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

[Eric Blake]

On 5/4/21 10:20 AM, 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 
> ---
>  block/qcow2-refcount.c | 30 +-
>  1 file changed, 29 insertions(+), 1 deletion(-)
> 

Reviewed-by: Eric Blake 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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

[Vladimir Sementsov-Ogievskiy]

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 
---
 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 62d59eb2e9..dc940f3003 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, , );
 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, _overlap);
+if (metadata_overlap) {
+return ret;
+}
+}
+}
 break;
 
 default:
-- 
2.29.2