On 4/10/25 7:00 PM, Ming Lei wrote:
> +int elevator_change_done(struct request_queue *q, struct elev_change_ctx *ctx)
> +{
> + int ret = 0;
> +
> + if (ctx->old) {
> + elv_unregister_queue(q, ctx->old);
> + kobject_put(&ctx->old->kobj);
> + }
> + if (ctx->new) {
> + ret = elv_register_queue(q, ctx->new, ctx->uevent);
> + if (ret) {
> + unsigned memflags = blk_mq_freeze_queue(q);
> +
> + mutex_lock(&q->elevator_lock);
> + elevator_exit(q);
> + mutex_unlock(&q->elevator_lock);
> + blk_mq_unfreeze_queue(q, memflags);
> + }
> + }
> + return 0;
> +}
> +
We could have sysf elevator attributes simultaneously accessed while this function
adds/removes sysfs elevator attributes without any protection. In fact, the show/store
methods of elevator attributes runs with e->sysfs_lock held. So it seems moving
the above function out of lock protection might cause crash or other side effects?
Thanks,
--Nilay
