Import of CMU's RAIDframe via NetBSD.

1 files changed, 717 insertions, 0 deletions

diff --git a/sys/dev/raidframe/rf_sstf.c b/sys/dev/raidframe/rf_sstf.c
new file mode 100644
index 00000000000..21d97eef046
--- /dev/null
+++ b/sys/dev/raidframe/rf_sstf.c
@@ -0,0 +1,717 @@
+/*	$OpenBSD: rf_sstf.c,v 1.1 1999/01/11 14:29:50 niklas Exp $	*/
+/*	$NetBSD: rf_sstf.c,v 1.1 1998/11/13 04:20:34 oster Exp $	*/
+/*
+ * Copyright (c) 1995 Carnegie-Mellon University.
+ * All rights reserved.
+ *
+ * Author: Jim Zelenka
+ *
+ * Permission to use, copy, modify and distribute this software and
+ * its documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ *
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
+ * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ *
+ * Carnegie Mellon requests users of this software to return to
+ *
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ *
+ * any improvements or extensions that they make and grant Carnegie the
+ * rights to redistribute these changes.
+ */
+
+/*******************************************************************************
+ *
+ * sstf.c --  prioritized shortest seek time first disk queueing code
+ *
+ ******************************************************************************/
+
+/*
+ * :  
+ * Log: rf_sstf.c,v 
+ * Revision 1.7  1996/06/19 14:09:56  jimz
+ * SstfPeek wasn't calling closest_to_arm() properly- would bogart
+ * low priority I/Os
+ *
+ * Revision 1.6  1996/06/18  20:53:11  jimz
+ * fix up disk queueing (remove configure routine,
+ * add shutdown list arg to create routines)
+ *
+ * Revision 1.5  1996/06/13  20:42:13  jimz
+ * add scan, cscan
+ *
+ * Revision 1.4  1996/06/07  22:26:27  jimz
+ * type-ify which_ru (RF_ReconUnitNum_t)
+ *
+ * Revision 1.3  1996/06/07  21:33:04  jimz
+ * begin using consistent types for sector numbers,
+ * stripe numbers, row+col numbers, recon unit numbers
+ *
+ * Revision 1.2  1996/06/06  01:11:35  jimz
+ * fixed many priority-related bugs
+ *
+ * Revision 1.1  1996/06/05  19:17:40  jimz
+ * Initial revision
+ *
+ */
+
+#include "rf_alloclist.h"
+#include "rf_stripelocks.h"
+#include "rf_layout.h"
+#include "rf_diskqueue.h"
+#include "rf_sstf.h"
+#include "rf_debugMem.h"
+#include "rf_general.h"
+#include "rf_threadid.h"
+#include "rf_options.h"
+
+#define DIR_LEFT   1
+#define DIR_RIGHT  2
+#define DIR_EITHER 3
+
+#define SNUM_DIFF(_a_,_b_) (((_a_)>(_b_))?((_a_)-(_b_)):((_b_)-(_a_)))
+
+#define QSUM(_sstfq_) (((_sstfq_)->lopri.qlen)+((_sstfq_)->left.qlen)+((_sstfq_)->right.qlen))
+
+
+static void do_sstf_ord_q(RF_DiskQueueData_t  **,
+			  RF_DiskQueueData_t  **,
+			  RF_DiskQueueData_t   *);
+
+static RF_DiskQueueData_t *closest_to_arm(RF_SstfQ_t *,
+					  RF_SectorNum_t,
+					  int *,
+					  int);
+static void do_dequeue(RF_SstfQ_t          *, RF_DiskQueueData_t  *);
+
+
+static void do_sstf_ord_q(queuep, tailp, req)
+  RF_DiskQueueData_t  **queuep;
+  RF_DiskQueueData_t  **tailp;
+  RF_DiskQueueData_t   *req;
+{
+	RF_DiskQueueData_t *r, *s;
+
+	if (*queuep == NULL) {
+		*queuep = req;
+		*tailp = req;
+		req->next = NULL;
+		req->prev = NULL;
+		return;
+	}
+	if (req->sectorOffset <= (*queuep)->sectorOffset) {
+		req->next = *queuep;
+		req->prev = NULL;
+		(*queuep)->prev = req;
+		*queuep = req;
+		return;
+	}
+	if (req->sectorOffset > (*tailp)->sectorOffset) {
+		/* optimization */
+		r = NULL;
+		s = *tailp;
+		goto q_at_end;
+	}
+	for(s=NULL,r=*queuep;r;s=r,r=r->next) {
+		if (r->sectorOffset >= req->sectorOffset) {
+			/* insert after s, before r */
+			RF_ASSERT(s);
+			req->next = r;
+			r->prev = req;
+			s->next = req;
+			req->prev = s;
+			return;
+		}
+	}
+q_at_end:
+	/* insert after s, at end of queue */
+	RF_ASSERT(r == NULL);
+	RF_ASSERT(s);
+	RF_ASSERT(s == (*tailp));
+	req->next = NULL;
+	req->prev = s;
+	s->next = req;
+	*tailp = req;
+}
+
+/* for removing from head-of-queue */
+#define DO_HEAD_DEQ(_r_,_q_) { \
+	_r_ = (_q_)->queue; \
+	RF_ASSERT((_r_) != NULL); \
+	(_q_)->queue = (_r_)->next; \
+	(_q_)->qlen--; \
+	if ((_q_)->qlen == 0) { \
+		RF_ASSERT((_r_) == (_q_)->qtail); \
+		RF_ASSERT((_q_)->queue == NULL); \
+		(_q_)->qtail = NULL; \
+	} \
+	else { \
+		RF_ASSERT((_q_)->queue->prev == (_r_)); \
+		(_q_)->queue->prev = NULL; \
+	} \
+}
+
+/* for removing from end-of-queue */
+#define DO_TAIL_DEQ(_r_,_q_) { \
+	_r_ = (_q_)->qtail; \
+	RF_ASSERT((_r_) != NULL); \
+	(_q_)->qtail = (_r_)->prev; \
+	(_q_)->qlen--; \
+	if ((_q_)->qlen == 0) { \
+		RF_ASSERT((_r_) == (_q_)->queue); \
+		RF_ASSERT((_q_)->qtail == NULL); \
+		(_q_)->queue = NULL; \
+	} \
+	else { \
+		RF_ASSERT((_q_)->qtail->next == (_r_)); \
+		(_q_)->qtail->next = NULL; \
+	} \
+}
+
+#define DO_BEST_DEQ(_l_,_r_,_q_) { \
+	if (SNUM_DIFF((_q_)->queue->sectorOffset,_l_) \
+		< SNUM_DIFF((_q_)->qtail->sectorOffset,_l_)) \
+	{ \
+		DO_HEAD_DEQ(_r_,_q_); \
+	} \
+	else { \
+		DO_TAIL_DEQ(_r_,_q_); \
+	} \
+}
+
+static RF_DiskQueueData_t *closest_to_arm(queue, arm_pos, dir, allow_reverse)
+  RF_SstfQ_t      *queue;
+  RF_SectorNum_t   arm_pos;
+  int             *dir;
+  int              allow_reverse;
+{
+	RF_SectorNum_t best_pos_l=0, this_pos_l=0, last_pos=0;
+	RF_SectorNum_t best_pos_r=0, this_pos_r=0;
+	RF_DiskQueueData_t *r, *best_l, *best_r;
+
+	best_r = best_l = NULL;
+	for(r=queue->queue;r;r=r->next) {
+		if (r->sectorOffset < arm_pos) {
+			if (best_l == NULL) {
+				best_l = r;
+				last_pos = best_pos_l = this_pos_l;
+			}
+			else {
+				this_pos_l = arm_pos - r->sectorOffset;
+				if (this_pos_l < best_pos_l) {
+					best_l = r;
+					last_pos = best_pos_l = this_pos_l;
+				}
+				else {
+					last_pos = this_pos_l;
+				}
+			}
+		}
+		else {
+			if (best_r == NULL) {
+				best_r = r;
+				last_pos = best_pos_r = this_pos_r;
+			}
+			else {
+				this_pos_r = r->sectorOffset - arm_pos;
+				if (this_pos_r < best_pos_r) {
+					best_r = r;
+					last_pos = best_pos_r = this_pos_r;
+				}
+				else {
+					last_pos = this_pos_r;
+				}
+				if (this_pos_r > last_pos) {
+					/* getting farther away */
+					break;
+				}
+			}
+		}
+	}
+	if ((best_r == NULL) && (best_l == NULL))
+		return(NULL);
+	if ((*dir == DIR_RIGHT) && best_r)
+		return(best_r);
+	if ((*dir == DIR_LEFT) && best_l)
+		return(best_l);
+	if (*dir == DIR_EITHER) {
+		if (best_l == NULL)
+			return(best_r);
+		if (best_r == NULL)
+			return(best_l);
+		if (best_pos_r < best_pos_l)
+			return(best_r);
+		else
+			return(best_l);
+	}
+	/*
+	 * Nothing in the direction we want to go. Reverse or
+	 * reset the arm. We know we have an I/O in the other
+	 * direction.
+	 */
+	if (allow_reverse) {
+		if (*dir == DIR_RIGHT) {
+			*dir = DIR_LEFT;
+			return(best_l);
+		}
+		else {
+			*dir = DIR_RIGHT;
+			return(best_r);
+		}
+	}
+	/*
+	 * Reset (beginning of queue).
+	 */
+	RF_ASSERT(*dir == DIR_RIGHT);
+	return(queue->queue);
+}
+
+void *rf_SstfCreate(sect_per_disk, cl_list, listp)
+  RF_SectorCount_t      sect_per_disk;
+  RF_AllocListElem_t   *cl_list;
+  RF_ShutdownList_t   **listp;
+{
+	RF_Sstf_t *sstfq;
+
+	RF_CallocAndAdd(sstfq, 1, sizeof(RF_Sstf_t), (RF_Sstf_t *), cl_list);
+	sstfq->dir = DIR_EITHER;
+	sstfq->allow_reverse = 1;
+	return((void *)sstfq);
+}
+
+void *rf_ScanCreate(sect_per_disk, cl_list, listp)
+  RF_SectorCount_t      sect_per_disk;
+  RF_AllocListElem_t   *cl_list;
+  RF_ShutdownList_t   **listp;
+{
+	RF_Sstf_t *scanq;
+
+	RF_CallocAndAdd(scanq, 1, sizeof(RF_Sstf_t), (RF_Sstf_t *), cl_list);
+	scanq->dir = DIR_RIGHT;
+	scanq->allow_reverse = 1;
+	return((void *)scanq);
+}
+
+void *rf_CscanCreate(sect_per_disk, cl_list, listp)
+  RF_SectorCount_t      sect_per_disk;
+  RF_AllocListElem_t   *cl_list;
+  RF_ShutdownList_t   **listp;
+{
+	RF_Sstf_t *cscanq;
+
+	RF_CallocAndAdd(cscanq, 1, sizeof(RF_Sstf_t), (RF_Sstf_t *), cl_list);
+	cscanq->dir = DIR_RIGHT;
+	return((void *)cscanq);
+}
+
+void rf_SstfEnqueue(qptr, req, priority)
+  void                *qptr;
+  RF_DiskQueueData_t  *req;
+  int                  priority;
+{
+	RF_Sstf_t *sstfq;
+
+	sstfq = (RF_Sstf_t *)qptr;
+
+	if (priority == RF_IO_LOW_PRIORITY) {
+		if (rf_sstfDebug || rf_scanDebug || rf_cscanDebug) {
+			RF_DiskQueue_t *dq;
+			int tid;
+			rf_get_threadid(tid);
+			dq = (RF_DiskQueue_t *)req->queue;
+			printf("[%d] ENQ lopri %d,%d queues are %d,%d,%d\n",
+				tid, dq->row, dq->col, sstfq->left.qlen, sstfq->right.qlen,
+				sstfq->lopri.qlen);
+		}
+		do_sstf_ord_q(&sstfq->lopri.queue, &sstfq->lopri.qtail, req);
+		sstfq->lopri.qlen++;
+	}
+	else {
+		if (req->sectorOffset < sstfq->last_sector) {
+			do_sstf_ord_q(&sstfq->left.queue, &sstfq->left.qtail, req);
+			sstfq->left.qlen++;
+		}
+		else {
+			do_sstf_ord_q(&sstfq->right.queue, &sstfq->right.qtail, req);
+			sstfq->right.qlen++;
+		}
+	}
+}
+
+static void do_dequeue(queue, req)
+  RF_SstfQ_t          *queue;
+  RF_DiskQueueData_t  *req;
+{
+	RF_DiskQueueData_t  *req2;
+
+	if (rf_sstfDebug || rf_scanDebug || rf_cscanDebug) {
+		int tid;
+		rf_get_threadid(tid);
+		printf("[%d] do_dequeue\n", tid);
+	}
+	if (req == queue->queue) {
+		DO_HEAD_DEQ(req2,queue);
+		RF_ASSERT(req2 == req);
+	}
+	else if (req == queue->qtail) {
+		DO_TAIL_DEQ(req2,queue);
+		RF_ASSERT(req2 == req);
+	}
+	else {
+		/* dequeue from middle of list */
+		RF_ASSERT(req->next);
+		RF_ASSERT(req->prev);
+		queue->qlen--;
+		req->next->prev = req->prev;
+		req->prev->next = req->next;
+		req->next = req->prev = NULL;
+	}
+}
+
+RF_DiskQueueData_t *rf_SstfDequeue(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req=NULL;
+	RF_Sstf_t *sstfq;
+
+	sstfq = (RF_Sstf_t *)qptr;
+
+	if (rf_sstfDebug) {
+		RF_DiskQueue_t *dq;
+		int tid;
+		rf_get_threadid(tid);
+		dq = (RF_DiskQueue_t *)req->queue;
+		RF_ASSERT(QSUM(sstfq)==dq->queueLength);
+		printf("[%d] sstf: Dequeue %d,%d queues are %d,%d,%d\n", tid,
+			dq->row, dq->col, sstfq->left.qlen, sstfq->right.qlen,
+			sstfq->lopri.qlen);
+	}
+	if (sstfq->left.queue == NULL) {
+		RF_ASSERT(sstfq->left.qlen == 0);
+		if (sstfq->right.queue == NULL) {
+			RF_ASSERT(sstfq->right.qlen == 0);
+			if (sstfq->lopri.queue == NULL) {
+				RF_ASSERT(sstfq->lopri.qlen == 0);
+				return(NULL);
+			}
+			if (rf_sstfDebug) {
+				int tid;
+				rf_get_threadid(tid);
+				printf("[%d] sstf: check for close lopri", tid);
+			}
+			req = closest_to_arm(&sstfq->lopri, sstfq->last_sector,
+				&sstfq->dir, sstfq->allow_reverse);
+			if (rf_sstfDebug) {
+				int tid;
+				rf_get_threadid(tid);
+				printf("[%d] sstf: closest_to_arm said %lx", tid, (long)req);
+			}
+			if (req == NULL)
+				return(NULL);
+			do_dequeue(&sstfq->lopri, req);
+		}
+		else {
+			DO_BEST_DEQ(sstfq->last_sector,req,&sstfq->right);
+		}
+	}
+	else {
+		if (sstfq->right.queue == NULL) {
+			RF_ASSERT(sstfq->right.qlen == 0);
+			DO_BEST_DEQ(sstfq->last_sector,req,&sstfq->left);
+		}
+		else {
+			if (SNUM_DIFF(sstfq->last_sector,sstfq->right.queue->sectorOffset)
+				< SNUM_DIFF(sstfq->last_sector,sstfq->left.qtail->sectorOffset))
+			{
+				DO_HEAD_DEQ(req,&sstfq->right);
+			}
+			else {
+				DO_TAIL_DEQ(req,&sstfq->left);
+			}
+		}
+	}
+	RF_ASSERT(req);
+	sstfq->last_sector = req->sectorOffset;
+	return(req);
+}
+
+RF_DiskQueueData_t *rf_ScanDequeue(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req=NULL;
+	RF_Sstf_t *scanq;
+
+	scanq = (RF_Sstf_t *)qptr;
+
+	if (rf_scanDebug) {
+		RF_DiskQueue_t *dq;
+		int tid;
+		rf_get_threadid(tid);
+		dq = (RF_DiskQueue_t *)req->queue;
+		RF_ASSERT(QSUM(scanq)==dq->queueLength);
+		printf("[%d] scan: Dequeue %d,%d queues are %d,%d,%d\n", tid,
+			dq->row, dq->col, scanq->left.qlen, scanq->right.qlen,
+			scanq->lopri.qlen);
+	}
+	if (scanq->left.queue == NULL) {
+		RF_ASSERT(scanq->left.qlen == 0);
+		if (scanq->right.queue == NULL) {
+			RF_ASSERT(scanq->right.qlen == 0);
+			if (scanq->lopri.queue == NULL) {
+				RF_ASSERT(scanq->lopri.qlen == 0);
+				return(NULL);
+			}
+			req = closest_to_arm(&scanq->lopri, scanq->last_sector,
+				&scanq->dir, scanq->allow_reverse);
+			if (req == NULL)
+				return(NULL);
+			do_dequeue(&scanq->lopri, req);
+		}
+		else {
+			scanq->dir = DIR_RIGHT;
+			DO_HEAD_DEQ(req,&scanq->right);
+		}
+	}
+	else if (scanq->right.queue == NULL) {
+		RF_ASSERT(scanq->right.qlen == 0);
+		RF_ASSERT(scanq->left.queue);
+		scanq->dir = DIR_LEFT;
+		DO_TAIL_DEQ(req,&scanq->left);
+	}
+	else {
+		RF_ASSERT(scanq->right.queue);
+		RF_ASSERT(scanq->left.queue);
+		if (scanq->dir == DIR_RIGHT) {
+			DO_HEAD_DEQ(req,&scanq->right);
+		}
+		else {
+			DO_TAIL_DEQ(req,&scanq->left);
+		}
+	}
+	RF_ASSERT(req);
+	scanq->last_sector = req->sectorOffset;
+	return(req);
+}
+
+RF_DiskQueueData_t *rf_CscanDequeue(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req=NULL;
+	RF_Sstf_t *cscanq;
+
+	cscanq = (RF_Sstf_t *)qptr;
+
+	RF_ASSERT(cscanq->dir == DIR_RIGHT);
+	if (rf_cscanDebug) {
+		RF_DiskQueue_t *dq;
+		int tid;
+		rf_get_threadid(tid);
+		dq = (RF_DiskQueue_t *)req->queue;
+		RF_ASSERT(QSUM(cscanq)==dq->queueLength);
+		printf("[%d] scan: Dequeue %d,%d queues are %d,%d,%d\n", tid,
+			dq->row, dq->col, cscanq->left.qlen, cscanq->right.qlen,
+			cscanq->lopri.qlen);
+	}
+	if (cscanq->right.queue) {
+		DO_HEAD_DEQ(req,&cscanq->right);
+	}
+	else {
+		RF_ASSERT(cscanq->right.qlen == 0);
+		if (cscanq->left.queue == NULL) {
+			RF_ASSERT(cscanq->left.qlen == 0);
+			if (cscanq->lopri.queue == NULL) {
+				RF_ASSERT(cscanq->lopri.qlen == 0);
+				return(NULL);
+			}
+			req = closest_to_arm(&cscanq->lopri, cscanq->last_sector,
+				&cscanq->dir, cscanq->allow_reverse);
+			if (req == NULL)
+				return(NULL);
+			do_dequeue(&cscanq->lopri, req);
+		}
+		else {
+			/*
+			 * There's I/Os to the left of the arm. Swing
+			 * on back (swap queues).
+			 */
+			cscanq->right = cscanq->left;
+			cscanq->left.qlen = 0;
+			cscanq->left.queue = cscanq->left.qtail = NULL;
+			DO_HEAD_DEQ(req,&cscanq->right);
+		}
+	}
+	RF_ASSERT(req);
+	cscanq->last_sector = req->sectorOffset;
+	return(req);
+}
+
+RF_DiskQueueData_t *rf_SstfPeek(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req;
+	RF_Sstf_t *sstfq;
+
+	sstfq = (RF_Sstf_t *)qptr;
+
+	if ((sstfq->left.queue == NULL) && (sstfq->right.queue == NULL)) {
+		req = closest_to_arm(&sstfq->lopri, sstfq->last_sector, &sstfq->dir,
+			sstfq->allow_reverse);
+	}
+	else {
+		if (sstfq->left.queue == NULL)
+			req = sstfq->right.queue;
+		else {
+			if (sstfq->right.queue == NULL)
+				req = sstfq->left.queue;
+			else {
+				if (SNUM_DIFF(sstfq->last_sector,sstfq->right.queue->sectorOffset)
+					<SNUM_DIFF(sstfq->last_sector,sstfq->left.qtail->sectorOffset))
+				{
+					req = sstfq->right.queue;
+				}
+				else {
+					req = sstfq->left.qtail;
+				}
+			}
+		}
+	}
+	if (req == NULL) {
+		RF_ASSERT(QSUM(sstfq) == 0);
+	}
+	return(req);
+}
+
+RF_DiskQueueData_t *rf_ScanPeek(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req;
+	RF_Sstf_t *scanq;
+	int dir;
+
+	scanq = (RF_Sstf_t *)qptr;
+	dir = scanq->dir;
+
+	if (scanq->left.queue == NULL) {
+		RF_ASSERT(scanq->left.qlen == 0);
+		if (scanq->right.queue == NULL) {
+			RF_ASSERT(scanq->right.qlen == 0);
+			if (scanq->lopri.queue == NULL) {
+				RF_ASSERT(scanq->lopri.qlen == 0);
+				return(NULL);
+			}
+			req = closest_to_arm(&scanq->lopri, scanq->last_sector,
+				&dir, scanq->allow_reverse);
+		}
+		else {
+			req = scanq->right.queue;
+		}
+	}
+	else if (scanq->right.queue == NULL) {
+		RF_ASSERT(scanq->right.qlen == 0);
+		RF_ASSERT(scanq->left.queue);
+		req = scanq->left.qtail;
+	}
+	else {
+		RF_ASSERT(scanq->right.queue);
+		RF_ASSERT(scanq->left.queue);
+		if (scanq->dir == DIR_RIGHT) {
+			req = scanq->right.queue;
+		}
+		else {
+			req = scanq->left.qtail;
+		}
+	}
+	if (req == NULL) {
+		RF_ASSERT(QSUM(scanq) == 0);
+	}
+	return(req);
+}
+
+RF_DiskQueueData_t *rf_CscanPeek(qptr)
+  void  *qptr;
+{
+	RF_DiskQueueData_t *req;
+	RF_Sstf_t *cscanq;
+
+	cscanq = (RF_Sstf_t *)qptr;
+
+	RF_ASSERT(cscanq->dir == DIR_RIGHT);
+	if (cscanq->right.queue) {
+		req = cscanq->right.queue;
+	}
+	else {
+		RF_ASSERT(cscanq->right.qlen == 0);
+		if (cscanq->left.queue == NULL) {
+			RF_ASSERT(cscanq->left.qlen == 0);
+			if (cscanq->lopri.queue == NULL) {
+				RF_ASSERT(cscanq->lopri.qlen == 0);
+				return(NULL);
+			}
+			req = closest_to_arm(&cscanq->lopri, cscanq->last_sector,
+				&cscanq->dir, cscanq->allow_reverse);
+		}
+		else {
+			/*
+			 * There's I/Os to the left of the arm. We'll end
+			 * up swinging on back.
+			 */
+			req = cscanq->left.queue;
+		}
+	}
+	if (req == NULL) {
+		RF_ASSERT(QSUM(cscanq) == 0);
+	}
+	return(req);
+}
+
+int rf_SstfPromote(qptr, parityStripeID, which_ru)
+  void               *qptr;
+  RF_StripeNum_t      parityStripeID;
+  RF_ReconUnitNum_t   which_ru;
+{
+	RF_DiskQueueData_t *r, *next;
+	RF_Sstf_t *sstfq;
+	int n;
+
+	sstfq = (RF_Sstf_t *)qptr;
+
+	n = 0;
+	if (rf_sstfDebug || rf_scanDebug || rf_cscanDebug) {
+		int tid;
+		rf_get_threadid(tid);
+		printf("[%d] promote %ld %d  queues are %d,%d,%d\n",
+		       tid, (long)parityStripeID, (int)which_ru, 
+		       sstfq->left.qlen, 
+		       sstfq->right.qlen,
+		       sstfq->lopri.qlen);
+	}
+	for(r=sstfq->lopri.queue;r;r=next) {
+		next = r->next;
+		if (rf_sstfDebug || rf_scanDebug || rf_cscanDebug) {
+			int tid;
+			rf_get_threadid(tid);
+			printf("[%d] check promote %lx\n", tid, (long)r);
+		}
+		if ((r->parityStripeID == parityStripeID)
+			&& (r->which_ru == which_ru))
+		{
+			do_dequeue(&sstfq->lopri, r);
+			rf_SstfEnqueue(qptr, r, RF_IO_NORMAL_PRIORITY);
+			n++;
+		}
+	}
+	if (rf_sstfDebug || rf_scanDebug || rf_cscanDebug) {
+		int tid;
+		rf_get_threadid(tid);
+		printf("[%d] promoted %d matching I/Os queues are %d,%d,%d\n",
+			tid, n, sstfq->left.qlen, sstfq->right.qlen, sstfq->lopri.qlen);
+	}
+	return(n);
+}