block: Allow changing bs->file on reopen

When the x-blockdev-reopen was added it allowed reconfiguring the
graph by replacing backing files, but changing the 'file' option was
forbidden. Because of this restriction some operations are not
possible, notably inserting and removing block filters.

This patch adds support for replacing the 'file' option. This is
similar to replacing the backing file and the user is likewise
responsible for the correctness of the resulting graph, otherwise this
can lead to data corruption.

Signed-off-by: Alberto Garcia <berto@igalia.com>
 [vsementsov: bdrv_reopen_parse_file_or_backing() is modified a lot]
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-9-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 12 insertions, 11 deletions

diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index c7d6713..d955e0d 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -146,8 +146,8 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         self.reopen(opts, {'driver': 'raw'}, "Cannot change the option 'driver'")
         self.reopen(opts, {'driver': ''}, "Invalid parameter ''")
         self.reopen(opts, {'driver': None}, "Invalid parameter type for 'driver', expected: string")
-        self.reopen(opts, {'file': 'not-found'}, "Cannot change the option 'file'")
-        self.reopen(opts, {'file': ''}, "Cannot change the option 'file'")
+        self.reopen(opts, {'file': 'not-found'}, "Cannot find device='' nor node-name='not-found'")
+        self.reopen(opts, {'file': ''}, "Cannot find device='' nor node-name=''")
         self.reopen(opts, {'file': None}, "Invalid parameter type for 'file', expected: BlockdevRef")
         self.reopen(opts, {'file.node-name': 'newname'}, "Cannot change the option 'node-name'")
         self.reopen(opts, {'file.driver': 'host_device'}, "Cannot change the option 'driver'")
@@ -443,7 +443,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal operation: hd2 is a child of hd1
         self.reopen(opts[2], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
+                    "Making 'hd1' a backing child of 'hd2' would create a cycle")
 
         # hd2 <- hd0, hd2 <- hd1
         self.reopen(opts[0], {'backing': 'hd2'})
@@ -454,8 +454,9 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # More illegal operations
         self.reopen(opts[2], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
-        self.reopen(opts[2], {'file': 'hd0-file'}, "Cannot change the option 'file'")
+                    "Making 'hd1' a backing child of 'hd2' would create a cycle")
+        self.reopen(opts[2], {'file': 'hd0-file'},
+                    "Permission conflict on node 'hd0-file': permissions 'write, resize' are both required by node 'hd0' (uses node 'hd0-file' as 'file' child) and unshared by node 'hd2' (uses node 'hd0-file' as 'file' child).")
 
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd2')
         self.assert_qmp(result, 'error/class', 'GenericError')
@@ -497,18 +498,18 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal: hd2 is backed by hd1
         self.reopen(opts[1], {'backing': 'hd2'},
-                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd2' a backing child of 'hd1' would create a cycle")
 
         # hd1 <- hd0 <- hd2
         self.reopen(opts[2], {'backing': 'hd0'})
 
         # Illegal: hd2 is backed by hd0, which is backed by hd1
         self.reopen(opts[1], {'backing': 'hd2'},
-                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd2' a backing child of 'hd1' would create a cycle")
 
         # Illegal: hd1 cannot point to itself
         self.reopen(opts[1], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd1' a backing child of 'hd1' would create a cycle")
 
         # Remove all backing files
         self.reopen(opts[0])
@@ -530,7 +531,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal: hd0 is a child of the blkverify node
         self.reopen(opts[0], {'backing': 'bv'},
-                    "Making 'bv' a backing file of 'hd0' would create a cycle")
+                    "Making 'bv' a backing child of 'hd0' would create a cycle")
 
         # Delete the blkverify node
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'bv')
@@ -563,7 +564,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         # You can't make quorum0 a backing file of hd0:
         # hd0 is already a child of quorum0.
         self.reopen(hd_opts(0), {'backing': 'quorum0'},
-                    "Making 'quorum0' a backing file of 'hd0' would create a cycle")
+                    "Making 'quorum0' a backing child of 'hd0' would create a cycle")
 
         # Delete quorum0
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'quorum0')
@@ -969,7 +970,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd1 while the commit job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change backing link if 'hd0' has an implicit backing file")
+        self.reopen(opts, {}, "Cannot replace implicit backing child of hd0")
 
         # hd2 <- hd0
         self.vm.run_job('commit0', auto_finalize = False, auto_dismiss = True)