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Commit dbecf3ab authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Jens Axboe
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[PATCH 2/2] cfq: fix cic's rbtree traversal 



When queue dies, we set cic->key=NULL as dead mark. So, when we
traverse a rbtree, we must check whether it's still valid key. if it
was invalidated, drop it, then restart the traversal from top.

Signed-off-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent fba82272

block/cfq-iosched.c

+27 −6
Original line number Diff line number Diff line
@@ -1472,15 +1472,31 @@ cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, 
	return cfqq;

}



static void

cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)

{

	read_lock(&cfq_exit_lock);

	rb_erase(&cic->rb_node, &ioc->cic_root);

	read_unlock(&cfq_exit_lock);

	kmem_cache_free(cfq_ioc_pool, cic);

	atomic_dec(&ioc_count);

}



static struct cfq_io_context *

cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)

{

	struct rb_node *n = ioc->cic_root.rb_node;

	struct rb_node *n;

	struct cfq_io_context *cic;

	void *key = cfqd;



restart:

	n = ioc->cic_root.rb_node;

	while (n) {

		cic = rb_entry(n, struct cfq_io_context, rb_node);

		if (unlikely(!cic->key)) {

			cfq_drop_dead_cic(ioc, cic);

			goto restart;

		}



		if (key < cic->key)

			n = n->rb_left;
@@ -1497,20 +1513,24 @@ static inline void 
cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,

	     struct cfq_io_context *cic)

{

	struct rb_node **p = &ioc->cic_root.rb_node;

	struct rb_node *parent = NULL;

	struct rb_node **p;

	struct rb_node *parent;

	struct cfq_io_context *__cic;



	read_lock(&cfq_exit_lock);



	cic->ioc = ioc;

	cic->key = cfqd;



	ioc->set_ioprio = cfq_ioc_set_ioprio;



restart:

	parent = NULL;

	p = &ioc->cic_root.rb_node;

	while (*p) {

		parent = *p;

		__cic = rb_entry(parent, struct cfq_io_context, rb_node);

		if (unlikely(!__cic->key)) {

			cfq_drop_dead_cic(ioc, cic);

			goto restart;

		}



		if (cic->key < __cic->key)

			p = &(*p)->rb_left;
@@ -1520,6 +1540,7 @@ cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 
			BUG();

	}



	read_lock(&cfq_exit_lock);

	rb_link_node(&cic->rb_node, parent, p);

	rb_insert_color(&cic->rb_node, &ioc->cic_root);

	list_add(&cic->queue_list, &cfqd->cic_list);