#include <linux/wait.h>#include <linux/backing-dev.h>#include <linux/fs.h>#include <linux/sched.h>#include <linux/module.h>#include <linux/writeback.h>#include <linux/device.h>static struct class *bdi_class;#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);}#elsestatic 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){}#endifstatic 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);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;	}	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);void bdi_unregister(struct backing_dev_info *bdi){	if (bdi->dev) {		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;	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]);	}	return err;}EXPORT_SYMBOL(bdi_init);void bdi_destroy(struct backing_dev_info *bdi){	int i;	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 rw){	enum bdi_state bit;	wait_queue_head_t *wqh = &congestion_wqh[rw];	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_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 rw){	enum bdi_state bit;	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;	set_bit(bit, &bdi->state);}EXPORT_SYMBOL(set_bdi_congested);/** * congestion_wait - wait for a backing_dev to become uncongested * @rw: READ or WRITE * @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 rw, long timeout){	long ret;	DEFINE_WAIT(wait);	wait_queue_head_t *wqh = &congestion_wqh[rw];	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);	ret = io_schedule_timeout(timeout);	finish_wait(wqh, &wait);	return ret;}EXPORT_SYMBOL(congestion_wait);