qmp: Allow to change password on named block driver states.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Fam Zheng <famz@redhat.com>

There was two candidate ways to implement named node manipulation:

1)
{ 'command': 'block_passwd', 'data': {'*device': 'str',
                                      '*node-name': 'str', 'password': 'str'}
}

2)

{ 'command': 'block_passwd', 'data': {'device': 'str',
                                      '*device-is-node': 'bool',
                                      'password': 'str'} }

Luiz proposed 1 and says 2 was an abuse of the QMP interface and proposed to
rewrite the QMP block interface for 2.0.

Luiz does not like in 1 the fact that 2 fields are optional but one of them must
be specified leading to an abuse of the QMP semantic.

Kevin argumented that 2 what a clear abuse of the device field and would not be
practical when reading fast some log file because the user would read "device"
and think that a device is manipulated when it's in fact a node name.
Documentation of 1 make it pretty clear what to do for the user.

Kevin argued that all bs are node including devices ones so 2 does not make
sense.

Kevin also argued that rewriting the QMP block interface would not make disapear
the current one.

Kevin pushed the argument that making the QAPI generator compatible with the
semantic of the operation would need a rewrite that no one has done yet.

A vote has been done on the list to elect the version to use and 1 won.

For reference the complete thread is:
"[Qemu-devel] [PATCH V4 4/7] qmp: Allow to change password on names block driver
states."

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/blockdev.c b/blockdev.c
index 0bfe38027b..2f4065e2cd 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1481,14 +1481,19 @@ void qmp_eject(const char *device, bool has_force, bool force, Error **errp)
     eject_device(bs, force, errp);
 }
 
-void qmp_block_passwd(const char *device, const char *password, Error **errp)
+void qmp_block_passwd(bool has_device, const char *device,
+                      bool has_node_name, const char *node_name,
+                      const char *password, Error **errp)
 {
+    Error *local_err = NULL;
     BlockDriverState *bs;
     int err;
 
-    bs = bdrv_find(device);
-    if (!bs) {
-        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+    bs = bdrv_lookup_bs(has_device ? device : NULL,
+                        has_node_name ? node_name : NULL,
+                        &local_err);
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
         return;
     }