Wenchao Xia <xiaw...@linux.vnet.ibm.com> writes:
> 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 <xiaw...@linux.vnet.ibm.com>
> Reviewed-by: Eric Blake <ebl...@redhat.com>
> ---
> 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)
> +{
> + BlockDriver *drv = bs->drv;
> + if (!drv || !bdrv_is_inserted(bs)) {
> + return false;
> + }
> +
> + if (!drv->bdrv_snapshot_create) {
> + if (bs->file != NULL) {
> + return bdrv_can_read_snapshot(bs->file);
> + }
> + return false;
> + }
> +
> + return true;
> +}
Looks like
bdrv_can_read_snapshot(bs) && !bdrv_is_read_only(bs) == bdrv_can_snapshot(bs)
Correct?
> +
> +/* return whether internal snapshot can be write on @bs */
"be written".
Or more succinctly:
/* Can @bs take a snapshot? */
> int bdrv_can_snapshot(BlockDriverState *bs)
> {
> BlockDriver *drv = bs->drv;
> diff --git a/include/block/block.h b/include/block/block.h
> index 5c3b911..4c48052 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -321,6 +321,7 @@ void bdrv_get_full_backing_filename(BlockDriverState *bs,
> char *dest, size_t sz);
> BlockInfo *bdrv_query_info(BlockDriverState *s);
> BlockStats *bdrv_query_stats(const BlockDriverState *bs);
> +bool bdrv_can_read_snapshot(BlockDriverState *bs);
> int bdrv_can_snapshot(BlockDriverState *bs);
> int bdrv_is_snapshot(BlockDriverState *bs);
> BlockDriverState *bdrv_snapshots(void);
