Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim

[Jeff Cody <jcody@redhat.com>]

On Tue, Aug 07, 2018 at 12:33:32AM -0400, John Snow wrote:
> Change the manual deferment to commit_complete into the implicit
> callback to job_exit.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  block/commit.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/block/commit.c b/block/commit.c
> index 620666161b..5bed098d5f 100644
> --- a/block/commit.c
> +++ b/block/commit.c
> @@ -68,19 +68,14 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
>      return 0;
>  }
>  
> -typedef struct {
> -    int ret;
> -} CommitCompleteData;
> -
> -static void commit_complete(Job *job, void *opaque)
> +static void commit_exit(Job *job)
>  {
>      CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
>      BlockJob *bjob = &s->common;
> -    CommitCompleteData *data = opaque;
>      BlockDriverState *top = blk_bs(s->top);
>      BlockDriverState *base = blk_bs(s->base);
>      BlockDriverState *commit_top_bs = s->commit_top_bs;
> -    int ret = data->ret;
> +    int ret = job->ret;
>      bool remove_commit_top_bs = false;
>  
>      /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */

Since 'ret' is only assigned to 'job->ret' outside of this line, we could
drop the local 'ret' and assign job->ret to the output of
brdrv_drop_intermediate() in this code below:

    if (!job_is_cancelled(job) && ret == 0) {
        /* success */
        ret = bdrv_drop_intermediate(s->commit_top_bs, base,
                                     s->backing_file_str);
    }

> @@ -117,9 +112,6 @@ static void commit_complete(Job *job, void *opaque)
>       * bdrv_set_backing_hd() to fail. */
>      block_job_remove_all_bdrv(bjob);
>  
> -    job_completed(job, ret);
> -    g_free(data);
> -
>      /* If bdrv_drop_intermediate() didn't already do that, remove the commit
>       * filter driver from the backing chain. Do this as the final step so that
>       * the 'consistent read' permission can be granted.  */
> @@ -132,12 +124,12 @@ static void commit_complete(Job *job, void *opaque)
>  
>      bdrv_unref(commit_top_bs);
>      bdrv_unref(top);
> +    job->ret = ret;

We could then drop this line as well.

(This may fall under bike shedding, so I don't feel strongly about it):

Reviewed-by: Jeff Cody <jcody@redhat.com>

>  }
>  
>  static void coroutine_fn commit_run(void *opaque)
>  {
>      CommitBlockJob *s = opaque;
> -    CommitCompleteData *data;
>      int64_t offset;
>      uint64_t delay_ns = 0;
>      int ret = 0;
> @@ -210,9 +202,7 @@ static void coroutine_fn commit_run(void *opaque)
>  out:
>      qemu_vfree(buf);
>  
> -    data = g_malloc(sizeof(*data));
> -    data->ret = ret;
> -    job_defer_to_main_loop(&s->common.job, commit_complete, data);
> +    s->common.job.ret = ret;
>  }
>  
>  static const BlockJobDriver commit_job_driver = {
> @@ -223,6 +213,7 @@ static const BlockJobDriver commit_job_driver = {
>          .user_resume   = block_job_user_resume,
>          .drain         = block_job_drain,
>          .start         = commit_run,
> +        .exit          = commit_exit,
>      },
>  };
>  
> -- 
> 2.14.4
>