[Qemu-devel] [PATCH v4 10/10] Add the drive-reopen command

[Paolo Bonzini <pbonzini@redhat.com>]

From: Federico Simoncelli <fsimonce@redhat.com>

Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 blockdev.c       |   63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 hmp-commands.hx  |   16 +++++++++++++
 hmp.c            |   11 +++++++++
 hmp.h            |    1 +
 qapi-schema.json |   22 ++++++++++++++++++
 qmp-commands.hx  |   30 +++++++++++++++++++++++++
 6 files changed, 143 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 2958419..df8ce14 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -646,6 +646,69 @@ void do_commit(Monitor *mon, const QDict *qdict)
     }
 }
 
+static void change_blockdev_image(const char *device, const char *new_image_file,
+                                  const char *format, Error **errp)
+{
+    BlockDriverState *bs;
+    BlockDriver *drv, *old_drv, *proto_drv;
+    int ret = 0;
+    int flags;
+    char old_filename[1024];
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+    if (bdrv_in_use(bs)) {
+        error_set(errp, QERR_DEVICE_IN_USE, device);
+        return;
+    }
+
+    pstrcpy(old_filename, sizeof(old_filename), bs->filename);
+
+    old_drv = bs->drv;
+    flags = bs->open_flags;
+
+    drv = bdrv_find_format(format);
+    if (!drv) {
+        error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
+        return;
+    }
+
+    proto_drv = bdrv_find_protocol(new_image_file);
+    if (!proto_drv) {
+        error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
+        return;
+    }
+
+    bdrv_drain_all();
+    bdrv_flush(bs);
+
+    bdrv_close(bs);
+    ret = bdrv_open(bs, new_image_file, flags, drv);
+    /*
+     * If reopening the image file we just created fails, fall back
+     * and try to re-open the original image. If that fails too, we
+     * are in serious trouble.
+     */
+    if (ret != 0) {
+        ret = bdrv_open(bs, old_filename, flags, old_drv);
+        if (ret != 0) {
+            error_set(errp, QERR_OPEN_FILE_FAILED, old_filename);
+        } else {
+            error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
+        }
+    }
+}
+
+void qmp_drive_reopen(const char *device, const char *new_image_file,
+                      bool has_format, const char *format, Error **errp)
+{
+    change_blockdev_image(device, new_image_file,
+                          has_format ? format : "qcow2", errp);
+}
+
 static void blockdev_do_action(int kind, void *data, Error **errp)
 {
     BlockdevAction action;
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 9c49c33..4afde71 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -925,6 +925,22 @@ using the specified target.
 ETEXI
 
     {
+        .name       = "drive_reopen",
+        .args_type  = "device:B,new-image-file:s,format:s?",
+        .params     = "device new-image-file [format]",
+        .help       = "Assigns a new image file to a device.\n\t\t\t"
+                      "The image will be opened using the format\n\t\t\t"
+                      "specified or 'qcow2' by default.\n\t\t\t",
+        .mhandler.cmd = hmp_drive_reopen,
+    },
+
+STEXI
+@item drive_reopen
+@findex drive_reopen
+Assigns a new image file to a device.
+ETEXI
+
+    {
         .name       = "drive_add",
         .args_type  = "pci_addr:s,opts:s",
         .params     = "[[<domain>:]<bus>:]<slot>\n"
diff --git a/hmp.c b/hmp.c
index e706db9..ec41d83 100644
--- a/hmp.c
+++ b/hmp.c
@@ -738,6 +738,17 @@ void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &errp);
 }
 
+void hmp_drive_reopen(Monitor *mon, const QDict *qdict)
+{
+    const char *device = qdict_get_str(qdict, "device");
+    const char *filename = qdict_get_str(qdict, "new-image-file");
+    const char *format = qdict_get_try_str(qdict, "format");
+    Error *errp = NULL;
+
+    qmp_drive_reopen(device, filename, !!format, format, &errp);
+    hmp_handle_error(mon, &errp);
+}
+
 void hmp_migrate_cancel(Monitor *mon, const QDict *qdict)
 {
     qmp_migrate_cancel(NULL);
diff --git a/hmp.h b/hmp.h
index 5352f00..648a84f 100644
--- a/hmp.h
+++ b/hmp.h
@@ -49,6 +49,7 @@ void hmp_balloon(Monitor *mon, const QDict *qdict);
 void hmp_block_resize(Monitor *mon, const QDict *qdict);
 void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict);
 void hmp_drive_mirror(Monitor *mon, const QDict *qdict);
+void hmp_drive_reopen(Monitor *mon, const QDict *qdict);
 void hmp_migrate_cancel(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict);
diff --git a/qapi-schema.json b/qapi-schema.json
index 4cebf78..21eb256 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1235,6 +1235,28 @@
             '*mode': 'NewImageMode'} }
 
 ##
+# @drive-reopen
+#
+# Assigns a new image file to a device.
+#
+# @device: the name of the device for which we are changing the image file.
+#
+# @new-image-file: the target of the new image. If the file doesn't exists the
+#                  command will fail.
+#
+# @format: #optional the format of the new image, default is 'qcow2'.
+#
+# Returns: nothing on success
+#          If @device is not a valid block device, DeviceNotFound
+#          If @new-image-file can't be opened, OpenFileFailed
+#          If @format is invalid, InvalidBlockFormat
+#
+# Since 1.1
+##
+{ 'command': 'drive-reopen',
+  'data': { 'device': 'str', 'new-image-file': 'str', '*format': 'str' } }
+
+##
 # @human-monitor-command:
 #
 # Execute a command on the human monitor and return the output.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 122ebe7..7fc30c2 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -818,6 +818,36 @@ Example:
 EQMP
 
     {
+        .name       = "drive-reopen",
+        .args_type  = "device:B,new-image-file:s,format:s?",
+        .mhandler.cmd_new = qmp_marshal_input_drive_reopen,
+    },
+
+SQMP
+drive-reopen
+------------
+
+Assigns a new image file to a device. Except extremely rare cases where the
+guest is expecting the drive to change its content, the new image should
+contain the same data of the current one.  One use case is to terminate
+a drive-mirror command.
+
+Arguments:
+
+- "device": device name to operate on (json-string)
+- "new-image-file": name of new image file (json-string)
+- "format": format of new image (json-string, optional)
+
+Example:
+
+-> { "execute": "drive-reopen", "arguments": {"device": "ide-hd0",
+                                    "new-image-file": "/some/place/my-image",
+                                    "format": "qcow2" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "balloon",
         .args_type  = "value:M",
         .mhandler.cmd_new = qmp_marshal_input_balloon,
-- 
1.7.7.6