Add support to resize rootfs if using LVM

cloudinit/config/cc_growpart.py

@@ -68,7 +68,9 @@
 import os.path
 import re
 import stat
+import platform
 
+from functools import lru_cache
 from cloudinit import log as logging
 from cloudinit.settings import PER_ALWAYS
 from cloudinit import subp
@@ -93,6 +95,58 @@ class RESIZE(object):
 LOG = logging.getLogger(__name__)
 
 
+@lru_cache()
+def is_lvm_lv(devpath):
+    if util.is_Linux():
+        # all lvm lvs will have a realpath as a 'dm-*' name.
+        rpath = os.path.realpath(devpath)
+        if not os.path.basename(rpath).startswith("dm-"):
+            return False
+        out, _ = subp.subp("udevadm", "info", devpath)
+        # lvs should have DM_LV_NAME=<lvmuuid> and also DM_VG_NAME
+        return 'DM_LV_NAME=' in out
+    else:
+        LOG.info("Not an LVM Logical Volume partition")
+        return False
+
+
+@lru_cache()
+def get_pvs_for_lv(devpath):
+    myenv = {'LANG': 'C'}
+
+    if not util.is_Linux():
+        LOG.info("No support for LVM on %s", platform.system())
+        return None
+    if not subp.which('lvm'):
+        LOG.info("No 'lvm' command present")
+        return None
+
+    try:
+        (out, _err) = subp.subp(["lvm", "lvs", devpath, "--options=vgname",
+                                 "--noheadings"], update_env=myenv)
+        vgname = out.strip()
+    except subp.ProcessExecutionError as e:
+        if e.exit_code != 0:
+            util.logexc(LOG, "Failed: can't get Volume Group information "
+                        "from %s", devpath)
+            raise ResizeFailedException(e) from e
+
+    try:
+        (out, _err) = subp.subp(["lvm", "vgs", vgname, "--options=pvname",
+                                 "--noheadings"], update_env=myenv)
+        pvs = [p.strip() for p in out.splitlines()]
+        if len(pvs) > 1:
+            LOG.info("Do not know how to resize multiple Physical"
+                     " Volumes")
+        else:
+            return pvs[0]
+    except subp.ProcessExecutionError as e:
+        if e.exit_code != 0:
+            util.logexc(LOG, "Failed: can't get Physical Volume "
+                        "information from Volume Group %s", vgname)
+            raise ResizeFailedException(e) from e
+
+
 def resizer_factory(mode):
     resize_class = None
     if mode == "auto":
@@ -208,13 +262,18 @@ def get_size(filename):
         os.close(fd)
 
 
-def device_part_info(devpath):
+def device_part_info(devpath, is_lvm):
     # convert an entry in /dev/ to parent disk and partition number
 
     # input of /dev/vdb or /dev/disk/by-label/foo
     # rpath is hopefully a real-ish path in /dev (vda, sdb..)
     rpath = os.path.realpath(devpath)
 
+    # first check if this is an LVM and get its PVs
+    lvm_rpath = get_pvs_for_lv(devpath)
+    if is_lvm and lvm_rpath:
+        rpath = lvm_rpath
+
     bname = os.path.basename(rpath)
     syspath = "/sys/class/block/%s" % bname
 
@@ -244,7 +303,7 @@ def device_part_info(devpath):
 
     # diskdevpath has something like 253:0
     # and udev has put links in /dev/block/253:0 to the device name in /dev/
-    return (diskdevpath, ptnum)
+    return diskdevpath, ptnum
 
 
 def devent2dev(devent):
@@ -294,8 +353,9 @@ def resize_devices(resizer, devices):
                          "device '%s' not a block device" % blockdev,))
             continue
 
+        is_lvm = is_lvm_lv(blockdev)
         try:
-            (disk, ptnum) = device_part_info(blockdev)
+            disk, ptnum = device_part_info(blockdev, is_lvm)
         except (TypeError, ValueError) as e:
             info.append((devent, RESIZE.SKIPPED,
                          "device_part_info(%s) failed: %s" % (blockdev, e),))
@@ -316,6 +376,23 @@ def resize_devices(resizer, devices):
                          "failed to resize: disk=%s, ptnum=%s: %s" %
                          (disk, ptnum, e),))
 
+        if is_lvm and isinstance(resizer, ResizeGrowPart):
+            try:
+                if len(devices) == 1:
+                    (_out, _err) = subp.subp(
+                        ["lvm", "lvextend", "--extents=100%FREE", blockdev],
+                        update_env={'LANG': 'C'})
+                    info.append((devent, RESIZE.CHANGED,
+                                 "Logical Volume %s extended" % devices[0],))
+                else:
+                    LOG.info("Exactly one device should be configured to be "
+                             "resized when using LVM. More than one configured"
+                             ": %s", devices)
+            except (subp.ProcessExecutionError, ValueError) as e:
+                info.append((devent, RESIZE.NOCHANGE,
+                             "Logical Volume %s resize failed: %s" %
+                             (blockdev, e),))
+
     return info
 
 

doc/examples/cloud-config-growpart.txt

@@ -13,6 +13,8 @@
 #
 # devices:
 #   a list of things to resize.
+#   if the devices are under LVM, the list should be a single entry,
+#   cloud-init will then extend the single entry, otherwise it will fail.
 #   items can be filesystem paths or devices (in /dev)
 #   examples:
 #     devices: [/, /dev/vdb1]

tests/unittests/test_handler/test_handler_growpart.py

@@ -172,6 +172,53 @@ def setUp(self):
         self.name = "growpart"
         self.log = logging.getLogger("TestResize")
 
+    def test_lvm_resize(self):
+        # LVM resize should work only if a single device is configured. More
+        # than one device should fail.
+        lvm_pass = ["/dev/XXdm-0"]
+        lvm_fail = ["/dev/XXdm-1", "/dev/YYdm-1"]
+        devstat_ret = Bunch(st_mode=25008, st_ino=6078, st_dev=5,
+                            st_nlink=1, st_uid=0, st_gid=6, st_size=0,
+                            st_atime=0, st_mtime=0, st_ctime=0)
+        real_stat = os.stat
+        resize_calls = []
+
+        class myresizer(object):
+            def resize(self, diskdev, partnum, partdev):
+                resize_calls.append((diskdev, partnum, partdev))
+                if partdev == "/dev/XXdm-0":
+                    return (1024, 2048)
+                return (1024, 1024)  # old size, new size
+
+        def mystat(path):
+            if path in lvm_pass or path in lvm_fail:
+                return devstat_ret
+            return real_stat(path)
+
+        try:
+            opinfo = cc_growpart.device_part_info
+            cc_growpart.device_part_info = simple_device_part_info_lvm
+            os.stat = mystat
+
+            resized = cc_growpart.resize_devices(myresizer(), lvm_pass)
+            not_resized = cc_growpart.resize_devices(myresizer(), lvm_fail)
+
+            def find(name, res):
+                for f in res:
+                    if f[0] == name:
+                        return f
+                return None
+
+            self.assertEqual(cc_growpart.RESIZE.CHANGED,
+                             find("/dev/XXdm-0", resized)[1])
+            self.assertEqual(cc_growpart.RESIZE.NOCHANGE,
+                             find("/dev/XXdm-1", not_resized)[1])
+            self.assertEqual(cc_growpart.RESIZE.NOCHANGE,
+                             find("/dev/YYdm-1", not_resized)[1])
+        finally:
+            cc_growpart.device_part_info = opinfo
+            os.stat = real_stat
+
     def test_simple_devices(self):
         # test simple device list
         # this patches out devent2dev, os.stat, and device_part_info
@@ -227,7 +274,14 @@ def find(name, res):
             os.stat = real_stat
 
 
-def simple_device_part_info(devpath):
+def simple_device_part_info_lvm(devpath, is_lvm):
+    # simple stupid return (/dev/vda, 1) for /dev/vda
+    ret = re.search("([^0-9]*)([0-9]*)$", devpath)
+    x = (ret.group(1), ret.group(2))
+    return x
+
+
+def simple_device_part_info(devpath, is_lvm):
     # simple stupid return (/dev/vda, 1) for /dev/vda
     ret = re.search("([^0-9]*)([0-9]*)$", devpath)
     x = (ret.group(1), ret.group(2))