block: package preparation code in qmp_transaction()

The code before really committing is moved into a function. Most
code is simply moved from qmp_transaction(), except that on fail it
just returns now. Other code such as input parsing is not touched,
to make it easier in review.
Signed-off-by: NWenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -785,83 +785,44 @@ typedef struct BlkTransactionStates {
     QSIMPLEQ_ENTRY(BlkTransactionStates) entry;
 } BlkTransactionStates;
 
-/*
- * 'Atomic' group snapshots.  The snapshots are taken as a set, and if any fail
- *  then we do not pivot any of the devices in the group, and abandon the
- *  snapshots
- */
-void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
+static void external_snapshot_prepare(const char *device,
+                                      const char *format,
+                                      const char *new_image_file,
+                                      enum NewImageMode mode,
+                                      BlkTransactionStates *states,
+                                      Error **errp)
 {
-    int ret = 0;
-    BlockdevActionList *dev_entry = dev_list;
-    BlkTransactionStates *states, *next;
-    Error *local_err = NULL;
-
-    QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionStates) snap_bdrv_states;
-    QSIMPLEQ_INIT(&snap_bdrv_states);
-
-    /* drain all i/o before any snapshots */
-    bdrv_drain_all();
-
-    /* We don't do anything in this loop that commits us to the snapshot */
-    while (NULL != dev_entry) {
-        BlockdevAction *dev_info = NULL;
     BlockDriver *proto_drv;
     BlockDriver *drv;
-        int flags;
-        enum NewImageMode mode;
-        const char *new_image_file;
-        const char *device;
-        const char *format = "qcow2";
-
-        dev_info = dev_entry->value;
-        dev_entry = dev_entry->next;
-
-        states = g_malloc0(sizeof(BlkTransactionStates));
-        QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, states, entry);
-
-        switch (dev_info->kind) {
-        case BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
-            device = dev_info->blockdev_snapshot_sync->device;
-            if (!dev_info->blockdev_snapshot_sync->has_mode) {
-                dev_info->blockdev_snapshot_sync->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
-            }
-            new_image_file = dev_info->blockdev_snapshot_sync->snapshot_file;
-            if (dev_info->blockdev_snapshot_sync->has_format) {
-                format = dev_info->blockdev_snapshot_sync->format;
-            }
-            mode = dev_info->blockdev_snapshot_sync->mode;
-            break;
-        default:
-            abort();
-        }
+    int flags, ret;
+    Error *local_err = NULL;
 
     drv = bdrv_find_format(format);
     if (!drv) {
         error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
-            goto delete_and_fail;
+        return;
     }
 
     states->old_bs = bdrv_find(device);
     if (!states->old_bs) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
-            goto delete_and_fail;
+        return;
     }
 
     if (!bdrv_is_inserted(states->old_bs)) {
         error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
-            goto delete_and_fail;
+        return;
     }
 
     if (bdrv_in_use(states->old_bs)) {
         error_set(errp, QERR_DEVICE_IN_USE, device);
-            goto delete_and_fail;
+        return;
     }
 
     if (!bdrv_is_read_only(states->old_bs)) {
         if (bdrv_flush(states->old_bs)) {
             error_set(errp, QERR_IO_ERROR);
-                goto delete_and_fail;
+            return;
         }
     }
 
@@ -870,7 +831,7 @@ void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
     proto_drv = bdrv_find_protocol(new_image_file);
     if (!proto_drv) {
         error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
-            goto delete_and_fail;
+        return;
     }
 
     /* create new image w/backing file */
@@ -881,7 +842,7 @@ void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
                         NULL, -1, flags, &local_err, false);
         if (error_is_set(&local_err)) {
             error_propagate(errp, local_err);
-                goto delete_and_fail;
+            return;
         }
     }
 
@@ -893,8 +854,62 @@ void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
                     flags | BDRV_O_NO_BACKING, drv);
     if (ret != 0) {
         error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
+    }
+}
+
+/*
+ * 'Atomic' group snapshots.  The snapshots are taken as a set, and if any fail
+ *  then we do not pivot any of the devices in the group, and abandon the
+ *  snapshots
+ */
+void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
+{
+    BlockdevActionList *dev_entry = dev_list;
+    BlkTransactionStates *states, *next;
+    Error *local_err = NULL;
+
+    QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionStates) snap_bdrv_states;
+    QSIMPLEQ_INIT(&snap_bdrv_states);
+
+    /* drain all i/o before any snapshots */
+    bdrv_drain_all();
+
+    /* We don't do anything in this loop that commits us to the snapshot */
+    while (NULL != dev_entry) {
+        BlockdevAction *dev_info = NULL;
+        enum NewImageMode mode;
+        const char *new_image_file;
+        const char *device;
+        const char *format = "qcow2";
+
+        dev_info = dev_entry->value;
+        dev_entry = dev_entry->next;
+
+        states = g_malloc0(sizeof(BlkTransactionStates));
+        QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, states, entry);
+
+        switch (dev_info->kind) {
+        case BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
+            device = dev_info->blockdev_snapshot_sync->device;
+            if (!dev_info->blockdev_snapshot_sync->has_mode) {
+                dev_info->blockdev_snapshot_sync->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
+            }
+            new_image_file = dev_info->blockdev_snapshot_sync->snapshot_file;
+            if (dev_info->blockdev_snapshot_sync->has_format) {
+                format = dev_info->blockdev_snapshot_sync->format;
+            }
+            mode = dev_info->blockdev_snapshot_sync->mode;
+            external_snapshot_prepare(device, format, new_image_file,
+                                      mode, states, &local_err);
+            if (error_is_set(&local_err)) {
+                error_propagate(errp, local_err);
                 goto delete_and_fail;
             }
+            break;
+        default:
+            abort();
+        }
+
     }