#include <linux/wait.h>#include <linux/backing-dev.h>#include <linux/fs.h>#include <linux/sched.h>#include <linux/module.h> 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); long congestion_wait_interruptible(int rw, long timeout){	long ret;	DEFINE_WAIT(wait);	wait_queue_head_t *wqh = &congestion_wqh[rw]; 	prepare_to_wait(wqh, &wait, TASK_INTERRUPTIBLE);	if (signal_pending(current))		ret = -ERESTARTSYS;	else		ret = io_schedule_timeout(timeout);	finish_wait(wqh, &wait);	return ret;}EXPORT_SYMBOL(congestion_wait_interruptible); /** * congestion_end - wake up sleepers on a congested backing_dev_info * @rw: READ or WRITE */void congestion_end(int rw){	wait_queue_head_t *wqh = &congestion_wqh[rw]; 	if (waitqueue_active(wqh))		wake_up(wqh);}EXPORT_SYMBOL(congestion_end);