qcow2: Fix .bdrv_has_zero_init()
If a qcow2 file is preallocated, it can no longer guarantee that it
initially appears as filled with zeroes.
So implement .bdrv_has_zero_init() by checking whether the file is
preallocated; if so, forward the call to the underlying storage node,
except for when it is encrypted: Encrypted preallocated images always
return effectively random data, so .bdrv_has_zero_init() must always
return 0 for them.
.bdrv_has_zero_init_truncate() can remain bdrv_has_zero_init_1(),
because it presupposes PREALLOC_MODE_OFF.
Reported-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190724171239.8764-7-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index ea3b42f..7c5a485 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4632,6 +4632,33 @@
return spec_info;
}
+static int qcow2_has_zero_init(BlockDriverState *bs)
+{
+ BDRVQcow2State *s = bs->opaque;
+ bool preallocated;
+
+ if (qemu_in_coroutine()) {
+ qemu_co_mutex_lock(&s->lock);
+ }
+ /*
+ * Check preallocation status: Preallocated images have all L2
+ * tables allocated, nonpreallocated images have none. It is
+ * therefore enough to check the first one.
+ */
+ preallocated = s->l1_size > 0 && s->l1_table[0] != 0;
+ if (qemu_in_coroutine()) {
+ qemu_co_mutex_unlock(&s->lock);
+ }
+
+ if (!preallocated) {
+ return 1;
+ } else if (bs->encrypted) {
+ return 0;
+ } else {
+ return bdrv_has_zero_init(s->data_file->bs);
+ }
+}
+
static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t pos)
{
@@ -5187,7 +5214,7 @@
.bdrv_child_perm = bdrv_format_default_perms,
.bdrv_co_create_opts = qcow2_co_create_opts,
.bdrv_co_create = qcow2_co_create,
- .bdrv_has_zero_init = bdrv_has_zero_init_1,
+ .bdrv_has_zero_init = qcow2_has_zero_init,
.bdrv_has_zero_init_truncate = bdrv_has_zero_init_1,
.bdrv_co_block_status = qcow2_co_block_status,
