Re: [Qemu-block] [RFC PATCH 20/41] hw/block: Introduce share-rw qdev property

[Max Reitz]

On 13.02.2017 18:22, Kevin Wolf wrote:
> By default, don't allow another writer for block devices that are
> attached to a guest device. For the cases where this setup is intended
> (e.g. using a cluster filesystem on the disk), the new option can be
> used to allow it.
> 
> This change affects only devices using DEFINE_BLOCK_PROPERTIES().
> Devices directly using DEFINE_PROP_DRIVE() still accept writers
> unconditionally.
> 
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  hw/block/block.c           | 14 ++++++------
>  include/hw/block/block.h   |  4 +++-
>  tests/qemu-iotests/172.out | 53 
> ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 64 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/block/block.c b/hw/block/block.c
> index c3d3901..3c218eb 100644
> --- a/hw/block/block.c
> +++ b/hw/block/block.c
> @@ -56,7 +56,7 @@ void blkconf_apply_backend_options(BlockConf *conf, bool 
> readonly,
>  {
>      BlockBackend *blk = conf->blk;
>      BlockdevOnError rerror, werror;
> -    uint64_t perm;
> +    uint64_t perm, shared_perm;
>      bool wce;
>      int ret;
>  
> @@ -65,11 +65,13 @@ void blkconf_apply_backend_options(BlockConf *conf, bool 
> readonly,
>          perm |= BLK_PERM_WRITE;
>      }
>  
> -    /* TODO Remove BLK_PERM_WRITE unless explicitly configured so */
> -    ret = blk_set_perm(blk, perm,
> -                       BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
> -                       BLK_PERM_GRAPH_MOD | BLK_PERM_RESIZE | BLK_PERM_WRITE,
> -                       errp);
> +    shared_perm = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
> +                  BLK_PERM_GRAPH_MOD | BLK_PERM_RESIZE;

I'm not so sure BLK_PERM_RESIZE belongs here.

Max

> +    if (conf->share_rw) {
> +        shared_perm |= BLK_PERM_WRITE;
> +    }
> +
> +    ret = blk_set_perm(blk, perm, shared_perm, errp);
>      if (ret < 0) {
>          return;
>      }

[...]

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