Re: [Qemu-devel] [PATCH] luks: Allow share-rw=on

[Daniel P . Berrangé]

On Tue, Aug 14, 2018 at 03:25:51PM +0800, Fam Zheng wrote:
> Format drivers such as qcow2 don't allow sharing the same image between
> two QEMU instances in order to prevent image corruptions, because of
> metadata cache. LUKS driver don't modify metadata except for when
> creating image, so it is safe to relax the permission. This makes
> share-rw=on property work on virtual devices.
> 
> Suggested-by: Daniel P. Berrangé <address@hidden>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  block/crypto.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index 146d81c90a..33ee01bebd 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -627,7 +627,9 @@ BlockDriver bdrv_crypto_luks = {
>      .bdrv_probe         = block_crypto_probe_luks,
>      .bdrv_open          = block_crypto_open_luks,
>      .bdrv_close         = block_crypto_close,
> -    .bdrv_child_perm    = bdrv_format_default_perms,
> +    /* This driver doesn't modify LUKS metadata except when creating image.
> +     * Allow share-rw=on as a special case. */
> +    .bdrv_child_perm    = bdrv_filter_default_perms,
>      .bdrv_co_create     = block_crypto_co_create_luks,
>      .bdrv_co_create_opts = block_crypto_co_create_opts_luks,
>      .bdrv_co_truncate   = block_crypto_co_truncate,

Reviewed-by: Daniel P. Berrangé <address@hidden>


Regards,
Daniel
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