[Qemu-devel] [PATCH v4 06/11] block: add refcount to Job object

[John Snow <jsnow@redhat.com>]

If we want to get at the job after the life of the job,
we'll need a refcount for this object.

This may occur for example if we wish to inspect the actions
taken by a particular job after a transactional group of jobs
runs, and further actions are required.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
 blockjob.c               | 18 ++++++++++++++++--
 include/block/blockjob.h | 21 +++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/blockjob.c b/blockjob.c
index 2755465..9b3456f 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -35,6 +35,19 @@
 #include "qemu/timer.h"
 #include "qapi-event.h"
 
+void block_job_incref(BlockJob *job)
+{
+    job->refcount++;
+}
+
+void block_job_decref(BlockJob *job)
+{
+    job->refcount--;
+    if (job->refcount == 0) {
+        g_free(job);
+    }
+}
+
 void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
                        int64_t speed, BlockCompletionFunc *cb,
                        void *opaque, Error **errp)
@@ -57,6 +70,7 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
     job->cb            = cb;
     job->opaque        = opaque;
     job->busy          = true;
+    job->refcount      = 1;
     bs->job = job;
 
     /* Only set speed when necessary to avoid NotSupported error */
@@ -68,7 +82,7 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
             bs->job = NULL;
             bdrv_op_unblock_all(bs, job->blocker);
             error_free(job->blocker);
-            g_free(job);
+            block_job_decref(job);
             error_propagate(errp, local_err);
             return NULL;
         }
@@ -85,7 +99,7 @@ void block_job_completed(BlockJob *job, int ret)
     bs->job = NULL;
     bdrv_op_unblock_all(bs, job->blocker);
     error_free(job->blocker);
-    g_free(job);
+    block_job_decref(job);
 }
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 57d8ef1..86d770a 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -122,6 +122,9 @@ struct BlockJob {
 
     /** The opaque value that is passed to the completion function.  */
     void *opaque;
+
+    /** A reference count, allowing for post-job actions in e.g. transactions */
+    int refcount;
 };
 
 /**
@@ -147,6 +150,24 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
                        void *opaque, Error **errp);
 
 /**
+ * block_job_incref:
+ * @job: The job to pick up a handle to
+ *
+ * Increment the refcount on @job, to be able to use it asynchronously
+ * from the job it is being used for. Put down the reference when done
+ * with @block_job_unref.
+ */
+void block_job_incref(BlockJob *job);
+
+/**
+ * block_job_decref:
+ * @job: The job to unreference and delete.
+ *
+ * Decrement the refcount on @job and delete it if there are no more references.
+ */
+void block_job_decref(BlockJob *job);
+
+/**
  * block_job_sleep_ns:
  * @job: The job that calls the function.
  * @clock: The clock to sleep on.
-- 
2.1.0