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Subject: Re: [bug report] blk-mq-sched: add framework for MQ capable IO
 schedulers
To: Dan Carpenter <dan.carpenter@oracle.com>
References: <20170119073238.GA9834@mwanda>
CC: <linux-block@vger.kernel.org>
From: Jens Axboe <axboe@fb.com>
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Date: Thu, 19 Jan 2017 06:11:45 -0800
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On 01/18/2017 11:32 PM, Dan Carpenter wrote:
> Hello Jens Axboe,
> 
> This is a semi-automatic email about new static checker warnings.
> 
> The patch bd166ef183c2: "blk-mq-sched: add framework for MQ capable
> IO schedulers" from Jan 17, 2017, leads to the following Smatch
> complaint:
> 
> block/elevator.c:234 elevator_init()
> 	 error: we previously assumed 'e' could be null (see line 229)
> 
> block/elevator.c
>    228	
>    229			if (!e) {
>                             ^^
> Null.
> 
>    230				printk(KERN_ERR
>    231					"Default I/O scheduler not found. " \
>    232					"Using noop/none.\n");
>    233				if (q->mq_ops) {
>    234					elevator_put(e);
>                                         ^^^^^^^^^^^^^^^
> This will Oops.
> 
>    235					return 0;
>    236				}

Good find, thanks Dan. I've killed the elevator_put().

-- 
Jens Axboe