include/block/blockjob_int.h: split header into I/O and GS API

Since the I/O functions are not many, keep a single file.
Also split the function pointers in BlockJobDriver.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220303151616.325444-16-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/block/blockjob_int.h

@@ -38,6 +38,13 @@ struct BlockJobDriver {
     /** Generic JobDriver callbacks and settings */
     JobDriver job_driver;
 
+    /*
+     * I/O API functions. These functions are thread-safe.
+     *
+     * See include/block/block-io.h for more information about
+     * the I/O API.
+     */
+
     /*
      * Returns whether the job has pending requests for the child or will
      * submit new requests before the next pause point. This callback is polled
@@ -46,6 +53,13 @@ struct BlockJobDriver {
      */
     bool (*drained_poll)(BlockJob *job);
 
+    /*
+     * Global state (GS) API. These functions run under the BQL.
+     *
+     * See include/block/block-global-state.h for more information about
+     * the GS API.
+     */
+
     /*
      * If the callback is not NULL, it will be invoked before the job is
      * resumed in a new AioContext.  This is the place to move any resources
@@ -56,6 +70,13 @@ struct BlockJobDriver {
     void (*set_speed)(BlockJob *job, int64_t speed);
 };
 
+/*
+ * Global state (GS) API. These functions run under the BQL.
+ *
+ * See include/block/block-global-state.h for more information about
+ * the GS API.
+ */
+
 /**
  * block_job_create:
  * @job_id: The id of the newly-created job, or %NULL to have one
@@ -98,6 +119,13 @@ void block_job_free(Job *job);
  */
 void block_job_user_resume(Job *job);
 
+/*
+ * I/O API functions. These functions are thread-safe.
+ *
+ * See include/block/block-io.h for more information about
+ * the I/O API.
+ */
+
 /**
  * block_job_ratelimit_get_delay:
  *