Re: [Qemu-devel] [PATCH v3 5/9] block/mirror: utilize job_exit shim

[Jeff Cody <jcody@redhat.com>]

On Wed, Aug 29, 2018 at 09:57:30PM -0400, John Snow wrote:
> Change the manual deferment to mirror_exit into the implicit
> callback to job_exit and the mirror_exit callback.
> 
> This does change the order of some bdrv_unref calls and job_completed,
> but thanks to the new context in which we call .exit, this is safe to
> defer the possible flushing of any nodes to the job_finalize_single
> cleanup stage.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>

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

> ---
>  block/mirror.c | 29 +++++++++++------------------
>  1 file changed, 11 insertions(+), 18 deletions(-)
> 
> diff --git a/block/mirror.c b/block/mirror.c
> index be5dc6b7b0..b8941db6c1 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -607,26 +607,22 @@ static void mirror_wait_for_all_io(MirrorBlockJob *s)
>      }
>  }
>  
> -typedef struct {
> -    int ret;
> -} MirrorExitData;
> -
> -static void mirror_exit(Job *job, void *opaque)
> +static void mirror_exit(Job *job)
>  {
>      MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
>      BlockJob *bjob = &s->common;
> -    MirrorExitData *data = opaque;
>      MirrorBDSOpaque *bs_opaque = s->mirror_top_bs->opaque;
>      AioContext *replace_aio_context = NULL;
>      BlockDriverState *src = s->mirror_top_bs->backing->bs;
>      BlockDriverState *target_bs = blk_bs(s->target);
>      BlockDriverState *mirror_top_bs = s->mirror_top_bs;
>      Error *local_err = NULL;
> +    int ret = job->ret;
>  
>      bdrv_release_dirty_bitmap(src, s->dirty_bitmap);
>  
> -    /* Make sure that the source BDS doesn't go away before we called
> -     * job_completed(). */
> +    /* Make sure that the source BDS doesn't go away during bdrv_replace_node,
> +     * before we can call bdrv_drained_end */
>      bdrv_ref(src);
>      bdrv_ref(mirror_top_bs);
>      bdrv_ref(target_bs);
> @@ -652,7 +648,7 @@ static void mirror_exit(Job *job, void *opaque)
>              bdrv_set_backing_hd(target_bs, backing, &local_err);
>              if (local_err) {
>                  error_report_err(local_err);
> -                data->ret = -EPERM;
> +                ret = -EPERM;
>              }
>          }
>      }
> @@ -662,7 +658,7 @@ static void mirror_exit(Job *job, void *opaque)
>          aio_context_acquire(replace_aio_context);
>      }
>  
> -    if (s->should_complete && data->ret == 0) {
> +    if (s->should_complete && ret == 0) {
>          BlockDriverState *to_replace = src;
>          if (s->to_replace) {
>              to_replace = s->to_replace;
> @@ -679,7 +675,7 @@ static void mirror_exit(Job *job, void *opaque)
>          bdrv_drained_end(target_bs);
>          if (local_err) {
>              error_report_err(local_err);
> -            data->ret = -EPERM;
> +            ret = -EPERM;
>          }
>      }
>      if (s->to_replace) {
> @@ -710,12 +706,12 @@ static void mirror_exit(Job *job, void *opaque)
>      blk_insert_bs(bjob->blk, mirror_top_bs, &error_abort);
>  
>      bs_opaque->job = NULL;
> -    job_completed(job, data->ret);
>  
> -    g_free(data);
>      bdrv_drained_end(src);
>      bdrv_unref(mirror_top_bs);
>      bdrv_unref(src);
> +
> +    job->ret = ret;
>  }
>  
>  static void mirror_throttle(MirrorBlockJob *s)
> @@ -815,7 +811,6 @@ static int mirror_flush(MirrorBlockJob *s)
>  static int coroutine_fn mirror_run(Job *job, Error **errp)
>  {
>      MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
> -    MirrorExitData *data;
>      BlockDriverState *bs = s->mirror_top_bs->backing->bs;
>      BlockDriverState *target_bs = blk_bs(s->target);
>      bool need_drain = true;
> @@ -1035,14 +1030,10 @@ immediate_exit:
>      g_free(s->in_flight_bitmap);
>      bdrv_dirty_iter_free(s->dbi);
>  
> -    data = g_malloc(sizeof(*data));
> -    data->ret = ret;
> -
>      if (need_drain) {
>          bdrv_drained_begin(bs);
>      }
>  
> -    job_defer_to_main_loop(&s->common.job, mirror_exit, data);
>      return ret;
>  }
>  
> @@ -1141,6 +1132,7 @@ static const BlockJobDriver mirror_job_driver = {
>          .user_resume            = block_job_user_resume,
>          .drain                  = block_job_drain,
>          .run                    = mirror_run,
> +        .exit                   = mirror_exit,
>          .pause                  = mirror_pause,
>          .complete               = mirror_complete,
>      },
> @@ -1157,6 +1149,7 @@ static const BlockJobDriver commit_active_job_driver = {
>          .user_resume            = block_job_user_resume,
>          .drain                  = block_job_drain,
>          .run                    = mirror_run,
> +        .exit                   = mirror_exit,
>          .pause                  = mirror_pause,
>          .complete               = mirror_complete,
>      },
> -- 
> 2.14.4
>