[sheepdog] [PATCH v2] dog: allow vdi snapshot without snapshot tag

[Hitoshi Mitake]

The commit a21bf27906b23448b92cca9943e1019105ffac2f makes
$ dog vdi snapshot <vdi>
fail if the <vdi> is an ordinal vdi because newly created VDIs have
snapid 0. This patch avoids the failure with checking the VDI is
snapshot or not.

Cc: Ruoyu <liangry at ucweb.com>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
---
 dog/vdi.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

v2: correct vdi existence checking

diff --git a/dog/vdi.c b/dog/vdi.c
index fa6130e..58b0a71 100644
--- a/dog/vdi.c
+++ b/dog/vdi.c
@@ -567,6 +567,7 @@ static int vdi_snapshot(int argc, char **argv)
 	int vs_count = 0;
 	struct node_id owners[SD_MAX_COPIES];
 	int nr_owners = 0, nr_issued_prevent_inode_update = 0;
+	bool fail_if_snapshot = false;
 
 	if (vdi_cmd_data.snapshot_id != 0) {
 		sd_err("Please specify a non-integer value for "
@@ -584,16 +585,29 @@ static int vdi_snapshot(int argc, char **argv)
 	case SD_RES_NO_TAG:
 		break;
 	default:
-		sd_err("Failed to create snapshot for %s, maybe "
-			"snapshot id (%d) or tag (%s) is existed",
-			vdiname, vdi_cmd_data.snapshot_id,
-			vdi_cmd_data.snapshot_tag);
-		return EXIT_FAILURE;
+		fail_if_snapshot = true;
+		break;
 	}
 
-	ret = read_vdi_obj(vdiname, 0, "", &vid, inode, SD_INODE_HEADER_SIZE);
-	if (ret != EXIT_SUCCESS)
-		return ret;
+	if (fail_if_snapshot) {
+		ret = dog_read_object(vid_to_vdi_oid(vid), inode,
+				      SD_INODE_HEADER_SIZE, 0, true);
+		if (ret != EXIT_SUCCESS)
+			return ret;
+
+		if (vdi_is_snapshot(inode)) {
+			sd_err("Failed to create snapshot for %s, maybe "
+			       "snapshot id (%d) or tag (%s) is existed",
+			       vdiname, vdi_cmd_data.snapshot_id,
+			       vdi_cmd_data.snapshot_tag);
+			return EXIT_FAILURE;
+		}
+	} else {
+		ret = read_vdi_obj(vdiname, 0, "", &vid, inode,
+				   SD_INODE_HEADER_SIZE);
+		if (ret != EXIT_SUCCESS)
+			return ret;
+	}
 
 	if (inode->store_policy) {
 		sd_err("creating a snapshot of hypervolume is not supported");
-- 
1.8.3.2