# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.814   -> 1.815  
#	include/linux/blkdev.h	1.77    -> 1.78   
#	drivers/block/elevator.c	1.30    -> 1.31   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/28	axboe@burns.home.kernel.dk	1.815
# Extend q->prep_rq_fn() to return one of three values:
# 
# o BLKPREP_OK: request is good, return it
# o BLKPREP_KILL: request is bad, end it completely
# o BLKPREP_DEFER: request is good, but we can't take it now
# 
# We maintain compatability with old prep functions (if any, outside of
# ide-cd). This change is needed or SCSI to use prep function for command
# init, if sg table allocation fails we can just defer the request.
# --------------------------------------------
#
diff -Nru a/drivers/block/elevator.c b/drivers/block/elevator.c
--- a/drivers/block/elevator.c	Mon Oct 28 18:01:23 2002
+++ b/drivers/block/elevator.c	Mon Oct 28 18:01:23 2002
@@ -303,8 +303,14 @@
 struct request *elv_next_request(request_queue_t *q)
 {
 	struct request *rq;
+	int ret;
 
 	while ((rq = __elv_next_request(q))) {
+		/*
+		 * just mark as started even if we don't start it, a request
+		 * that has been delayed should not be passed by new incoming
+		 * requests
+		 */
 		rq->flags |= REQ_STARTED;
 
 		if (&rq->queuelist == q->last_merge)
@@ -313,20 +319,22 @@
 		if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
 			break;
 
-		/*
-		 * all ok, break and return it
-		 */
-		if (!q->prep_rq_fn(q, rq))
+		ret = q->prep_rq_fn(q, rq);
+		if (ret == BLKPREP_OK) {
 			break;
-
-		/*
-		 * prep said no-go, kill it
-		 */
-		blkdev_dequeue_request(rq);
-		if (end_that_request_first(rq, 0, rq->nr_sectors))
-			BUG();
-
-		end_that_request_last(rq);
+		} else if (ret == BLKPREP_DEFER) {
+			rq = NULL;
+			break;
+		} else if (ret == BLKPREP_KILL) {
+			blkdev_dequeue_request(rq);
+			rq->flags |= REQ_QUIET;
+			while (end_that_request_first(rq, 0, rq->nr_sectors))
+				;
+			end_that_request_last(rq);
+		} else {
+			printk("%s: bad return=%d\n", __FUNCTION__, ret);
+			break;
+		}
 	}
 
 	return rq;
diff -Nru a/include/linux/blkdev.h b/include/linux/blkdev.h
--- a/include/linux/blkdev.h	Mon Oct 28 18:01:23 2002
+++ b/include/linux/blkdev.h	Mon Oct 28 18:01:23 2002
@@ -254,6 +254,13 @@
  */
 #define blk_queue_headactive(q, head_active)
 
+/*
+ * q->prep_rq_fn return values
+ */
+#define BLKPREP_OK		0	/* serve it */
+#define BLKPREP_KILL		1	/* fatal error, kill */
+#define BLKPREP_DEFER		2	/* leave on queue */
+
 extern unsigned long blk_max_low_pfn, blk_max_pfn;
 
 /*