Re: [Qemu-devel] [PATCH 1/5] qcow2: Add corrupt bit

[Kevin Wolf <kwolf@redhat.com>]

Am 26.08.2013 um 15:04 hat Max Reitz geschrieben:
> This adds an incompatible bit indicating corruption to qcow2. Any image
> with this bit set may not be written to unless for repairing (and
> subsequently clearing the bit if the repair has been successful).
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2.c              | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  block/qcow2.h              |  7 ++++++-
>  docs/specs/qcow2.txt       |  7 ++++++-
>  include/block/block.h      |  2 ++
>  qemu-img.c                 |  2 +-
>  tests/qemu-iotests/031.out | 12 ++++++------
>  tests/qemu-iotests/036.out |  2 +-
>  7 files changed, 66 insertions(+), 10 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 3376901..1d0d7ca 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -272,6 +272,37 @@ static int qcow2_mark_clean(BlockDriverState *bs)
>      return 0;
>  }
>  
> +/*
> + * Marks the image as corrupt.
> + */
> +int qcow2_mark_corrupt(BlockDriverState *bs)
> +{
> +    BDRVQcowState *s = bs->opaque;
> +
> +    s->incompatible_features |= QCOW2_INCOMPAT_CORRUPT;
> +    return qcow2_update_header(bs);
> +}
> +
> +/*
> + * Marks the image as consistent, i.e., unsets the corrupt bit, and flushes
> + * before if necessary.
> + */
> +int qcow2_mark_consistent(BlockDriverState *bs)
> +{
> +    BDRVQcowState *s = bs->opaque;
> +
> +    if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
> +        int ret = bdrv_flush(bs);
> +        if (ret < 0) {
> +            return ret;
> +        }
> +
> +        s->incompatible_features &= ~QCOW2_INCOMPAT_CORRUPT;
> +        return qcow2_update_header(bs);
> +    }
> +    return 0;
> +}
> +
>  static int qcow2_check(BlockDriverState *bs, BdrvCheckResult *result,
>                         BdrvCheckMode fix)
>  {
> @@ -402,6 +433,14 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
>          goto fail;
>      }
>  
> +    if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
> +        /* Corrupt images may not be written to unless they are being repaired */
> +        if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_REPAIR)) {

Isn't BDRV_O_REPAIR equivalent to BDRV_O_CHECK && BDRV_O_RDWR, or is
there an advantage in using a new bit?

Looks good otherwise.

Kevin