[Qemu-devel] [PATCH v2 2/5] block: Allow stream_start to return job references

[John Snow]

stream_start now picks up a reference for its return value, a copy of
the job started. callers are responsible for putting it down when they
are done with it.

This removes a minor reference to bs->job in qmp_block_stream, for
a simple tracing function.

Reviewed-by: Kevin Wolf <kw...@redhat.com>
Signed-off-by: John Snow <js...@redhat.com>
---
 block/stream.c            | 8 +++++---
 blockdev.c                | 8 +++++---
 include/block/block_int.h | 9 +++++----
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/block/stream.c b/block/stream.c
index cafaa07..26a2990 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -214,7 +214,7 @@ static const BlockJobDriver stream_job_driver = {
     .set_speed     = stream_set_speed,
 };
 
-void stream_start(BlockDriverState *bs, BlockDriverState *base,
+BlockJob *stream_start(BlockDriverState *bs, BlockDriverState *base,
                   const char *backing_file_str, int64_t speed,
                   BlockdevOnError on_error,
                   BlockCompletionFunc *cb,
@@ -226,19 +226,21 @@ void stream_start(BlockDriverState *bs, BlockDriverState 
*base,
          on_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
         (!bs->blk || !blk_iostatus_is_enabled(bs->blk))) {
         error_setg(errp, QERR_INVALID_PARAMETER, "on-error");
-        return;
+        return NULL;
     }
 
     s = block_job_create(&stream_job_driver, bs, speed, cb, opaque, errp);
     if (!s) {
-        return;
+        return NULL;
     }
 
     s->base = base;
     s->backing_file_str = g_strdup(backing_file_str);
 
     s->on_error = on_error;
+    block_job_ref(&s->common);
     s->common.co = qemu_coroutine_create(stream_run);
     trace_stream_start(bs, base, s, s->common.co, opaque);
     qemu_coroutine_enter(s->common.co, s);
+    return &s->common;
 }
diff --git a/blockdev.c b/blockdev.c
index c0b9b12..5a74c81 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2883,6 +2883,7 @@ void qmp_block_stream(const char *device,
     BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *base_bs = NULL;
+    BlockJob *job;
     AioContext *aio_context;
     Error *local_err = NULL;
     const char *base_name = NULL;
@@ -2932,14 +2933,15 @@ void qmp_block_stream(const char *device,
     /* backing_file string overrides base bs filename */
     base_name = has_backing_file ? backing_file : base_name;
 
-    stream_start(bs, base_bs, base_name, has_speed ? speed : 0,
-                 on_error, block_job_cb, bs, &local_err);
+    job = stream_start(bs, base_bs, base_name, has_speed ? speed : 0,
+                       on_error, block_job_cb, bs, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         goto out;
     }
 
-    trace_qmp_block_stream(bs, bs->job);
+    trace_qmp_block_stream(bs, job);
+    block_job_unref(job);
 
 out:
     aio_context_release(aio_context);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index de4c3c6..7a86d7f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -598,10 +598,11 @@ int is_windows_drive(const char *filename);
  * streaming job, the backing file of @bs will be changed to
  * @base_id in the written image and to @base in the live BlockDriverState.
  */
-void stream_start(BlockDriverState *bs, BlockDriverState *base,
-                  const char *base_id, int64_t speed, BlockdevOnError on_error,
-                  BlockCompletionFunc *cb,
-                  void *opaque, Error **errp);
+BlockJob *stream_start(BlockDriverState *bs, BlockDriverState *base,
+                       const char *base_id, int64_t speed,
+                       BlockdevOnError on_error,
+                       BlockCompletionFunc *cb,
+                       void *opaque, Error **errp);
 
 /**
  * commit_start:
-- 
2.4.3