IB/core: Change idr objects to use the new schema

This changes only the handlers which deals with idr based objects to
use the new idr allocation, fetching and destruction schema.
This patch consists of the following changes:
(1) Allocation, fetching and destruction is done via idr ops.
(2) Context initializing and release is done through
    uverbs_initialize_ucontext and uverbs_cleanup_ucontext.
(3) Ditching the live flag. Mostly, this is pretty straight
    forward. The only place that is a bit trickier is in
    ib_uverbs_open_qp. Commit [1] added code to check whether
    the uobject is already live and initialized. This mostly
    happens because of a race between open_qp and events.
    We delayed assigning the uobject's pointer in order to
    eliminate this race without using the live variable.

[1] commit a040f95
	("IB/core: Fix XRC race condition in ib_uverbs_open_qp")

Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/rdma_core.h

@@ -52,4 +52,19 @@
 void uverbs_cleanup_ucontext(struct ib_ucontext *ucontext, bool device_removed);
 void uverbs_initialize_ucontext(struct ib_ucontext *ucontext);
 
+/*
+ * uverbs_uobject_get is called in order to increase the reference count on
+ * an uobject. This is useful when a handler wants to keep the uobject's memory
+ * alive, regardless if this uobject is still alive in the context's objects
+ * repository. Objects are put via uverbs_uobject_put.
+ */
+void uverbs_uobject_get(struct ib_uobject *uobject);
+
+/*
+ * In order to indicate we no longer needs this uobject, uverbs_uobject_put
+ * is called. When the reference count is decreased, the uobject is freed.
+ * For example, this is used when attaching a completion channel to a CQ.
+ */
+void uverbs_uobject_put(struct ib_uobject *uobject);
+
 #endif /* RDMA_CORE_H */

drivers/infiniband/core/uverbs.h

@@ -180,8 +180,6 @@ struct ib_ucq_object {
 	u32			async_events_reported;
 };
 
-void idr_remove_uobj(struct ib_uobject *uobj);
-
 struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 					struct ib_device *ib_dev,
 					int is_async);