If a reference count is not representable with the current refcount
order, the image check should point to qemu-img amend for increasing the
refcount order. However, qemu-img amend needs write access to the image
which cannot be provided if the image is marked corrupt; and the image
check will not mark the image consistent unless everything actually is
consistent.
Therefore, if an image is marked corrupt and the image check encounters
a reference count overflow, it cannot be fixed by using qemu-img amend
to increase the refcount order. Instead, one has to use qemu-img convert
to create a completely new copy of the image in this case.
Alternatively, we may want to give the user a way of manually removing
the corrupt flag, maybe through qemu-img amend, but this is not part of
this patch.
Signed-off-by: Max Reitz <mre...@redhat.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
---
block/qcow2-refcount.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 7c3f8e0..7c9b334 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1370,6 +1370,9 @@ static int inc_refcounts(BlockDriverState *bs,
if (refcount == s->refcount_max) {
fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
"\n", cluster_offset);
+ fprintf(stderr, "Use qemu-img amend to increase the refcount entry
"
+ "width or qemu-img convert to create a clean copy if the "
+ "image cannot be opened for writing\n");
res->corruptions++;
continue;
}
--
1.9.3
