xfs_scrub_all: escape paths being passed to systemd service instances

systemd doesn't like unit instance names with slashes in them, so it
replaces them with dashes when it invokes the service.  However, it's
not smart enough to convert the dashes to something else, so when it
unescapes the instance name to feed to xfs_scrub, it turns all dashes
into slashes.  "/moo-cow" becomes "-moo-cow" becomes "/moo/cow", which
is wrong.  systemd actually /can/ escape the dashes correctly if it is
told that this is a path (and not a unit name), but it didn't do this
prior to January 2017, so fix this for them.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/scrub/xfs_scrub_all.in b/scrub/xfs_scrub_all.in
index aed66a1ac26a0c8781fa49df35950a6f0bb4cb1b..83c4e21847faf175a22e7e84dd48da48c47748a7 100644 (file)
--- a/scrub/xfs_scrub_all.in
+++ b/scrub/xfs_scrub_all.in
@@ -87,6 +87,28 @@ def run_killable(cmd, stdout, killfuncs, kill_fn):
        except:
                return -1
 
+# systemd doesn't like unit instance names with slashes in them, so it
+# replaces them with dashes when it invokes the service.  However, it's not
+# smart enough to convert the dashes to something else, so when it unescapes
+# the instance name to feed to xfs_scrub, it turns all dashes into slashes.
+# "/moo-cow" becomes "-moo-cow" becomes "/moo/cow", which is wrong.  systemd
+# actually /can/ escape the dashes correctly if it is told that this is a path
+# (and not a unit name), but it didn't do this prior to January 2017, so fix
+# this for them.
+def systemd_escape(path):
+       '''Escape a path to avoid mangled systemd mangling.'''
+
+       if '-' not in path:
+               return path
+       cmd = ['systemd-escape', '--path', path]
+       try:
+               proc = subprocess.Popen(cmd, stdout = subprocess.PIPE)
+               proc.wait()
+               for line in proc.stdout:
+                       return '-' + line.decode(sys.stdout.encoding).strip()
+       except:
+               return path
+
 def run_scrub(mnt, cond, running_devs, mntdevs, killfuncs):
        '''Run a scrub process.'''
        global retcode, terminate
@@ -99,7 +121,7 @@ def run_scrub(mnt, cond, running_devs, mntdevs, killfuncs):
                        return
 
                # Try it the systemd way
-               cmd=['systemctl', 'start', 'xfs_scrub@%s' % mnt]
+               cmd=['systemctl', 'start', 'xfs_scrub@%s' % systemd_escape(mnt)]
                ret = run_killable(cmd, DEVNULL(), killfuncs, \
                                lambda proc: kill_systemd('xfs_scrub@%s' % mnt, proc))
                if ret == 0 or ret == 1: