vinyl: rename some members of vy_scheduler and vy_task struct

I'm planning to add some new members and remove some old members from
those structs. For this to play nicely, let's do some renames:

  vy_scheduler::workers_available => idle_worker_count
  vy_scheduler::input_queue       => pending_tasks
  vy_scheduler::output_queue      => processed_tasks
  vy_task::link                   => in_pending, in_processed

src/box/vy_scheduler.c

@@ -119,11 +119,6 @@ struct vy_task {
 	 * need to remember the slices we are compacting.
 	 */
 	struct vy_slice *first_slice, *last_slice;
-	/**
-	 * Link in the list of pending or processed tasks.
-	 * See vy_scheduler::input_queue, output_queue.
-	 */
-	struct stailq_entry link;
 	/**
 	 * Index options may be modified while a task is in
 	 * progress so we save them here to safely access them
@@ -131,6 +126,10 @@ struct vy_task {
 	 */
 	double bloom_fpr;
 	int64_t page_size;
+	/** Link in vy_scheduler::pending_tasks. */
+	struct stailq_entry in_pending;
+	/** Link in vy_scheduler::processed_tasks. */
+	struct stailq_entry in_processed;
 };
 
 /**
@@ -259,7 +258,7 @@ vy_scheduler_start_workers(struct vy_scheduler *scheduler)
 	assert(scheduler->worker_pool_size >= 2);
 
 	scheduler->is_worker_pool_running = true;
-	scheduler->workers_available = scheduler->worker_pool_size;
+	scheduler->idle_worker_count = scheduler->worker_pool_size;
 	scheduler->worker_pool = calloc(scheduler->worker_pool_size,
 					sizeof(struct cord));
 	if (scheduler->worker_pool == NULL)
@@ -318,8 +317,8 @@ vy_scheduler_create(struct vy_scheduler *scheduler, int write_threads,
 	scheduler->worker_pool_size = write_threads;
 	mempool_create(&scheduler->task_pool, cord_slab_cache(),
 		       sizeof(struct vy_task));
-	stailq_create(&scheduler->input_queue);
-	stailq_create(&scheduler->output_queue);
+	stailq_create(&scheduler->pending_tasks);
+	stailq_create(&scheduler->processed_tasks);
 
 	tt_pthread_cond_init(&scheduler->worker_cond, NULL);
 	tt_pthread_mutex_init(&scheduler->mutex, NULL);
@@ -1422,7 +1421,7 @@ vy_schedule(struct vy_scheduler *scheduler, struct vy_task **ptask)
 	if (*ptask != NULL)
 		return 0;
 
-	if (scheduler->workers_available <= 1) {
+	if (scheduler->idle_worker_count <= 1) {
 		/*
 		 * If all worker threads are busy doing compaction
 		 * when we run out of quota, ongoing transactions will
@@ -1501,26 +1500,27 @@ vy_scheduler_f(va_list va)
 	vy_scheduler_start_workers(scheduler);
 
 	while (scheduler->scheduler_fiber != NULL) {
-		struct stailq output_queue;
+		struct stailq processed_tasks;
 		struct vy_task *task, *next;
 		int tasks_failed = 0, tasks_done = 0;
 		bool was_empty;
 
 		/* Get the list of processed tasks. */
-		stailq_create(&output_queue);
+		stailq_create(&processed_tasks);
 		tt_pthread_mutex_lock(&scheduler->mutex);
-		stailq_concat(&output_queue, &scheduler->output_queue);
+		stailq_concat(&processed_tasks, &scheduler->processed_tasks);
 		tt_pthread_mutex_unlock(&scheduler->mutex);
 
 		/* Complete and delete all processed tasks. */
-		stailq_foreach_entry_safe(task, next, &output_queue, link) {
+		stailq_foreach_entry_safe(task, next, &processed_tasks,
+					  in_processed) {
 			if (vy_task_complete(task) != 0)
 				tasks_failed++;
 			else
 				tasks_done++;
 			vy_task_delete(task);
-			scheduler->workers_available++;
-			assert(scheduler->workers_available <=
+			scheduler->idle_worker_count++;
+			assert(scheduler->idle_worker_count <=
 			       scheduler->worker_pool_size);
 		}
 		/*
@@ -1534,7 +1534,7 @@ vy_scheduler_f(va_list va)
 			 * opens a time window for a worker to submit
 			 * a processed task and wake up the scheduler
 			 * (via scheduler_async). Hence we should go
-			 * and recheck the output_queue in order not
+			 * and recheck the processed_tasks in order not
 			 * to lose a wakeup event and hang for good.
 			 */
 			continue;
@@ -1543,7 +1543,7 @@ vy_scheduler_f(va_list va)
 		if (tasks_failed > 0)
 			goto error;
 		/* All worker threads are busy. */
-		if (scheduler->workers_available == 0)
+		if (scheduler->idle_worker_count == 0)
 			goto wait;
 		/* Get a task to schedule. */
 		if (vy_schedule(scheduler, &task) != 0)
@@ -1554,13 +1554,14 @@ vy_scheduler_f(va_list va)
 
 		/* Queue the task and notify workers if necessary. */
 		tt_pthread_mutex_lock(&scheduler->mutex);
-		was_empty = stailq_empty(&scheduler->input_queue);
-		stailq_add_tail_entry(&scheduler->input_queue, task, link);
+		was_empty = stailq_empty(&scheduler->pending_tasks);
+		stailq_add_tail_entry(&scheduler->pending_tasks,
+				      task, in_pending);
 		if (was_empty)
 			tt_pthread_cond_signal(&scheduler->worker_cond);
 		tt_pthread_mutex_unlock(&scheduler->mutex);
 
-		scheduler->workers_available--;
+		scheduler->idle_worker_count--;
 		fiber_reschedule();
 		continue;
 error:
@@ -1605,7 +1606,7 @@ vy_worker_f(void *arg)
 	tt_pthread_mutex_lock(&scheduler->mutex);
 	while (scheduler->is_worker_pool_running) {
 		/* Wait for a task */
-		if (stailq_empty(&scheduler->input_queue)) {
+		if (stailq_empty(&scheduler->pending_tasks)) {
 			/* Wake scheduler up if there are no more tasks */
 			ev_async_send(scheduler->scheduler_loop,
 				      &scheduler->scheduler_async);
@@ -1613,8 +1614,8 @@ vy_worker_f(void *arg)
 					     &scheduler->mutex);
 			continue;
 		}
-		task = stailq_shift_entry(&scheduler->input_queue,
-					  struct vy_task, link);
+		task = stailq_shift_entry(&scheduler->pending_tasks,
+					  struct vy_task, in_pending);
 		tt_pthread_mutex_unlock(&scheduler->mutex);
 		assert(task != NULL);
 
@@ -1628,7 +1629,8 @@ vy_worker_f(void *arg)
 
 		/* Return processed task to scheduler */
 		tt_pthread_mutex_lock(&scheduler->mutex);
-		stailq_add_tail_entry(&scheduler->output_queue, task, link);
+		stailq_add_tail_entry(&scheduler->processed_tasks,
+				      task, in_processed);
 	}
 	tt_pthread_mutex_unlock(&scheduler->mutex);
 	return NULL;

src/box/vy_scheduler.h

@@ -77,13 +77,13 @@ struct vy_scheduler {
 	/** Total number of worker threads. */
 	int worker_pool_size;
 	/** Number worker threads that are currently idle. */
-	int workers_available;
+	int idle_worker_count;
 	/** Memory pool used for allocating vy_task objects. */
 	struct mempool task_pool;
-	/** Queue of pending tasks, linked by vy_task::link. */
-	struct stailq input_queue;
-	/** Queue of processed tasks, linked by vy_task::link. */
-	struct stailq output_queue;
+	/** Queue of pending tasks, linked by vy_task::in_pending. */
+	struct stailq pending_tasks;
+	/** Queue of processed tasks, linked by vy_task::in_processed. */
+	struct stailq processed_tasks;
 	/**
 	 * Signaled to wake up a worker when there is
 	 * a pending task in the input queue. Also used