Re: [PATCH 3/3] migration: stop returning errno from load_snapshot()

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

On 08.10.2020 20:48, Philippe Mathieu-Daudé wrote:
> From: Daniel P. Berrangé <berrange@redhat.com>
> 
> None of the callers care about the errno value since there is a full
> Error object populated. This gives consistency with save_snapshot()
> which already just returns a boolean value.
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> [PMD: Return false/true instead of -1/0, document function]
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Acked-by: Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>

> ---
>   include/migration/snapshot.h |  9 ++++++++-
>   migration/savevm.c           | 19 +++++++++----------
>   monitor/hmp-cmds.c           |  2 +-
>   replay/replay-snapshot.c     |  2 +-
>   softmmu/vl.c                 |  2 +-
>   5 files changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/include/migration/snapshot.h b/include/migration/snapshot.h
> index a40c34307b..9bc989a6b4 100644
> --- a/include/migration/snapshot.h
> +++ b/include/migration/snapshot.h
> @@ -23,6 +23,13 @@
>    * On failure, store an error through @errp and return %false.
>    */
>   bool save_snapshot(const char *name, Error **errp);
> -int load_snapshot(const char *name, Error **errp);
> +/**
> + * save_snapshot: Load a snapshot.
> + * @name: path to snapshot
> + * @errp: pointer to error object
> + * On success, return %true.
> + * On failure, store an error through @errp and return %false.
> + */
> +bool load_snapshot(const char *name, Error **errp);
>   
>   #endif
> diff --git a/migration/savevm.c b/migration/savevm.c
> index fd2e5e8b66..531bb2eca1 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2864,7 +2864,7 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
>       migration_incoming_state_destroy();
>   }
>   
> -int load_snapshot(const char *name, Error **errp)
> +bool load_snapshot(const char *name, Error **errp)
>   {
>       BlockDriverState *bs_vm_state;
>       QEMUSnapshotInfo sn;
> @@ -2874,16 +2874,16 @@ int load_snapshot(const char *name, Error **errp)
>       MigrationIncomingState *mis = migration_incoming_get_current();
>   
>       if (!bdrv_all_can_snapshot(errp)) {
> -        return -ENOTSUP;
> +        return false;
>       }
>       ret = bdrv_all_find_snapshot(name, errp);
>       if (ret < 0) {
> -        return ret;
> +        return false;
>       }
>   
>       bs_vm_state = bdrv_all_find_vmstate_bs(errp);
>       if (!bs_vm_state) {
> -        return -ENOTSUP;
> +        return false;
>       }
>       aio_context = bdrv_get_aio_context(bs_vm_state);
>   
> @@ -2892,11 +2892,11 @@ int load_snapshot(const char *name, Error **errp)
>       ret = bdrv_snapshot_find(bs_vm_state, &sn, name);
>       aio_context_release(aio_context);
>       if (ret < 0) {
> -        return ret;
> +        return false;
>       } else if (sn.vm_state_size == 0) {
>           error_setg(errp, "This is a disk-only snapshot. Revert to it "
>                      " offline using qemu-img");
> -        return -EINVAL;
> +        return false;
>       }
>   
>       /*
> @@ -2917,7 +2917,6 @@ int load_snapshot(const char *name, Error **errp)
>       f = qemu_fopen_bdrv(bs_vm_state, 0);
>       if (!f) {
>           error_setg(errp, "Could not open VM state file");
> -        ret = -EINVAL;
>           goto err_drain;
>       }
>   
> @@ -2933,14 +2932,14 @@ int load_snapshot(const char *name, Error **errp)
>   
>       if (ret < 0) {
>           error_setg(errp, "Error %d while loading VM state", ret);
> -        return ret;
> +        return false;
>       }
>   
> -    return 0;
> +    return true;
>   
>   err_drain:
>       bdrv_drain_all_end();
> -    return ret;
> +    return false;
>   }
>   
>   void vmstate_register_ram(MemoryRegion *mr, DeviceState *dev)
> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> index 14848a3381..ff0e3df8a3 100644
> --- a/monitor/hmp-cmds.c
> +++ b/monitor/hmp-cmds.c
> @@ -1123,7 +1123,7 @@ void hmp_loadvm(Monitor *mon, const QDict *qdict)
>   
>       vm_stop(RUN_STATE_RESTORE_VM);
>   
> -    if (load_snapshot(name, &err) == 0 && saved_vm_running) {
> +    if (!load_snapshot(name, &err) && saved_vm_running) {
>           vm_start();
>       }
>       hmp_handle_error(mon, err);
> diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
> index 4f2560d156..b289365937 100644
> --- a/replay/replay-snapshot.c
> +++ b/replay/replay-snapshot.c
> @@ -83,7 +83,7 @@ void replay_vmstate_init(void)
>                   exit(1);
>               }
>           } else if (replay_mode == REPLAY_MODE_PLAY) {
> -            if (load_snapshot(replay_snapshot, &err) != 0) {
> +            if (!load_snapshot(replay_snapshot, &err)) {
>                   error_report_err(err);
>                   error_report("Could not load snapshot for icount replay");
>                   exit(1);
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index 5a11a62f78..6eaa6b3a09 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -4478,7 +4478,7 @@ void qemu_init(int argc, char **argv, char **envp)
>       register_global_state();
>       if (loadvm) {
>           Error *local_err = NULL;
> -        if (load_snapshot(loadvm, &local_err) < 0) {
> +        if (!load_snapshot(loadvm, &local_err)) {
>               error_report_err(local_err);
>               autostart = 0;
>               exit(1);
>