cc_resizefs on FreeBSD: Fix _can_skip_ufs_resize (#655)

On FreeBSD, if a UFS has trim: (-t) or MAC multilabel: (-l) flag, resize
FS fail, because the _can_skip_ufs_resize check gets tripped up by the
missing options.

This was reported at FreeBSD Bugzilla: 
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250496 and as
LP: #1901958

Rather than fixing the parser as in the patches proposed there (and
attempted in #636) this pull-request rips out all of it, and simplifies
the code.  We now use `growfs -N` and check if that returns an error. If
it returns the correct kind of error, we can skip the resize, because we
either are at the correct size, or the filesystem in question is broken
or not UFS. If it returns the wrong kind of error, we just re-raise it.

LP: #1901958

1 files changed, 16 insertions, 52 deletions

diff --git a/cloudinit/config/cc_resizefs.py b/cloudinit/config/cc_resizefs.py
index 978d2ee0..9afbb847 100644
--- a/cloudinit/config/cc_resizefs.py
+++ b/cloudinit/config/cc_resizefs.py
@@ -9,10 +9,7 @@
 """Resizefs: cloud-config module which resizes the filesystem"""
 
 import errno
-import getopt
 import os
-import re
-import shlex
 import stat
 from textwrap import dedent
 
@@ -88,56 +85,23 @@ def _resize_zfs(mount_point, devpth):
     return ('zpool', 'online', '-e', mount_point, devpth)
 
 
-def _get_dumpfs_output(mount_point):
-    return subp.subp(['dumpfs', '-m', mount_point])[0]
-
-
-def _get_gpart_output(part):
-    return subp.subp(['gpart', 'show', part])[0]
-
-
 def _can_skip_resize_ufs(mount_point, devpth):
-    # extract the current fs sector size
-    """
-    # dumpfs -m /
-    # newfs command for / (/dev/label/rootfs)
-      newfs -L rootf -O 2 -U -a 4 -b 32768 -d 32768 -e 4096 -f 4096 -g 16384
-            -h 64 -i 8192 -j -k 6408 -m 8 -o time -s 58719232 /dev/label/rootf
-    """
-    cur_fs_sz = None
-    frag_sz = None
-    dumpfs_res = _get_dumpfs_output(mount_point)
-    for line in dumpfs_res.splitlines():
-        if not line.startswith('#'):
-            newfs_cmd = shlex.split(line)
-            opt_value = 'O:Ua:s:b:d:e:f:g:h:i:jk:m:o:L:'
-            optlist, _args = getopt.getopt(newfs_cmd[1:], opt_value)
-            for o, a in optlist:
-                if o == "-s":
-                    cur_fs_sz = int(a)
-                if o == "-f":
-                    frag_sz = int(a)
-    # check the current partition size
-    # Example output from `gpart show /dev/da0`:
-    # =>      40  62914480  da0  GPT  (30G)
-    #         40      1024    1  freebsd-boot  (512K)
-    #       1064  58719232    2  freebsd-ufs  (28G)
-    #   58720296   3145728    3  freebsd-swap  (1.5G)
-    #   61866024   1048496       - free -  (512M)
-    expect_sz = None
-    m = re.search('^(/dev/.+)p([0-9])$', devpth)
-    gpart_res = _get_gpart_output(m.group(1))
-    for line in gpart_res.splitlines():
-        if re.search(r"freebsd-ufs", line):
-            fields = line.split()
-            expect_sz = int(fields[1])
-    # Normalize the gpart sector size,
-    # because the size is not exactly the same as fs size.
-    normal_expect_sz = (expect_sz - expect_sz % (frag_sz / 512))
-    if normal_expect_sz == cur_fs_sz:
-        return True
-    else:
-        return False
+    # possible errors cases on the code-path to growfs -N following:
+    # https://github.com/freebsd/freebsd/blob/HEAD/sbin/growfs/growfs.c
+    # This is the "good" error:
+    skip_start = "growfs: requested size"
+    skip_contain = "is not larger than the current filesystem size"
+    # growfs exits with 1 for almost all cases up to this one.
+    # This means we can't just use rcs=[0, 1] as subp parameter:
+    try:
+        subp.subp(['growfs', '-N', devpth])
+    except subp.ProcessExecutionError as e:
+        if e.stderr.startswith(skip_start) and skip_contain in e.stderr:
+            # This FS is already at the desired size
+            return True
+        else:
+            raise e
+    return False
 
 
 # Do not use a dictionary as these commands should be able to be used