Re: [PATCH V8 15/15] iothread: simplify API by merging iothread_get_aio_context variants

[Markus Armbruster <armbru@redhat.com>]

Zhang Chen <zhangckid@gmail.com> writes:

> Simplify the interface by merging iothread_ref_and_get_aio_context()
> into iothread_get_aio_context(). The updated function now requires a
> 'holder' parameter, ensuring that every retrieval of an AioContext for
> long-term use is automatically registered in the IOThread's holder list.
>
> Update all callers across block, virtio, scsi, net, and monitor
> subsystems to match the new signature. This cleanup reduces code
> redundancy and improves the reliability of IOThread introspection.
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  block/export/export.c           | 5 ++---
>  hw/block/dataplane/xen-block.c  | 4 ++--
>  hw/block/virtio-blk.c           | 4 ++--
>  hw/scsi/virtio-scsi-dataplane.c | 4 ++--
>  hw/vfio-user/proxy.c            | 3 +--
>  hw/virtio/iothread-vq-mapping.c | 3 +--
>  hw/virtio/virtio-balloon.c      | 2 +-
>  include/system/iothread.h       | 6 +++---
>  iothread.c                      | 9 ++-------
>  monitor/monitor.c               | 2 +-
>  net/colo-compare.c              | 2 +-
>  11 files changed, 18 insertions(+), 26 deletions(-)
>
> diff --git a/block/export/export.c b/block/export/export.c
> index b6c07f69b5..acd061e86e 100644
> --- a/block/export/export.c
> +++ b/block/export/export.c
> @@ -146,7 +146,7 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
>              .u.block_node.node_name = (char *)holder_name,
>          };
>  
> -        new_ctx = iothread_ref_and_get_aio_context(iothread, &holder);
> +        new_ctx = iothread_get_aio_context(iothread, &holder);
>          multithread_count = 1;
>          local_iothreads = g_new0(IOThread *, 1);
>          local_iothreads[0] = iothread;
> @@ -190,8 +190,7 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
>                  goto fail;
>              }
>              local_iothreads[i] = iothread;
> -            multithread_ctxs[i++] = iothread_ref_and_get_aio_context(iothread,
> -                                                                     &holder);
> +            multithread_ctxs[i++] = iothread_get_aio_context(iothread, &holder);
>          }
>          assert(i == multithread_count);
>      }
> diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c
> index b5bf8d359f..46bfd62f5a 100644
> --- a/hw/block/dataplane/xen-block.c
> +++ b/hw/block/dataplane/xen-block.c
> @@ -628,8 +628,8 @@ XenBlockDataPlane *xen_block_dataplane_create(XenDevice *xendev,
>          };
>  
>          dataplane->iothread = iothread;
> -        dataplane->ctx = iothread_ref_and_get_aio_context(dataplane->iothread,
> -                                                          &io_holder);
> +        dataplane->ctx = iothread_get_aio_context(dataplane->iothread,
> +                                                  &io_holder);
>      } else {
>          dataplane->ctx = qemu_get_aio_context();
>      }
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index d8dc1dd136..d1d2bd7025 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -1502,8 +1502,8 @@ static bool virtio_blk_vq_aio_context_init(VirtIOBlock *s, Error **errp)
>              .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT,
>              .u.qom_object.qom_path = (char *)path,
>          };
> -        AioContext *ctx = iothread_ref_and_get_aio_context(conf->iothread,
> -                                                           &io_holder);
> +        AioContext *ctx = iothread_get_aio_context(conf->iothread,
> +                                                   &io_holder);
>          for (unsigned i = 0; i < conf->num_queues; i++) {
>              s->vq_aio_context[i] = ctx;
>          }
> diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
> index c71f33b41e..76ab22610f 100644
> --- a/hw/scsi/virtio-scsi-dataplane.c
> +++ b/hw/scsi/virtio-scsi-dataplane.c
> @@ -78,8 +78,8 @@ void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
>              .type = IO_THREAD_HOLDER_KIND_QOM_OBJECT,
>              .u.qom_object.qom_path = (char *)path,
>          };
> -        AioContext *ctx = iothread_ref_and_get_aio_context(vs->conf.iothread,
> -                                                           &io_holder);
> +        AioContext *ctx = iothread_get_aio_context(vs->conf.iothread,
> +                                                   &io_holder);
>          for (uint16_t i = 0; i < vs->conf.num_queues; i++) {
>              s->vq_aio_context[VIRTIO_SCSI_VQ_NUM_FIXED + i] = ctx;
>          }
> diff --git a/hw/vfio-user/proxy.c b/hw/vfio-user/proxy.c
> index 756f368849..24af3c791b 100644
> --- a/hw/vfio-user/proxy.c
> +++ b/hw/vfio-user/proxy.c
> @@ -942,8 +942,7 @@ VFIOUserProxy *vfio_user_connect_dev(SocketAddress *addr, Error **errp)
>          vfio_user_iothread = iothread_create("VFIO user", errp);
>      }
>  
> -    proxy->ctx = iothread_ref_and_get_aio_context(vfio_user_iothread,
> -                                                  &io_holder);
> +    proxy->ctx = iothread_get_aio_context(vfio_user_iothread, &io_holder);
>      proxy->req_bh = qemu_bh_new(vfio_user_request, proxy);
>  
>      QTAILQ_INIT(&proxy->outgoing);
> diff --git a/hw/virtio/iothread-vq-mapping.c b/hw/virtio/iothread-vq-mapping.c
> index 2cb48dd387..727358a483 100644
> --- a/hw/virtio/iothread-vq-mapping.c
> +++ b/hw/virtio/iothread-vq-mapping.c
> @@ -99,8 +99,7 @@ bool iothread_vq_mapping_apply(
>              .u.qom_object.qom_path = (char *)holder,
>          };
>  
> -        AioContext *ctx = iothread_ref_and_get_aio_context(iothread,
> -                                                           &io_holder);
> +        AioContext *ctx = iothread_get_aio_context(iothread, &io_holder);
>  
>          if (node->value->vqs) {
>              uint16List *vq;
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index e9d023b4ec..4405a87ed0 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -903,7 +903,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
>          precopy_add_notifier(&s->free_page_hint_notify);
>  
>          s->free_page_bh = aio_bh_new_guarded(
> -                      iothread_ref_and_get_aio_context(s->iothread, &io_holder),
> +                      iothread_get_aio_context(s->iothread, &io_holder),
>                        virtio_ballloon_get_free_page_hints, s,
>                        &dev->mem_reentrancy_guard);
>      }
> diff --git a/include/system/iothread.h b/include/system/iothread.h
> index 064c05e78d..e5db215954 100644
> --- a/include/system/iothread.h
> +++ b/include/system/iothread.h
> @@ -70,15 +70,15 @@ DECLARE_INSTANCE_CHECKER(IOThread, IOTHREAD,
>  
>  char *iothread_get_id(IOThread *iothread);
>  IOThread *iothread_by_id(const char *id);
> -AioContext *iothread_get_aio_context(IOThread *iothread);
> +
>  /*
>   * The iothread_unsafe_get_aio_context() is a low-level unsafe way of getting
>   * the AioContext, recommend migrating to the new API with IOThreadHolder
>   * as much as possible.
>   */
>  AioContext *iothread_unsafe_get_aio_context(IOThread *iothread);
> -AioContext *iothread_ref_and_get_aio_context(IOThread *iothread,
> -                                             const IOThreadHolder *holder);
> +AioContext *iothread_get_aio_context(IOThread *iothread,
> +                                     const IOThreadHolder *holder);
>  void iothread_put_aio_context(IOThread *iothread, const IOThreadHolder *holder);
>  GMainContext *iothread_get_g_main_context(IOThread *iothread);
>  
> diff --git a/iothread.c b/iothread.c
> index 5949785b32..9bc8e359c1 100644
> --- a/iothread.c
> +++ b/iothread.c
> @@ -469,13 +469,8 @@ char *iothread_get_id(IOThread *iothread)
>      return g_strdup(object_get_canonical_path_component(OBJECT(iothread)));
>  }
>  
> -AioContext *iothread_get_aio_context(IOThread *iothread)
> -{
> -    return iothread->ctx;
> -}
> -
> -AioContext *iothread_ref_and_get_aio_context(IOThread *iothread,
> -                                             const IOThreadHolder *holder)
> +AioContext *iothread_get_aio_context(IOThread *iothread,
> +                                     const IOThreadHolder *holder)
>  {
>      /* Add IOThreadHolder to the list */
>      iothread_ref(iothread, holder);
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index 7eec6f967d..4d00cf499c 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -617,7 +617,7 @@ void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
>              .type = IO_THREAD_HOLDER_KIND_MONITOR_NAME,
>              .u.monitor_name.monitor_name = (char *)mon->id,
>          };
> -        mon->ctx = iothread_ref_and_get_aio_context(mon_iothread, &holder);
> +        mon->ctx = iothread_get_aio_context(mon_iothread, &holder);
>      }
>      qemu_mutex_init(&mon->mon_lock);
>      mon->is_qmp = is_qmp;
> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index 4f180936e3..820ea4d824 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -973,7 +973,7 @@ static void colo_compare_iothread(CompareState *s)
>          .u.qom_object.qom_path = (char *)path,
>      };
>  
> -    AioContext *ctx = iothread_ref_and_get_aio_context(s->iothread, &io_holder);
> +    AioContext *ctx = iothread_get_aio_context(s->iothread, &io_holder);
>  
>      s->iothread_ctx = ctx;
>      s->worker_context = iothread_get_g_main_context(s->iothread);


The patch appears to delete unused iothread_get_aio_context() from
iothread.[cg] and to rename iothread_ref_and_get_aio_context() to
iothread_get_aio_context().  It leaves iothread_get_aio_context() in
tests/unit/iothread.[ch] alone.  The result is confusing: test's
iothread_get_aio_context() takes now one parameter less than the regular
one.

Should you change both versions?