[mirror_ubuntu-artful-kernel.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 - we don't steal tags
 * unless enough percpu freelists have tags on them that it's possible more than
 * half the total tags could be stuck on remote percpu freelists.
 *
 * 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 * pool->percpu_max_size > pool->nr_tags / 2;
	     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
 * @gfp: gfp flags
 *
 * 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
 * __GFP_WAIT, 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 __GFP_WAIT.
 */
int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp)
{
	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
		 */
		prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);

		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 || !(gfp & __GFP_WAIT))
			break;

		schedule();

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

	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	*
	57	* We first check how many percpu freelists have tags - we don't steal tags
	58	* unless enough percpu freelists have tags on them that it's possible more than
	59	* half the total tags could be stuck on remote percpu freelists.
	60	*
	61	* Then we iterate through the cpus until we find some tags - we don't attempt
	62	* to find the "best" cpu to steal from, to keep cacheline bouncing to a
	63	* minimum.
	64	*/
	65	static inline void steal_tags(struct percpu_ida *pool,
	66	struct percpu_ida_cpu *tags)
	67	{
	68	unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
	69	struct percpu_ida_cpu *remote;
	70
	71	for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
e26b53d0	72	cpus_have_tags * pool->percpu_max_size > pool->nr_tags / 2;
798ab48e KO	73	cpus_have_tags--) {
	74	cpu = cpumask_next(cpu, &pool->cpus_have_tags);
	75
	76	if (cpu >= nr_cpu_ids) {
	77	cpu = cpumask_first(&pool->cpus_have_tags);
	78	if (cpu >= nr_cpu_ids)
	79	BUG();
	80	}
	81
	82	pool->cpu_last_stolen = cpu;
	83	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	84
	85	cpumask_clear_cpu(cpu, &pool->cpus_have_tags);
	86
	87	if (remote == tags)
	88	continue;
	89
	90	spin_lock(&remote->lock);
	91
	92	if (remote->nr_free) {
	93	memcpy(tags->freelist,
	94	remote->freelist,
	95	sizeof(unsigned) * remote->nr_free);
	96
	97	tags->nr_free = remote->nr_free;
	98	remote->nr_free = 0;
	99	}
	100
	101	spin_unlock(&remote->lock);
	102
	103	if (tags->nr_free)
	104	break;
	105	}
	106	}
	107
	108	/*
	109	* Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
	110	* our percpu freelist:
	111	*/
	112	static inline void alloc_global_tags(struct percpu_ida *pool,
	113	struct percpu_ida_cpu *tags)
	114	{
	115	move_tags(tags->freelist, &tags->nr_free,
	116	pool->freelist, &pool->nr_free,
e26b53d0	117	min(pool->nr_free, pool->percpu_batch_size));
798ab48e KO	118	}
798ab48e KO	119
6b378382	120	static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
798ab48e KO	121	{
	122	int tag = -ENOSPC;
	123
	124	spin_lock(&tags->lock);
	125	if (tags->nr_free)
	126	tag = tags->freelist[--tags->nr_free];
	127	spin_unlock(&tags->lock);
	128
	129	return tag;
	130	}
	131
	132	/**
	133	* percpu_ida_alloc - allocate a tag
	134	* @pool: pool to allocate from
	135	* @gfp: gfp flags
	136	*
	137	* Returns a tag - an integer in the range [0..nr_tags) (passed to
	138	* tag_pool_init()), or otherwise -ENOSPC on allocation failure.
	139	*
	140	* Safe to be called from interrupt context (assuming it isn't passed
	141	* __GFP_WAIT, of course).
	142	*
	143	* @gfp indicates whether or not to wait until a free id is available (it's not
	144	* used for internal memory allocations); thus if passed __GFP_WAIT we may sleep
	145	* however long it takes until another thread frees an id (same semantics as a
	146	* mempool).
	147	*
	148	* Will not fail if passed __GFP_WAIT.
	149	*/
	150	int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp)
	151	{
	152	DEFINE_WAIT(wait);
	153	struct percpu_ida_cpu *tags;
	154	unsigned long flags;
	155	int tag;
	156
	157	local_irq_save(flags);
	158	tags = this_cpu_ptr(pool->tag_cpu);
	159
	160	/* Fastpath */
6b378382	161	tag = alloc_local_tag(tags);
798ab48e KO	162	if (likely(tag >= 0)) {
	163	local_irq_restore(flags);
	164	return tag;
	165	}
	166
	167	while (1) {
	168	spin_lock(&pool->lock);
	169
	170	/*
	171	* prepare_to_wait() must come before steal_tags(), in case
	172	* percpu_ida_free() on another cpu flips a bit in
	173	* cpus_have_tags
	174	*
	175	* global lock held and irqs disabled, don't need percpu lock
	176	*/
	177	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
	178
	179	if (!tags->nr_free)
	180	alloc_global_tags(pool, tags);
	181	if (!tags->nr_free)
	182	steal_tags(pool, tags);
	183
	184	if (tags->nr_free) {
	185	tag = tags->freelist[--tags->nr_free];
	186	if (tags->nr_free)
	187	cpumask_set_cpu(smp_processor_id(),
	188	&pool->cpus_have_tags);
	189	}
	190
	191	spin_unlock(&pool->lock);
	192	local_irq_restore(flags);
	193
	194	if (tag >= 0 \|\| !(gfp & __GFP_WAIT))
	195	break;
	196
	197	schedule();
	198
	199	local_irq_save(flags);
	200	tags = this_cpu_ptr(pool->tag_cpu);
	201	}
	202
	203	finish_wait(&pool->wait, &wait);
	204	return tag;
	205	}
	206	EXPORT_SYMBOL_GPL(percpu_ida_alloc);
	207
	208	/**
	209	* percpu_ida_free - free a tag
	210	* @pool: pool @tag was allocated from
	211	* @tag: a tag previously allocated with percpu_ida_alloc()
	212	*
	213	* Safe to be called from interrupt context.
	214	*/
	215	void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
	216	{
	217	struct percpu_ida_cpu *tags;
	218	unsigned long flags;
	219	unsigned nr_free;
	220
	221	BUG_ON(tag >= pool->nr_tags);
	222
	223	local_irq_save(flags);
	224	tags = this_cpu_ptr(pool->tag_cpu);
	225
226	spin_lock(&tags->lock);
227	tags->freelist[tags->nr_free++] = tag;
228
229	nr_free = tags->nr_free;
230	spin_unlock(&tags->lock);
231
232	if (nr_free == 1) {
233	cpumask_set_cpu(smp_processor_id(),
234	&pool->cpus_have_tags);
235	wake_up(&pool->wait);
236	}
237
e26b53d0	238	if (nr_free == pool->percpu_max_size) {
798ab48e KO	239	spin_lock(&pool->lock);
	240
	241	/*
	242	* Global lock held and irqs disabled, don't need percpu
	243	* lock
	244	*/
e26b53d0	245	if (tags->nr_free == pool->percpu_max_size) {
798ab48e KO	246	move_tags(pool->freelist, &pool->nr_free,
798ab48e KO	247	tags->freelist, &tags->nr_free,
e26b53d0	248	pool->percpu_batch_size);
798ab48e KO	249
	250	wake_up(&pool->wait);
	251	}
	252	spin_unlock(&pool->lock);
	253	}
	254
	255	local_irq_restore(flags);
	256	}
	257	EXPORT_SYMBOL_GPL(percpu_ida_free);
	258
	259	/**
	260	* percpu_ida_destroy - release a tag pool's resources
	261	* @pool: pool to free
	262	*
	263	* Frees the resources allocated by percpu_ida_init().
	264	*/
	265	void percpu_ida_destroy(struct percpu_ida *pool)
	266	{
	267	free_percpu(pool->tag_cpu);
	268	free_pages((unsigned long) pool->freelist,
	269	get_order(pool->nr_tags * sizeof(unsigned)));
	270	}
	271	EXPORT_SYMBOL_GPL(percpu_ida_destroy);
	272
	273	/**
	274	* percpu_ida_init - initialize a percpu tag pool
	275	* @pool: pool to initialize
	276	* @nr_tags: number of tags that will be available for allocation
	277	*
	278	* Initializes @pool so that it can be used to allocate tags - integers in the
	279	* range [0, nr_tags). Typically, they'll be used by driver code to refer to a
	280	* preallocated array of tag structures.
	281	*
	282	* Allocation is percpu, but sharding is limited by nr_tags - for best
	283	* performance, the workload should not span more cpus than nr_tags / 128.
	284	*/
e26b53d0 SL	285	int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
e26b53d0 SL	286	unsigned long max_size, unsigned long batch_size)
798ab48e KO	287	{
	288	unsigned i, cpu, order;
	289
	290	memset(pool, 0, sizeof(*pool));
	291
	292	init_waitqueue_head(&pool->wait);
	293	spin_lock_init(&pool->lock);
	294	pool->nr_tags = nr_tags;
e26b53d0 SL	295	pool->percpu_max_size = max_size;
e26b53d0 SL	296	pool->percpu_batch_size = batch_size;
798ab48e KO	297
	298	/* Guard against overflow */
	299	if (nr_tags > (unsigned) INT_MAX + 1) {
	300	pr_err("percpu_ida_init(): nr_tags too large\n");
	301	return -EINVAL;
	302	}
	303
	304	order = get_order(nr_tags * sizeof(unsigned));
	305	pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
	306	if (!pool->freelist)
	307	return -ENOMEM;
	308
	309	for (i = 0; i < nr_tags; i++)
	310	pool->freelist[i] = i;
	311
	312	pool->nr_free = nr_tags;
	313
	314	pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
e26b53d0	315	pool->percpu_max_size * sizeof(unsigned),
798ab48e KO	316	sizeof(unsigned));
	317	if (!pool->tag_cpu)
	318	goto err;
	319
	320	for_each_possible_cpu(cpu)
	321	spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);
	322
	323	return 0;
	324	err:
	325	percpu_ida_destroy(pool);
	326	return -ENOMEM;
	327	}
e26b53d0	328	EXPORT_SYMBOL_GPL(__percpu_ida_init);
7fc2ba17 SL	329
	330	/**
	331	* percpu_ida_for_each_free - iterate free ids of a pool
	332	* @pool: pool to iterate
	333	* @fn: interate callback function
	334	* @data: parameter for @fn
	335	*
	336	* Note, this doesn't guarantee to iterate all free ids restrictly. Some free
	337	* ids might be missed, some might be iterated duplicated, and some might
	338	* be iterated and not free soon.
	339	*/
	340	int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
	341	void *data)
	342	{
	343	unsigned long flags;
	344	struct percpu_ida_cpu *remote;
	345	unsigned cpu, i, err = 0;
	346
	347	local_irq_save(flags);
	348	for_each_possible_cpu(cpu) {
	349	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	350	spin_lock(&remote->lock);
	351	for (i = 0; i < remote->nr_free; i++) {
	352	err = fn(remote->freelist[i], data);
	353	if (err)
	354	break;
	355	}
	356	spin_unlock(&remote->lock);
	357	if (err)
	358	goto out;
	359	}
	360
	361	spin_lock(&pool->lock);
	362	for (i = 0; i < pool->nr_free; i++) {
	363	err = fn(pool->freelist[i], data);
	364	if (err)
	365	break;
	366	}
	367	spin_unlock(&pool->lock);
	368	out:
	369	local_irq_restore(flags);
	370	return err;
	371	}
	372	EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
1dddc01a SL	373
	374	/**
	375	* percpu_ida_free_tags - return free tags number of a specific cpu or global pool
	376	* @pool: pool related
	377	* @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
	378	*
	379	* Note: this just returns a snapshot of free tags number.
	380	*/
	381	unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
	382	{
	383	struct percpu_ida_cpu *remote;
	384	if (cpu == nr_cpu_ids)
	385	return pool->nr_free;
	386	remote = per_cpu_ptr(pool->tag_cpu, cpu);
	387	return remote->nr_free;
	388	}
	389	EXPORT_SYMBOL_GPL(percpu_ida_free_tags);