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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: Fabio Checconi <fabio@gandalf.sssup.it>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Fabio Checconi 2008-04-02 14:31:02 +02:00 committed by Jens Axboe
parent 00d61e3e8c
commit 34e6bbf23c
2 changed files with 30 additions and 30 deletions
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57
block/cfq-iosched.c
View File

@ -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,
void (*func)(struct io_context *, struct cfq_io_context *))
{
struct cfq_io_context *cic;
struct hlist_node *n;
int called = 0;
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);
called++;
}
rcu_read_unlock();
}
return called;
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);
}
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)
@ -1174,24 +1187,18 @@ static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
hlist_del_rcu(&cic->cic_list);
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)
{
int freed;
/*
* ioc->refcount is zero here, so no more cic's are allowed to be
* linked into this ioc. So it should be ok to iterate over the known
* list, we will see all cic's since no new ones are added.
* ioc->refcount is zero here, or we are called from elv_unregister(),
* so no more cic's are allowed to be linked into this ioc. So it
* 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);
elv_ioc_count_mod(ioc_count, -freed);
if (ioc_gone && !elv_ioc_count_read(ioc_count))
complete(ioc_gone);
call_for_each_cic(ioc, cic_free_func);
}
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;
}
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.
*/
@ -2138,7 +2136,7 @@ static int __init cfq_slab_setup(void)
if (!cfq_pool)
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)
goto fail;
@ -2286,7 +2284,6 @@ static void __exit cfq_exit(void)
smp_wmb();
if (elv_ioc_count_read(ioc_count))
wait_for_completion(ioc_gone);
synchronize_rcu();
cfq_slab_kill();
}

3
include/linux/iocontext.h
View File

@ -2,6 +2,7 @@
#define IOCONTEXT_H
#include <linux/radix-tree.h>
#include <linux/rcupdate.h>
/*
* 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 (*exit)(struct io_context *); /* called on task exit */
struct rcu_head rcu_head;
};
/*