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block, cfq: kill ioc_gone 

Now that cic's are immediately unlinked under both locks, there's no
need to count and drain cic's before module unload.  RCU callback
completion is waited with rcu_barrier().

While at it, remove residual RCU operations on cic_list.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2011-12-14 00:33:39 +01:00 committed by Jens Axboe
parent b9a1920837
commit b50b636bce
2 changed files with 5 additions and 55 deletions
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43
block/cfq-iosched.c
View File

@ -62,10 +62,6 @@ static const int cfq_hist_divisor = 4;
static struct kmem_cache *cfq_pool;
static struct kmem_cache *cfq_ioc_pool;
static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
static struct completion *ioc_gone;
static DEFINE_SPINLOCK(ioc_gone_lock);
#define CFQ_PRIO_LISTS IOPRIO_BE_NR
#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
@ -2671,26 +2667,8 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
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(cfq_ioc_count);
if (ioc_gone) {
/*
* CFQ scheduler is exiting, grab exit lock and check
* the pending io context count. If it hits zero,
* complete ioc_gone and set it back to NULL
*/
spin_lock(&ioc_gone_lock);
if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
complete(ioc_gone);
ioc_gone = NULL;
}
spin_unlock(&ioc_gone_lock);
}
kmem_cache_free(cfq_ioc_pool,
container_of(head, struct cfq_io_context, rcu_head));
}
static void cfq_cic_free(struct cfq_io_context *cic)
@ -2705,7 +2683,7 @@ static void cfq_release_cic(struct cfq_io_context *cic)
BUG_ON(!(dead_key & CIC_DEAD_KEY));
radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT);
hlist_del_rcu(&cic->cic_list);
hlist_del(&cic->cic_list);
cfq_cic_free(cic);
}
@ -2782,7 +2760,6 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
INIT_HLIST_NODE(&cic->cic_list);
cic->exit = cfq_exit_cic;
cic->release = cfq_release_cic;
elv_ioc_count_inc(cfq_ioc_count);
}
return cic;
@ -3072,7 +3049,7 @@ static int cfq_create_cic(struct cfq_data *cfqd, gfp_t gfp_mask)
ret = radix_tree_insert(&ioc->radix_root, q->id, cic);
if (likely(!ret)) {
hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
hlist_add_head(&cic->cic_list, &ioc->cic_list);
list_add(&cic->queue_list, &cfqd->cic_list);
cic = NULL;
} else if (ret == -EEXIST) {
@ -4156,19 +4133,9 @@ static int __init cfq_init(void)
static void __exit cfq_exit(void)
{
DECLARE_COMPLETION_ONSTACK(all_gone);
blkio_policy_unregister(&blkio_policy_cfq);
elv_unregister(&iosched_cfq);
ioc_gone = &all_gone;
/* ioc_gone's update must be visible before reading ioc_count */
smp_wmb();
/*
* this also protects us from entering cfq_slab_kill() with
* pending RCU callbacks
*/
if (elv_ioc_count_read(cfq_ioc_count))
wait_for_completion(&all_gone);
rcu_barrier(); /* make sure all cic RCU frees are complete */
cfq_slab_kill();
}

17
include/linux/elevator.h
View File

@ -196,22 +196,5 @@ enum {
INIT_LIST_HEAD(&(rq)->csd.list); \
} while (0)
/*
* io context count accounting
*/
#define elv_ioc_count_mod(name, __val) this_cpu_add(name, __val)
#define elv_ioc_count_inc(name) this_cpu_inc(name)
#define elv_ioc_count_dec(name) this_cpu_dec(name)
#define elv_ioc_count_read(name) \
({ \
unsigned long __val = 0; \
int __cpu; \
smp_wmb(); \
for_each_possible_cpu(__cpu) \
__val += per_cpu(name, __cpu); \
__val; \
})
#endif /* CONFIG_BLOCK */
#endif