[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>

1 files changed, 27 insertions, 6 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 01820b1094e9..246feae16c60 100644
--- 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);