Re: [PATCH 1/4] migration/savevm: respect qemu_fclose() error code in save_snapshot()

[Dr. David Alan Gilbert]

* Denis V. Lunev (den@openvz.org) wrote:
> qemu_fclose() could return error, f.e. if bdrv_co_flush() will return
> the error.
> 
> This validation will become more important once we will start waiting of
> asynchronous IO operations, started from bdrv_write_vmstate(), which are
> coming soon.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Fam Zheng <fam@euphon.net>
> CC: Juan Quintela <quintela@redhat.com>
> CC: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> CC: Denis Plotnikov <dplotnikov@virtuozzo.com>

We check the return value in very few other places; I think in the
migration case we do flushes and assume that if the flushes work we
were OK; then most of the closes happen on error paths or after points
we think we're done.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/savevm.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index c00a6807d9..0ff5bb40ed 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2628,7 +2628,7 @@ int save_snapshot(const char *name, Error **errp)
>  {
>      BlockDriverState *bs, *bs1;
>      QEMUSnapshotInfo sn1, *sn = &sn1, old_sn1, *old_sn = &old_sn1;
> -    int ret = -1;
> +    int ret = -1, ret2;
>      QEMUFile *f;
>      int saved_vm_running;
>      uint64_t vm_state_size;
> @@ -2712,10 +2712,14 @@ int save_snapshot(const char *name, Error **errp)
>      }
>      ret = qemu_savevm_state(f, errp);
>      vm_state_size = qemu_ftell(f);
> -    qemu_fclose(f);
> +    ret2 = qemu_fclose(f);
>      if (ret < 0) {
>          goto the_end;
>      }
> +    if (ret2 < 0) {
> +        ret = ret2;
> +        goto the_end;
> +    }
>  
>      /* The bdrv_all_create_snapshot() call that follows acquires the 
> AioContext
>       * for itself.  BDRV_POLL_WHILE() does not support nested locking because
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK