Re: [PATCH v3 04/26] migration: Always report an error in ram_save_setup()

[Fabiano Rosas]

Cédric Le Goater <clg@redhat.com> writes:

> This will prepare ground for futur changes adding an Error** argument
> to the save_setup() handler. We need to make sure that on failure,
> ram_save_setup() sets a new error.
>
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
>  migration/ram.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 
> 45a00b45edd429ef0568adce09b7459883e00167..dbd04d8ee2167881007c836a6bbc79c1aced72d0
>  100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2937,12 +2937,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>      int ret;
>  
>      if (compress_threads_save_setup()) {
> +        error_report("%s: failed to start compress threads", __func__);
>          return -1;
>      }
>  
>      /* migration has already setup the bitmap, reuse it. */
>      if (!migration_in_colo_state()) {
>          if (ram_init_all(rsp) != 0) {
> +            error_report("%s: failed to setup RAM for migration", __func__);
>              compress_threads_save_cleanup();
>              return -1;
>          }
> @@ -2969,12 +2971,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>  
>      ret = rdma_registration_start(f, RAM_CONTROL_SETUP);
>      if (ret < 0) {
> +        error_report("%s: failed to start RDMA registration", __func__);
>          qemu_file_set_error(f, ret);
>          return ret;
>      }
>  
>      ret = rdma_registration_stop(f, RAM_CONTROL_SETUP);
>      if (ret < 0) {
> +        error_report("%s: failed to stop RDMA registration", __func__);
>          qemu_file_set_error(f, ret);
>          return ret;
>      }
> @@ -2986,6 +2990,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>      ret = multifd_send_sync_main();
>      bql_lock();
>      if (ret < 0) {
> +        error_report("%s: multifd synchronization failed", __func__);
>          return ret;
>      }
>  
> @@ -2994,7 +2999,11 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>      }
>  
>      qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
> -    return qemu_fflush(f);
> +    ret = qemu_fflush(f);
> +    if (ret) {
> +        error_report("%s failed : %s", __func__, strerror(ret));

Here it should be -ret

The qemu_fflush function returns the QEMUFile error (f->last_error) and
that is expected to be a -errno value.

I started making sure all callers of qemu_file_set_error() use a
negative value, but got lost in the vmstate code and never finished:

https://lore.kernel.org/r/20230706195201.18595-1-farosas@suse.de