cfq-iosched: preparation to handle multiple service trees

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>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 19 insertions, 11 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 97d946585bc3..c95c69e199f4 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -75,8 +75,9 @@ 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
@@ -128,6 +129,7 @@ struct cfq_queue {
 
         pid_t pid;
 
+        struct cfq_rb_root *service_tree;
         struct cfq_queue *new_cfqq;
 };
 
@@ -503,6 +505,7 @@ 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;
 }
 
 /*
@@ -553,11 +556,12 @@ 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;
@@ -575,7 +579,7 @@ 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;
         }
 
@@ -586,12 +590,14 @@ 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;
 
@@ -623,11 +629,12 @@ 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 *
@@ -730,8 +737,10 @@ 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;
@@ -2292,10 +2301,9 @@ 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);
 }