cpus_have_tags
	171	*
	172	* global lock held and irqs disabled, don't need percpu lock
	173	*/
6f6b5d1e KO	174	if (state != TASK_RUNNING)
6f6b5d1e KO	175	prepare_to_wait(&pool->wait, &wait, state);
798ab48e KO	176
	177	if (!tags->nr_free)
	178	alloc_global_tags(pool, tags);
	179	if (!tags->nr_free)
	180	steal_tags(pool, tags);
	181
	182	if (tags->nr_free) {
	183	tag = tags->freelist[--tags->nr_free];
	184	if (tags->nr_free)
	185	cpumask_set_cpu(smp_processor_id(),
	186	&pool->cpus_have_tags);
	187	}
	188
	189	spin_unlock(&pool->lock);
	190	local_irq_restore(flags);
	191
6f6b5d1e	192	if (tag >= 0 \|\| state == TASK_RUNNING)
798ab48e KO	193	break;
798ab48e KO	194
555b270e NB	195	if (signal_pending_state(state, current)) {
	196	tag = -ERESTARTSYS;
	197	break;
	198	}
	199
798ab48e KO	200	schedule();
	201
	202	local_irq_save(flags);
	203	tags = this_cpu_ptr(pool->tag_cpu);
	204	}
6f6b5d1e KO	205	if (state != TASK_RUNNING)
6f6b5d1e KO	206	finish_wait(&pool->wait, &wait);
798ab48e	207
798ab48e KO	208	return tag;
	209	}
	210	EXPORT_SYMBOL_GPL(percpu_ida_alloc);
	211
	212	/**
	213	* percpu_ida_free - free a tag
	214	* @pool: pool @tag was allocated from
	215	* @tag: a tag previously allocated with percpu_ida_alloc()
	216	*
	217	* Safe to be called from interrupt context.
	218	*/
	219	void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
	220	{
	221	struct percpu_ida_cpu *tags;
	222	unsigned long flags;
	223	unsigned nr_free;
	224
	225	BUG_ON(tag >= pool->nr_tags);
	226
	227	local_irq_save(flags);
	228	tags = this_cpu_ptr(pool->tag_cpu);
	229
	230	spin_lock(&tags->lock);
	231	tags->freelist[tags->nr_free++] = tag;
	232
	233	nr_free = tags->nr_free;
	234	spin_unlock(&tags->lock);
	235
	236	if (nr_free == 1) {
	237	cpumask_set_cpu(smp_processor_id(),
	238	&pool->cpus_have_tags);
	239	wake_up(&pool->wait);
	240	}
	241
e26b53d0	242	if (nr_free == pool->percpu_max_size) {
798ab48e KO	243	spin_lock(&pool->lock);
	244
	245	/*
	246	* Global lock held and irqs disabled, don't need percpu
	247	* lock
	248	*/
e26b53d0	249	if (tags->nr_free == pool->percpu_max_size) {
798ab48e KO	250	move_tags(pool->freelist, &pool->nr_free,
798ab48e KO	251	tags->freelist, &tags->nr_free,
e26b53d0	252	pool->percpu_batch_size);
798ab48e KO	253
	254	wake_up(&pool->wait);
	255	}
	256	spin_unlock(&pool->lock);
	257	}
	258
	259	local_irq_restore(flags);
	260	}
	261	EXPORT_SYMBOL_GPL(percpu_ida_free);
	262
	263	/**
	264	* percpu_ida_destroy - release a tag pool's resources
	265	* @pool: pool to free
	266	*
	267	* Frees the resources allocated by percpu_ida_init().
	268	*/
	269	void percpu_ida_destroy(struct percpu_ida *pool)
	270	{
	271	free_percpu(pool->tag_cpu);
	272	free_pages((unsigned long) pool->freelist,
	273	get_order(pool->nr_tags * sizeof(unsigned)));
	274	}
	275	EXPORT_SYMBOL_GPL(percpu_ida_destroy);
	276
	277	/**
	278	* percpu_ida_init - initialize a percpu tag pool
	279	* @pool: pool to initialize
	280	* @nr_tags: number of tags that will be available for allocation
	281	*
	282	* Initializes @pool so that it can be used to allocate tags - integers in the
	283	* range [0, nr_tags). Typically, they'll be used by driver code to refer to a
	284	* preallocated array of tag structures.
	285	*
	286	* Allocation is percpu, but sharding is limited by nr_tags - for best
	287	* performance, the workload should not span more cpus than nr_tags / 128.
	288	*/
e26b53d0 SL	289	int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
e26b53d0 SL	290	unsigned long max_size, unsigned long batch_size)
798ab48e KO	291	{
	292	unsigned i, cpu, order;
	293
	294	memset(pool, 0, sizeof(*pool));
	295
	296	init_waitqueue_head(&pool->wait);
	297	spin_lock_init(&pool->lock);
	298	pool->nr_tags = nr_tags;
e26b53d0 SL	299	pool->percpu_max_size = max_size;
e26b53d0 SL	300	pool->percpu_batch_size = batch_size;
798ab48e KO	301
	302	/* Guard against overflow */
	303	if (nr_tags > (unsigned) INT_MAX + 1) {
	304	pr_err("percpu_ida_init(): nr_tags too large\n");
	305	return -EINVAL;
	306	}
	307
	308	order = get_order(nr_tags * sizeof(unsigned));
	309	pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
	310	if (!pool->freelist)
	311	return -ENOMEM;
	312
	313	for (i = 0; i < nr_tags; i++)
	314	pool->freelist[i] = i;
	315
	316	pool->nr_free = nr_tags;
	317
	318	pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
e26b53d0	319	pool->percpu_max_size * sizeof(unsigned),
798ab48e KO	320	sizeof(unsigned));
	321	if (!pool->tag_cpu)
	322	goto err;
	323
	324	for_each_possible_cpu(cpu)
	325	spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);
	326
	327	return 0;
	328	err:
	329	percpu_ida_destroy(pool);
	330	return -ENOMEM;
	331	}
e26b53d0	332	EXPORT_SYMBOL_GPL(__percpu_ida_init);
7fc2ba17 SL	333
	334	/**
	335	* percpu_ida_for_each_free - iterate free ids of a pool
	336	* @pool: pool to iterate
	337	* @fn: interate callback function
	338	* @data: parameter for @fn
	339	*
	340	* Note, this doesn't guarantee to iterate all free ids restrictly. Some free
	341	* ids might be missed, some might be iterated duplicated, and some might
	342	* be iterated and not free soon.
	343	*/
	344	int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
	345	void *data)
	346	{
	347	unsigned long flags;
	348	struct percpu_ida_cpu *remote;
	349	unsigned cpu, i, err = 0;
	350
	351	local_irq_save(flags);
	352	for_each_possible_cpu(cpu) {
	353	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	354	spin_lock(&remote->lock);
	355	for (i = 0; i < remote->nr_free; i++) {
	356	err = fn(remote->freelist[i], data);
	357	if (err)
	358	break;
	359	}
	360	spin_unlock(&remote->lock);
	361	if (err)
	362	goto out;
	363	}
	364
	365	spin_lock(&pool->lock);
	366	for (i = 0; i < pool->nr_free; i++) {
	367	err = fn(pool->freelist[i], data);
	368	if (err)
	369	break;
	370	}
	371	spin_unlock(&pool->lock);
	372	out:
	373	local_irq_restore(flags);
	374	return err;
	375	}
	376	EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
1dddc01a SL	377
	378	/**
	379	* percpu_ida_free_tags - return free tags number of a specific cpu or global pool
	380	* @pool: pool related
	381	* @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
	382	*
	383	* Note: this just returns a snapshot of free tags number.
	384	*/
	385	unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
	386	{
	387	struct percpu_ida_cpu *remote;
	388	if (cpu == nr_cpu_ids)
	389	return pool->nr_free;
	390	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	391	return remote->nr_free;
	392	}
	393	EXPORT_SYMBOL_GPL(percpu_ida_free_tags);