[linux.git] / block / blk-ioc.c

/*
 * Functions related to io context handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/bootmem.h>	/* for max_pfn/max_low_pfn */

#include "blk.h"

/*
 * For io context allocations
 */
static struct kmem_cache *iocontext_cachep;

static void cfq_dtor(struct io_context *ioc)
{
	if (!hlist_empty(&ioc->cic_list)) {
		struct cfq_io_context *cic;

		cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
								cic_list);
		cic->dtor(ioc);
	}
}

/*
 * IO Context helper functions. put_io_context() returns 1 if there are no
 * more users of this io context, 0 otherwise.
 */
int put_io_context(struct io_context *ioc)
{
	if (ioc == NULL)
		return 1;

	BUG_ON(atomic_read(&ioc->refcount) == 0);

	if (atomic_dec_and_test(&ioc->refcount)) {
		rcu_read_lock();
		if (ioc->aic && ioc->aic->dtor)
			ioc->aic->dtor(ioc->aic);
		cfq_dtor(ioc);
		rcu_read_unlock();

		kmem_cache_free(iocontext_cachep, ioc);
		return 1;
	}
	return 0;
}
EXPORT_SYMBOL(put_io_context);

static void cfq_exit(struct io_context *ioc)
{
	rcu_read_lock();

	if (!hlist_empty(&ioc->cic_list)) {
		struct cfq_io_context *cic;

		cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
								cic_list);
		cic->exit(ioc);
	}
	rcu_read_unlock();
}

/* Called by the exitting task */
void exit_io_context(void)
{
	struct io_context *ioc;

	task_lock(current);
	ioc = current->io_context;
	current->io_context = NULL;
	task_unlock(current);

	if (atomic_dec_and_test(&ioc->nr_tasks)) {
		if (ioc->aic && ioc->aic->exit)
			ioc->aic->exit(ioc->aic);
		cfq_exit(ioc);

		put_io_context(ioc);
	}
}

struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
{
	struct io_context *ret;

	ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
	if (ret) {
		atomic_set(&ret->refcount, 1);
		atomic_set(&ret->nr_tasks, 1);
		spin_lock_init(&ret->lock);
		ret->ioprio_changed = 0;
		ret->ioprio = 0;
		ret->last_waited = jiffies; /* doesn't matter... */
		ret->nr_batch_requests = 0; /* because this is 0 */
		ret->aic = NULL;
		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
		INIT_HLIST_HEAD(&ret->cic_list);
		ret->ioc_data = NULL;
	}

	return ret;
}

/*
 * If the current task has no IO context then create one and initialise it.
 * Otherwise, return its existing IO context.
 *
 * This returned IO context doesn't have a specifically elevated refcount,
 * but since the current task itself holds a reference, the context can be
 * used in general code, so long as it stays within `current` context.
 */
struct io_context *current_io_context(gfp_t gfp_flags, int node)
{
	struct task_struct *tsk = current;
	struct io_context *ret;

	ret = tsk->io_context;
	if (likely(ret))
		return ret;

	ret = alloc_io_context(gfp_flags, node);
	if (ret) {
		/* make sure set_task_ioprio() sees the settings above */
		smp_wmb();
		tsk->io_context = ret;
	}

	return ret;
}

/*
 * If the current task has no IO context then create one and initialise it.
 * If it does have a context, take a ref on it.
 *
 * This is always called in the context of the task which submitted the I/O.
 */
struct io_context *get_io_context(gfp_t gfp_flags, int node)
{
	struct io_context *ret = NULL;

	/*
	 * Check for unlikely race with exiting task. ioc ref count is
	 * zero when ioc is being detached.
	 */
	do {
		ret = current_io_context(gfp_flags, node);
		if (unlikely(!ret))
			break;
	} while (!atomic_inc_not_zero(&ret->refcount));

	return ret;
}
EXPORT_SYMBOL(get_io_context);

void copy_io_context(struct io_context **pdst, struct io_context **psrc)
{
	struct io_context *src = *psrc;
	struct io_context *dst = *pdst;

	if (src) {
		BUG_ON(atomic_read(&src->refcount) == 0);
		atomic_inc(&src->refcount);
		put_io_context(dst);
		*pdst = src;
	}
}
EXPORT_SYMBOL(copy_io_context);

static int __init blk_ioc_init(void)
{
	iocontext_cachep = kmem_cache_create("blkdev_ioc",
			sizeof(struct io_context), 0, SLAB_PANIC, NULL);
	return 0;
}
subsys_initcall(blk_ioc_init);
Commit	Line	Data
86db1e29 JA	1	/*
	2	* Functions related to io context handling
	3	*/
	4	#include <linux/kernel.h>
	5	#include <linux/module.h>
	6	#include <linux/init.h>
	7	#include <linux/bio.h>
	8	#include <linux/blkdev.h>
	9	#include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
	10
	11	#include "blk.h"
	12
	13	/*
	14	* For io context allocations
	15	*/
	16	static struct kmem_cache *iocontext_cachep;
	17
	18	static void cfq_dtor(struct io_context *ioc)
	19	{
ffc4e759 JA	20	if (!hlist_empty(&ioc->cic_list)) {
	21	struct cfq_io_context *cic;
	22
	23	cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
	24	cic_list);
	25	cic->dtor(ioc);
	26	}
86db1e29 JA	27	}
	28
	29	/*
	30	* IO Context helper functions. put_io_context() returns 1 if there are no
	31	* more users of this io context, 0 otherwise.
	32	*/
	33	int put_io_context(struct io_context *ioc)
	34	{
	35	if (ioc == NULL)
	36	return 1;
	37
	38	BUG_ON(atomic_read(&ioc->refcount) == 0);
	39
	40	if (atomic_dec_and_test(&ioc->refcount)) {
	41	rcu_read_lock();
	42	if (ioc->aic && ioc->aic->dtor)
	43	ioc->aic->dtor(ioc->aic);
86db1e29	44	cfq_dtor(ioc);
07416d29	45	rcu_read_unlock();
86db1e29 JA	46
	47	kmem_cache_free(iocontext_cachep, ioc);
	48	return 1;
	49	}
	50	return 0;
	51	}
	52	EXPORT_SYMBOL(put_io_context);
	53
	54	static void cfq_exit(struct io_context *ioc)
	55	{
86db1e29	56	rcu_read_lock();
86db1e29	57
ffc4e759 JA	58	if (!hlist_empty(&ioc->cic_list)) {
	59	struct cfq_io_context *cic;
	60
	61	cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
	62	cic_list);
	63	cic->exit(ioc);
	64	}
	65	rcu_read_unlock();
86db1e29 JA	66	}
	67
	68	/* Called by the exitting task */
	69	void exit_io_context(void)
	70	{
	71	struct io_context *ioc;
	72
	73	task_lock(current);
	74	ioc = current->io_context;
	75	current->io_context = NULL;
	76	task_unlock(current);
	77
	78	if (atomic_dec_and_test(&ioc->nr_tasks)) {
	79	if (ioc->aic && ioc->aic->exit)
	80	ioc->aic->exit(ioc->aic);
	81	cfq_exit(ioc);
	82
	83	put_io_context(ioc);
	84	}
	85	}
	86
	87	struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
	88	{
	89	struct io_context *ret;
	90
	91	ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
	92	if (ret) {
	93	atomic_set(&ret->refcount, 1);
	94	atomic_set(&ret->nr_tasks, 1);
	95	spin_lock_init(&ret->lock);
	96	ret->ioprio_changed = 0;
	97	ret->ioprio = 0;
	98	ret->last_waited = jiffies; /* doesn't matter... */
	99	ret->nr_batch_requests = 0; /* because this is 0 */
	100	ret->aic = NULL;
	101	INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC \| __GFP_HIGH);
ffc4e759	102	INIT_HLIST_HEAD(&ret->cic_list);
86db1e29 JA	103	ret->ioc_data = NULL;
	104	}
	105
	106	return ret;
	107	}
	108
	109	/*
	110	* If the current task has no IO context then create one and initialise it.
	111	* Otherwise, return its existing IO context.
	112	*
	113	* This returned IO context doesn't have a specifically elevated refcount,
	114	* but since the current task itself holds a reference, the context can be
	115	* used in general code, so long as it stays within `current` context.
	116	*/
	117	struct io_context *current_io_context(gfp_t gfp_flags, int node)
	118	{
	119	struct task_struct *tsk = current;
	120	struct io_context *ret;
	121
	122	ret = tsk->io_context;
	123	if (likely(ret))
	124	return ret;
	125
	126	ret = alloc_io_context(gfp_flags, node);
	127	if (ret) {
	128	/* make sure set_task_ioprio() sees the settings above */
	129	smp_wmb();
	130	tsk->io_context = ret;
	131	}
	132
	133	return ret;
	134	}
	135
	136	/*
	137	* If the current task has no IO context then create one and initialise it.
	138	* If it does have a context, take a ref on it.
	139	*
	140	* This is always called in the context of the task which submitted the I/O.
	141	*/
	142	struct io_context *get_io_context(gfp_t gfp_flags, int node)
	143	{
	144	struct io_context *ret = NULL;
	145
	146	/*
	147	* Check for unlikely race with exiting task. ioc ref count is
	148	* zero when ioc is being detached.
	149	*/
	150	do {
	151	ret = current_io_context(gfp_flags, node);
	152	if (unlikely(!ret))
	153	break;
	154	} while (!atomic_inc_not_zero(&ret->refcount));
	155
	156	return ret;
	157	}
	158	EXPORT_SYMBOL(get_io_context);
	159
	160	void copy_io_context(struct io_context pdst, struct io_context psrc)
	161	{
	162	struct io_context src = psrc;
	163	struct io_context dst = pdst;
	164
	165	if (src) {
	166	BUG_ON(atomic_read(&src->refcount) == 0);
167	atomic_inc(&src->refcount);
168	put_io_context(dst);
169	*pdst = src;
170	}
171	}
172	EXPORT_SYMBOL(copy_io_context);
173
13341598	174	static int __init blk_ioc_init(void)
86db1e29 JA	175	{
	176	iocontext_cachep = kmem_cache_create("blkdev_ioc",
	177	sizeof(struct io_context), 0, SLAB_PANIC, NULL);
	178	return 0;
	179	}
	180	subsys_initcall(blk_ioc_init);