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    Subject[PATCH 04/16] elevator: make elevator_init_fn() return 0/-errno
    Date
    From: Tejun Heo <tejun@google.com>

    elevator_ops->elevator_init_fn() has a weird return value. It returns
    a void * which the caller should assign to q->elevator->elevator_data
    and %NULL return denotes init failure.

    Update such that it returns integer 0/-errno and sets elevator_data
    directly as necessary.

    This makes the interface more conventional and eases further cleanup.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Vivek Goyal <vgoyal@redhat.com>
    ---
    block/cfq-iosched.c | 9 +++++----
    block/deadline-iosched.c | 8 +++++---
    block/elevator.c | 12 ++----------
    block/noop-iosched.c | 8 +++++---
    include/linux/elevator.h | 2 +-
    5 files changed, 18 insertions(+), 21 deletions(-)

    diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
    index 529dfba..f3d6b04 100644
    --- a/block/cfq-iosched.c
    +++ b/block/cfq-iosched.c
    @@ -3662,7 +3662,7 @@ static void cfq_exit_queue(struct elevator_queue *e)
    kfree(cfqd);
    }

    -static void *cfq_init_queue(struct request_queue *q)
    +static int cfq_init_queue(struct request_queue *q)
    {
    struct cfq_data *cfqd;
    int i, j;
    @@ -3671,7 +3671,7 @@ static void *cfq_init_queue(struct request_queue *q)

    cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
    if (!cfqd)
    - return NULL;
    + return -ENOMEM;

    /* Init root service tree */
    cfqd->grp_service_tree = CFQ_RB_ROOT;
    @@ -3698,7 +3698,7 @@ static void *cfq_init_queue(struct request_queue *q)
    if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
    kfree(cfqg);
    kfree(cfqd);
    - return NULL;
    + return -ENOMEM;
    }

    rcu_read_lock();
    @@ -3729,6 +3729,7 @@ static void *cfq_init_queue(struct request_queue *q)
    cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);

    cfqd->queue = q;
    + q->elevator->elevator_data = cfqd;

    init_timer(&cfqd->idle_slice_timer);
    cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
    @@ -3753,7 +3754,7 @@ static void *cfq_init_queue(struct request_queue *q)
    * second, in order to have larger depth for async operations.
    */
    cfqd->last_delayed_sync = jiffies - HZ;
    - return cfqd;
    + return 0;
    }

    /*
    diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
    index 7bf12d7..599b12e 100644
    --- a/block/deadline-iosched.c
    +++ b/block/deadline-iosched.c
    @@ -337,13 +337,13 @@ static void deadline_exit_queue(struct elevator_queue *e)
    /*
    * initialize elevator private data (deadline_data).
    */
    -static void *deadline_init_queue(struct request_queue *q)
    +static int deadline_init_queue(struct request_queue *q)
    {
    struct deadline_data *dd;

    dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
    if (!dd)
    - return NULL;
    + return -ENOMEM;

    INIT_LIST_HEAD(&dd->fifo_list[READ]);
    INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
    @@ -354,7 +354,9 @@ static void *deadline_init_queue(struct request_queue *q)
    dd->writes_starved = writes_starved;
    dd->front_merges = 1;
    dd->fifo_batch = fifo_batch;
    - return dd;
    +
    + q->elevator->elevator_data = dd;
    + return 0;
    }

    /*
    diff --git a/block/elevator.c b/block/elevator.c
    index 42543e3..8dc65b1 100644
    --- a/block/elevator.c
    +++ b/block/elevator.c
    @@ -168,14 +168,6 @@ static struct elevator_type *elevator_get(const char *name)
    return e;
    }

    -static int elevator_init_queue(struct request_queue *q)
    -{
    - q->elevator->elevator_data = q->elevator->type->ops.elevator_init_fn(q);
    - if (q->elevator->elevator_data)
    - return 0;
    - return -ENOMEM;
    -}
    -
    static char chosen_elevator[ELV_NAME_MAX];

    static int __init elevator_setup(char *str)
    @@ -271,7 +263,7 @@ int elevator_init(struct request_queue *q, char *name)
    if (!q->elevator)
    return -ENOMEM;

    - err = elevator_init_queue(q);
    + err = e->ops.elevator_init_fn(q);
    if (err) {
    kobject_put(&q->elevator->kobj);
    return err;
    @@ -974,7 +966,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
    if (!q->elevator)
    goto fail_init;

    - err = elevator_init_queue(q);
    + err = new_e->ops.elevator_init_fn(q);
    if (err) {
    kobject_put(&q->elevator->kobj);
    goto fail_init;
    diff --git a/block/noop-iosched.c b/block/noop-iosched.c
    index 413a0b1..5d1bf70 100644
    --- a/block/noop-iosched.c
    +++ b/block/noop-iosched.c
    @@ -59,15 +59,17 @@ noop_latter_request(struct request_queue *q, struct request *rq)
    return list_entry(rq->queuelist.next, struct request, queuelist);
    }

    -static void *noop_init_queue(struct request_queue *q)
    +static int noop_init_queue(struct request_queue *q)
    {
    struct noop_data *nd;

    nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
    if (!nd)
    - return NULL;
    + return -ENOMEM;
    +
    INIT_LIST_HEAD(&nd->queue);
    - return nd;
    + q->elevator->elevator_data = nd;
    + return 0;
    }

    static void noop_exit_queue(struct elevator_queue *e)
    diff --git a/include/linux/elevator.h b/include/linux/elevator.h
    index c24f3d7..d7726c9 100644
    --- a/include/linux/elevator.h
    +++ b/include/linux/elevator.h
    @@ -33,7 +33,7 @@ typedef void (elevator_put_req_fn) (struct request *);
    typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
    typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);

    -typedef void *(elevator_init_fn) (struct request_queue *);
    +typedef int (elevator_init_fn) (struct request_queue *);
    typedef void (elevator_exit_fn) (struct elevator_queue *);

    struct elevator_ops
    --
    1.7.7.3


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