Re: [Qemu-devel] [PATCH 5/5] migration: Route more error paths

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Xu (peterx@redhat.com) wrote:
> On Tue, Sep 19, 2017 at 07:00:38PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > vmstate_save is called in a few places, and vmstate_save_state is
> > called in lots of places.
> > 
> > Route error returns from the easier cases back up;  there are lots
> > of more complex cases where there own error paths need fixing.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> IIUC we are touching up the put()s hooks.  Then do we need this as
> well below?

You're right - 'put' has returned int since Jianjun's patches but
I seem to have missed that it never wired the check up.

> -----
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 3226e8e..70e1e14 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -355,7 +355,10 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
>                  } else if (field->flags & VMS_STRUCT) {
>                      vmstate_save_state(f, field->vmsd, curr_elem, vmdesc_loop);
>                  } else {
> -                    field->info->put(f, curr_elem, size, field, vmdesc_loop);
> +                    ret = field->info->put(f, curr_elem, size, field, vmdesc_loop);
> +                    if (ret) {
> +                        return ret;
> +                    }
>                  }
>  
>                  written_bytes = qemu_ftell_fast(f) - old_offset;
> -----
> 
> Or these errors won't really stop the migration?

Added as a separate patch (with an error report in the if)

Thanks,

Dave

> 
> > ---
> >  hw/display/virtio-gpu.c    |  4 +---
> >  hw/virtio/virtio.c         | 13 +++++++------
> >  include/hw/virtio/virtio.h |  2 +-
> >  migration/vmstate-types.c  | 11 ++++++++---
> >  tests/test-vmstate.c       |  6 +++---
> >  5 files changed, 20 insertions(+), 16 deletions(-)
> > 
> > diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> > index 622ee300f9..c9494e8a79 100644
> > --- a/hw/display/virtio-gpu.c
> > +++ b/hw/display/virtio-gpu.c
> > @@ -996,9 +996,7 @@ static int virtio_gpu_save(QEMUFile *f, void *opaque, size_t size,
> >      }
> >      qemu_put_be32(f, 0); /* end of list */
> >  
> > -    vmstate_save_state(f, &vmstate_virtio_gpu_scanouts, g, NULL);
> > -
> > -    return 0;
> > +    return vmstate_save_state(f, &vmstate_virtio_gpu_scanouts, g, NULL);
> >  }
> >  
> >  static int virtio_gpu_load(QEMUFile *f, void *opaque, size_t size,
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index 464947f76d..860333788b 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -1899,7 +1899,7 @@ static const VMStateDescription vmstate_virtio = {
> >      }
> >  };
> >  
> > -void virtio_save(VirtIODevice *vdev, QEMUFile *f)
> > +int virtio_save(VirtIODevice *vdev, QEMUFile *f)
> >  {
> >      BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> >      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> > @@ -1949,20 +1949,21 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
> >      }
> >  
> >      if (vdc->vmsd) {
> > -        vmstate_save_state(f, vdc->vmsd, vdev, NULL);
> > +        int ret = vmstate_save_state(f, vdc->vmsd, vdev, NULL);
> > +        if (ret) {
> > +            return ret;
> > +        }
> >      }
> >  
> >      /* Subsections */
> > -    vmstate_save_state(f, &vmstate_virtio, vdev, NULL);
> > +    return vmstate_save_state(f, &vmstate_virtio, vdev, NULL);
> >  }
> >  
> >  /* A wrapper for use as a VMState .put function */
> >  static int virtio_device_put(QEMUFile *f, void *opaque, size_t size,
> >                                VMStateField *field, QJSON *vmdesc)
> >  {
> > -    virtio_save(VIRTIO_DEVICE(opaque), f);
> > -
> > -    return 0;
> > +    return virtio_save(VIRTIO_DEVICE(opaque), f);
> >  }
> >  
> >  /* A wrapper for use as a VMState .get function */
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index 80c45c321e..5abada6966 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -188,7 +188,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
> >  void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq);
> >  void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);
> >  
> > -void virtio_save(VirtIODevice *vdev, QEMUFile *f);
> > +int virtio_save(VirtIODevice *vdev, QEMUFile *f);
> >  
> >  extern const VMStateInfo virtio_vmstate_info;
> >  
> > diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
> > index c056c98bdb..48184c380d 100644
> > --- a/migration/vmstate-types.c
> > +++ b/migration/vmstate-types.c
> > @@ -550,13 +550,14 @@ static int put_tmp(QEMUFile *f, void *pv, size_t size, VMStateField *field,
> >  {
> >      const VMStateDescription *vmsd = field->vmsd;
> >      void *tmp = g_malloc(size);
> > +    int ret;
> >  
> >      /* Writes the parent field which is at the start of the tmp */
> >      *(void **)tmp = pv;
> > -    vmstate_save_state(f, vmsd, tmp, vmdesc);
> > +    ret = vmstate_save_state(f, vmsd, tmp, vmdesc);
> >      g_free(tmp);
> >  
> > -    return 0;
> > +    return ret;
> >  }
> >  
> >  const VMStateInfo vmstate_info_tmp = {
> > @@ -657,12 +658,16 @@ static int put_qtailq(QEMUFile *f, void *pv, size_t unused_size,
> >      /* offset of the QTAILQ entry in a QTAILQ element*/
> >      size_t entry_offset = field->start;
> >      void *elm;
> > +    int ret;
> >  
> >      trace_put_qtailq(vmsd->name, vmsd->version_id);
> >  
> >      QTAILQ_RAW_FOREACH(elm, pv, entry_offset) {
> >          qemu_put_byte(f, true);
> > -        vmstate_save_state(f, vmsd, elm, vmdesc);
> > +        ret = vmstate_save_state(f, vmsd, elm, vmdesc);
> > +        if (ret) {
> > +            return ret;
> > +        }
> >      }
> >      qemu_put_byte(f, false);
> >  
> > diff --git a/tests/test-vmstate.c b/tests/test-vmstate.c
> > index e643ac662b..ab3e430c2c 100644
> > --- a/tests/test-vmstate.c
> > +++ b/tests/test-vmstate.c
> > @@ -70,7 +70,7 @@ static void save_vmstate(const VMStateDescription *desc, void *obj)
> >      QEMUFile *f = open_test_file(true);
> >  
> >      /* Save file with vmstate */
> > -    vmstate_save_state(f, desc, obj, NULL);
> > +    g_assert(!vmstate_save_state(f, desc, obj, NULL));
> >      qemu_put_byte(f, QEMU_VM_EOF);
> >      g_assert(!qemu_file_get_error(f));
> >      qemu_fclose(f);
> > @@ -381,7 +381,7 @@ static void test_save_noskip(void)
> >      QEMUFile *fsave = open_test_file(true);
> >      TestStruct obj = { .a = 1, .b = 2, .c = 3, .d = 4, .e = 5, .f = 6,
> >                         .skip_c_e = false };
> > -    vmstate_save_state(fsave, &vmstate_skipping, &obj, NULL);
> > +    g_assert(!vmstate_save_state(fsave, &vmstate_skipping, &obj, NULL));
> >      g_assert(!qemu_file_get_error(fsave));
> >  
> >      uint8_t expected[] = {
> > @@ -402,7 +402,7 @@ static void test_save_skip(void)
> >      QEMUFile *fsave = open_test_file(true);
> >      TestStruct obj = { .a = 1, .b = 2, .c = 3, .d = 4, .e = 5, .f = 6,
> >                         .skip_c_e = true };
> > -    vmstate_save_state(fsave, &vmstate_skipping, &obj, NULL);
> > +    g_assert(!vmstate_save_state(fsave, &vmstate_skipping, &obj, NULL));
> >      g_assert(!qemu_file_get_error(fsave));
> >  
> >      uint8_t expected[] = {
> > -- 
> > 2.13.5
> > 
> 
> -- 
> Peter Xu
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK