blockjob: introduce block_job_early_fail

Outside blockjob.c, block_job_unref is only used when a block job fails
to start, and block_job_ref is not used at all.  The reference counting
thus is pretty well hidden.  Introduce a separate function to be used
by block jobs; because block_job_ref and block_job_unref now become
static, move them earlier in blockjob.c.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Message-id: 20170508141310.8674-4-pbonzini@redhat.com
Signed-off-by: Jeff Cody <jcody@redhat.com>

block/backup.c

@@ -692,7 +692,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     }
     if (job) {
         backup_clean(&job->common);
-        block_job_unref(&job->common);
+        block_job_early_fail(&job->common);
     }
 
     return NULL;

block/commit.c

@@ -426,7 +426,7 @@ fail:
     if (commit_top_bs) {
         bdrv_set_backing_hd(overlay_bs, top, &error_abort);
     }
-    block_job_unref(&s->common);
+    block_job_early_fail(&s->common);
 }
 
 

block/mirror.c

@@ -1252,7 +1252,7 @@ fail:
 
         g_free(s->replaces);
         blk_unref(s->target);
-        block_job_unref(&s->common);
+        block_job_early_fail(&s->common);
     }
 
     bdrv_child_try_set_perm(mirror_top_bs->backing, 0, BLK_PERM_ALL,

blockjob.c

@@ -106,6 +106,32 @@ BlockJob *block_job_get(const char *id)
     return NULL;
 }
 
+static void block_job_ref(BlockJob *job)
+{
+    ++job->refcnt;
+}
+
+static void block_job_attached_aio_context(AioContext *new_context,
+                                           void *opaque);
+static void block_job_detach_aio_context(void *opaque);
+
+static void block_job_unref(BlockJob *job)
+{
+    if (--job->refcnt == 0) {
+        BlockDriverState *bs = blk_bs(job->blk);
+        bs->job = NULL;
+        block_job_remove_all_bdrv(job);
+        blk_remove_aio_context_notifier(job->blk,
+                                        block_job_attached_aio_context,
+                                        block_job_detach_aio_context, job);
+        blk_unref(job->blk);
+        error_free(job->blocker);
+        g_free(job->id);
+        QLIST_REMOVE(job, job_list);
+        g_free(job);
+    }
+}
+
 static void block_job_attached_aio_context(AioContext *new_context,
                                            void *opaque)
 {
@@ -293,26 +319,9 @@ void block_job_start(BlockJob *job)
     bdrv_coroutine_enter(blk_bs(job->blk), job->co);
 }
 
-void block_job_ref(BlockJob *job)
+void block_job_early_fail(BlockJob *job)
 {
-    ++job->refcnt;
-}
-
-void block_job_unref(BlockJob *job)
-{
-    if (--job->refcnt == 0) {
-        BlockDriverState *bs = blk_bs(job->blk);
-        bs->job = NULL;
-        block_job_remove_all_bdrv(job);
-        blk_remove_aio_context_notifier(job->blk,
-                                        block_job_attached_aio_context,
-                                        block_job_detach_aio_context, job);
-        blk_unref(job->blk);
-        error_free(job->blocker);
-        g_free(job->id);
-        QLIST_REMOVE(job, job_list);
-        g_free(job);
-    }
+    block_job_unref(job);
 }
 
 static void block_job_completed_single(BlockJob *job)

include/block/blockjob_int.h

@@ -156,21 +156,12 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns);
 void block_job_yield(BlockJob *job);
 
 /**
- * block_job_ref:
+ * block_job_early_fail:
  * @bs: The block device.
  *
- * Grab a reference to the block job. Should be paired with block_job_unref.
+ * The block job could not be started, free it.
  */
-void block_job_ref(BlockJob *job);
-
-/**
- * block_job_unref:
- * @bs: The block device.
- *
- * Release reference to the block job and release resources if it is the last
- * reference.
- */
-void block_job_unref(BlockJob *job);
+void block_job_early_fail(BlockJob *job);
 
 /**
  * block_job_completed:

tests/test-blockjob.c

@@ -116,11 +116,11 @@ static void test_job_ids(void)
     job[1] = do_test_id(blk[1], "id0", false);
 
     /* But once job[0] finishes we can reuse its ID */
-    block_job_unref(job[0]);
+    block_job_early_fail(job[0]);
     job[1] = do_test_id(blk[1], "id0", true);
 
     /* No job ID specified, defaults to the backend name ('drive1') */
-    block_job_unref(job[1]);
+    block_job_early_fail(job[1]);
     job[1] = do_test_id(blk[1], NULL, true);
 
     /* Duplicate job ID */
@@ -133,9 +133,9 @@ static void test_job_ids(void)
     /* This one is valid */
     job[2] = do_test_id(blk[2], "id_2", true);
 
-    block_job_unref(job[0]);
-    block_job_unref(job[1]);
-    block_job_unref(job[2]);
+    block_job_early_fail(job[0]);
+    block_job_early_fail(job[1]);
+    block_job_early_fail(job[2]);
 
     destroy_blk(blk[0]);
     destroy_blk(blk[1]);