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Commit 34e6bbf2 authored by Fabio Checconi's avatar Fabio Checconi Committed by Jens Axboe
Browse files

cfq-iosched: fix rcu freeing of cfq io contexts 



SLAB_DESTROY_BY_RCU is not a direct substitute for normal call_rcu()
freeing, since it'll page freeing but NOT object freeing. So change
cfq to do the freeing on its own.

Signed-off-by: default avatarFabio Checconi <fabio@gandalf.sssup.it>
Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 00d61e3e

block/cfq-iosched.c

+27 −30
Original line number Original line Diff line number Diff line
@@ -1143,24 +1143,37 @@ static void cfq_put_queue(struct cfq_queue *cfqq) 
}

}





/*

/*

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

 * Call func for each cic attached to this ioc.

 */

 */

static unsigned int

static void

call_for_each_cic(struct io_context *ioc,

call_for_each_cic(struct io_context *ioc,

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

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

{

{

	struct cfq_io_context *cic;

	struct cfq_io_context *cic;

	struct hlist_node *n;

	struct hlist_node *n;

	int called = 0;





	rcu_read_lock();

	rcu_read_lock();

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

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

		func(ioc, cic);

		func(ioc, cic);

		called++;

	}

	rcu_read_unlock();

	rcu_read_unlock();

}



static void cfq_cic_free_rcu(struct rcu_head *head)

{

	struct cfq_io_context *cic;



	cic = container_of(head, struct cfq_io_context, rcu_head);



	kmem_cache_free(cfq_ioc_pool, cic);

	elv_ioc_count_dec(ioc_count);



	if (ioc_gone && !elv_ioc_count_read(ioc_count))

		complete(ioc_gone);

}





	return called;

static void cfq_cic_free(struct cfq_io_context *cic)

{

	call_rcu(&cic->rcu_head, cfq_cic_free_rcu);

}

}





static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)

static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
@@ -1174,24 +1187,18 @@ static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 
	hlist_del_rcu(&cic->cic_list);

	hlist_del_rcu(&cic->cic_list);

	spin_unlock_irqrestore(&ioc->lock, flags);

	spin_unlock_irqrestore(&ioc->lock, flags);





	kmem_cache_free(cfq_ioc_pool, cic);

	cfq_cic_free(cic);

}

}





static void cfq_free_io_context(struct io_context *ioc)

static void cfq_free_io_context(struct io_context *ioc)

{

{

	int freed;



	/*

	/*

	 * ioc->refcount is zero here, so no more cic's are allowed to be

	 * ioc->refcount is zero here, or we are called from elv_unregister(),

	 * linked into this ioc. So it should be ok to iterate over the known

	 * so no more cic's are allowed to be linked into this ioc.  So it

	 * list, we will see all cic's since no new ones are added.

	 * should be ok to iterate over the known list, we will see all cic's

	 * since no new ones are added.

	 */

	 */

	freed = call_for_each_cic(ioc, cic_free_func);

	call_for_each_cic(ioc, cic_free_func);



	elv_ioc_count_mod(ioc_count, -freed);



	if (ioc_gone && !elv_ioc_count_read(ioc_count))

		complete(ioc_gone);

}

}





static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)

static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
@@ -1458,15 +1465,6 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, 
	return cfqq;

	return cfqq;

}

}





static void cfq_cic_free(struct cfq_io_context *cic)

{

	kmem_cache_free(cfq_ioc_pool, cic);

	elv_ioc_count_dec(ioc_count);



	if (ioc_gone && !elv_ioc_count_read(ioc_count))

		complete(ioc_gone);

}



/*

/*

 * We drop cfq io contexts lazily, so we may find a dead one.

 * We drop cfq io contexts lazily, so we may find a dead one.

 */

 */
@@ -2138,7 +2136,7 @@ static int __init cfq_slab_setup(void) 
	if (!cfq_pool)

	if (!cfq_pool)

		goto fail;

		goto fail;





	cfq_ioc_pool = KMEM_CACHE(cfq_io_context, SLAB_DESTROY_BY_RCU);

	cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);

	if (!cfq_ioc_pool)

	if (!cfq_ioc_pool)

		goto fail;

		goto fail;
@@ -2286,7 +2284,6 @@ static void __exit cfq_exit(void) 
	smp_wmb();

	smp_wmb();

	if (elv_ioc_count_read(ioc_count))

	if (elv_ioc_count_read(ioc_count))

		wait_for_completion(ioc_gone);

		wait_for_completion(ioc_gone);

	synchronize_rcu();

	cfq_slab_kill();

	cfq_slab_kill();

}

}

include/linux/iocontext.h

+3 −0
Original line number Original line Diff line number Diff line
@@ -2,6 +2,7 @@ 
#define IOCONTEXT_H

#define IOCONTEXT_H





#include <linux/radix-tree.h>

#include <linux/radix-tree.h>

#include <linux/rcupdate.h>





/*

/*

 * This is the per-process anticipatory I/O scheduler state.

 * This is the per-process anticipatory I/O scheduler state.
@@ -54,6 +55,8 @@ struct cfq_io_context { 




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

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

	void (*exit)(struct io_context *); /* called on task exit */

	void (*exit)(struct io_context *); /* called on task exit */



	struct rcu_head rcu_head;

};

};





/*

/*