[Qemu-devel] [PATCH 2/2] Add the blockdev-reopen and blockdev-migrate commands

[Federico Simoncelli]

Signed-off-by: Federico Simoncelli <address@hidden>
---
 block/blkmirror.c |    2 +-
 blockdev.c        |  109 +++++++++++++++++++++++++++++++++++++++++++++++------
 hmp-commands.hx   |   36 +++++++++++++++++
 hmp.c             |   30 ++++++++++++++
 hmp.h             |    2 +
 qapi-schema.json  |   63 ++++++++++++++++++++++++++++++
 6 files changed, 229 insertions(+), 13 deletions(-)

diff --git a/block/blkmirror.c b/block/blkmirror.c
index 39927c8..49e3381 100644
--- a/block/blkmirror.c
+++ b/block/blkmirror.c
@@ -81,7 +81,7 @@ static int blkmirror_open(BlockDriverState *bs, const char 
*filename, int flags)
         bdrv_delete(m->bs[0]);
         return -ENOMEM;
     }
-    ret = bdrv_open(m->bs[1], filename, flags, NULL);
+    ret = bdrv_open(m->bs[1], filename, flags | BDRV_O_NO_BACKING, NULL);
     if (ret < 0) {
         bdrv_delete(m->bs[0]);
         return ret;
diff --git a/blockdev.c b/blockdev.c
index 2c132a3..1df2542 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -646,9 +646,8 @@ void do_commit(Monitor *mon, const QDict *qdict)
     }
 }
 
-void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
-                                bool has_format, const char *format,
-                                Error **errp)
+static void change_blockdev_image(const char *device, const char 
*new_image_file,
+                                  const char *format, bool create, Error 
**errp)
 {
     BlockDriverState *bs;
     BlockDriver *drv, *old_drv, *proto_drv;
@@ -671,7 +670,7 @@ void qmp_blockdev_snapshot_sync(const char *device, const 
char *snapshot_file,
     old_drv = bs->drv;
     flags = bs->open_flags;
 
-    if (!has_format) {
+    if (!format) {
         format = "qcow2";
     }
 
@@ -681,24 +680,26 @@ void qmp_blockdev_snapshot_sync(const char *device, const 
char *snapshot_file,
         return;
     }
 
-    proto_drv = bdrv_find_protocol(snapshot_file);
+    proto_drv = bdrv_find_protocol(new_image_file);
     if (!proto_drv) {
         error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
         return;
     }
 
-    ret = bdrv_img_create(snapshot_file, format, bs->filename,
-                          bs->drv->format_name, NULL, -1, flags);
-    if (ret) {
-        error_set(errp, QERR_UNDEFINED_ERROR);
-        return;
+    if (create) {
+        ret = bdrv_img_create(new_image_file, format, bs->filename,
+                              bs->drv->format_name, NULL, -1, flags);
+        if (ret) {
+            error_set(errp, QERR_UNDEFINED_ERROR);
+            return;
+        }
     }
 
     bdrv_drain_all();
     bdrv_flush(bs);
 
     bdrv_close(bs);
-    ret = bdrv_open(bs, snapshot_file, flags, drv);
+    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
@@ -709,11 +710,95 @@ void qmp_blockdev_snapshot_sync(const char *device, const 
char *snapshot_file,
         if (ret != 0) {
             error_set(errp, QERR_OPEN_FILE_FAILED, old_filename);
         } else {
-            error_set(errp, QERR_OPEN_FILE_FAILED, snapshot_file);
+            error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
         }
     }
 }
 
+void qmp_blockdev_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 : NULL, false, errp);
+}
+
+void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
+                                bool has_format, const char *format,
+                                Error **errp)
+{
+    change_blockdev_image(device, snapshot_file,
+                          has_format ? format : NULL, true, errp);
+}
+
+void qmp_blockdev_migrate(const char *device, BlockMigrateOp mode,
+                          const char *destination, bool has_new_image_file,
+                          const char *new_image_file, Error **errp)
+{
+    BlockDriverState *bs;
+    BlockDriver *drv;
+    int i, j, escape;
+    char filename[2048];
+
+    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;
+    }
+
+    if (mode == BLOCK_MIGRATE_OP_MIRROR) {
+        drv = bdrv_find_format("blkmirror");
+        if (!drv) {
+            error_set(errp, QERR_INVALID_BLOCK_FORMAT, "blkmirror");
+            return;
+        }
+
+        if (!has_new_image_file) {
+            new_image_file = bs->filename;
+        }
+
+        pstrcpy(filename, sizeof(filename), "blkmirror:");
+        i = strlen("blkmirror:");
+
+        escape = 0;
+        for (j = 0; j < strlen(new_image_file); j++) {
+ loop:
+            if (!(i < sizeof(filename) - 2)) {
+                error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+                          "new-image-file", "shorter filename");
+                return;
+            }
+
+            if (new_image_file[j] == ':' || new_image_file[j] == '\\') {
+                if (!escape) {
+                    filename[i++] = '\\', escape = 1;
+                    goto loop;
+                } else {
+                    escape = 0;
+                }
+            }
+
+            filename[i++] = new_image_file[j];
+        }
+
+        if (i + strlen(destination) + 2 > sizeof(filename)) {
+            error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+                      "destination", "shorter filename");
+            return;
+        }
+
+        filename[i++] = ':';
+        pstrcpy(filename + i, sizeof(filename) - i - 2, destination);
+
+        change_blockdev_image(device, filename, "blkmirror", false, errp);
+    } else if (mode == BLOCK_MIGRATE_OP_STREAM) {
+        error_set(errp, QERR_NOT_SUPPORTED);
+    }
+}
+
 static void eject_device(BlockDriverState *bs, int force, Error **errp)
 {
     if (bdrv_in_use(bs)) {
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 573b823..ccb1f62 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -886,6 +886,42 @@ Snapshot device, using snapshot file as target if provided
 ETEXI
 
     {
+        .name       = "blkdev_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.",
+        .mhandler.cmd = hmp_blkdev_reopen,
+    },
+
+STEXI
address@hidden blkdev_reopen
address@hidden blkdev_reopen
+Assigns a new image file to a device.
+ETEXI
+
+    {
+        .name       = "blkdev_migrate",
+        .args_type  = "mirror:-m,device:B,destination:s,new-image-file:s?",
+        .params     = "device mode destination [new-image-file]",
+        .help       = "Migrates the device to a new destination.\n\t\t\t"
+                      "The default migration method is 'stream',\n\t\t\t"
+                      "the option -m is used to select 'mirror'\n\t\t\t"
+                      "(currently the only method supported).\n\t\t\t"
+                      "An optional existing image file that will\n\t\t\t"
+                      "replace the current one in the device\n\t\t\t"
+                      "can be specified.",
+        .mhandler.cmd = hmp_blkdev_migrate,
+    },
+
+STEXI
address@hidden blkdev_migrate
address@hidden blkdev_migrate
+Migrates the device to a new destination.
+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 8ff8c94..b687b8f 100644
--- a/hmp.c
+++ b/hmp.c
@@ -701,6 +701,36 @@ void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &errp);
 }
 
+void hmp_blkdev_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_blockdev_reopen(device, filename, !!format, format, &errp);
+    hmp_handle_error(mon, &errp);
+}
+
+void hmp_blkdev_migrate(Monitor *mon, const QDict *qdict)
+{
+    bool mirror = qdict_get_try_bool(qdict, "mirror", 0);
+    const char *device = qdict_get_str(qdict, "device");
+    const char *destination = qdict_get_str(qdict, "destination");
+    const char *new_image_file = qdict_get_try_str(qdict, "new-image-file");
+    BlockMigrateOp mode;
+    Error *errp = NULL;
+
+    if (mirror)
+        mode = BLOCK_MIGRATE_OP_MIRROR;
+    else
+        mode = BLOCK_MIGRATE_OP_STREAM;
+
+    qmp_blockdev_migrate(device, mode, destination,
+                         !!new_image_file, new_image_file, &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 18eecbd..f4e802b 100644
--- a/hmp.h
+++ b/hmp.h
@@ -47,6 +47,8 @@ void hmp_block_passwd(Monitor *mon, const QDict *qdict);
 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_blkdev_reopen(Monitor *mon, const QDict *qdict);
+void hmp_blkdev_migrate(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 d02ee86..c86796a 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1136,6 +1136,69 @@
   'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str' } }
 
 ##
+# @blockdev-reopen
+#
+# Assigns a new image file to a device.
+#
+# @device: the name of the device for which we are chainging 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': 'blockdev-reopen',
+  'data': { 'device': 'str', 'new-image-file': 'str', '*format': 'str' } }
+
+##
+# @BlockMigrateOp:
+#
+# An enumeration of block migration methods.
+#
+# @mirror: Only mirror future writes to the destination
+#
+# @stream: Stream the image to the destination
+#
+# Since 1.1
+##
+{ 'enum' : 'BlockMigrateOp', 'data': [ 'mirror', 'stream' ] }
+
+
+##
+# @blockdev-migrate
+#
+# Migrates the device to a new destination.
+#
+# @device: the name of the block device to migrate.
+#
+# @mode: the block migration method to be used.
+#
+# @destination: the destination of the block migration.
+#
+# @new-image-file: #optional an existing image file that will replace
+#                  the current one in the device.
+#
+# Returns: nothing on success
+#          If @device is not a valid block device, DeviceNotFound
+#          If @mode is not a valid migration mode, InvalidParameterValue
+#          If @destination can't be opened, OpenFileFailed
+#          If @new-image-file can't be opened, OpenFileFailed
+#
+# Since 1.1
+##
+{ 'command': 'blockdev-migrate',
+  'data': { 'device': 'str', 'mode' : 'BlockMigrateOp',
+            'destination': 'str', '*new-image-file': 'str' } }
+
+##
 # @human-monitor-command:
 #
 # Execute a command on the human monitor and return the output.
-- 
1.7.1