Commit 8c0785a5 authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
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drbd: allow to dequeue batches of work at a time 



cherry-picked and adapted from drbd 9 devel branch

In 8.4, we still use drbd_queue_work_front(),
so in normal operation, we can not dequeue batches,
but only single items.

Still, followup commits will wake the worker
without explicitly queueing a work item,
so up() is replaced by a simple wake_up().

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent b379c41e

drivers/block/drbd/drbd_int.h

+3 −5
Original line number Diff line number Diff line
@@ -735,8 +735,8 @@ enum bm_flag { 


struct drbd_work_queue {

	struct list_head q;

	struct semaphore s; /* producers up it, worker down()s it */

	spinlock_t q_lock;  /* to protect the list. */

	wait_queue_head_t q_wait;

};



struct drbd_socket {
@@ -1832,9 +1832,8 @@ drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w) 
	unsigned long flags;

	spin_lock_irqsave(&q->q_lock, flags);

	list_add(&w->list, &q->q);

	up(&q->s); /* within the spinlock,

		      see comment near end of drbd_worker() */

	spin_unlock_irqrestore(&q->q_lock, flags);

	wake_up(&q->q_wait);

}



static inline void
@@ -1843,9 +1842,8 @@ drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w) 
	unsigned long flags;

	spin_lock_irqsave(&q->q_lock, flags);

	list_add_tail(&w->list, &q->q);

	up(&q->s); /* within the spinlock,

		      see comment near end of drbd_worker() */

	spin_unlock_irqrestore(&q->q_lock, flags);

	wake_up(&q->q_wait);

}



static inline void wake_asender(struct drbd_tconn *tconn)

drivers/block/drbd/drbd_main.c

+1 −1
Original line number Diff line number Diff line
@@ -2535,9 +2535,9 @@ out: 


static void drbd_init_workqueue(struct drbd_work_queue* wq)

{

	sema_init(&wq->s, 0);

	spin_lock_init(&wq->q_lock);

	INIT_LIST_HEAD(&wq->q);

	init_waitqueue_head(&wq->q_wait);

}



struct drbd_tconn *conn_get_by_name(const char *name)

drivers/block/drbd/drbd_worker.c

+39 −49
Original line number Diff line number Diff line
@@ -1673,6 +1673,23 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side) 
	mutex_unlock(mdev->state_mutex);

}



bool dequeue_work_batch(struct drbd_work_queue *queue, struct list_head *work_list)

{

	spin_lock_irq(&queue->q_lock);

	list_splice_init(&queue->q, work_list);

	spin_unlock_irq(&queue->q_lock);

	return !list_empty(work_list);

}



bool dequeue_work_item(struct drbd_work_queue *queue, struct list_head *work_list)

{

	spin_lock_irq(&queue->q_lock);

	if (!list_empty(&queue->q))

		list_move(queue->q.next, work_list);

	spin_unlock_irq(&queue->q_lock);

	return !list_empty(work_list);

}



int drbd_worker(struct drbd_thread *thi)

{

	struct drbd_tconn *tconn = thi->tconn;
@@ -1680,15 +1697,21 @@ int drbd_worker(struct drbd_thread *thi) 
	struct drbd_conf *mdev;

	struct net_conf *nc;

	LIST_HEAD(work_list);

	int vnr, intr = 0;

	int vnr;

	int cork;



	while (get_t_state(thi) == RUNNING) {

		drbd_thread_current_set_cpu(thi);



		if (down_trylock(&tconn->data.work.s)) {

			mutex_lock(&tconn->data.mutex);

		/* as long as we use drbd_queue_work_front(),

		 * we may only dequeue single work items here, not batches. */

		if (list_empty(&work_list))

			dequeue_work_item(&tconn->data.work, &work_list);



		/* Still nothing to do? Poke TCP, just in case,

		 * then wait for new work (or signal). */

		if (list_empty(&work_list)) {

			mutex_lock(&tconn->data.mutex);

			rcu_read_lock();

			nc = rcu_dereference(tconn->net_conf);

			cork = nc ? nc->tcp_cork : 0;
@@ -1698,7 +1721,8 @@ int drbd_worker(struct drbd_thread *thi) 
				drbd_tcp_uncork(tconn->data.socket);

			mutex_unlock(&tconn->data.mutex);



			intr = down_interruptible(&tconn->data.work.s);

			wait_event_interruptible(tconn->data.work.q_wait,

				dequeue_work_item(&tconn->data.work, &work_list));



			mutex_lock(&tconn->data.mutex);

			if (tconn->data.socket && cork)
@@ -1706,7 +1730,7 @@ int drbd_worker(struct drbd_thread *thi) 
			mutex_unlock(&tconn->data.mutex);

		}



		if (intr) {

		if (signal_pending(current)) {

			flush_signals(current);

			if (get_t_state(thi) == RUNNING) {

				conn_warn(tconn, "Worker got an unexpected signal\n");
@@ -1717,59 +1741,25 @@ int drbd_worker(struct drbd_thread *thi) 


		if (get_t_state(thi) != RUNNING)

			break;

		/* With this break, we have done a down() but not consumed

		   the entry from the list. The cleanup code takes care of

		   this...   */



		w = NULL;

		spin_lock_irq(&tconn->data.work.q_lock);

		if (list_empty(&tconn->data.work.q)) {

			/* something terribly wrong in our logic.

			 * we were able to down() the semaphore,

			 * but the list is empty... doh.

			 *

			 * what is the best thing to do now?

			 * try again from scratch, restarting the receiver,

			 * asender, whatnot? could break even more ugly,

			 * e.g. when we are primary, but no good local data.

			 *

			 * I'll try to get away just starting over this loop.

			 */

			conn_warn(tconn, "Work list unexpectedly empty\n");

			spin_unlock_irq(&tconn->data.work.q_lock);

			continue;

		}

		w = list_entry(tconn->data.work.q.next, struct drbd_work, list);

		list_del_init(&w->list);

		spin_unlock_irq(&tconn->data.work.q_lock);



		if (w->cb(w, tconn->cstate < C_WF_REPORT_PARAMS)) {

			/* dev_warn(DEV, "worker: a callback failed! \n"); */

		while (!list_empty(&work_list)) {

			w = list_first_entry(&work_list, struct drbd_work, list);

			list_del_init(&w->list);

			if (w->cb(w, tconn->cstate < C_WF_REPORT_PARAMS) == 0)

				continue;

			if (tconn->cstate >= C_WF_REPORT_PARAMS)

				conn_request_state(tconn, NS(conn, C_NETWORK_FAILURE), CS_HARD);

		}

	}



	spin_lock_irq(&tconn->data.work.q_lock);

	while (!list_empty(&tconn->data.work.q)) {

		list_splice_init(&tconn->data.work.q, &work_list);

		spin_unlock_irq(&tconn->data.work.q_lock);



	do {

		while (!list_empty(&work_list)) {

			w = list_entry(work_list.next, struct drbd_work, list);

			w = list_first_entry(&work_list, struct drbd_work, list);

			list_del_init(&w->list);

			w->cb(w, 1);

		}



		spin_lock_irq(&tconn->data.work.q_lock);

	}

	sema_init(&tconn->data.work.s, 0);

	/* DANGEROUS race: if someone did queue his work within the spinlock,

	 * but up() ed outside the spinlock, we could get an up() on the

	 * semaphore without corresponding list entry.

	 * So don't do that.

	 */

	spin_unlock_irq(&tconn->data.work.q_lock);

		dequeue_work_batch(&tconn->data.work, &work_list);

	} while (!list_empty(&work_list));



	rcu_read_lock();

	idr_for_each_entry(&tconn->volumes, mdev, vnr) {

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