[net-next-2.6.git] / mm / backing-dev.c


#include <linux/wait.h>
#include <linux/backing-dev.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/writeback.h>
#include <linux/device.h>

void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
{
}
EXPORT_SYMBOL(default_unplug_io_fn);

struct backing_dev_info default_backing_dev_info = {
	.ra_pages	= VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
	.state		= 0,
	.capabilities	= BDI_CAP_MAP_COPY,
	.unplug_io_fn	= default_unplug_io_fn,
};
EXPORT_SYMBOL_GPL(default_backing_dev_info);

static struct class *bdi_class;
DEFINE_MUTEX(bdi_lock);
LIST_HEAD(bdi_list);

#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#include <linux/seq_file.h>

static struct dentry *bdi_debug_root;

static void bdi_debug_init(void)
{
	bdi_debug_root = debugfs_create_dir("bdi", NULL);
}

static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
	struct backing_dev_info *bdi = m->private;
	unsigned long background_thresh;
	unsigned long dirty_thresh;
	unsigned long bdi_thresh;

	get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);

#define K(x) ((x) << (PAGE_SHIFT - 10))
	seq_printf(m,
		   "BdiWriteback:     %8lu kB\n"
		   "BdiReclaimable:   %8lu kB\n"
		   "BdiDirtyThresh:   %8lu kB\n"
		   "DirtyThresh:      %8lu kB\n"
		   "BackgroundThresh: %8lu kB\n",
		   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
		   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
		   K(bdi_thresh),
		   K(dirty_thresh),
		   K(background_thresh));
#undef K

	return 0;
}

static int bdi_debug_stats_open(struct inode *inode, struct file *file)
{
	return single_open(file, bdi_debug_stats_show, inode->i_private);
}

static const struct file_operations bdi_debug_stats_fops = {
	.open		= bdi_debug_stats_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
{
	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
					       bdi, &bdi_debug_stats_fops);
}

static void bdi_debug_unregister(struct backing_dev_info *bdi)
{
	debugfs_remove(bdi->debug_stats);
	debugfs_remove(bdi->debug_dir);
}
#else
static inline void bdi_debug_init(void)
{
}
static inline void bdi_debug_register(struct backing_dev_info *bdi,
				      const char *name)
{
}
static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
{
}
#endif

static ssize_t read_ahead_kb_store(struct device *dev,
				  struct device_attribute *attr,
				  const char *buf, size_t count)
{
	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	char *end;
	unsigned long read_ahead_kb;
	ssize_t ret = -EINVAL;

	read_ahead_kb = simple_strtoul(buf, &end, 10);
	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
		bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
		ret = count;
	}
	return ret;
}

#define K(pages) ((pages) << (PAGE_SHIFT - 10))

#define BDI_SHOW(name, expr)						\
static ssize_t name##_show(struct device *dev,				\
			   struct device_attribute *attr, char *page)	\
{									\
	struct backing_dev_info *bdi = dev_get_drvdata(dev);		\
									\
	return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);	\
}

BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))

static ssize_t min_ratio_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t count)
{
	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	char *end;
	unsigned int ratio;
	ssize_t ret = -EINVAL;

	ratio = simple_strtoul(buf, &end, 10);
	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
		ret = bdi_set_min_ratio(bdi, ratio);
		if (!ret)
			ret = count;
	}
	return ret;
}
BDI_SHOW(min_ratio, bdi->min_ratio)

static ssize_t max_ratio_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t count)
{
	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	char *end;
	unsigned int ratio;
	ssize_t ret = -EINVAL;

	ratio = simple_strtoul(buf, &end, 10);
	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
		ret = bdi_set_max_ratio(bdi, ratio);
		if (!ret)
			ret = count;
	}
	return ret;
}
BDI_SHOW(max_ratio, bdi->max_ratio)

#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)

static struct device_attribute bdi_dev_attrs[] = {
	__ATTR_RW(read_ahead_kb),
	__ATTR_RW(min_ratio),
	__ATTR_RW(max_ratio),
	__ATTR_NULL,
};

static __init int bdi_class_init(void)
{
	bdi_class = class_create(THIS_MODULE, "bdi");
	bdi_class->dev_attrs = bdi_dev_attrs;
	bdi_debug_init();
	return 0;
}
postcore_initcall(bdi_class_init);

static int __init default_bdi_init(void)
{
	int err;

	err = bdi_init(&default_backing_dev_info);
	if (!err)
		bdi_register(&default_backing_dev_info, NULL, "default");

	return err;
}
subsys_initcall(default_bdi_init);

int bdi_register(struct backing_dev_info *bdi, struct device *parent,
		const char *fmt, ...)
{
	va_list args;
	int ret = 0;
	struct device *dev;

	if (bdi->dev)	/* The driver needs to use separate queues per device */
		goto exit;

	va_start(args, fmt);
	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
	va_end(args);
	if (IS_ERR(dev)) {
		ret = PTR_ERR(dev);
		goto exit;
	}

	mutex_lock(&bdi_lock);
	list_add_tail(&bdi->bdi_list, &bdi_list);
	mutex_unlock(&bdi_lock);

	bdi->dev = dev;
	bdi_debug_register(bdi, dev_name(dev));

exit:
	return ret;
}
EXPORT_SYMBOL(bdi_register);

int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
{
	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
}
EXPORT_SYMBOL(bdi_register_dev);

static void bdi_remove_from_list(struct backing_dev_info *bdi)
{
	mutex_lock(&bdi_lock);
	list_del(&bdi->bdi_list);
	mutex_unlock(&bdi_lock);
}

void bdi_unregister(struct backing_dev_info *bdi)
{
	if (bdi->dev) {
		bdi_remove_from_list(bdi);
		bdi_debug_unregister(bdi);
		device_unregister(bdi->dev);
		bdi->dev = NULL;
	}
}
EXPORT_SYMBOL(bdi_unregister);

int bdi_init(struct backing_dev_info *bdi)
{
	int i;
	int err;

	bdi->dev = NULL;

	bdi->min_ratio = 0;
	bdi->max_ratio = 100;
	bdi->max_prop_frac = PROP_FRAC_BASE;
	INIT_LIST_HEAD(&bdi->bdi_list);
	INIT_LIST_HEAD(&bdi->b_io);
	INIT_LIST_HEAD(&bdi->b_dirty);
	INIT_LIST_HEAD(&bdi->b_more_io);

	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
		err = percpu_counter_init(&bdi->bdi_stat[i], 0);
		if (err)
			goto err;
	}

	bdi->dirty_exceeded = 0;
	err = prop_local_init_percpu(&bdi->completions);

	if (err) {
err:
		while (i--)
			percpu_counter_destroy(&bdi->bdi_stat[i]);

		bdi_remove_from_list(bdi);
	}

	return err;
}
EXPORT_SYMBOL(bdi_init);

void bdi_destroy(struct backing_dev_info *bdi)
{
	int i;

	WARN_ON(!list_empty(&bdi->b_dirty));
	WARN_ON(!list_empty(&bdi->b_io));
	WARN_ON(!list_empty(&bdi->b_more_io));

	bdi_unregister(bdi);

	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
		percpu_counter_destroy(&bdi->bdi_stat[i]);

	prop_local_destroy_percpu(&bdi->completions);
}
EXPORT_SYMBOL(bdi_destroy);

static wait_queue_head_t congestion_wqh[2] = {
		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
	};

void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
	enum bdi_state bit;
	wait_queue_head_t *wqh = &congestion_wqh[sync];

	bit = sync ? BDI_sync_congested : BDI_async_congested;
	clear_bit(bit, &bdi->state);
	smp_mb__after_clear_bit();
	if (waitqueue_active(wqh))
		wake_up(wqh);
}
EXPORT_SYMBOL(clear_bdi_congested);

void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
	enum bdi_state bit;

	bit = sync ? BDI_sync_congested : BDI_async_congested;
	set_bit(bit, &bdi->state);
}
EXPORT_SYMBOL(set_bdi_congested);

/**
 * congestion_wait - wait for a backing_dev to become uncongested
 * @sync: SYNC or ASYNC IO
 * @timeout: timeout in jiffies
 *
 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 * write congestion.  If no backing_devs are congested then just wait for the
 * next write to be completed.
 */
long congestion_wait(int sync, long timeout)
{
	long ret;
	DEFINE_WAIT(wait);
	wait_queue_head_t *wqh = &congestion_wqh[sync];

	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
	ret = io_schedule_timeout(timeout);
	finish_wait(wqh, &wait);
	return ret;
}
EXPORT_SYMBOL(congestion_wait);
Commit	Line	Data
3fcfab16 AM	1
	2	#include <linux/wait.h>
	3	#include <linux/backing-dev.h>
	4	#include <linux/fs.h>
26160158	5	#include <linux/pagemap.h>
3fcfab16 AM	6	#include <linux/sched.h>
3fcfab16 AM	7	#include <linux/module.h>
cf0ca9fe PZ	8	#include <linux/writeback.h>
	9	#include <linux/device.h>
	10
26160158 JA	11	void default_unplug_io_fn(struct backing_dev_info bdi, struct page page)
	12	{
	13	}
	14	EXPORT_SYMBOL(default_unplug_io_fn);
	15
	16	struct backing_dev_info default_backing_dev_info = {
	17	.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
	18	.state = 0,
	19	.capabilities = BDI_CAP_MAP_COPY,
	20	.unplug_io_fn = default_unplug_io_fn,
	21	};
	22	EXPORT_SYMBOL_GPL(default_backing_dev_info);
cf0ca9fe PZ	23
cf0ca9fe PZ	24	static struct class *bdi_class;
66f3b8e2 JA	25	DEFINE_MUTEX(bdi_lock);
66f3b8e2 JA	26	LIST_HEAD(bdi_list);
cf0ca9fe	27
76f1418b MS	28	#ifdef CONFIG_DEBUG_FS
	29	#include <linux/debugfs.h>
	30	#include <linux/seq_file.h>
	31
	32	static struct dentry *bdi_debug_root;
	33
	34	static void bdi_debug_init(void)
	35	{
	36	bdi_debug_root = debugfs_create_dir("bdi", NULL);
	37	}
	38
	39	static int bdi_debug_stats_show(struct seq_file m, void v)
	40	{
	41	struct backing_dev_info *bdi = m->private;
364aeb28 DR	42	unsigned long background_thresh;
	43	unsigned long dirty_thresh;
	44	unsigned long bdi_thresh;
76f1418b MS	45
	46	get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
	47
	48	#define K(x) ((x) << (PAGE_SHIFT - 10))
	49	seq_printf(m,
	50	"BdiWriteback: %8lu kB\n"
	51	"BdiReclaimable: %8lu kB\n"
	52	"BdiDirtyThresh: %8lu kB\n"
	53	"DirtyThresh: %8lu kB\n"
	54	"BackgroundThresh: %8lu kB\n",
	55	(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
	56	(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
	57	K(bdi_thresh),
	58	K(dirty_thresh),
	59	K(background_thresh));
	60	#undef K
	61
	62	return 0;
	63	}
	64
	65	static int bdi_debug_stats_open(struct inode inode, struct file file)
	66	{
	67	return single_open(file, bdi_debug_stats_show, inode->i_private);
	68	}
	69
	70	static const struct file_operations bdi_debug_stats_fops = {
	71	.open = bdi_debug_stats_open,
	72	.read = seq_read,
	73	.llseek = seq_lseek,
	74	.release = single_release,
	75	};
	76
	77	static void bdi_debug_register(struct backing_dev_info bdi, const char name)
	78	{
	79	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
	80	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
	81	bdi, &bdi_debug_stats_fops);
	82	}
	83
	84	static void bdi_debug_unregister(struct backing_dev_info *bdi)
	85	{
	86	debugfs_remove(bdi->debug_stats);
	87	debugfs_remove(bdi->debug_dir);
	88	}
	89	#else
	90	static inline void bdi_debug_init(void)
	91	{
	92	}
	93	static inline void bdi_debug_register(struct backing_dev_info *bdi,
	94	const char *name)
	95	{
	96	}
	97	static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
	98	{
	99	}
	100	#endif
	101
cf0ca9fe PZ	102	static ssize_t read_ahead_kb_store(struct device *dev,
	103	struct device_attribute *attr,
	104	const char *buf, size_t count)
	105	{
	106	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	107	char *end;
	108	unsigned long read_ahead_kb;
	109	ssize_t ret = -EINVAL;
	110
	111	read_ahead_kb = simple_strtoul(buf, &end, 10);
	112	if (*buf && (end[0] == '\0' \|\| (end[0] == '\n' && end[1] == '\0'))) {
	113	bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
	114	ret = count;
	115	}
	116	return ret;
	117	}
	118
	119	#define K(pages) ((pages) << (PAGE_SHIFT - 10))
	120
	121	#define BDI_SHOW(name, expr) \
	122	static ssize_t name##_show(struct device *dev, \
	123	struct device_attribute attr, char page) \
	124	{ \
	125	struct backing_dev_info *bdi = dev_get_drvdata(dev); \
	126	\
	127	return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
	128	}
	129
	130	BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
	131
189d3c4a PZ	132	static ssize_t min_ratio_store(struct device *dev,
	133	struct device_attribute attr, const char buf, size_t count)
	134	{
	135	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	136	char *end;
	137	unsigned int ratio;
	138	ssize_t ret = -EINVAL;
	139
	140	ratio = simple_strtoul(buf, &end, 10);
	141	if (*buf && (end[0] == '\0' \|\| (end[0] == '\n' && end[1] == '\0'))) {
	142	ret = bdi_set_min_ratio(bdi, ratio);
	143	if (!ret)
	144	ret = count;
	145	}
	146	return ret;
	147	}
	148	BDI_SHOW(min_ratio, bdi->min_ratio)
	149
a42dde04 PZ	150	static ssize_t max_ratio_store(struct device *dev,
	151	struct device_attribute attr, const char buf, size_t count)
	152	{
	153	struct backing_dev_info *bdi = dev_get_drvdata(dev);
	154	char *end;
	155	unsigned int ratio;
	156	ssize_t ret = -EINVAL;
	157
	158	ratio = simple_strtoul(buf, &end, 10);
	159	if (*buf && (end[0] == '\0' \|\| (end[0] == '\n' && end[1] == '\0'))) {
	160	ret = bdi_set_max_ratio(bdi, ratio);
	161	if (!ret)
	162	ret = count;
	163	}
	164	return ret;
	165	}
	166	BDI_SHOW(max_ratio, bdi->max_ratio)
	167
cf0ca9fe PZ	168	#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
	169
	170	static struct device_attribute bdi_dev_attrs[] = {
	171	__ATTR_RW(read_ahead_kb),
189d3c4a	172	__ATTR_RW(min_ratio),
a42dde04	173	__ATTR_RW(max_ratio),
cf0ca9fe PZ	174	__ATTR_NULL,
	175	};
	176
	177	static __init int bdi_class_init(void)
	178	{
	179	bdi_class = class_create(THIS_MODULE, "bdi");
	180	bdi_class->dev_attrs = bdi_dev_attrs;
76f1418b	181	bdi_debug_init();
cf0ca9fe PZ	182	return 0;
cf0ca9fe PZ	183	}
76f1418b	184	postcore_initcall(bdi_class_init);
cf0ca9fe	185
26160158 JA	186	static int __init default_bdi_init(void)
	187	{
	188	int err;
	189
	190	err = bdi_init(&default_backing_dev_info);
	191	if (!err)
	192	bdi_register(&default_backing_dev_info, NULL, "default");
	193
	194	return err;
	195	}
	196	subsys_initcall(default_bdi_init);
	197
cf0ca9fe PZ	198	int bdi_register(struct backing_dev_info bdi, struct device parent,
	199	const char *fmt, ...)
	200	{
cf0ca9fe PZ	201	va_list args;
	202	int ret = 0;
	203	struct device *dev;
	204
69fc208b	205	if (bdi->dev) /* The driver needs to use separate queues per device */
f1d0b063 KS	206	goto exit;
f1d0b063 KS	207
cf0ca9fe	208	va_start(args, fmt);
19051c50	209	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
cf0ca9fe	210	va_end(args);
cf0ca9fe PZ	211	if (IS_ERR(dev)) {
	212	ret = PTR_ERR(dev);
	213	goto exit;
	214	}
	215
66f3b8e2 JA	216	mutex_lock(&bdi_lock);
	217	list_add_tail(&bdi->bdi_list, &bdi_list);
	218	mutex_unlock(&bdi_lock);
	219
cf0ca9fe	220	bdi->dev = dev;
19051c50	221	bdi_debug_register(bdi, dev_name(dev));
cf0ca9fe PZ	222
cf0ca9fe PZ	223	exit:
cf0ca9fe PZ	224	return ret;
	225	}
	226	EXPORT_SYMBOL(bdi_register);
	227
	228	int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
	229	{
	230	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
	231	}
	232	EXPORT_SYMBOL(bdi_register_dev);
	233
66f3b8e2 JA	234	static void bdi_remove_from_list(struct backing_dev_info *bdi)
	235	{
	236	mutex_lock(&bdi_lock);
	237	list_del(&bdi->bdi_list);
	238	mutex_unlock(&bdi_lock);
	239	}
	240
cf0ca9fe PZ	241	void bdi_unregister(struct backing_dev_info *bdi)
	242	{
	243	if (bdi->dev) {
66f3b8e2	244	bdi_remove_from_list(bdi);
76f1418b	245	bdi_debug_unregister(bdi);
cf0ca9fe PZ	246	device_unregister(bdi->dev);
	247	bdi->dev = NULL;
	248	}
	249	}
	250	EXPORT_SYMBOL(bdi_unregister);
3fcfab16	251
b2e8fb6e PZ	252	int bdi_init(struct backing_dev_info *bdi)
b2e8fb6e PZ	253	{
4b01a0b1	254	int i;
b2e8fb6e PZ	255	int err;
b2e8fb6e PZ	256
cf0ca9fe PZ	257	bdi->dev = NULL;
cf0ca9fe PZ	258
189d3c4a	259	bdi->min_ratio = 0;
a42dde04 PZ	260	bdi->max_ratio = 100;
a42dde04 PZ	261	bdi->max_prop_frac = PROP_FRAC_BASE;
66f3b8e2 JA	262	INIT_LIST_HEAD(&bdi->bdi_list);
	263	INIT_LIST_HEAD(&bdi->b_io);
	264	INIT_LIST_HEAD(&bdi->b_dirty);
	265	INIT_LIST_HEAD(&bdi->b_more_io);
189d3c4a	266
b2e8fb6e	267	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
ea319518	268	err = percpu_counter_init(&bdi->bdi_stat[i], 0);
04fbfdc1 PZ	269	if (err)
	270	goto err;
	271	}
	272
	273	bdi->dirty_exceeded = 0;
	274	err = prop_local_init_percpu(&bdi->completions);
	275
	276	if (err) {
	277	err:
4b01a0b1	278	while (i--)
04fbfdc1	279	percpu_counter_destroy(&bdi->bdi_stat[i]);
66f3b8e2 JA	280
66f3b8e2 JA	281	bdi_remove_from_list(bdi);
b2e8fb6e PZ	282	}
	283
	284	return err;
	285	}
	286	EXPORT_SYMBOL(bdi_init);
	287
	288	void bdi_destroy(struct backing_dev_info *bdi)
	289	{
	290	int i;
	291
66f3b8e2 JA	292	WARN_ON(!list_empty(&bdi->b_dirty));
	293	WARN_ON(!list_empty(&bdi->b_io));
	294	WARN_ON(!list_empty(&bdi->b_more_io));
	295
cf0ca9fe PZ	296	bdi_unregister(bdi);
cf0ca9fe PZ	297
b2e8fb6e PZ	298	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
b2e8fb6e PZ	299	percpu_counter_destroy(&bdi->bdi_stat[i]);
04fbfdc1 PZ	300
04fbfdc1 PZ	301	prop_local_destroy_percpu(&bdi->completions);
b2e8fb6e PZ	302	}
	303	EXPORT_SYMBOL(bdi_destroy);
	304
3fcfab16 AM	305	static wait_queue_head_t congestion_wqh[2] = {
	306	__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
	307	__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
	308	};
	309
1faa16d2	310	void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 AM	311	{
3fcfab16 AM	312	enum bdi_state bit;
1faa16d2	313	wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16	314
1faa16d2	315	bit = sync ? BDI_sync_congested : BDI_async_congested;
3fcfab16 AM	316	clear_bit(bit, &bdi->state);
	317	smp_mb__after_clear_bit();
	318	if (waitqueue_active(wqh))
	319	wake_up(wqh);
	320	}
	321	EXPORT_SYMBOL(clear_bdi_congested);
	322
1faa16d2	323	void set_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 AM	324	{
	325	enum bdi_state bit;
	326
1faa16d2	327	bit = sync ? BDI_sync_congested : BDI_async_congested;
3fcfab16 AM	328	set_bit(bit, &bdi->state);
	329	}
	330	EXPORT_SYMBOL(set_bdi_congested);
	331
	332	/**
	333	* congestion_wait - wait for a backing_dev to become uncongested
8aa7e847	334	* @sync: SYNC or ASYNC IO
3fcfab16 AM	335	* @timeout: timeout in jiffies
	336	*
	337	* Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
	338	* write congestion. If no backing_devs are congested then just wait for the
	339	* next write to be completed.
	340	*/
8aa7e847	341	long congestion_wait(int sync, long timeout)
3fcfab16 AM	342	{
	343	long ret;
	344	DEFINE_WAIT(wait);
8aa7e847	345	wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 AM	346
	347	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
	348	ret = io_schedule_timeout(timeout);
	349	finish_wait(wqh, &wait);
	350	return ret;
	351	}
	352	EXPORT_SYMBOL(congestion_wait);
04fbfdc1	353