Re: [Qemu-devel] [RFC PATCH v3 2/3] block: call the snapshot handlers of the protocol drivers

[Kevin Wolf <kwolf@redhat.com>]

Am 17.05.2010 12:19, schrieb MORITA Kazutaka:
> When snapshot handlers are not defined in the format driver, it is
> better to call the ones of the protocol driver.  This enables us to
> implement snapshot support in the protocol driver.
> 
> We need to call bdrv_close() and bdrv_open() handlers of the format
> driver before and after bdrv_snapshot_goto() call of the protocol.  It is
> because the contents of the block driver state may need to be changed
> after loading vmstate.
> 
> Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
> ---
>  block.c |   61 +++++++++++++++++++++++++++++++++++++++++++------------------
>  1 files changed, 43 insertions(+), 18 deletions(-)
> 
> diff --git a/block.c b/block.c
> index f3bf3f2..c987e57 100644
> --- a/block.c
> +++ b/block.c
> @@ -1683,9 +1683,11 @@ int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
>      BlockDriver *drv = bs->drv;
>      if (!drv)
>          return -ENOMEDIUM;
> -    if (!drv->bdrv_save_vmstate)
> -        return -ENOTSUP;
> -    return drv->bdrv_save_vmstate(bs, buf, pos, size);
> +    if (drv->bdrv_save_vmstate)
> +        return drv->bdrv_save_vmstate(bs, buf, pos, size);
> +    if (bs->file)
> +        return bdrv_save_vmstate(bs->file, buf, pos, size);
> +    return -ENOTSUP;
>  }
>  
>  int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
> @@ -1694,9 +1696,11 @@ int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
>      BlockDriver *drv = bs->drv;
>      if (!drv)
>          return -ENOMEDIUM;
> -    if (!drv->bdrv_load_vmstate)
> -        return -ENOTSUP;
> -    return drv->bdrv_load_vmstate(bs, buf, pos, size);
> +    if (drv->bdrv_load_vmstate)
> +        return drv->bdrv_load_vmstate(bs, buf, pos, size);
> +    if (bs->file)
> +        return bdrv_load_vmstate(bs->file, buf, pos, size);
> +    return -ENOTSUP;
>  }
>  
>  void bdrv_debug_event(BlockDriverState *bs, BlkDebugEvent event)
> @@ -1720,20 +1724,37 @@ int bdrv_snapshot_create(BlockDriverState *bs,
>      BlockDriver *drv = bs->drv;
>      if (!drv)
>          return -ENOMEDIUM;
> -    if (!drv->bdrv_snapshot_create)
> -        return -ENOTSUP;
> -    return drv->bdrv_snapshot_create(bs, sn_info);
> +    if (drv->bdrv_snapshot_create)
> +        return drv->bdrv_snapshot_create(bs, sn_info);
> +    if (bs->file)
> +        return bdrv_snapshot_create(bs->file, sn_info);
> +    return -ENOTSUP;
>  }
>  
>  int bdrv_snapshot_goto(BlockDriverState *bs,
>                         const char *snapshot_id)
>  {
>      BlockDriver *drv = bs->drv;
> +    int ret, open_ret;
> +
>      if (!drv)
>          return -ENOMEDIUM;
> -    if (!drv->bdrv_snapshot_goto)
> -        return -ENOTSUP;
> -    return drv->bdrv_snapshot_goto(bs, snapshot_id);
> +    if (drv->bdrv_snapshot_goto)
> +        return drv->bdrv_snapshot_goto(bs, snapshot_id);
> +
> +    if (bs->file) {
> +        drv->bdrv_close(bs);
> +        ret = bdrv_snapshot_goto(bs->file, snapshot_id);
> +        open_ret = drv->bdrv_open(bs, bs->open_flags);
> +        if (open_ret < 0) {
> +            bdrv_delete(bs);

I think you mean bs->file here.

Kevin

> +            bs->drv = NULL;
> +            return open_ret;
> +        }
> +        return ret;
> +    }
> +
> +    return -ENOTSUP;
>  }
>  
>  int bdrv_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)