On Sat, Jul 19, 2025 at 06:56:47PM +0530, Nilay Shroff wrote:
> 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);
Looks fine,
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Thanks,
Ming
