1 files changed, 20 insertions, 2 deletions

diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 81a8870ac224..6f1a2608e91f 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -100,6 +100,7 @@ struct io_cq {
  */
 struct io_context {
         atomic_long_t refcount;
+        atomic_t active_ref;
         atomic_t nr_tasks;
 
         /* all the fields below are protected by this lock */
@@ -120,17 +121,34 @@ struct io_context {
         struct work_struct release_work;
 };
 
-static inline void ioc_task_link(struct io_context *ioc)
+/**
+ * get_io_context_active - get active reference on ioc
+ * @ioc: ioc of interest
+ *
+ * Only iocs with active reference can issue new IOs.  This function
+ * acquires an active reference on @ioc.  The caller must already have an
+ * active reference on @ioc.
+ */
+static inline void get_io_context_active(struct io_context *ioc)
 {
         WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);
-        WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
+        WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0);
         atomic_long_inc(&ioc->refcount);
+        atomic_inc(&ioc->active_ref);
+}
+
+static inline void ioc_task_link(struct io_context *ioc)
+{
+        get_io_context_active(ioc);
+
+        WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
         atomic_inc(&ioc->nr_tasks);
 }
 
 struct task_struct;
 #ifdef CONFIG_BLOCK
 void put_io_context(struct io_context *ioc);
+void put_io_context_active(struct io_context *ioc);
 void exit_io_context(struct task_struct *task);
 struct io_context *get_task_io_context(struct task_struct *task,
                                        gfp_t gfp_flags, int node);