RDMA/core: Add UVERBS_METHOD_ASYNC_EVENT_ALLOC

Allow the async FD to be allocated separately from the context.

This is necessary to introduce the ioctl to create a context, as an ioctl
should only ever create a single uobject at a time.

If multiple async FDs are created then the first one is used to deliver
affiliated events from any ib_uevent_object, with all subsequent ones will
receive only unaffiliated events.

Link: https://lore.kernel.org/r/1578506740-22188-3-git-send-email-yishaih@mellanox.com
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_main.c

@@ -475,7 +475,9 @@ void ib_uverbs_init_async_event_file(
 
 	ib_uverbs_init_event_queue(&async_file->ev_queue);
 
-	if (!WARN_ON(uverbs_file->async_file)) {
+	/* The first async_event_file becomes the default one for the file. */
+	lockdep_assert_held(&uverbs_file->ucontext_lock);
+	if (!uverbs_file->async_file) {
 		/* Pairs with the put in ib_uverbs_release_file */
 		uverbs_uobject_get(&async_file->uobj);
 		smp_store_release(&uverbs_file->async_file, async_file);

drivers/infiniband/core/uverbs_std_types_async_fd.c

@@ -8,6 +8,19 @@
 #include "rdma_core.h"
 #include "uverbs.h"
 
+static int UVERBS_HANDLER(UVERBS_METHOD_ASYNC_EVENT_ALLOC)(
+	struct uverbs_attr_bundle *attrs)
+{
+	struct ib_uobject *uobj =
+		uverbs_attr_get_uobject(attrs, UVERBS_METHOD_ASYNC_EVENT_ALLOC);
+
+	mutex_lock(&attrs->ufile->ucontext_lock);
+	ib_uverbs_init_async_event_file(
+		container_of(uobj, struct ib_uverbs_async_event_file, uobj));
+	mutex_unlock(&attrs->ufile->ucontext_lock);
+	return 0;
+}
+
 static int uverbs_async_event_destroy_uobj(struct ib_uobject *uobj,
 					   enum rdma_remove_reason why)
 {
@@ -19,13 +32,21 @@ static int uverbs_async_event_destroy_uobj(struct ib_uobject *uobj,
 	return 0;
 }
 
+DECLARE_UVERBS_NAMED_METHOD(
+	UVERBS_METHOD_ASYNC_EVENT_ALLOC,
+	UVERBS_ATTR_FD(UVERBS_ATTR_ASYNC_EVENT_ALLOC_FD_HANDLE,
+		       UVERBS_OBJECT_ASYNC_EVENT,
+		       UVERBS_ACCESS_NEW,
+		       UA_MANDATORY));
+
 DECLARE_UVERBS_NAMED_OBJECT(
 	UVERBS_OBJECT_ASYNC_EVENT,
 	UVERBS_TYPE_ALLOC_FD(sizeof(struct ib_uverbs_async_event_file),
 			     uverbs_async_event_destroy_uobj,
 			     &uverbs_async_event_fops,
 			     "[infinibandevent]",
-			     O_RDONLY));
+			     O_RDONLY),
+	&UVERBS_METHOD(UVERBS_METHOD_ASYNC_EVENT_ALLOC));
 
 const struct uapi_definition uverbs_def_obj_async_fd[] = {
 	UAPI_DEF_CHAIN_OBJ_TREE_NAMED(UVERBS_OBJECT_ASYNC_EVENT),

include/uapi/rdma/ib_user_ioctl_cmds.h

@@ -242,4 +242,12 @@ enum uverbs_attrs_flow_destroy_ids {
 	UVERBS_ATTR_DESTROY_FLOW_HANDLE,
 };
 
+enum uverbs_method_async_event {
+	UVERBS_METHOD_ASYNC_EVENT_ALLOC,
+};
+
+enum uverbs_attrs_async_event_create {
+	UVERBS_ATTR_ASYNC_EVENT_ALLOC_FD_HANDLE,
+};
+
 #endif