Re: [Qemu-devel] [PATCH v2 10/12] savevm: update error reporting of qemu_savevm_state() and related functions

[Kevin Wolf <kwolf@redhat.com>]

Am 24.04.2013 um 17:32 hat Pavel Hrdina geschrieben:
> Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
> ---
>  include/sysemu/sysemu.h |  7 ++++---
>  migration.c             |  6 +++---
>  savevm.c                | 38 +++++++++++++++++++-------------------
>  3 files changed, 26 insertions(+), 25 deletions(-)

> --- a/migration.c
> +++ b/migration.c
> @@ -508,7 +508,7 @@ static void *migration_thread(void *opaque)
>      bool old_vm_running = false;
>  
>      DPRINTF("beginning savevm\n");
> -    qemu_savevm_state_begin(s->file, &s->params);
> +    qemu_savevm_state_begin(s->file, &s->params, NULL);
>  
>      while (s->state == MIG_STATE_ACTIVE) {
>          int64_t current_time;
> @@ -519,7 +519,7 @@ static void *migration_thread(void *opaque)
>              pending_size = qemu_savevm_state_pending(s->file, max_size);
>              DPRINTF("pending size %lu max %lu\n", pending_size, max_size);
>              if (pending_size && pending_size >= max_size) {
> -                qemu_savevm_state_iterate(s->file);
> +                qemu_savevm_state_iterate(s->file, NULL);
>              } else {
>                  DPRINTF("done iterating\n");
>                  qemu_mutex_lock_iothread();
> @@ -528,7 +528,7 @@ static void *migration_thread(void *opaque)
>                  old_vm_running = runstate_is_running();
>                  vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
>                  qemu_file_set_rate_limit(s->file, INT_MAX);
> -                qemu_savevm_state_complete(s->file);
> +                qemu_savevm_state_complete(s->file, NULL);
>                  qemu_mutex_unlock_iothread();
>                  if (!qemu_file_get_error(s->file)) {
>                      migrate_finish_set_state(s, MIG_STATE_COMPLETED);

Why is it okay to ignore any errors in this function?

> diff --git a/savevm.c b/savevm.c
> index 6458621..749d49d 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -1972,37 +1976,33 @@ void qemu_savevm_state_cancel(void)
>      }
>  }
>  
> -static int qemu_savevm_state(QEMUFile *f)
> +static void qemu_savevm_state(QEMUFile *f, Error **errp)
>  {
> -    int ret;
>      MigrationParams params = {
>          .blk = 0,
>          .shared = 0
>      };
>  
> -    if (qemu_savevm_state_blocked(NULL)) {
> -        return -EINVAL;
> +    if (qemu_savevm_state_blocked(errp)) {
> +        return;
>      }
>  
>      qemu_mutex_unlock_iothread();
> -    qemu_savevm_state_begin(f, &params);
> +    qemu_savevm_state_begin(f, &params, errp);
>      qemu_mutex_lock_iothread();

You need to check errp here.

>      while (qemu_file_get_error(f) == 0) {
> -        if (qemu_savevm_state_iterate(f) > 0) {
> +        if (qemu_savevm_state_iterate(f, errp) > 0) {
>              break;
>          }

And here as well.

The problem is that you must not overwrite an error, therefore you need
to explicitly free and ignore unused errors, and decide which one takes
precedence.

>      }
>  
> -    ret = qemu_file_get_error(f);
> -    if (ret == 0) {
> -        qemu_savevm_state_complete(f);
> -        ret = qemu_file_get_error(f);
> +    if (!qemu_file_get_error(f)) {
> +        qemu_savevm_state_complete(f, errp);
>      }
> -    if (ret != 0) {
> +    if (qemu_file_get_error(f)) {
>          qemu_savevm_state_cancel();
>      }
> -    return ret;
>  }

Kevin