[PATCH] fix the exclusion for ioprio_set()

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

1 files changed, 13 insertions, 1 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 63bfe4b494ba..3bacf4bb7dd2 100644
--- 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;
         }