Re: [PATCH]cfq-iosched: fix an oops caused by slab leak

[Jeff Moyer <jmoyer@redhat.com>]

Shaohua Li <shaohua.li@intel.com> writes:

> I got below oops when unloading cfq-iosched. Considering scenario:
> queue A merge to B, C merge to D and B will be merged to D. Before B is merged
> to D, we do split B. We should put B's reference for D.
[...]
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index ed897b5..855fd5f 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -2537,15 +2537,10 @@ static void cfq_free_io_context(struct io_context *ioc)
>  	__call_for_each_cic(ioc, cic_free_func);
>  }
>  
> -static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> +static void cfq_put_cooperator(struct cfq_queue *cfqq)
>  {
>  	struct cfq_queue *__cfqq, *next;
>  
> -	if (unlikely(cfqq == cfqd->active_queue)) {
> -		__cfq_slice_expired(cfqd, cfqq, 0);
> -		cfq_schedule_dispatch(cfqd);
> -	}
> -
>  	/*
>  	 * If this queue was scheduled to merge with another queue, be
>  	 * sure to drop the reference taken on that queue (and others in
> @@ -2561,6 +2556,16 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
>  		cfq_put_queue(__cfqq);
>  		__cfqq = next;
>  	}
> +}
> +
> +static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> +{
> +	if (unlikely(cfqq == cfqd->active_queue)) {
> +		__cfq_slice_expired(cfqd, cfqq, 0);
> +		cfq_schedule_dispatch(cfqd);
> +	}
> +
> +	cfq_put_cooperator(cfqq);
>  
>  	cfq_put_queue(cfqq);
>  }
> @@ -3516,6 +3521,9 @@ split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
>  	}
>  
>  	cic_set_cfqq(cic, NULL, 1);
> +
> +	cfq_put_cooperator(cfqq);
> +
>  	cfq_put_queue(cfqq);
>  	return NULL;
>  }

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>