block: Expose stacked device queues in sysfs
Currently stacking devices do not have a queue directory in sysfs.
However, many of the I/O characteristics like sector size, maximum
request size, etc. are queue properties.
This patch enables the queue directory for MD/DM devices. The elevator
code has been modified to deal with queues that do not have an I/O
scheduler.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 142a4ac..3ccdadb 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -395,9 +395,6 @@
if (WARN_ON(!q))
return -ENXIO;
- if (!q->request_fn)
- return 0;
-
ret = kobject_add(&q->kobj, kobject_get(&disk_to_dev(disk)->kobj),
"%s", "queue");
if (ret < 0)
@@ -405,6 +402,9 @@
kobject_uevent(&q->kobj, KOBJ_ADD);
+ if (!q->request_fn)
+ return 0;
+
ret = elv_register_queue(q);
if (ret) {
kobject_uevent(&q->kobj, KOBJ_REMOVE);
diff --git a/block/elevator.c b/block/elevator.c
index ebee948..bd78f69 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -575,6 +575,9 @@
*/
void elv_quiesce_start(struct request_queue *q)
{
+ if (!q->elevator)
+ return;
+
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
/*
@@ -1050,6 +1053,9 @@
char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
+ if (!q->elevator)
+ return count;
+
strlcpy(elevator_name, name, sizeof(elevator_name));
strstrip(elevator_name);
@@ -1073,10 +1079,15 @@
ssize_t elv_iosched_show(struct request_queue *q, char *name)
{
struct elevator_queue *e = q->elevator;
- struct elevator_type *elv = e->elevator_type;
+ struct elevator_type *elv;
struct elevator_type *__e;
int len = 0;
+ if (!q->elevator)
+ return sprintf(name, "none\n");
+
+ elv = e->elevator_type;
+
spin_lock(&elv_list_lock);
list_for_each_entry(__e, &elv_list, list) {
if (!strcmp(elv->elevator_name, __e->elevator_name))
