Re: [Qemu-devel] [PATCH V7 02/14] block: add bdrv_can_read_snapshot() function

[Stefan Hajnoczi]

On Tue, Feb 26, 2013 at 06:40:16PM +0800, Wenchao Xia wrote:
>   Compared to bdrv_can_snapshot(), this function return whether
> bs* is ready to read snapshot info from instead of write. If yes,
> caller can then query snapshot information, but taking snapshot
> is not always possible for that *bs may be read only.
> 
> Signed-off-by: Wenchao Xia <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> ---
>  block.c               |   19 +++++++++++++++++++
>  include/block/block.h |    1 +
>  2 files changed, 20 insertions(+), 0 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 50dab8e..19c2d7b 100644
> --- a/block.c
> +++ b/block.c
> @@ -3058,6 +3058,25 @@ bool bdrv_debug_is_suspended(BlockDriverState *bs, 
> const char *tag)
>  /**************************************************************/
>  /* handling of snapshots */
>  
> +/* return whether internal snapshot can be read on @bs */
> +bool bdrv_can_read_snapshot(BlockDriverState *bs)

Which operations are included in "read a snapshot"?

Candidate list:
 * bdrv_snapshot_load_tmp()
 * bdrv_snapshot_list()
 * bdrv_snapshot_dump()
 * bdrv_load_vmstate()
 * others?

Please document the meaning of this function so that others can
use/modify it correctly in the future.

Stefan