block: bdrv_reopen_parse_backing(): don't check frozen child

bdrv_set_backing_noperm() takes care of it (actual check is in
bdrv_set_file_or_backing_noperm()), so we don't need to check it here.

While being here, improve error message a bit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-5-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 5 insertions, 17 deletions

diff --git a/block.c b/block.c
index 69dc9d1..6472866 100644
--- a/block.c
+++ b/block.c
@@ -4308,19 +4308,7 @@ static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
                        "an implicit backing file", bs->node_name);
             return -EPERM;
         }
-        /*
-         * Check if the backing link that we want to replace is frozen.
-         * Note that
-         * bdrv_filter_or_cow_child(overlay_bs) == overlay_bs->backing,
-         * because we know that overlay_bs == bs, and that @bs
-         * either is a filter that uses ->backing or a COW format BDS
-         * with bs->drv->supports_backing == true.
-         */
-        if (bdrv_is_backing_chain_frozen(overlay_bs,
-                                         child_bs(overlay_bs->backing), errp))
-        {
-            return -EPERM;
-        }
+
         reopen_state->replace_backing_bs = true;
         reopen_state->old_backing_bs = bs->backing ? bs->backing->bs : NULL;
         ret = bdrv_set_backing_noperm(bs, new_backing_bs, set_backings_tran,
diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index fc5297e..c7d6713 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -878,7 +878,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd1 while the stream job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd0' to 'hd1'")
 
         self.vm.run_job('stream0', auto_finalize = False, auto_dismiss = True)
 
@@ -910,7 +910,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         # We can't remove hd2 while the stream job is ongoing
         opts['backing']['backing'] = None
         self.reopen(opts['backing'], {'read-only': False},
-                    "Cannot change 'backing' link from 'hd1' to 'hd2'")
+                    "Cannot change frozen 'backing' link from 'hd1' to 'hd2'")
 
         # We can detach hd1 from hd0 because it doesn't affect the stream job
         opts['backing'] = None
@@ -933,11 +933,11 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd2 while the commit job is ongoing
         opts['backing']['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd1' to 'hd2'")
 
         # We can't remove hd1 while the commit job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd0' to 'hd1'")
 
         event = self.vm.event_wait(name='BLOCK_JOB_READY')
         self.assert_qmp(event, 'data/device', 'commit0')