[PATCH] deadline scheduler

This introduces the deadline-ioscheduler, making it the default.  2nd
patch coming that deletes elevator_linus in a minute.

This one has read_expire at 500ms, and writes_starved at 2.

drivers/block/Makefile

@@ -9,9 +9,9 @@
 #
 
 export-objs	:= elevator.o ll_rw_blk.o loop.o genhd.o acsi.o \
-		   block_ioctl.o
+		   block_ioctl.o deadline-iosched.o
 
-obj-y	:= elevator.o ll_rw_blk.o blkpg.o genhd.o block_ioctl.o
+obj-y	:= elevator.o ll_rw_blk.o blkpg.o genhd.o block_ioctl.o deadline-iosched.o
 
 obj-$(CONFIG_MAC_FLOPPY)	+= swim3.o
 obj-$(CONFIG_BLK_DEV_FD)	+= floppy.o

drivers/block/ll_rw_blk.c

@@ -1175,7 +1175,7 @@ int blk_init_queue(request_queue_t *q, request_fn_proc *rfn, spinlock_t *lock)
 	if (blk_init_free_list(q))
 		return -ENOMEM;
 
-	if ((ret = elevator_init(q, &q->elevator, elevator_linus))) {
+	if ((ret = elevator_init(q, &q->elevator, iosched_deadline))) {
 		blk_cleanup_queue(q);
 		return ret;
 	}

include/linux/elevator.h

@@ -59,6 +59,12 @@ extern elevator_t elevator_linus;
 #define elv_linus_sequence(rq)	((long)(rq)->elevator_private)
 #define ELV_LINUS_SEEK_COST	16
 
+/*
+ * deadline i/o scheduler. uses request time outs to prevent indefinite
+ * starvation
+ */
+extern elevator_t iosched_deadline;
+
 /*
  * use the /proc/iosched interface, all the below is history ->
  */