Re: [Qemu-devel] [PATCH v10 3/9] qcow2: Make sizes more humanly readable

[Eric Blake]

On 9/21/18 12:23 PM, Leonid Bloch wrote:
> Signed-off-by: Leonid Bloch <address@hidden>
> Reviewed-by: Alberto Garcia <address@hidden>
> ---
>   block/qcow2.c | 2 +-
>   block/qcow2.h | 9 +++++----
>   2 files changed, 6 insertions(+), 5 deletions(-)

> +++ b/block/qcow2.h
> @@ -27,6 +27,7 @@
>   
>   #include "crypto/block.h"
>   #include "qemu/coroutine.h"
> +#include "qemu/units.h"
>   
>   //#define DEBUG_ALLOC
>   //#define DEBUG_ALLOC2
> @@ -43,11 +44,11 @@
>   
>   /* 8 MB refcount table is enough for 2 PB images at 64k cluster size
>    * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
> -#define QCOW_MAX_REFTABLE_SIZE 0x800000
> +#define QCOW_MAX_REFTABLE_SIZE S_8MiB

Why not (8 * MiB)?  Where does this get stringified that you have to 
introduce a new macro? Can we instead fix the stringification location 
to call a convenience helper that converts arbitrary values into 
convenient strings at runtime, rather than having to worry about a 
separate macro just for stringification purposes?

>   
>   /* 32 MB L1 table is enough for 2 PB images at 64k cluster size
>    * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
> -#define QCOW_MAX_L1_SIZE 0x2000000
> +#define QCOW_MAX_L1_SIZE S_32MiB

Again, why not (32 * MiB)?

>   
>   /* Allow for an average of 1k per snapshot table entry, should be plenty of
>    * space for snapshot names and IDs */
> @@ -75,9 +76,9 @@
>   
>   /* Whichever is more */
>   #define DEFAULT_L2_CACHE_CLUSTERS 8 /* clusters */
> -#define DEFAULT_L2_CACHE_BYTE_SIZE 1048576 /* bytes */
> +#define DEFAULT_L2_CACHE_SIZE S_1MiB

and (1 * MiB)

>   
> -#define DEFAULT_CLUSTER_SIZE 65536
> +#define DEFAULT_CLUSTER_SIZE S_64KiB

and (64 * KiB)

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