[PATCH 2/2] cfq: fix cic's rbtree traversal

When queue dies, we set cic->key=NULL as dead mark. So, when we
traverse a rbtree, we must check whether it's still valid key. if it
was invalidated, drop it, then restart the traversal from top.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Jens Axboe <axboe@suse.de>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 01820b1..246feae 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1472,15 +1472,31 @@ out:
        return cfqq;
 }
 
+static void
+cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
+{
+       read_lock(&cfq_exit_lock);
+       rb_erase(&cic->rb_node, &ioc->cic_root);
+       read_unlock(&cfq_exit_lock);
+       kmem_cache_free(cfq_ioc_pool, cic);
+       atomic_dec(&ioc_count);
+}
+
 static struct cfq_io_context *
 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
 {
-       struct rb_node *n = ioc->cic_root.rb_node;
+       struct rb_node *n;
        struct cfq_io_context *cic;
        void *key = cfqd;
 
+restart:
+       n = ioc->cic_root.rb_node;
        while (n) {
                cic = rb_entry(n, struct cfq_io_context, rb_node);
+               if (unlikely(!cic->key)) {
+                       cfq_drop_dead_cic(ioc, cic);
+                       goto restart;
+               }
 
                if (key < cic->key)
                        n = n->rb_left;
@@ -1497,20 +1513,24 @@ static inline void
 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
             struct cfq_io_context *cic)
 {
-       struct rb_node **p = &ioc->cic_root.rb_node;
-       struct rb_node *parent = NULL;
+       struct rb_node **p;
+       struct rb_node *parent;
        struct cfq_io_context *__cic;
 
-       read_lock(&cfq_exit_lock);
-
        cic->ioc = ioc;
        cic->key = cfqd;
 
        ioc->set_ioprio = cfq_ioc_set_ioprio;
-
+restart:
+       parent = NULL;
+       p = &ioc->cic_root.rb_node;
        while (*p) {
                parent = *p;
                __cic = rb_entry(parent, struct cfq_io_context, rb_node);
+               if (unlikely(!__cic->key)) {
+                       cfq_drop_dead_cic(ioc, cic);
+                       goto restart;
+               }
 
                if (cic->key < __cic->key)
                        p = &(*p)->rb_left;
@@ -1520,6 +1540,7 @@ cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
                        BUG();
        }
 
+       read_lock(&cfq_exit_lock);
        rb_link_node(&cic->rb_node, parent, p);
        rb_insert_color(&cic->rb_node, &ioc->cic_root);
        list_add(&cic->queue_list, &cfqd->cic_list);