[PATCH] fix the exclusion for ioprio_set()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 63bfe4b494ba3a13244fa5e042d4500e74153522..3bacf4bb7dd2ce62495c68f57ab65fda06bb5c16 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -47,6 +47,8 @@ static int cfq_slice_idle = HZ / 100;
  */
 static const int cfq_max_depth = 2;
 
+static DEFINE_RWLOCK(cfq_exit_lock);
+
 /*
  * for the hash of cfqq inside the cfqd
  */
@@ -1354,13 +1356,19 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
  */
 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
 {
-       struct cfq_io_context *cic = ioc->cic;
+       struct cfq_io_context *cic;
+
+       write_lock(&cfq_exit_lock);
+
+       cic = ioc->cic;
 
        changed_ioprio(cic);
 
        list_for_each_entry(cic, &cic->list, list)
                changed_ioprio(cic);
 
+       write_unlock(&cfq_exit_lock);
+
        return 0;
 }
 
@@ -1450,8 +1458,10 @@ cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, gfp_t gfp_mask)
                 */
                cic->ioc = ioc;
                cic->key = cfqd;
+               read_lock(&cfq_exit_lock);
                ioc->set_ioprio = cfq_ioc_set_ioprio;
                ioc->cic = cic;
+               read_unlock(&cfq_exit_lock);
        } else {
                struct cfq_io_context *__cic;
 
@@ -1487,7 +1497,9 @@ cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, gfp_t gfp_mask)
 
                __cic->ioc = ioc;
                __cic->key = cfqd;
+               read_lock(&cfq_exit_lock);
                list_add(&__cic->list, &cic->list);
+               read_unlock(&cfq_exit_lock);
                cic = __cic;
        }