During probe, when the block layer registers a request queue, it
defaults to the mq-deadline I/O scheduler if the device is single-queue
and the mq-deadline module is available. To determine availability, the
elevator_set_default() invokes elevator_find_get(), which increments the
module's reference count. However, this reference is never released,
resulting in a module reference leak that prevents the mq-deadline module
from being unloaded.
This patch fixes the issue by ensuring the acquired module reference is
properly released.
Fixes: 1e44bedbc921 ("block: unifying elevator change")
Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
---
Note: This patch is based on https://lore.kernel.org/all/20250718133232.626418-1-nilay@xxxxxxxxxxxxx/
So please apply this patch after the above is merged.
---
block/elevator.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/block/elevator.c b/block/elevator.c
index 83d0bfb90a03..2bbf7ad7f4db 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -719,7 +719,8 @@ void elevator_set_default(struct request_queue *q)
.name = "mq-deadline",
.no_uevent = true,
};
- int err = 0;
+ int err;
+ struct elevator_type *e;
/* now we allow to switch elevator */
blk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);
@@ -732,12 +733,18 @@ void elevator_set_default(struct request_queue *q)
* have multiple queues or mq-deadline is not available, default
* to "none".
*/
- if (elevator_find_get(ctx.name) && (q->nr_hw_queues == 1 ||
- blk_mq_is_shared_tags(q->tag_set->flags)))
+ e = elevator_find_get(ctx.name);
+ if (!e)
+ return;
+
+ if ((q->nr_hw_queues == 1 ||
+ blk_mq_is_shared_tags(q->tag_set->flags))) {
err = elevator_change(q, &ctx);
- if (err < 0)
- pr_warn("\"%s\" elevator initialization, failed %d, "
- "falling back to \"none\"\n", ctx.name, err);
+ if (err < 0)
+ pr_warn("\"%s\" elevator initialization, failed %d, falling back to \"none\"\n",
+ ctx.name, err);
+ }
+ elevator_put(e);
}
void elevator_set_none(struct request_queue *q)
--
2.50.1
