job: Add reference counting

This moves reference counting from BlockJob to Job.

In order to keep calling the BlockJob cleanup code when the job is
deleted via job_unref(), introduce a new JobDriver.free callback. Every
block job must use block_job_free() for this callback, this is asserted
in block_job_create().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

block/backup.c

@@ -526,6 +526,7 @@ static const BlockJobDriver backup_job_driver = {
     .job_driver = {
         .instance_size          = sizeof(BackupBlockJob),
         .job_type               = JOB_TYPE_BACKUP,
+        .free                   = block_job_free,
     },
     .start                  = backup_run,
     .commit                 = backup_commit,

block/commit.c

@@ -218,6 +218,7 @@ static const BlockJobDriver commit_job_driver = {
     .job_driver = {
         .instance_size = sizeof(CommitBlockJob),
         .job_type      = JOB_TYPE_COMMIT,
+        .free          = block_job_free,
     },
     .start         = commit_run,
 };

block/mirror.c

@@ -989,6 +989,7 @@ static const BlockJobDriver mirror_job_driver = {
     .job_driver = {
         .instance_size          = sizeof(MirrorBlockJob),
         .job_type               = JOB_TYPE_MIRROR,
+        .free                   = block_job_free,
     },
     .start                  = mirror_run,
     .complete               = mirror_complete,
@@ -1001,6 +1002,7 @@ static const BlockJobDriver commit_active_job_driver = {
     .job_driver = {
         .instance_size          = sizeof(MirrorBlockJob),
         .job_type               = JOB_TYPE_COMMIT,
+        .free                   = block_job_free,
     },
     .start                  = mirror_run,
     .complete               = mirror_complete,

block/stream.c

@@ -212,6 +212,7 @@ static const BlockJobDriver stream_job_driver = {
     .job_driver = {
         .instance_size = sizeof(StreamBlockJob),
         .job_type      = JOB_TYPE_STREAM,
+        .free          = block_job_free,
     },
     .start         = stream_run,
 };

blockjob.c

@@ -190,31 +190,25 @@ static void block_job_resume(BlockJob *job)
     block_job_enter_cond(job, block_job_timer_not_pending);
 }
 
-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);
 
-void block_job_unref(BlockJob *job)
+void block_job_free(Job *job)
 {
-    if (--job->refcnt == 0) {
-        assert(job->job.status == JOB_STATUS_NULL);
-        assert(!job->txn);
-        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);
-        assert(!timer_pending(&job->sleep_timer));
-        job_delete(&job->job);
-    }
+    BlockJob *bjob = container_of(job, BlockJob, job);
+    BlockDriverState *bs = blk_bs(bjob->blk);
+
+    assert(!bjob->txn);
+
+    bs->job = NULL;
+    block_job_remove_all_bdrv(bjob);
+    blk_remove_aio_context_notifier(bjob->blk,
+                                    block_job_attached_aio_context,
+                                    block_job_detach_aio_context, bjob);
+    blk_unref(bjob->blk);
+    error_free(bjob->blocker);
+    assert(!timer_pending(&bjob->sleep_timer));
 }
 
 static void block_job_attached_aio_context(AioContext *new_context,
@@ -245,7 +239,7 @@ static void block_job_detach_aio_context(void *opaque)
     BlockJob *job = opaque;
 
     /* In case the job terminates during aio_poll()... */
-    block_job_ref(job);
+    job_ref(&job->job);
 
     block_job_pause(job);
 
@@ -253,7 +247,7 @@ static void block_job_detach_aio_context(void *opaque)
         block_job_drain(job);
     }
 
-    block_job_unref(job);
+    job_unref(&job->job);
 }
 
 static char *child_job_get_parent_desc(BdrvChild *c)
@@ -367,7 +361,7 @@ static void block_job_decommission(BlockJob *job)
     job->deferred_to_main_loop = true;
     block_job_txn_del_job(job);
     job_state_transition(&job->job, JOB_STATUS_NULL);
-    block_job_unref(job);
+    job_unref(&job->job);
 }
 
 static void block_job_do_dismiss(BlockJob *job)
@@ -506,14 +500,14 @@ static int block_job_finish_sync(BlockJob *job,
 
     assert(blk_bs(job->blk)->job == job);
 
-    block_job_ref(job);
+    job_ref(&job->job);
 
     if (finish) {
         finish(job, &local_err);
     }
     if (local_err) {
         error_propagate(errp, local_err);
-        block_job_unref(job);
+        job_unref(&job->job);
         return -EBUSY;
     }
     /* block_job_drain calls block_job_enter, and it should be enough to
@@ -526,7 +520,7 @@ static int block_job_finish_sync(BlockJob *job,
         aio_poll(qemu_get_aio_context(), true);
     }
     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
-    block_job_unref(job);
+    job_unref(&job->job);
     return ret;
 }
 
@@ -909,6 +903,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     }
 
     assert(is_block_job(&job->job));
+    assert(job->job.driver->free == &block_job_free);
 
     job->driver        = driver;
     job->blk           = blk;
@@ -917,7 +912,6 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     job->busy          = false;
     job->paused        = true;
     job->pause_count   = 1;
-    job->refcnt        = 1;
     job->auto_finalize = !(flags & BLOCK_JOB_MANUAL_FINALIZE);
     job->auto_dismiss  = !(flags & BLOCK_JOB_MANUAL_DISMISS);
     aio_timer_init(qemu_get_aio_context(), &job->sleep_timer,

include/block/blockjob.h

@@ -132,9 +132,6 @@ typedef struct BlockJob {
     /** The opaque value that is passed to the completion function.  */
     void *opaque;
 
-    /** Reference count of the block job */
-    int refcnt;
-
     /** True when job has reported completion by calling block_job_completed. */
     bool completed;
 
@@ -399,24 +396,6 @@ void block_job_iostatus_reset(BlockJob *job);
  */
 BlockJobTxn *block_job_txn_new(void);
 
-/**
- * block_job_ref:
- *
- * Add a reference to BlockJob refcnt, it will be decreased with
- * block_job_unref, and then be freed if it comes to be the last
- * reference.
- */
-void block_job_ref(BlockJob *job);
-
-/**
- * block_job_unref:
- *
- * Release a reference that was previously acquired with block_job_ref
- * or block_job_create. If it's the last reference to the object, it will be
- * freed.
- */
-void block_job_unref(BlockJob *job);
-
 /**
  * block_job_txn_unref:
  *

include/block/blockjob_int.h

@@ -143,6 +143,13 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
                        uint64_t shared_perm, int64_t speed, int flags,
                        BlockCompletionFunc *cb, void *opaque, Error **errp);
 
+/**
+ * block_job_free:
+ * Callback to be used for JobDriver.free in all block jobs. Frees block job
+ * specific resources in @job.
+ */
+void block_job_free(Job *job);
+
 /**
  * block_job_sleep_ns:
  * @job: The job that calls the function.

include/qemu/job.h

@@ -41,6 +41,9 @@ typedef struct Job {
     /** The type of this job. */
     const JobDriver *driver;
 
+    /** Reference count of the block job */
+    int refcnt;
+
     /** Current state; See @JobStatus for details. */
     JobStatus status;
 
@@ -57,6 +60,9 @@ struct JobDriver {
 
     /** Enum describing the operation */
     JobType job_type;
+
+    /** Called when the job is freed */
+    void (*free)(Job *job);
 };
 
 
@@ -69,8 +75,17 @@ struct JobDriver {
  */
 void *job_create(const char *job_id, const JobDriver *driver, Error **errp);
 
-/** Frees the @job object. */
-void job_delete(Job *job);
+/**
+ * Add a reference to Job refcnt, it will be decreased with job_unref, and then
+ * be freed if it comes to be the last reference.
+ */
+void job_ref(Job *job);
+
+/**
+ * Release a reference that was previously acquired with job_ref() or
+ * job_create(). If it's the last reference to the object, it will be freed.
+ */
+void job_unref(Job *job);
 
 /** Returns the JobType of a given Job. */
 JobType job_type(const Job *job);

job.c

@@ -134,6 +134,7 @@ void *job_create(const char *job_id, const JobDriver *driver, Error **errp)
     job = g_malloc0(driver->instance_size);
     job->driver        = driver;
     job->id            = g_strdup(job_id);
+    job->refcnt        = 1;
 
     job_state_transition(job, JOB_STATUS_CREATED);
 
@@ -142,10 +143,23 @@ void *job_create(const char *job_id, const JobDriver *driver, Error **errp)
     return job;
 }
 
-void job_delete(Job *job)
+void job_ref(Job *job)
 {
-    QLIST_REMOVE(job, job_list);
-
-    g_free(job->id);
-    g_free(job);
+    ++job->refcnt;
+}
+
+void job_unref(Job *job)
+{
+    if (--job->refcnt == 0) {
+        assert(job->status == JOB_STATUS_NULL);
+
+        if (job->driver->free) {
+            job->driver->free(job);
+        }
+
+        QLIST_REMOVE(job, job_list);
+
+        g_free(job->id);
+        g_free(job);
+    }
 }

qemu-img.c

@@ -861,7 +861,7 @@ static void run_block_job(BlockJob *job, Error **errp)
     int ret = 0;
 
     aio_context_acquire(aio_context);
-    block_job_ref(job);
+    job_ref(&job->job);
     do {
         aio_poll(aio_context, true);
         qemu_progress_print(job->len ?
@@ -873,7 +873,7 @@ static void run_block_job(BlockJob *job, Error **errp)
     } else {
         ret = job->ret;
     }
-    block_job_unref(job);
+    job_unref(&job->job);
     aio_context_release(aio_context);
 
     /* publish completion progress only when success */

tests/test-bdrv-drain.c

@@ -522,6 +522,7 @@ static void test_job_complete(BlockJob *job, Error **errp)
 BlockJobDriver test_job_driver = {
     .job_driver = {
         .instance_size  = sizeof(TestBlockJob),
+        .free           = block_job_free,
     },
     .start          = test_job_start,
     .complete       = test_job_complete,

tests/test-blockjob-txn.c

@@ -76,6 +76,7 @@ static void test_block_job_cb(void *opaque, int ret)
 static const BlockJobDriver test_block_job_driver = {
     .job_driver = {
         .instance_size = sizeof(TestBlockJob),
+        .free          = block_job_free,
     },
     .start = test_block_job_run,
 };

tests/test-blockjob.c

@@ -19,6 +19,7 @@
 static const BlockJobDriver test_block_job_driver = {
     .job_driver = {
         .instance_size = sizeof(BlockJob),
+        .free          = block_job_free,
     },
 };
 
@@ -196,6 +197,7 @@ static void coroutine_fn cancel_job_start(void *opaque)
 static const BlockJobDriver test_cancel_driver = {
     .job_driver = {
         .instance_size = sizeof(CancelJob),
+        .free          = block_job_free,
     },
     .start         = cancel_job_start,
     .complete      = cancel_job_complete,
@@ -210,7 +212,7 @@ static CancelJob *create_common(BlockJob **pjob)
     blk = create_blk(NULL);
     job = mk_job(blk, "Steve", &test_cancel_driver, true,
                  BLOCK_JOB_MANUAL_FINALIZE | BLOCK_JOB_MANUAL_DISMISS);
-    block_job_ref(job);
+    job_ref(&job->job);
     assert(job->job.status == JOB_STATUS_CREATED);
     s = container_of(job, CancelJob, common);
     s->blk = blk;
@@ -231,7 +233,7 @@ static void cancel_common(CancelJob *s)
         block_job_dismiss(&dummy, &error_abort);
     }
     assert(job->job.status == JOB_STATUS_NULL);
-    block_job_unref(job);
+    job_unref(&job->job);
     destroy_blk(blk);
 }