[v4,1/3] block: Introduce BDRV_O_NO_BACKING

If an image references a backing file that doesn't exist, qemu-img info fails
to open this image. Exactly in this case the info would be valuable, though:
the user might want to find out which file is missing.

This patch introduces a BDRV_O_NO_BACKING flag to ignore the backing file when
opening the image. qemu-img info is the first user and provides info now even
if the backing file is invalid.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c    |    4 ++--
 block.h    |    1 +
 qemu-img.c |    2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

On 01/12/2010 05:55 AM, Kevin Wolf wrote:
> If an image references a backing file that doesn't exist, qemu-img info fails
> to open this image. Exactly in this case the info would be valuable, though:
> the user might want to find out which file is missing.
>
> This patch introduces a BDRV_O_NO_BACKING flag to ignore the backing file when
> opening the image. qemu-img info is the first user and provides info now even
> if the backing file is invalid.
>
> Signed-off-by: Kevin Wolf<kwolf@redhat.com>
>    

Applied all.  Thanks.

Regards,

Anthony Liguori
> ---
>   block.c    |    4 ++--
>   block.h    |    1 +
>   qemu-img.c |    2 +-
>   3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/block.c b/block.c
> index 30ae2b1..994109e 100644
> --- a/block.c
> +++ b/block.c
> @@ -477,7 +477,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
>           unlink(filename);
>       }
>   #endif
> -    if (bs->backing_file[0] != '\0') {
> +    if ((flags&  BDRV_O_NO_BACKING) == 0&&  bs->backing_file[0] != '\0') {
>           /* if there is a backing file, use it */
>           BlockDriver *back_drv = NULL;
>           bs->backing_hd = bdrv_new("");
> @@ -1352,7 +1352,7 @@ const char *bdrv_get_encrypted_filename(BlockDriverState *bs)
>   void bdrv_get_backing_filename(BlockDriverState *bs,
>                                  char *filename, int filename_size)
>   {
> -    if (!bs->backing_hd) {
> +    if (!bs->backing_file) {
>           pstrcpy(filename, filename_size, "");
>       } else {
>           pstrcpy(filename, filename_size, bs->backing_file);
> diff --git a/block.h b/block.h
> index fa51ddf..f660d5f 100644
> --- a/block.h
> +++ b/block.h
> @@ -39,6 +39,7 @@ typedef struct QEMUSnapshotInfo {
>   #define BDRV_O_NOCACHE     0x0020 /* do not use the host page cache */
>   #define BDRV_O_CACHE_WB    0x0040 /* use write-back caching */
>   #define BDRV_O_NATIVE_AIO  0x0080 /* use native AIO instead of the thread pool */
> +#define BDRV_O_NO_BACKING  0x0100 /* don't open the backing file */
>
>   #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_CACHE_WB)
>
> diff --git a/qemu-img.c b/qemu-img.c
> index 1d97f2e..5ad88bf 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -884,7 +884,7 @@ static int img_info(int argc, char **argv)
>       } else {
>           drv = NULL;
>       }
> -    if (bdrv_open2(bs, filename, BRDV_O_FLAGS, drv)<  0) {
> +    if (bdrv_open2(bs, filename, BRDV_O_FLAGS | BDRV_O_NO_BACKING, drv)<  0) {
>           error("Could not open '%s'", filename);
>       }
>       bdrv_get_format(bs, fmt_name, sizeof(fmt_name));
>