block: add io_context->active_ref

[deliverable/linux.git] / include / linux / iocontext.h

diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 1a30180630343dabd49aa886fc7621964912afdf..6f1a2608e91f36704c9638cb2d84a7f23f95f502 100644 (file)
--- 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 */
@@ -120,23 +121,34 @@ struct io_context {
        struct work_struct release_work;
 };
 
-static inline struct io_context *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)
 {
-       /*
-        * if ref count is zero, don't allow sharing (ioc is going away, it's
-        * a race).
-        */
-       if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {
-               atomic_inc(&ioc->nr_tasks);
-               return ioc;
-       }
+       WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 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);
 
-       return NULL;
+       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);