[PATCH 2/4] blkdev: iosched selection for queue creation

Peter Zijlstra
2006-08-25T15:45:12Z

Provide an block queue init function that allows to set an elevator.
And a function to pin the current elevator.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Daniel Phillips <phillips@google.com>
---
block/elevator.c | 5 +++++
block/ll_rw_blk.c | 12 ++++++++++--
include/linux/blkdev.h | 9 +++++++++
3 files changed, 24 insertions(+), 2 deletions(-)

Index: linux-2.6/block/ll_rw_blk.c
===================================================================
--- linux-2.6.orig/block/ll_rw_blk.c
+++ linux-2.6/block/ll_rw_blk.c
@@ -1899,6 +1899,14 @@ EXPORT_SYMBOL(blk_init_queue);
request_queue_t *
blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
{
+ return blk_init_queue_node_elv(rfn, lock, node_id, NULL);
+}
+EXPORT_SYMBOL(blk_init_queue_node);
+
+request_queue_t *
+blk_init_queue_node_elv(request_fn_proc *rfn, spinlock_t *lock, int node_id,
+ char *elv_name)
+{
request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);

if (!q)
@@ -1939,7 +1947,7 @@ blk_init_queue_node(request_fn_proc *rfn
/*
* all done
*/
- if (!elevator_init(q, NULL)) {
+ if (!elevator_init(q, elv_name)) {
blk_queue_congestion_threshold(q);
return q;
}
@@ -1947,7 +1955,7 @@ blk_init_queue_node(request_fn_proc *rfn
blk_put_queue(q);
return NULL;
}
-EXPORT_SYMBOL(blk_init_queue_node);
+EXPORT_SYMBOL(blk_init_queue_node_elv);

int blk_get_queue(request_queue_t *q)
{
Index: linux-2.6/include/linux/blkdev.h
===================================================================
--- linux-2.6.orig/include/linux/blkdev.h
+++ linux-2.6/include/linux/blkdev.h
@@ -444,6 +444,12 @@ struct request_queue
#define QUEUE_FLAG_REENTER 6 /* Re-entrancy avoidance */
#define QUEUE_FLAG_PLUGGED 7 /* queue is plugged */
#define QUEUE_FLAG_ELVSWITCH 8 /* don't use elevator, just do FIFO */
+#define QUEUE_FLAG_ELVPINNED 9 /* pin the current elevator */
+
+static inline void blk_queue_pin_elevator(struct request_queue *q)
+{
+ set_bit(QUEUE_FLAG_ELVPINNED, &q->queue_flags);
+}

enum {
/*
@@ -696,6 +702,9 @@ static inline void elv_dispatch_add_tail
/*
* Access functions for manipulating queue properties
*/
+extern request_queue_t *blk_init_queue_node_elv(request_fn_proc *rfn,
+ spinlock_t *lock, int node_id,
+ char *elv_name);
extern request_queue_t *blk_init_queue_node(request_fn_proc *rfn,
spinlock_t *lock, int node_id);
extern request_queue_t *blk_init_queue(request_fn_proc *, spinlock_t *);
Index: linux-2.6/block/elevator.c
===================================================================
--- linux-2.6.orig/block/elevator.c
+++ linux-2.6/block/elevator.c
@@ -861,6 +861,11 @@ ssize_t elv_iosched_store(request_queue_
size_t len;
struct elevator_type *e;

+ if (test_bit(QUEUE_FLAG_ELVPINNED, &q->queue_flags)) {
+ printk(KERN_NOTICE "elevator: cannot switch elevator, pinned\n");
+ return count;
+ }
+
elevator_name[sizeof(elevator_name) - 1] = '\0';
strncpy(elevator_name, name, sizeof(elevator_name) - 1);
len = strlen(elevator_name);