Re: [Qemu-block] [PATCH v6 24/39] blockdev: Do not create BDS for empty drive

[Kevin Wolf]

Am 12.10.2015 um 22:00 hat Max Reitz geschrieben:
> Do not use "rudimentary" BDSs for empty drives any longer (for
> freshly created drives).
> 
> After a follow-up patch, empty drives will generally use a NULL BDS, not
> only the freshly created drives.
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>  blockdev.c | 72 
> ++++++++++++++++++++++++++++++++++++++------------------------
>  1 file changed, 44 insertions(+), 28 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 35efe84..845a1c1 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -514,16 +514,44 @@ static BlockBackend *blockdev_init(const char *file, 
> QDict *bs_opts,
>          goto early_err;
>      }
>  
> +    if (snapshot) {
> +        /* always use cache=unsafe with snapshot */
> +        bdrv_flags &= ~BDRV_O_CACHE_MASK;
> +        bdrv_flags |= (BDRV_O_SNAPSHOT|BDRV_O_CACHE_WB|BDRV_O_NO_FLUSH);
> +    }
> +
> +    if (copy_on_read) {
> +        bdrv_flags |= BDRV_O_COPY_ON_READ;
> +    }
> +
> +    if (runstate_check(RUN_STATE_INMIGRATE)) {
> +        bdrv_flags |= BDRV_O_INCOMING;
> +    }

Bad conflict resolution when you added patch 2, which moved the
BDRV_O_INCOMING code to block.c?

That patch is actually essential here as well: The flag would ends up in
the root state, and bdrv_invalidate_cache_all() doesn't clear the flag
any more. So we might end up opening an image with BDRV_O_INCOMING even
though migration has long finished.

Kevin