Re: [Qemu-devel] [PATCH v2 8/9] block: Fix bdrv_co_truncate overlap check

[Eric Blake]

On 07/05/2018 02:37 AM, Fam Zheng wrote:
> If we are growing the image and potentially using preallocation for the
> new area, we need to make sure that no write requests are made to the
> "preallocated" area which address@hidden, @offset), not address@hidden, offset 
> * 2

s/which/which is/

> - @old_size).
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>   block/io.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Eric Blake <address@hidden>

> diff --git a/block/io.c b/block/io.c
> index d07849fa96..ed18eb0ca3 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -3070,7 +3070,8 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, 
> int64_t offset,
>       }
>   
>       bdrv_inc_in_flight(bs);
> -    tracked_request_begin(&req, bs, offset, new_bytes, BDRV_TRACKED_TRUNCATE);
> +    tracked_request_begin(&req, bs, offset - new_bytes, new_bytes,
> +                          BDRV_TRACKED_TRUNCATE);

Is it any more legible to do s/offset - new_bytes/old_size/, since those 
are equivalent?

>   
>       /* If we are growing the image and potentially using preallocation for the
>        * new area, we need to make sure that no write requests are made to it

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org