On 24.05.21 16:20, 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 <vsement...@virtuozzo.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Tested-by: Kirill Tkhai <ktk...@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);
This is a declaration after a statement. (Easily fixable by moving the
l2_entry declaration here, though. Or by putting the l2_bitmap
declaration where l2_entry is declared.)
[...]
@@ -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);
I believe this is indeed the correct repair method for
QCOW2_CLUSTER_ZERO_PLAIN, but I’m not so sure for
QCOW2_CLUSTER_UNALLOCATED. As far as I can tell,
qcow2_get_subcluster_type() will return QCOW2_SUBCLUSTER_INVALID for
this case, and so trying to read from this clusters will produce I/O
errors. But still, shouldn’t we rather make such a cluster unallocated
rather than zero then?
And as for QCOW2_CLUSTER_ZERO_PLAIN, I believe qcow2_get_cluster_type()
will never return it when subclusters are enabled. So this repair path
will never happen with a cluster type of ZERO_PLAIN, but only for
UNALLOCATED.
Hanna
+ if (metadata_overlap) {
+ return ret;
+ }
+ }
+ }
break;
default:
