Re: [Qemu-devel] [PATCH for-2.7 v2 01/17] block: Add BDRV_O_NO_LOCK

["Denis V. Lunev" <den@openvz.org>]

On 04/15/2016 06:27 AM, Fam Zheng wrote:
> Later the block layer will automatically lock the images to avoid unexpected
> concurrent accesses to the same image, which will easily corrupt the metadata
> or user data, unless in some very special cases, like migration.
>
> The exceptional cases like shared storage migration and testing should set
> BDRV_O_NO_LOCK the flag indicating that the block layer should skip the
> automatic locking of the image, like the old behavior.
>
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>   include/block/block.h | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/include/block/block.h b/include/block/block.h
> index 3a73137..b803597 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -94,6 +94,7 @@ typedef struct HDGeometry {
>                                         select an appropriate protocol driver,
>                                         ignoring the format layer */
>   #define BDRV_O_NO_IO       0x10000 /* don't initialize for I/O */
> +#define BDRV_O_NO_LOCK     0x20000 /* don't lock image file */
>   
>   #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
>   
Reviewed-by: Denis V. Lunev <den@openvz.org>