io context sharing: preliminary support

[linux-2.6-omap-h63xx.git] / include / linux / iocontext.h

diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 186807ea62e21d6bbceb8ba1bd1701e358a72b16..cd44d458124ae21d4a57d88d571914dceede0738 100644 (file)
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -54,13 +54,15 @@ struct cfq_io_context {
 };
 
 /*
- * This is the per-process I/O subsystem state.  It is refcounted and
- * kmalloc'ed. Currently all fields are modified in process io context
- * (apart from the atomic refcount), so require no locking.
+ * I/O subsystem state of the associated processes.  It is refcounted
+ * and kmalloc'ed. These could be shared between processes.
  */
 struct io_context {
        atomic_t refcount;
-       struct task_struct *task;
+       atomic_t nr_tasks;
+
+       /* all the fields below are protected by this lock */
+       spinlock_t lock;
 
        unsigned short ioprio;
        unsigned short ioprio_changed;
@@ -76,4 +78,16 @@ struct io_context {
        void *ioc_data;
 };
 
+static inline struct io_context *ioc_task_link(struct io_context *ioc)
+{
+       /*
+        * if ref count is zero, don't allow sharing (ioc is going away, it's
+        * a race).
+        */
+       if (ioc && atomic_inc_not_zero(&ioc->refcount))
+               return ioc;
+
+       return NULL;
+}
+
 #endif