linux-kernel - Re: [BUG] rbtree bug with mmotm 2009-04-14-17-24

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Date:	Wed, 22 Apr 2009 21:22:16 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Steve Wise <swise@...ngridcomputing.com>
Cc:	balbir@...ux.vnet.ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Wolfram Strepp <wstrepp@....de>
Subject: Re: [BUG] rbtree bug with mmotm 2009-04-14-17-24

On Wed, Apr 22 2009, Steve Wise wrote:
>
>> Odd... Can you try this variant?
>>
>> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
>> index 7e13f04..3a97c18 100644
>> --- a/block/cfq-iosched.c
>> +++ b/block/cfq-iosched.c
>> @@ -154,6 +154,7 @@ struct cfq_queue {
>>  	unsigned long rb_key;
>>  	/* prio tree member */
>>  	struct rb_node p_node;
>> +	struct rb_root *p_root;
>>  	/* sorted list of pending requests */
>>  	struct rb_root sort_list;
>>  	/* if fifo isn't expired, next request to serve */
>> @@ -594,22 +595,25 @@ cfq_prio_tree_lookup(struct cfq_data *cfqd, int ioprio, sector_t sector,
>>   static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue 
>> *cfqq)
>>  {
>> -	struct rb_root *root = &cfqd->prio_trees[cfqq->ioprio];
>> +	struct rb_root *root = &cfqd->prio_trees[cfqq->org_ioprio];
>>  	struct rb_node **p, *parent;
>>  	struct cfq_queue *__cfqq;
>>  -	if (!RB_EMPTY_NODE(&cfqq->p_node))
>> -		rb_erase_init(&cfqq->p_node, root);
>> +	if (cfqq->p_root) {
>> +		rb_erase_init(&cfqq->p_node, cfqq->p_root);
>> +		cfqq->p_root = NULL;
>> +	}
>>   	if (cfq_class_idle(cfqq))
>>  		return;
>>  	if (!cfqq->next_rq)
>>  		return;
>>  -	__cfqq = cfq_prio_tree_lookup(cfqd, cfqq->ioprio, 
>> cfqq->next_rq->sector,
>> -					 &parent, &p);
>> +	__cfqq = cfq_prio_tree_lookup(cfqd, cfqq->org_ioprio,
>> +					cfqq->next_rq->sector, &parent, &p);
>>  	BUG_ON(__cfqq);
>>  +	cfqq->p_root = root;
>>  	rb_link_node(&cfqq->p_node, parent, p);
>>  	rb_insert_color(&cfqq->p_node, root);
>>  }
>> @@ -656,8 +660,10 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
>>   	if (!RB_EMPTY_NODE(&cfqq->rb_node))
>>  		cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
>> -	if (!RB_EMPTY_NODE(&cfqq->p_node))
>> -		rb_erase_init(&cfqq->p_node, &cfqd->prio_trees[cfqq->ioprio]);
>> +	if (cfqq->p_root) {
>> +		rb_erase_init(&cfqq->p_node, cfqq->p_root);
>> +		cfqq->p_root = NULL;
>> +	}
>>   	BUG_ON(!cfqd->busy_queues);
>>  	cfqd->busy_queues--;
>> @@ -976,7 +982,7 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
>>  	 * First, if we find a request starting at the end of the last
>>  	 * request, choose it.
>>  	 */
>> -	__cfqq = cfq_prio_tree_lookup(cfqd, cur_cfqq->ioprio,
>> +	__cfqq = cfq_prio_tree_lookup(cfqd, cur_cfqq->org_ioprio,
>>  				      sector, &parent, NULL);
>>  	if (__cfqq)
>>  		return __cfqq;
>>
>>   
>
> Still crashes with this variant:

OK, so please try and revert a36e71f996e25d6213f57951f7ae1874086ec57e
and see if that works?

Or, better yet, please try and revert
55a63998b8967615a15e2211ba0ff3a84a565824 first. If that doesn't work,
try the above revert.

-- 
Jens Axboe

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