Re: [Qemu-block] [PATCH 07/21] qcow2: add bitmaps extension

[Max Reitz]

On 22.11.2016 18:26, Vladimir Sementsov-Ogievskiy wrote:
> Add bitmap extension as specified in docs/specs/qcow2.txt.
> For now, just mirror extension header into Qcow2 state and check
> constraints.
> 
> For now, disable image resize if it has bitmaps. It will be fixed later.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Reviewed-by: John Snow <address@hidden>
> ---
>  block/qcow2.c | 107 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  block/qcow2.h |  24 +++++++++++++
>  2 files changed, 129 insertions(+), 2 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 6d5689a..7908657 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -63,6 +63,7 @@ typedef struct {
>  #define  QCOW2_EXT_MAGIC_END 0
>  #define  QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
>  #define  QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
> +#define  QCOW2_EXT_MAGIC_BITMAPS 0x23852875
>  
>  static int qcow2_probe(const uint8_t *buf, int buf_size, const char 
> *filename)
>  {
> @@ -92,6 +93,7 @@ static int qcow2_read_extensions(BlockDriverState *bs, 
> uint64_t start_offset,
>      QCowExtension ext;
>      uint64_t offset;
>      int ret;
> +    Qcow2BitmapHeaderExt bitmaps_ext;
>  
>  #ifdef DEBUG_EXT
>      printf("qcow2_read_extensions: start=%ld end=%ld\n", start_offset, 
> end_offset);
> @@ -162,6 +164,81 @@ static int qcow2_read_extensions(BlockDriverState *bs, 
> uint64_t start_offset,
>              }
>              break;
>  
> +        case QCOW2_EXT_MAGIC_BITMAPS:
> +            if (ext.len != sizeof(bitmaps_ext)) {
> +                error_setg_errno(errp, -ret, "bitmaps_ext: "
> +                                 "Invalid extension length");
> +                return -EINVAL;
> +            }
> +
> +            if (!(s->autoclear_features & QCOW2_AUTOCLEAR_BITMAPS)) {
> +                fprintf(stderr,
> +                        "WARNING: a program lacking bitmap support modified "
> +                        "this file, so all bitmaps are now considered "
> +                        "inconsistent");
> +                break;
> +            }

I think It would be nice if qemu-img check could remove all bitmaps and
related data if this bit is not set. Otherwise, we're practically
leaking data.

(But this can be added in a later patch.)

Reviewed-by: Max Reitz <address@hidden>

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