IB/core: Add support to finalize objects in one transaction

The new ioctl based infrastructure either commits or rollbacks
all objects of the method as one transaction. In order to do
that, we introduce a notion of dealing with a collection of
objects that are related to a specific method.

This also requires adding a notion of a method and attribute.
A method contains a hash of attributes, where each bucket
contains several attributes. The attributes are hashed according
to their namespace which resides in the four upper bits of the id.

For example, an object could be a CQ, which has an action of CREATE_CQ.
This action has multiple attributes. For example, the CQ's new handle
and the comp_channel. Each layer in this hierarchy - objects, methods
and attributes is split into namespaces. The basic example for that is
one namespace representing the default entities and another one
representing the driver specific entities.

When declaring these methods and attributes, we actually declare
their specifications. When a method is executed, we actually
allocates some space to hold auxiliary information. This auxiliary
information contains meta-data about the required objects, such
as pointers to their type information, pointers to the uobjects
themselves (if exist), etc.
The specification, along with the auxiliary information we allocated
and filled is given to the finalize_objects function.

Signed-off-by: Matan Barak <[email protected]>
Reviewed-by: Yishai Hadas <[email protected]>
Signed-off-by: Doug Ledford <[email protected]>

Author: matanb10

drivers/infiniband/core/rdma_core.c

@@ -683,3 +683,43 @@ int uverbs_finalize_object(struct ib_uobject *uobj,
 
 	return ret;
 }
+
+int uverbs_finalize_objects(struct uverbs_attr_bundle *attrs_bundle,
+			    struct uverbs_attr_spec_hash * const *spec_hash,
+			    size_t num,
+			    bool commit)
+{
+	unsigned int i;
+	int ret = 0;
+
+	for (i = 0; i < num; i++) {
+		struct uverbs_attr_bundle_hash *curr_bundle =
+			&attrs_bundle->hash[i];
+		const struct uverbs_attr_spec_hash *curr_spec_bucket =
+			spec_hash[i];
+		unsigned int j;
+
+		for (j = 0; j < curr_bundle->num_attrs; j++) {
+			struct uverbs_attr *attr;
+			const struct uverbs_attr_spec *spec;
+
+			if (!uverbs_attr_is_valid_in_hash(curr_bundle, j))
+				continue;
+
+			attr = &curr_bundle->attrs[j];
+			spec = &curr_spec_bucket->attrs[j];
+
+			if (spec->type == UVERBS_ATTR_TYPE_IDR ||
+			    spec->type == UVERBS_ATTR_TYPE_FD) {
+				int current_ret;
+
+				current_ret = uverbs_finalize_object(attr->obj_attr.uobject,
+								     spec->obj.access,
+								     commit);
+				if (!ret)
+					ret = current_ret;
+			}
+		}
+	}
+	return ret;
+}

drivers/infiniband/core/rdma_core.h

@@ -82,7 +82,8 @@ void uverbs_close_fd(struct file *f);
  * applicable.
  * This function could create (access == NEW), destroy (access == DESTROY)
  * or unlock (access == READ || access == WRITE) objects if required.
- * The action will be finalized only when uverbs_finalize_object is called.
+ * The action will be finalized only when uverbs_finalize_object or
+ * uverbs_finalize_objects are called.
  */
 struct ib_uobject *uverbs_get_uobject_from_context(const struct uverbs_obj_type *type_attrs,
 						   struct ib_ucontext *ucontext,
@@ -91,5 +92,24 @@ struct ib_uobject *uverbs_get_uobject_from_context(const struct uverbs_obj_type
 int uverbs_finalize_object(struct ib_uobject *uobj,
 			   enum uverbs_obj_access access,
 			   bool commit);
+/*
+ * Note that certain finalize stages could return a status:
+ *   (a) alloc_commit could return a failure if the object is committed at the
+ *       same time when the context is destroyed.
+ *   (b) remove_commit could fail if the object wasn't destroyed successfully.
+ * Since multiple objects could be finalized in one transaction, it is very NOT
+ * recommended to have several finalize actions which have side effects.
+ * For example, it's NOT recommended to have a certain action which has both
+ * a commit action and a destroy action or two destroy objects in the same
+ * action. The rule of thumb is to have one destroy or commit action with
+ * multiple lookups.
+ * The first non zero return value of finalize_object is returned from this
+ * function. For example, this could happen when we couldn't destroy an
+ * object.
+ */
+int uverbs_finalize_objects(struct uverbs_attr_bundle *attrs_bundle,
+			    struct uverbs_attr_spec_hash * const *spec_hash,
+			    size_t num,
+			    bool commit);
 
 #endif /* RDMA_CORE_H */

include/rdma/uverbs_ioctl.h

@@ -41,12 +41,65 @@
  * =======================================
  */
 
+enum uverbs_attr_type {
+	UVERBS_ATTR_TYPE_NA,
+	UVERBS_ATTR_TYPE_IDR,
+	UVERBS_ATTR_TYPE_FD,
+};
+
 enum uverbs_obj_access {
 	UVERBS_ACCESS_READ,
 	UVERBS_ACCESS_WRITE,
 	UVERBS_ACCESS_NEW,
 	UVERBS_ACCESS_DESTROY
 };
 
+struct uverbs_attr_spec {
+	enum uverbs_attr_type		type;
+	struct {
+		/*
+		 * higher bits mean the namespace and lower bits mean
+		 * the type id within the namespace.
+		 */
+		u16			obj_type;
+		u8			access;
+	} obj;
+};
+
+struct uverbs_attr_spec_hash {
+	size_t				num_attrs;
+	struct uverbs_attr_spec		attrs[0];
+};
+
+struct uverbs_obj_attr {
+	struct ib_uobject		*uobject;
+};
+
+struct uverbs_attr {
+	struct uverbs_obj_attr	obj_attr;
+};
+
+struct uverbs_attr_bundle_hash {
+	/* if bit i is set, it means attrs[i] contains valid information */
+	unsigned long *valid_bitmap;
+	size_t num_attrs;
+	/*
+	 * arrays of attributes, each element corresponds to the specification
+	 * of the attribute in the same index.
+	 */
+	struct uverbs_attr *attrs;
+};
+
+struct uverbs_attr_bundle {
+	size_t				num_buckets;
+	struct uverbs_attr_bundle_hash  hash[];
+};
+
+static inline bool uverbs_attr_is_valid_in_hash(const struct uverbs_attr_bundle_hash *attrs_hash,
+						unsigned int idx)
+{
+	return test_bit(idx, attrs_hash->valid_bitmap);
+}
+
 #endif