Re: [PATCH v2 06/10] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

[Kirill Tkhai]

On 05.05.2021 09:59, Vladimir Sementsov-Ogievskiy wrote:
> Check subcluster bitmap of the l2 entry for different types of
> clusters:
> 
>  - for compressed it must be zero
>  - for allocated check consistency of two parts of the bitmap
>  - for unallocated all subclusters should be unallocated
>    (or zero-plain)
> 
> For unallocated clusters we can safely fix the entry by making it
> zero-plain.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>

Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>

> ---
>  block/qcow2-refcount.c | 30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index f48c5e1b5d..062ec48a15 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1681,6 +1681,7 @@ static int check_refcounts_l2(BlockDriverState *bs, 
> BdrvCheckResult *res,
>          uint64_t coffset;
>          int csize;
>          l2_entry = get_l2_entry(s, l2_table, i);
> +        uint64_t l2_bitmap = get_l2_bitmap(s, l2_table, i);
>  
>          switch (qcow2_get_cluster_type(bs, l2_entry)) {
>          case QCOW2_CLUSTER_COMPRESSED:
> @@ -1700,6 +1701,14 @@ static int check_refcounts_l2(BlockDriverState *bs, 
> BdrvCheckResult *res,
>                  break;
>              }
>  
> +            if (l2_bitmap) {
> +                fprintf(stderr, "ERROR compressed cluster %d with non-zero "
> +                        "subcluster allocation bitmap, entry=0x%" PRIx64 
> "\n",
> +                        i, l2_entry);
> +                res->corruptions++;
> +                break;
> +            }
> +
>              /* Mark cluster as used */
>              qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
>              ret = qcow2_inc_refcounts_imrt(
> @@ -1727,13 +1736,19 @@ static int check_refcounts_l2(BlockDriverState *bs, 
> BdrvCheckResult *res,
>          {
>              uint64_t offset = l2_entry & L2E_OFFSET_MASK;
>  
> +            if ((l2_bitmap >> 32) & l2_bitmap) {
> +                res->corruptions++;
> +                fprintf(stderr, "ERROR offset=%" PRIx64 ": Allocated "
> +                        "cluster has corrupted subcluster allocation 
> bitmap\n",
> +                        offset);
> +            }
> +
>              /* Correct offsets are cluster aligned */
>              if (offset_into_cluster(s, offset)) {
>                  bool contains_data;
>                  res->corruptions++;
>  
>                  if (has_subclusters(s)) {
> -                    uint64_t l2_bitmap = get_l2_bitmap(s, l2_table, i);
>                      contains_data = (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC);
>                  } else {
>                      contains_data = !(l2_entry & QCOW_OFLAG_ZERO);
> @@ -1800,6 +1815,19 @@ static int check_refcounts_l2(BlockDriverState *bs, 
> BdrvCheckResult *res,
>  
>          case QCOW2_CLUSTER_ZERO_PLAIN:
>          case QCOW2_CLUSTER_UNALLOCATED:
> +            if (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC) {
> +                res->corruptions++;
> +                fprintf(stderr, "%s: Unallocated "
> +                        "cluster has non-zero subcluster allocation map\n",
> +                        fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR");
> +                if (fix & BDRV_FIX_ERRORS) {
> +                    ret = fix_l2_entry_by_zero(bs, res, l2_offset, l2_table, 
> i,
> +                                               active, &metadata_overlap);
> +                    if (metadata_overlap) {
> +                        return ret;
> +                    }
> +                }
> +            }
>              break;
>  
>          default:
>