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>

1 files changed, 3 insertions, 3 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 142a4acddd43..3ccdadb8e204 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -395,9 +395,6 @@ int blk_register_queue(struct gendisk *disk)
         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 @@ int blk_register_queue(struct gendisk *disk)
 
         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);