Merge pull request rockstor#2911 from phillxnet/2902-replication-rece…

…ived_uuid-blocker-re-snap-to-share-promotion

replication received_uuid blocker re snap to share promotion rockstor#2902

src/rockstor/fs/btrfs.py

@@ -1181,7 +1181,7 @@ def remove_share(pool, share_name, pqgroup, force=False):
     # TODO: Consider also using the following command to allow delete of the
     # initial (anomalous) temp replication snap as share; but this also blindly
     # circumvents ro 'protection' for any other share!
-    # set_property(subvol_mnt_pt, 'ro', 'false', mount=False)
+    # set_property(subvol_mnt_pt, 'ro', 'false', mount=False, force=True)
     toggle_path_rw(subvol_mnt_pt, rw=True)
     if force:
         o, e, rc = run_command([BTRFS, "subvolume", "list", "-o", subvol_mnt_pt])
@@ -2308,9 +2308,16 @@ def btrfs_uuid(disk):
     return o[0].split()[3]
 
 
-def set_property(mnt_pt, name, val, mount=True):
+def set_property(mnt_pt, name, val, mount=True, force=False):
+    """
+    https://btrfs.readthedocs.io/en/latest/btrfs-property.html
+    https://btrfs.readthedocs.io/en/latest/btrfs-subvolume.html
+    """
     if mount is not True or is_mounted(mnt_pt):
-        cmd = [BTRFS, "property", "set", mnt_pt, name, val]
+        if not force:
+            cmd = [BTRFS, "property", "set", mnt_pt, name, val]
+        else:
+            cmd = [BTRFS, "property", "set", "-f", mnt_pt, name, val]
         return run_command(cmd)
 
 

src/rockstor/storageadmin/views/clone_helpers.py

@@ -41,7 +41,7 @@
 
 def create_repclone(share, request, logger, snapshot):
     """
-    Variant of create_clone but where the share already exists and is to be
+    Variant of create_clone but where the share may already exist and is to be
     supplanted by a snapshot which is effectively moved into the shares prior
     position, both in the db and on the file system. This is achieved thus:
     Unmount target share - (via remove_share()).
@@ -74,7 +74,7 @@ def create_repclone(share, request, logger, snapshot):
         # Normalise source name across initial quirk share & subsequent snaps.
         source_name = snapshot.name.split("/")[-1]
         # Note in the above we have to use Object.name for polymorphism, but
-        # our share is passed by it's subvol (potential fragility point).
+        # our share is passed by its subvol (potential fragility point).
         snap_path = "{}/.snapshots/{}/{}".format(
             share.pool.mnt_pt, share.name, source_name
         ).replace("//", "/")
@@ -91,7 +91,11 @@ def create_repclone(share, request, logger, snapshot):
         # unmounts and then subvol deletes our on disk share
         remove_share(share.pool, share.name, PQGROUP_DEFAULT)
         # Remove read only flag on our snapshot subvol
-        set_property(snap_path, "ro", "false", mount=False)
+        # N.B. more recent btrfs has force requirement re safeguard on received_uuid set.
+        # However, Rockstor replication cascades ro snapshots used in send/receive.
+        # The oldest of 3 received snapshot sends is promoted to Share, from 4th replication event onwards.
+        # As such this subvol is no longer referenced in the ongoing btrfs send/receive cascade.
+        set_property(snap_path, "ro", "false", mount=False, force=True)
         # Ensure removed share path is clean, ie remove mount point.
         run_command(["/usr/bin/rm", "-rf", share_path], throw=False)
         # Now move snapshot to prior shares location. Given both a share and