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    Subject[RFC V2 PATCH 2/5] cfq-iosched: preparation to handle multiple service trees
    Date
    We embed a pointer to the service tree in each queue, to handle multiple
    service trees easily.
    Service trees are enriched with a counter.
    cfq_add_rq_rb is invoked after putting the rq in the fifo, to ensure
    that all fields in rq are properly initialized.

    Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
    ---
    block/cfq-iosched.c | 33 ++++++++++++++++++++++-----------
    1 files changed, 22 insertions(+), 11 deletions(-)

    diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
    index 25a3f46..c59609c 100644
    --- a/block/cfq-iosched.c
    +++ b/block/cfq-iosched.c
    @@ -69,8 +69,9 @@ static DEFINE_SPINLOCK(ioc_gone_lock);
    struct cfq_rb_root {
    struct rb_root rb;
    struct rb_node *left;
    + unsigned count;
    };
    -#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
    +#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }

    /*
    * Per process-grouping structure
    @@ -115,6 +116,9 @@ struct cfq_queue {
    unsigned short ioprio_class, org_ioprio_class;

    pid_t pid;
    +
    + struct cfq_rb_root *service_tree;
    + struct cfq_io_context *cic;
    };

    /*
    @@ -254,6 +258,7 @@ static inline void cic_set_cfqq(struct cfq_io_context *cic,
    struct cfq_queue *cfqq, bool is_sync)
    {
    cic->cfqq[is_sync] = cfqq;
    + cfqq->cic = cic;
    }

    /*
    @@ -482,6 +487,7 @@ static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
    if (root->left == n)
    root->left = NULL;
    rb_erase_init(n, &root->rb);
    + --root->count;
    }

    /*
    @@ -532,11 +538,12 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
    struct rb_node **p, *parent;
    struct cfq_queue *__cfqq;
    unsigned long rb_key;
    + struct cfq_rb_root *service_tree = &cfqd->service_tree;
    int left;

    if (cfq_class_idle(cfqq)) {
    rb_key = CFQ_IDLE_DELAY;
    - parent = rb_last(&cfqd->service_tree.rb);
    + parent = rb_last(&service_tree->rb);
    if (parent && parent != &cfqq->rb_node) {
    __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
    rb_key += __cfqq->rb_key;
    @@ -554,7 +561,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
    cfqq->slice_resid = 0;
    } else {
    rb_key = -HZ;
    - __cfqq = cfq_rb_first(&cfqd->service_tree);
    + __cfqq = cfq_rb_first(service_tree);
    rb_key += __cfqq ? __cfqq->rb_key : jiffies;
    }

    @@ -565,12 +572,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
    if (rb_key == cfqq->rb_key)
    return;

    - cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
    + cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
    + cfqq->service_tree = NULL;
    }

    left = 1;
    parent = NULL;
    - p = &cfqd->service_tree.rb.rb_node;
    + cfqq->service_tree = service_tree;
    + p = &service_tree->rb.rb_node;
    while (*p) {
    struct rb_node **n;

    @@ -602,11 +611,12 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
    }

    if (left)
    - cfqd->service_tree.left = &cfqq->rb_node;
    + service_tree->left = &cfqq->rb_node;

    cfqq->rb_key = rb_key;
    rb_link_node(&cfqq->rb_node, parent, p);
    - rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
    + rb_insert_color(&cfqq->rb_node, &service_tree->rb);
    + service_tree->count++;
    }

    static struct cfq_queue *
    @@ -709,8 +719,10 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
    BUG_ON(!cfq_cfqq_on_rr(cfqq));
    cfq_clear_cfqq_on_rr(cfqq);

    - if (!RB_EMPTY_NODE(&cfqq->rb_node))
    - cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
    + if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
    + cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
    + cfqq->service_tree = NULL;
    + }
    if (cfqq->p_root) {
    rb_erase(&cfqq->p_node, cfqq->p_root);
    cfqq->p_root = NULL;
    @@ -2194,10 +2206,9 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
    cfq_log_cfqq(cfqd, cfqq, "insert_request");
    cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);

    - cfq_add_rq_rb(rq);
    -
    rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
    list_add_tail(&rq->queuelist, &cfqq->fifo);
    + cfq_add_rq_rb(rq);

    cfq_rq_enqueued(cfqd, cfqq, rq);
    }
    --
    1.6.2.5



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