io context sharing: preliminary support
Detach task state from ioc, instead keep track of how many processes
are accessing the ioc.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 510a18b..2483a05 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -34,7 +34,7 @@
#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */
-void put_io_context(struct io_context *ioc);
+int put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 186807e..cd44d45 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -54,13 +54,15 @@
};
/*
- * 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 @@
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