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Date: Tue, 25 Oct 2011 18:48:38 -0700
From: Tejun Heo <tj@...nel.org>
To: axboe@...nel.dk, vgoyal@...hat.com
Cc: ctalbott@...gle.com, rni@...gle.com, linux-kernel@...r.kernel.org,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 12/13] 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@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>
---
block/cfq-iosched.c | 43 +++++--------------------------------------
include/linux/elevator.h | 17 -----------------
2 files changed, 5 insertions(+), 55 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ff44435..ae7791a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -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();
}
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 2f6193e..a5a88f1 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -194,22 +194,5 @@ 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
--
1.7.3.1
--
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