[PATCH] as-iosched: use new io context counting mechanism

It's ok if the read path is a lot more costly, as long as inc/dec is
really cheap. The inc/dec will happen for each created/freed io context,
while the reading only happens when a disk queue exits.

Signed-off-by: Jens Axboe <axboe@suse.de>

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 66015bc..8e1fef1 100644 (file)
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -149,7 +149,7 @@ enum arq_state {
 #define RQ_STATE(rq)   ((enum arq_state)(rq)->elevator_private2)
 #define RQ_SET_STATE(rq, state)        ((rq)->elevator_private2 = (void *) state)
 
 #define RQ_STATE(rq)   ((enum arq_state)(rq)->elevator_private2)
 #define RQ_SET_STATE(rq, state)        ((rq)->elevator_private2 = (void *) state)
 

-static atomic_t ioc_count = ATOMIC_INIT(0);
+static DEFINE_PER_CPU(unsigned long, ioc_count);

 static struct completion *ioc_gone;
 
 static void as_move_to_dispatch(struct as_data *ad, struct request *rq);
 static struct completion *ioc_gone;
 
 static void as_move_to_dispatch(struct as_data *ad, struct request *rq);


@@ -163,7 +163,8 @@ static void as_antic_stop(struct as_data *ad);
 static void free_as_io_context(struct as_io_context *aic)
 {
        kfree(aic);
 static void free_as_io_context(struct as_io_context *aic)
 {
        kfree(aic);

-       if (atomic_dec_and_test(&ioc_count) && ioc_gone)
+       elv_ioc_count_dec(ioc_count);
+       if (ioc_gone && !elv_ioc_count_read(ioc_count))

                complete(ioc_gone);
 }
 
                complete(ioc_gone);
 }
 


@@ -199,7 +200,7 @@ static struct as_io_context *alloc_as_io_context(void)
                ret->seek_total = 0;
                ret->seek_samples = 0;
                ret->seek_mean = 0;
                ret->seek_total = 0;
                ret->seek_samples = 0;
                ret->seek_mean = 0;

-               atomic_inc(&ioc_count);
+               elv_ioc_count_inc(ioc_count);

        }
 
        return ret;
        }
 
        return ret;


@@ -1484,7 +1485,7 @@ static void __exit as_exit(void)
        ioc_gone = &all_gone;
        /* ioc_gone's update must be visible before reading ioc_count */
        smp_wmb();
        ioc_gone = &all_gone;
        /* ioc_gone's update must be visible before reading ioc_count */
        smp_wmb();

-       if (atomic_read(&ioc_count))
+       if (elv_ioc_count_read(ioc_count))

                wait_for_completion(ioc_gone);
        synchronize_rcu();
 }
                wait_for_completion(ioc_gone);
        synchronize_rcu();
 }