Re: [Qemu-devel] [PATCH v2 5/6] block: mirror - change string allocation to 2-bytes

[John Snow <jsnow@redhat.com>]

On 01/20/2015 12:31 PM, Jeff Cody wrote:
> The backing_filename string in mirror_run() is only used to check
> for a NULL string, so we don't need to allocate 1024 bytes (or, later,
> PATH_MAX bytes), when we only need to copy the first 2 characters.
>
> We technically only need 1 byte, as we are just checking for NULL, but
> since backing_filename[] is populated by bdrv_get_backing_filename(), a
> string size of 1 will always only return '\0';
>
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>   block/mirror.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 9019d1b..4056164 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -378,7 +378,8 @@ static void coroutine_fn mirror_run(void *opaque)
>       int64_t sector_num, end, sectors_per_chunk, length;
>       uint64_t last_pause_ns;
>       BlockDriverInfo bdi;
> -    char backing_filename[1024];
> +    char backing_filename[2]; /* we only need 2 characters because we are only
> +                                 checking for a NULL string */
>       int ret = 0;
>       int n;
>
>

Reviewed-by: John Snow <jsnow@redhat.com>