sys/kern/subr_disk.c

77  * current head position (bioq->last_offset) in the scan direction, i.e.
88  *   bioq_first()	return the head of the queue, without removing;
90  *   bioq_takefirst()	return and remove the head of the queue,
91  *		updating the 'current head position' as
94  * When updating the 'current head position', we assume that the result of
96  * represents the head position once the request is complete.
104  *	update, but its use tracks the head position in a better way.
105  *	Historical behaviour was also to update the head position when
108  *	has no method to update the head position; secondly, once
110  *	the actual head position, so the final one is our best guess.
122  * bioq_insert_head()	insert an entry at the head, update
128  *		bioq_takefirst() if invoked on the head of the queue.
138  * at the head of the queue even after subsequent bioq_disksort().
147 bioq_init(struct bio_queue_head *head)
150 	TAILQ_INIT(&head->queue);
151 	head->last_offset = 0;
152 	head->insert_point = NULL;
156 bioq_remove(struct bio_queue_head *head, struct bio *bp)
159 	if (head->insert_point == NULL) {
160 		if (bp == TAILQ_FIRST(&head->queue))
161 			head->last_offset = bp->bio_offset + bp->bio_length;
162 	} else if (bp == head->insert_point)
163 		head->insert_point = NULL;
165 	TAILQ_REMOVE(&head->queue, bp, bio_queue);
169 bioq_flush(struct bio_queue_head *head, struct devstat *stp, int error)
173 	while ((bp = bioq_takefirst(head)) != NULL)
178 bioq_insert_head(struct bio_queue_head *head, struct bio *bp)
181 	if (head->insert_point == NULL)
182 		head->last_offset = bp->bio_offset;
183 	TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
187 bioq_insert_tail(struct bio_queue_head *head, struct bio *bp)
190 	TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue);
191 	head->insert_point = bp;
192 	head->last_offset = bp->bio_offset;
196 bioq_first(struct bio_queue_head *head)
199 	return (TAILQ_FIRST(&head->queue));
203 bioq_takefirst(struct bio_queue_head *head)
207 	bp = TAILQ_FIRST(&head->queue);
209 		bioq_remove(head, bp);
219 bioq_bio_key(struct bio_queue_head *head, struct bio *bp)
222 	return ((uoff_t)(bp->bio_offset - head->last_offset));
233 bioq_disksort(struct bio_queue_head *head, struct bio *bp)
245 		bioq_insert_tail(head, bp);
256 		bioq_insert_tail(head, bp);
261 	key = bioq_bio_key(head, bp);
262 	cur = TAILQ_FIRST(&head->queue);
264 	if (head->insert_point) {
265 		prev = head->insert_point;
266 		cur = TAILQ_NEXT(head->insert_point, bio_queue);
269 	while (cur != NULL && key >= bioq_bio_key(head, cur)) {
275 		TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
277 		TAILQ_INSERT_AFTER(&head->queue, prev, bp, bio_queue);