Re: [Qemu-devel] [PATCH] block: Use BDRV_O_NO_BACKING where appropriate

[Fam Zheng <famz@redhat.com>]

On 2013年11月28日 19:02, Kevin Wolf wrote:
> If you open an image temporarily just because you want to check its size
> or get it flushed, there's no real reason to open the whole backing file
> chain.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block.c       | 3 ++-
>   block/qcow2.c | 3 ++-
>   block/vmdk.c  | 2 +-
>   3 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/block.c b/block.c
> index 03e45fc..e2745a5 100644
> --- a/block.c
> +++ b/block.c
> @@ -1061,7 +1061,8 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
>           /* Get the required size from the image */
>           bs1 = bdrv_new("");
>           QINCREF(options);
> -        ret = bdrv_open(bs1, filename, options, 0, drv, &local_err);
> +        ret = bdrv_open(bs1, filename, options, BDRV_O_NO_BACKING,
> +                        drv, &local_err);
>           if (ret < 0) {
>               bdrv_unref(bs1);
>               goto fail;
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 2fe37ed..8e2b6c7 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1588,7 +1588,8 @@ static int qcow2_create2(const char *filename, int64_t total_size,
>
>       /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
>       ret = bdrv_open(bs, filename, NULL,
> -                    BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
> +                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
> +                    drv, &local_err);
>       if (error_is_set(&local_err)) {
>           error_propagate(errp, local_err);
>           goto out;
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 6555663..5fb6c81 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1690,7 +1690,7 @@ static int vmdk_create(const char *filename, QEMUOptionParameter *options,
>       }
>       if (backing_file) {
>           BlockDriverState *bs = bdrv_new("");
> -        ret = bdrv_open(bs, backing_file, NULL, 0, NULL, errp);
> +        ret = bdrv_open(bs, backing_file, NULL, BDRV_O_NO_BACKING, NULL, errp);
>           if (ret != 0) {
>               bdrv_unref(bs);
>               return ret;
>

Reviewed-by: Fam Zheng <famz@redhat.com>