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/*
* queue.c - queues for requests to be submitted (tx_queue)
* and outstanding requests (rx_queue)
* Copyright (C) 2006 Thorsten Zitterell <thorsten@zitterell.de>
*/
#include <linux/blkdev.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/spinlock.h>
#include <linux/in.h>
#include "dnbd.h"
#include "queue.h"
/* enqueue to a queue */
void dnbd_enq_request(dnbd_queue_t * q, struct request *req, int wakeup)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
list_add(&req->queuelist, &q->head);
spin_unlock_irqrestore(&q->lock,flags);
if (wakeup)
wake_up(&q->waiters);
}
/* dequeue from a queue with position */
struct request *dnbd_deq_request_handle(dnbd_queue_t * q, uint64_t pos)
{
struct request *req = NULL;
struct list_head *tmp;
unsigned long flags;
spin_lock_irqsave(&q->lock,flags);
list_for_each(tmp, &q->head) {
req = blkdev_entry_to_request(tmp);
if (((u64) req->sector) << 9 == pos) {
list_del_init(&req->queuelist);
goto out;
}
}
req = NULL;
out:
spin_unlock_irqrestore(&q->lock,flags);
return req;
}
/* dequeue from queue */
struct request *dnbd_deq_request(dnbd_queue_t * q)
{
struct request *req = NULL;
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
if (!list_empty(&q->head)) {
req = blkdev_entry_to_request(q->head.prev);
list_del_init(&req->queuelist);
}
spin_unlock_irqrestore(&q->lock, flags);
return req;
}
/* sleep until request can be dequeued */
struct request *dnbd_try_deq_request(dnbd_queue_t * q)
{
struct request *req;
req = dnbd_deq_request(q);
if (!req) {
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
add_wait_queue(&q->waiters, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
req = dnbd_deq_request(q);
if (req || signal_pending(current))
break;
schedule();
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&q->waiters, &wait);
}
return req;
}
/* requeue requests with timeout */
int dnbd_requeue_requests(dnbd_queue_t * to, dnbd_queue_t * from,
unsigned long timeout)
{
struct request *req = NULL;
struct list_head *tmp, *keep;
int requeued = 0;
unsigned long flags;
spin_lock_irqsave(&from->lock,flags);
list_for_each_safe(tmp, keep, &from->head) {
req = blkdev_entry_to_request(tmp);
if (req->start_time < timeout) {
requeued++;
list_del_init(&req->queuelist);
spin_lock_irqsave(&to->lock,flags);
list_add(&req->queuelist, &to->head);
spin_unlock_irqrestore(&to->lock,flags);
}
}
spin_unlock_irqrestore(&from->lock,flags);
wake_up(&to->waiters);
return requeued;
}
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