Re: [PATCH v2 2/4] luks: implement .bdrv_measure()

[Max Reitz]

On 09.01.20 12:10, Stefan Hajnoczi wrote:
> Add qemu-img measure support in the "luks" block driver.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  block/crypto.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 82 insertions(+)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index ed32202fa2..51f37bb1f6 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -548,6 +548,87 @@ static int64_t block_crypto_getlength(BlockDriverState 
> *bs)

[...]

> +            if (ret & BDRV_BLOCK_ZERO) {
> +                /* Skip zero regions */
> +            } else if ((ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) ==
> +                       (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) {
> +                /* Count clusters we've seen */
> +                required += pnum;
> +            }

Don’t LUKS-encrypted files allocate effectively everything because zero
data has to be encrypted, too?

(“Effectively”, because you could zero out regions that are zero when
encrypted, but...)

> +        }
> +    }
> +
> +    /* Take into account preallocation.  Nothing special is needed for
> +     * PREALLOC_MODE_METADATA since metadata is always counted.
> +     */
> +    if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) {
> +        required = virtual_size;

Same here.  I think required should always be set to virtual_size.

Max

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