geo-rep: Fix geo-rep for older versions of unshare

Geo-rep mounts are private to worker. It uses
mount namespace using unshare command to achieve
the same. Well, the unshare command has to support
'--propagation' option. So geo-rep breaks on the
systems with older unshare version. The patch
makes it fall back to lazy umount behaviour if
the unshare does not support propagation option.

fixes: bz#1589782
Change-Id: Ia614f068aede288d63ac62fea4461b1865066054
Signed-off-by: Kotresh HR <khiremat@redhat.com>

geo-replication/syncdaemon/monitor.py

@@ -26,7 +26,7 @@ from syncdutils import set_term_handler, GsyncdError
 from syncdutils import Thread, finalize, Volinfo, VolinfoFromGconf
 from syncdutils import gf_event, EVENT_GEOREP_FAULTY, get_up_nodes
 from gsyncdstatus import GeorepStatus, set_monitor_status
-
+from syncdutils import unshare_propagation_supported
 
 ParseError = XET.ParseError if hasattr(XET, 'ParseError') else SyntaxError
 
@@ -225,9 +225,16 @@ class Monitor(object):
                 if access_mount:
                     os.execv(sys.executable, args_to_worker)
                 else:
-                    unshare_cmd = ['unshare', '-m', '--propagation', 'private']
-                    cmd = unshare_cmd + args_to_worker
-                    os.execvp("unshare", cmd)
+                    if unshare_propagation_supported():
+                        logging.debug("Worker would mount volume privately")
+                        unshare_cmd = ['unshare', '-m', '--propagation',
+                                       'private']
+                        cmd = unshare_cmd + args_to_worker
+                        os.execvp("unshare", cmd)
+                    else:
+                        logging.debug("Mount is not private. It would be lazy"
+                                      " umounted")
+                        os.execv(sys.executable, args_to_worker)
 
             cpids.add(cpid)
             agents.add(apid)

geo-replication/syncdaemon/resource.py

@@ -40,6 +40,7 @@ from syncdutils import GX_GFID_CANONICAL_LEN
 from gsyncdstatus import GeorepStatus
 from syncdutils import lf, Popen, sup, Volinfo
 from syncdutils import Xattr, matching_disk_gfid, get_gfid_from_mnt
+from syncdutils import unshare_propagation_supported
 
 
 ENOTSUP = getattr(errno, 'ENOTSUP', 'EOPNOTSUPP')
@@ -900,15 +901,25 @@ class Mounter(object):
                     assert(mntdata[-1] == '\0')
                     mntpt = mntdata[:-1]
                     assert(mntpt)
-                    if mounted and rconf.args.subcmd == "slave" \
+
+                    umount_master = False
+                    umount_slave = False
+                    if rconf.args.subcmd == "worker" \
+                       and not unshare_propagation_supported() \
+                       and not gconf.get("access-mount"):
+                        umount_master = True
+                    if rconf.args.subcmd == "slave" \
                        and not gconf.get("slave-access-mount"):
+                        umount_slave = True
+
+                    if mounted and (umount_master or umount_slave):
                         po = self.umount_l(mntpt)
                         po.terminate_geterr(fail_on_err=False)
                         if po.returncode != 0:
                             po.errlog()
                             rv = po.returncode
-                    if rconf.args.subcmd == "slave" \
-                       and not gconf.get("slave-access-mount"):
+                        logging.debug("Lazy umount done: %s" % mntpt)
+                    if umount_master or umount_slave:
                         self.cleanup_mntpt(mntpt)
             except:
                 logging.exception('mount cleanup failure:')

geo-replication/syncdaemon/syncdutils.py

@@ -65,6 +65,7 @@ CHANGELOG_AGENT_SERVER_VERSION = 1.0
 CHANGELOG_AGENT_CLIENT_VERSION = 1.0
 NodeID = None
 rsync_version = None
+unshare_mnt_propagation = None
 SPACE_ESCAPE_CHAR = "%20"
 NEWLINE_ESCAPE_CHAR = "%0A"
 PERCENTAGE_ESCAPE_CHAR = "%25"
@@ -626,6 +627,22 @@ def get_master_and_slave_data_from_args(args):
 
     return (master_name, slave_data)
 
+def unshare_propagation_supported():
+    global unshare_mnt_propagation
+    if unshare_mnt_propagation is not None:
+        return unshare_mnt_propagation
+
+    unshare_mnt_propagation = False
+    p = subprocess.Popen(["unshare", "--help"],
+                         stderr=subprocess.PIPE,
+                         stdout=subprocess.PIPE)
+    out, err = p.communicate()
+    if p.returncode == 0:
+        if "propagation" in out:
+            unshare_mnt_propagation = True
+
+    return unshare_mnt_propagation
+
 
 def get_rsync_version(rsync_cmd):
     global rsync_version