MFprojects/camlock r249505:

Change CCB queue resize logic to be able safely handle overallocations:
 - (re)allocate queue space in power of 2 chunks with 64 elements minimum
and never shrink it; with only 4/8 bytes per element size is insignificant.
 - automatically reallocate the queue to double size if it is overflowed.
 - if queue reallocation failed, store extra CCBs in unsorted TAILQ,
fetching them back as soon as some queue element is freed.

To free space in CCB for TAILQ linking, change highpowerq from keeping
high-power CCBs to keeping devices frozen due to high-power CCBs.

This encloses all pieces of queue resize logic inside of cam_queue.[ch],
removing some not obvious duties from xpt_release_ccb().

1 files changed, 52 insertions, 3 deletions

diff --git a/sys/cam/cam_queue.h b/sys/cam/cam_queue.h
index 9b27bae..0bb4491 100644
--- a/sys/cam/cam_queue.h
+++ b/sys/cam/cam_queue.h
@@ -57,6 +57,8 @@ SLIST_HEAD(ccb_hdr_slist, ccb_hdr);
 
 struct cam_ccbq {
 	struct	camq queue;
+	struct ccb_hdr_tailq	queue_extra_head;
+	int	queue_extra_entries;
 	int	devq_openings;
 	int	devq_allocating;
 	int	dev_openings;
@@ -177,7 +179,7 @@ cam_ccbq_release_opening(struct cam_ccbq *ccbq);
 static __inline int
 cam_ccbq_pending_ccb_count(struct cam_ccbq *ccbq)
 {
-	return (ccbq->queue.entries);
+	return (ccbq->queue.entries + ccbq->queue_extra_entries);
 }
 
 static __inline void
@@ -190,14 +192,61 @@ cam_ccbq_take_opening(struct cam_ccbq *ccbq)
 static __inline void
 cam_ccbq_insert_ccb(struct cam_ccbq *ccbq, union ccb *new_ccb)
 {
+	struct ccb_hdr *old_ccb;
+	struct camq *queue = &ccbq->queue;
+
 	ccbq->held--;
-	camq_insert(&ccbq->queue, &new_ccb->ccb_h.pinfo);
+
+	/*
+	 * If queue is already full, try to resize.
+	 * If resize fail, push CCB with lowest priority out to the TAILQ.
+	 */
+	if (queue->entries == queue->array_size &&
+	    camq_resize(&ccbq->queue, queue->array_size * 2) != CAM_REQ_CMP) {
+		old_ccb = (struct ccb_hdr *)camq_remove(queue, queue->entries);
+		TAILQ_INSERT_HEAD(&ccbq->queue_extra_head, old_ccb,
+		    xpt_links.tqe);
+		old_ccb->pinfo.index = CAM_EXTRAQ_INDEX;
+		ccbq->queue_extra_entries++;
+	}
+
+	camq_insert(queue, &new_ccb->ccb_h.pinfo);
 }
 
 static __inline void
 cam_ccbq_remove_ccb(struct cam_ccbq *ccbq, union ccb *ccb)
 {
-	camq_remove(&ccbq->queue, ccb->ccb_h.pinfo.index);
+	struct ccb_hdr *cccb, *bccb;
+	struct camq *queue = &ccbq->queue;
+
+	/* If the CCB is on the TAILQ, remove it from there. */
+	if (ccb->ccb_h.pinfo.index == CAM_EXTRAQ_INDEX) {
+		TAILQ_REMOVE(&ccbq->queue_extra_head, &ccb->ccb_h,
+		    xpt_links.tqe);
+		ccb->ccb_h.pinfo.index = CAM_UNQUEUED_INDEX;
+		ccbq->queue_extra_entries--;
+		return;
+	}
+
+	camq_remove(queue, ccb->ccb_h.pinfo.index);
+
+	/*
+	 * If there are some CCBs on TAILQ, find the best one and move it
+	 * to the emptied space in the queue.
+	 */
+	bccb = TAILQ_FIRST(&ccbq->queue_extra_head);
+	if (bccb == NULL)
+		return;
+	TAILQ_FOREACH(cccb, &ccbq->queue_extra_head, xpt_links.tqe) {
+		if (bccb->pinfo.priority > cccb->pinfo.priority ||
+		    (bccb->pinfo.priority == cccb->pinfo.priority &&
+		     GENERATIONCMP(bccb->pinfo.generation, >,
+		      cccb->pinfo.generation)))
+		        bccb = cccb;
+	}
+	TAILQ_REMOVE(&ccbq->queue_extra_head, bccb, xpt_links.tqe);
+	ccbq->queue_extra_entries--;
+	camq_insert(queue, &bccb->pinfo);
 }
 
 static __inline union ccb *