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    Subject[PATCH v3 1/8] cfq-iosched: add symmetric reference wrappers
    Date
    The cfq_group and cfq_queue objects did not have symmetric
    wrapper functions and many of the reference taking was
    open coded. For clarity add the following wrappers:

    cfq_group:
    - cfq_get_group_ref()
    - cfq_put_group_ref()

    cfq_queue:
    - cfq_get_queue_ref()
    - cfq_put_queue_ref()

    The use of '_ref' was done not to collide with existing
    function names.

    Signed-off-by: Justin TerAvest <teravest@google.com>
    ---
    block/cfq-iosched.c | 95 +++++++++++++++++++++++++++++---------------------
    1 files changed, 55 insertions(+), 40 deletions(-)

    diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
    index 12e380b..74510f5 100644
    --- a/block/cfq-iosched.c
    +++ b/block/cfq-iosched.c
    @@ -303,6 +303,11 @@ struct cfq_data {
    struct rcu_head rcu;
    };

    +static void cfq_get_group_ref(struct cfq_group *cfqg);
    +static void cfq_put_group_ref(struct cfq_group *cfqg);
    +static void cfq_get_queue_ref(struct cfq_queue *cfqq);
    +static void cfq_put_queue_ref(struct cfq_queue *cfqq);
    +
    static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);

    static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
    @@ -1048,7 +1053,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
    * elevator which will be dropped by either elevator exit
    * or cgroup deletion path depending on who is exiting first.
    */
    - cfqg->ref = 1;
    + cfq_get_group_ref(cfqg);

    /*
    * Add group onto cgroup list. It might happen that bdi->dev is
    @@ -1091,24 +1096,12 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
    return cfqg;
    }

    -static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
    +static void cfq_get_group_ref(struct cfq_group *cfqg)
    {
    cfqg->ref++;
    - return cfqg;
    }

    -static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
    -{
    - /* Currently, all async queues are mapped to root group */
    - if (!cfq_cfqq_sync(cfqq))
    - cfqg = &cfqq->cfqd->root_group;
    -
    - cfqq->cfqg = cfqg;
    - /* cfqq reference on cfqg */
    - cfqq->cfqg->ref++;
    -}
    -
    -static void cfq_put_cfqg(struct cfq_group *cfqg)
    +static void cfq_put_group_ref(struct cfq_group *cfqg)
    {
    struct cfq_rb_root *st;
    int i, j;
    @@ -1122,6 +1115,17 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
    kfree(cfqg);
    }

    +static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
    +{
    + /* Currently, all async queues are mapped to root group */
    + if (!cfq_cfqq_sync(cfqq))
    + cfqg = &cfqq->cfqd->root_group;
    +
    + cfqq->cfqg = cfqg;
    + /* cfqq reference on cfqg */
    + cfq_get_group_ref(cfqq->cfqg);
    +}
    +
    static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
    {
    /* Something wrong if we are trying to remove same group twice */
    @@ -1133,7 +1137,7 @@ static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
    * Put the reference taken at the time of creation so that when all
    * queues are gone, group can be destroyed.
    */
    - cfq_put_cfqg(cfqg);
    + cfq_put_group_ref(cfqg);
    }

    static void cfq_release_cfq_groups(struct cfq_data *cfqd)
    @@ -1177,14 +1181,18 @@ void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
    }

    #else /* GROUP_IOSCHED */
    -static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
    +
    +static void cfq_get_group_ref(struct cfq_group *cfqg)
    {
    - return &cfqd->root_group;
    }

    -static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
    +static void cfq_put_group_ref(struct cfq_group *cfqg)
    {
    - return cfqg;
    +}
    +
    +static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
    +{
    + return &cfqd->root_group;
    }

    static inline void
    @@ -1193,7 +1201,6 @@ cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
    }

    static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
    -static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}

    #endif /* GROUP_IOSCHED */

    @@ -2553,6 +2560,11 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
    return 1;
    }

    +static void cfq_get_queue_ref(struct cfq_queue *cfqq)
    +{
    + cfqq->ref++;
    +}
    +
    /*
    * task holds one reference to the queue, dropped when task exits. each rq
    * in-flight on this queue also holds a reference, dropped when rq is freed.
    @@ -2560,7 +2572,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
    * Each cfq queue took a reference on the parent group. Drop it now.
    * queue lock must be held here.
    */
    -static void cfq_put_queue(struct cfq_queue *cfqq)
    +static void cfq_put_queue_ref(struct cfq_queue *cfqq)
    {
    struct cfq_data *cfqd = cfqq->cfqd;
    struct cfq_group *cfqg;
    @@ -2583,7 +2595,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)

    BUG_ON(cfq_cfqq_on_rr(cfqq));
    kmem_cache_free(cfq_pool, cfqq);
    - cfq_put_cfqg(cfqg);
    + cfq_put_group_ref(cfqg);
    }

    /*
    @@ -2688,7 +2700,7 @@ static void cfq_put_cooperator(struct cfq_queue *cfqq)
    break;
    }
    next = __cfqq->new_cfqq;
    - cfq_put_queue(__cfqq);
    + cfq_put_queue_ref(__cfqq);
    __cfqq = next;
    }
    }
    @@ -2702,7 +2714,7 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)

    cfq_put_cooperator(cfqq);

    - cfq_put_queue(cfqq);
    + cfq_put_queue_ref(cfqq);
    }

    static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
    @@ -2844,7 +2856,7 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
    GFP_ATOMIC);
    if (new_cfqq) {
    cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
    - cfq_put_queue(cfqq);
    + cfq_put_queue_ref(cfqq);
    }
    }

    @@ -2903,7 +2915,7 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
    */
    cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
    cic_set_cfqq(cic, NULL, 1);
    - cfq_put_queue(sync_cfqq);
    + cfq_put_queue_ref(sync_cfqq);
    }

    spin_unlock_irqrestore(q->queue_lock, flags);
    @@ -3004,11 +3016,11 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
    * pin the queue now that it's allocated, scheduler exit will prune it
    */
    if (!is_sync && !(*async_cfqq)) {
    - cfqq->ref++;
    + cfq_get_queue_ref(cfqq);
    *async_cfqq = cfqq;
    }

    - cfqq->ref++;
    + cfq_get_queue_ref(cfqq);
    return cfqq;
    }

    @@ -3633,10 +3645,10 @@ static void cfq_put_request(struct request *rq)
    rq->elevator_private[1] = NULL;

    /* Put down rq reference on cfqg */
    - cfq_put_cfqg(RQ_CFQG(rq));
    + cfq_put_group_ref(RQ_CFQG(rq));
    rq->elevator_private[2] = NULL;

    - cfq_put_queue(cfqq);
    + cfq_put_queue_ref(cfqq);
    }
    }

    @@ -3647,7 +3659,7 @@ cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
    cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
    cic_set_cfqq(cic, cfqq->new_cfqq, 1);
    cfq_mark_cfqq_coop(cfqq->new_cfqq);
    - cfq_put_queue(cfqq);
    + cfq_put_queue_ref(cfqq);
    return cic_to_cfqq(cic, 1);
    }

    @@ -3669,7 +3681,7 @@ split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)

    cfq_put_cooperator(cfqq);

    - cfq_put_queue(cfqq);
    + cfq_put_queue_ref(cfqq);
    return NULL;
    }
    /*
    @@ -3722,10 +3734,12 @@ new_queue:

    cfqq->allocated[rw]++;

    - cfqq->ref++;
    + cfq_get_queue_ref(cfqq);
    rq->elevator_private[0] = cic;
    rq->elevator_private[1] = cfqq;
    - rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
    +
    + cfq_get_group_ref(cfqq->cfqg);
    + rq->elevator_private[2] = cfqq->cfqg;
    spin_unlock_irqrestore(q->queue_lock, flags);
    return 0;

    @@ -3818,13 +3832,13 @@ static void cfq_put_async_queues(struct cfq_data *cfqd)

    for (i = 0; i < IOPRIO_BE_NR; i++) {
    if (cfqd->async_cfqq[0][i])
    - cfq_put_queue(cfqd->async_cfqq[0][i]);
    + cfq_put_queue_ref(cfqd->async_cfqq[0][i]);
    if (cfqd->async_cfqq[1][i])
    - cfq_put_queue(cfqd->async_cfqq[1][i]);
    + cfq_put_queue_ref(cfqd->async_cfqq[1][i]);
    }

    if (cfqd->async_idle_cfqq)
    - cfq_put_queue(cfqd->async_idle_cfqq);
    + cfq_put_queue_ref(cfqd->async_idle_cfqq);
    }

    static void cfq_cfqd_free(struct rcu_head *head)
    @@ -3922,9 +3936,10 @@ static void *cfq_init_queue(struct request_queue *q)
    #ifdef CONFIG_CFQ_GROUP_IOSCHED
    /*
    * Take a reference to root group which we never drop. This is just
    - * to make sure that cfq_put_cfqg() does not try to kfree root group
    + * to make sure that cfq_put_group_ref() does not try to kfree
    + * root group
    */
    - cfqg->ref = 1;
    + cfq_get_group_ref(cfqg);
    rcu_read_lock();
    cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
    (void *)cfqd, 0);
    --
    1.7.3.1


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      Last update: 2011-03-30 18:55    [W:0.034 / U:117.352 seconds]
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