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>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ff44435fad50ab41e74874b4591191314555ac66..ae7791a8ded90af4a63c0ee259300e3060ed4c20 100644 (file)
--- 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 581dd1bd3d3ecfdcbd3c126e59396ec73f112b3d..02604c89ddde7fd7476c0a9d6d619452002293e7 100644 (file)
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -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