From ce7b70a0a59a571095a9bec614cce7b260c8c4fd Mon Sep 17 00:00:00 2001
From: Jeffrey Cody <jcody@redhat.com>
Date: Fri, 19 Sep 2014 03:18:59 +0200
Subject: [PATCH 4/4] block: add __com.redhat_change-backing-file qmp command

Message-id: <c7fc7cefc7588dca2d02b0cc0051cdbdadbf20ac.1411096194.git.jcody@redhat.com>
Patchwork-id: 61313
O-Subject: [PATCH qemu-kvm-rhev RHEL7.0.z 4/4] block: add __com.redhat_change-backing-file qmp command
Bugzilla: 1122925
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

Upstream, the QAPI command 'change-backing-file' was added in a patch,
as part of a series that allowed libvirt to specify backing file
names in block-commit and block-stream.

This standalone QAPI (change-backing-file) is not currently in use by
libvirt, except as a witness that QEMU has the ability to change backing
files in block-commit and block-stream.

However, change-backing-file also relies on node-names functionality,
which is not present in RHEL7.0.  The backport of node-names would also
be fairly instrusive, especially for a command that is not going to be
used beyond verifying its presence.

This downstream patch adds __com.redhat_change-backing-file, which
accepts the same arguments as its upstream namesake.  However, no action
is performed, and the command always returns QERR_UNSUPPORTED.

This is not placed inside the RHEL/RHEV differentiation commands, as it
is not a live block operation (upstream or the dummy version), and
returns synchronously.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 blockdev.c       |    8 ++++++++
 qapi-schema.json |   16 ++++++++++++++++
 qmp-commands.hx  |   22 ++++++++++++++++++++++
 3 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index c4fb129..ff0fe9d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1782,6 +1782,14 @@ void qmp_block_job_complete(const char *device, Error **errp)
     block_job_complete(job, errp);
 }
 
+void qmp___com_redhat_change_backing_file(const char *device,
+                                          const char *image_node_name,
+                                          const char *backing_file,
+                                          Error **errp)
+{
+    error_set(errp, QERR_UNSUPPORTED);
+}
+
 void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
 {
     QmpOutputVisitor *ov = qmp_output_visitor_new();
diff --git a/qapi-schema.json b/qapi-schema.json
index e11b641..3a5a743 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1826,6 +1826,22 @@
   'data': {'command-line': 'str', '*cpu-index': 'int'},
   'returns': 'str' }
 
+##
+# @__com.redhat_change-backing-file
+#
+# This is a placeholder function, that exists as a witness for libvirt
+# that the ability to specify backing files in block-commit and block-stream
+# exists in this version of QEMU.
+#
+# It has the same argument requirements as the upstream 'change-backing-file',
+# but performs no action.
+#
+# Returns: NotSupported
+##
+{ 'command': '__com.redhat_change-backing-file',
+  'data': { 'device': 'str', 'image-node-name': 'str',
+            'backing-file': 'str' } }
+
 #_rhev-only CONFIG_LIVE_BLOCK_OPS
 ##
 # @block-commit
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 94f8671..a300d10 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1241,6 +1241,28 @@ EQMP
 #endif
 
     {
+        .name       = RFQDN_REDHAT "change-backing-file",
+        .args_type  = "device:s,image-node-name:s,backing-file:s",
+        .mhandler.cmd_new = qmp_marshal_input___com_redhat_change_backing_file,
+    },
+
+SQMP
+@__com.redhat_change-backing-file
+-------------------
+@__com.redhat_change-backing-file
+
+This is a placeholder function, that exists as a witness for libvirt
+that the ability to specify backing files block-commit and block-stream
+exists in this version of QEMU.
+
+It has the same argument requirements as the upstream 'change-backing-file',
+but performs no action.
+
+Returns: NotSupported
+
+EQMP
+
+    {
         .name       = "balloon",
         .args_type  = "value:M",
         .mhandler.cmd_new = qmp_marshal_input_balloon,
-- 
1.7.1