linux-kernel - Re: [PATCH] elevator: fix double release for elevator module

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Date:	Thu, 23 Apr 2015 10:49:11 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Jeff Moyer <jmoyer@...hat.com>, Chao Yu <chao2.yu@...sung.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] elevator: fix double release for elevator module

On 04/23/2015 08:59 AM, Jeff Moyer wrote:
> Chao Yu <chao2.yu@...sung.com> writes:
>
>> Our issue is descripted in below call path:
>> ->elevator_init
>>   ->elevator_init_fn
>>    ->{cfq,deadline,noop}_init_queue
>>     ->elevator_alloc
>>      ->kzalloc_node
>>     fail to call kzalloc_node and then put module in elevator_alloc;
>> fail to call elevator_init_fn and then put module again in elevator_init.
>>
>> Remove elevator_put invoking in error path of elevator_alloc to avoid
>> double release issue.
>>
>> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
>> ---
>>   block/elevator.c | 5 +----
>>   1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/block/elevator.c b/block/elevator.c
>> index d146a5e..8985038 100644
>> --- a/block/elevator.c
>> +++ b/block/elevator.c
>> @@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>>
>>   	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
>>   	if (unlikely(!eq))
>> -		goto err;
>> +		return NULL;
>>
>>   	eq->type = e;
>>   	kobject_init(&eq->kobj, &elv_ktype);
>> @@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>>   	hash_init(eq->hash);
>>
>>   	return eq;
>> -err:
>> -	elevator_put(e);
>> -	return NULL;
>>   }
>>   EXPORT_SYMBOL(elevator_alloc);
>
> You could have posted the two patches together, as they are related.
> Anyway, looks good to me.
>
> Reviewed-by: Jeff Moyer <jmoyer@...hat.com>

Agree, it should be one patch. I've combined them, and applied the fix 
for 4.1. Thanks.

-- 
Jens Axboe

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