cfq-iosched: fix the setting of IOPS mode on SSDs

A previous commit wanted to make CFQ default to IOPS mode on
non-rotational storage, however it did so when the queue was
initialized and the non-rotational flag is only set later on
in the probe.

Add an elevator hook that gets called off the add_disk() path,
at that point we know that feature probing has finished, and
we can reliably check for the various flags that drivers can
set.

Fixes: 41c0126b ("block: Make CFQ default to IOPS mode on SSDs")
Tested-by: Romain Francoise <romain@orebokech.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 45a91474487d..638b324f0291 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -39,6 +39,7 @@ typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct reques
 typedef int (elevator_init_fn) (struct request_queue *,
                                 struct elevator_type *e);
 typedef void (elevator_exit_fn) (struct elevator_queue *);
+typedef void (elevator_registered_fn) (struct request_queue *);
 
 struct elevator_ops
 {
@@ -68,6 +69,7 @@ struct elevator_ops
 
         elevator_init_fn *elevator_init_fn;
         elevator_exit_fn *elevator_exit_fn;
+        elevator_registered_fn *elevator_registered_fn;
 };
 
 #define ELV_NAME_MAX    (16)