xfs_scrub_all: convert systemctl calls to dbus

Convert the systemctl invocations to direct dbus calls, which decouples
us from the CLI in favor of direct API calls.  This spares us from some
of the insanity of divining service state from program outputs.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/debian/control b/debian/control
index 344466de0161afe534ba310d95dac5a515d74c79..31773e53a19a45319514504d74e7a064a8aeb725 100644 (file)
--- a/debian/control
+++ b/debian/control
@@ -8,7 +8,7 @@ Standards-Version: 4.0.0
 Homepage: https://xfs.wiki.kernel.org/
 
 Package: xfsprogs
-Depends: ${shlibs:Depends}, ${misc:Depends}, python3:any
+Depends: ${shlibs:Depends}, ${misc:Depends}, python3-dbus, python3:any
 Provides: fsck-backend
 Suggests: xfsdump, acl, attr, quota
 Breaks: xfsdump (<< 3.0.0)

diff --git a/scrub/xfs_scrub_all.in b/scrub/xfs_scrub_all.in
index d5d1d13a2552a351bd19a23195f9c482961d8586..a09566efdcd8d27acf8e3a64bc2b37163f1ecfe4 100644 (file)
--- a/scrub/xfs_scrub_all.in
+++ b/scrub/xfs_scrub_all.in
@@ -15,6 +15,7 @@ import sys
 import os
 import argparse
 import signal
+import dbus
 from io import TextIOWrapper
 from pathlib import Path
 from datetime import timedelta
@@ -168,25 +169,57 @@ class scrub_service(scrub_control):
        '''Control object for xfs_scrub systemd service.'''
        def __init__(self, mnt, scrub_media):
                self.unitname = path_to_serviceunit(mnt, scrub_media)
+               self.prop = None
+               self.unit = None
+               self.bind()
+
+       def bind(self):
+               '''Bind to the dbus proxy object for this service.'''
+               sysbus = dbus.SystemBus()
+               systemd1 = sysbus.get_object('org.freedesktop.systemd1',
+                                           '/org/freedesktop/systemd1')
+               manager = dbus.Interface(systemd1,
+                               'org.freedesktop.systemd1.Manager')
+               path = manager.LoadUnit(self.unitname)
+
+               svc_obj = sysbus.get_object('org.freedesktop.systemd1', path)
+               self.prop = dbus.Interface(svc_obj,
+                               'org.freedesktop.DBus.Properties')
+               self.unit = dbus.Interface(svc_obj,
+                               'org.freedesktop.systemd1.Unit')
+
+       def state(self):
+               '''Retrieve the active state for a systemd service.  As of
+               systemd 249, this is supposed to be one of the following:
+               "active", "reloading", "inactive", "failed", "activating",
+               or "deactivating".  These strings are not localized.'''
+               global debug
+
+               try:
+                       return self.prop.Get('org.freedesktop.systemd1.Unit', 'ActiveState')
+               except Exception as e:
+                       if debug:
+                               print(e, file = sys.stderr)
+                       return 'failed'
 
        def wait(self, interval = 1):
                '''Wait until the service finishes.'''
+               global debug
 
-               # As of systemd 249, the is-active command returns any of the
-               # following states: active, reloading, inactive, failed,
-               # activating, deactivating, or maintenance.  Apparently these
-               # strings are not localized.
-               while True:
-                       try:
-                               for l in backtick(['systemctl', 'is-active', self.unitname]):
-                                       if l == 'failed':
-                                               return 1
-                                       if l == 'inactive':
-                                               return 0
-                       except:
-                               return -1
-
+               # Use a poll/sleep loop to wait for the service to finish.
+               # Avoid adding a dependency on python3 glib, which is required
+               # to use an event loop to receive a dbus signal.
+               s = self.state()
+               while s not in ['failed', 'inactive']:
+                       if debug:
+                               print('waiting %s %s' % (self.unitname, s))
                        time.sleep(interval)
+                       s = self.state()
+               if debug:
+                       print('waited %s %s' % (self.unitname, s))
+               if s == 'failed':
+                       return 1
+               return 0
 
        def start(self):
                '''Start the service and wait for it to complete.  Returns -1
@@ -194,34 +227,29 @@ class scrub_service(scrub_control):
                failed.'''
                global debug
 
-               cmd = ['systemctl', 'start', self.unitname]
+               if debug:
+                       print('starting %s' % self.unitname)
+
                try:
-                       if debug:
-                               print(' '.join(cmd))
-                       proc = subprocess.Popen(cmd, stdout = DEVNULL())
-                       proc.wait()
-                       ret = proc.returncode
-               except:
+                       self.unit.Start('replace')
+                       return self.wait()
+               except Exception as e:
+                       print(e, file = sys.stderr)
                        return -1
 
-               if ret != 1:
-                       return ret
-
-               # If systemctl-start returns 1, it's possible that the service
-               # failed or that dbus/systemd restarted and the client program
-               # lost its connection -- according to the systemctl man page, 1
-               # means "unit not failed".
-               return self.wait()
-
        def stop(self):
                '''Stop the service.'''
                global debug
 
-               cmd = ['systemctl', 'stop', self.unitname]
                if debug:
-                       print(' '.join(cmd))
-               x = subprocess.Popen(cmd)
-               x.wait()
+                       print('stopping %s' % self.unitname)
+
+               try:
+                       self.unit.Stop('replace')
+                       return self.wait()
+               except Exception as e:
+                       print(e, file = sys.stderr)
+                       return -1
 
 def run_service(mnt, scrub_media, killfuncs):
        '''Run scrub as a service.'''