Copy snapshots out of QCOW2 disk

In order to backup snapshots, created from QCOW2 iamge, we want to copy snapshots out of QCOW2 disk to a seperate storage.
The following patch adds a new option in "qemu-img": qemu-img convert -f qcow2 -O qcow2 -s snapshot_name src_img bck_img.
Right now, it only supports to copy the full snapshot, delta snapshot is on the way.

Changes from V1: all the comments from Kevin are addressed:
Add read-only checking
Fix coding style
Change the name from bdrv_snapshot_load to bdrv_snapshot_load_tmp

Signed-off-by: Disheng Su <edison@cloud.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/qemu-img.c b/qemu-img.c
index 578b8ebe8c..d4a3b4ebcf 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -646,13 +646,14 @@ static int img_convert(int argc, char **argv)
     BlockDriverInfo bdi;
     QEMUOptionParameter *param = NULL, *create_options = NULL;
     char *options = NULL;
+    const char *snapshot_name = NULL;
 
     fmt = NULL;
     out_fmt = "raw";
     out_baseimg = NULL;
     flags = 0;
     for(;;) {
-        c = getopt(argc, argv, "f:O:B:hce6o:");
+        c = getopt(argc, argv, "f:O:B:s:hce6o:");
         if (c == -1)
             break;
         switch(c) {
@@ -680,6 +681,9 @@ static int img_convert(int argc, char **argv)
         case 'o':
             options = optarg;
             break;
+        case 's':
+            snapshot_name = optarg;
+            break;
         }
     }
 
@@ -711,6 +715,19 @@ static int img_convert(int argc, char **argv)
         total_sectors += bs_sectors;
     }
 
+    if (snapshot_name != NULL) {
+        if (bs_n > 1) {
+            error("No support for concatenating multiple snapshot\n");
+            ret = -1;
+            goto out;
+        }
+        if (bdrv_snapshot_load_tmp(bs[0], snapshot_name) < 0) {
+            error("Failed to load snapshot\n");
+            ret = -1;
+            goto out;
+        }
+    }
+
     /* Find driver and parse its options */
     drv = bdrv_find_format(out_fmt);
     if (!drv) {