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Commit ffc4e759 authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: add hlist for browsing parallel to the radix tree 

It's cumbersome to browse a radix tree from start to finish, especially
since we modify keys when a process exits. So add a hlist for the single
purpose of browsing over all known cfq_io_contexts, used for exit,
io prio change, etc.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=9948



Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 84e9e03c

block/blk-ioc.c

+15 −20
Original line number Diff line number Diff line
@@ -17,17 +17,13 @@ static struct kmem_cache *iocontext_cachep; 


static void cfq_dtor(struct io_context *ioc)

{

	struct cfq_io_context *cic[1];

	int r;

	if (!hlist_empty(&ioc->cic_list)) {

		struct cfq_io_context *cic;



	/*

	 * We don't have a specific key to lookup with, so use the gang

	 * lookup to just retrieve the first item stored. The cfq exit

	 * function will iterate the full tree, so any member will do.

	 */

	r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);

	if (r > 0)

		cic[0]->dtor(ioc);

		cic = list_entry(ioc->cic_list.first, struct cfq_io_context,

								cic_list);

		cic->dtor(ioc);

	}

}



/*
@@ -57,18 +53,16 @@ EXPORT_SYMBOL(put_io_context); 


static void cfq_exit(struct io_context *ioc)

{

	struct cfq_io_context *cic[1];

	int r;



	rcu_read_lock();

	/*

	 * See comment for cfq_dtor()

	 */

	r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);

	rcu_read_unlock();



	if (r > 0)

		cic[0]->exit(ioc);

	if (!hlist_empty(&ioc->cic_list)) {

		struct cfq_io_context *cic;



		cic = list_entry(ioc->cic_list.first, struct cfq_io_context,

								cic_list);

		cic->exit(ioc);

	}

	rcu_read_unlock();

}



/* Called by the exitting task */
@@ -105,6 +99,7 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) 
		ret->nr_batch_requests = 0; /* because this is 0 */

		ret->aic = NULL;

		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);

		INIT_HLIST_HEAD(&ret->cic_list);

		ret->ioc_data = NULL;

	}

block/cfq-iosched.c

+12 −26
Original line number Diff line number Diff line
@@ -1145,38 +1145,19 @@ static void cfq_put_queue(struct cfq_queue *cfqq) 
/*

 * Call func for each cic attached to this ioc. Returns number of cic's seen.

 */

#define CIC_GANG_NR	16

static unsigned int

call_for_each_cic(struct io_context *ioc,

		  void (*func)(struct io_context *, struct cfq_io_context *))

{

	struct cfq_io_context *cics[CIC_GANG_NR];

	unsigned long index = 0;

	unsigned int called = 0;

	int nr;

	struct cfq_io_context *cic;

	struct hlist_node *n;

	int called = 0;



	rcu_read_lock();



	do {

		int i;



		/*

		 * Perhaps there's a better way - this just gang lookups from

		 * 0 to the end, restarting after each CIC_GANG_NR from the

		 * last key + 1.

		 */

		nr = radix_tree_gang_lookup(&ioc->radix_root, (void **) cics,

						index, CIC_GANG_NR);

		if (!nr)

			break;



		called += nr;

		index = 1 + (unsigned long) cics[nr - 1]->key;



		for (i = 0; i < nr; i++)

			func(ioc, cics[i]);

	} while (nr == CIC_GANG_NR);



	hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) {

		func(ioc, cic);

		called++;

	}

	rcu_read_unlock();



	return called;
@@ -1190,6 +1171,7 @@ static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 


	spin_lock_irqsave(&ioc->lock, flags);

	radix_tree_delete(&ioc->radix_root, cic->dead_key);

	hlist_del_rcu(&cic->cic_list);

	spin_unlock_irqrestore(&ioc->lock, flags);



	kmem_cache_free(cfq_ioc_pool, cic);
@@ -1280,6 +1262,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 
	if (cic) {

		cic->last_end_request = jiffies;

		INIT_LIST_HEAD(&cic->queue_list);

		INIT_HLIST_NODE(&cic->cic_list);

		cic->dtor = cfq_free_io_context;

		cic->exit = cfq_exit_io_context;

		elv_ioc_count_inc(ioc_count);
@@ -1501,6 +1484,7 @@ cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 
		rcu_assign_pointer(ioc->ioc_data, NULL);



	radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);

	hlist_del_rcu(&cic->cic_list);

	spin_unlock_irqrestore(&ioc->lock, flags);



	cfq_cic_free(cic);
@@ -1561,6 +1545,8 @@ static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 
		spin_lock_irqsave(&ioc->lock, flags);

		ret = radix_tree_insert(&ioc->radix_root,

						(unsigned long) cfqd, cic);

		if (!ret)

			hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);

		spin_unlock_irqrestore(&ioc->lock, flags);



		radix_tree_preload_end();

include/linux/iocontext.h

+2 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ struct cfq_io_context { 
	sector_t seek_mean;



	struct list_head queue_list;

	struct hlist_node cic_list;



	void (*dtor)(struct io_context *); /* destructor */

	void (*exit)(struct io_context *); /* called on task exit */
@@ -77,6 +78,7 @@ struct io_context { 


	struct as_io_context *aic;

	struct radix_tree_root radix_root;

	struct hlist_head cic_list;

	void *ioc_data;

};