Use full-stripe size in LVM growth

LVM has issues when growing stripped volumes, so it's best to specify
the growth in exact multiples of the full stripe size (as precise as
possible). For this we need to do a couple of changes:
  - in LVM Attach(), we query additionally the VG extent size and the LV
    stripe count; since this makes lvs return a (possibly) multi-line
    output, we now split it into lines and only take the last one
  - in LVM Grow(), we round up the increase in multiples of the full
    stripe size

The patch also sets the correct target size in DRBD growth.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>

lib/bdev.py

@@ -299,7 +299,7 @@ class LogicalVolume(BlockDev):
     self._vg_name, self._lv_name = unique_id
     self.dev_path = "/dev/%s/%s" % (self._vg_name, self._lv_name)
     self._degraded = True
-    self.major = self.minor = None
+    self.major = self.minor = self.pe_size = self.stripe_count = None
     self.Attach()
 
   @classmethod
@@ -411,19 +411,30 @@ class LogicalVolume(BlockDev):
     """
     self.attached = False
     result = utils.RunCmd(["lvs", "--noheadings", "--separator=,",
-                           "-olv_attr,lv_kernel_major,lv_kernel_minor",
-                           self.dev_path])
+                           "--units=m", "--nosuffix",
+                           "-olv_attr,lv_kernel_major,lv_kernel_minor,"
+                           "vg_extent_size,stripes", self.dev_path])
     if result.failed:
       logging.error("Can't find LV %s: %s, %s",
                     self.dev_path, result.fail_reason, result.output)
       return False
-    out = result.stdout.strip().rstrip(',')
+    # the output can (and will) have multiple lines for multi-segment
+    # LVs, as the 'stripes' parameter is a segment one, so we take
+    # only the last entry, which is the one we're interested in; note
+    # that with LVM2 anyway the 'stripes' value must be constant
+    # across segments, so this is a no-op actually
+    out = result.stdout.splitlines()
+    if not out: # totally empty result? splitlines() returns at least
+                # one line for any non-empty string
+      logging.error("Can't parse LVS output, no lines? Got '%s'", str(out))
+      return False
+    out = out[-1].strip().rstrip(',')
     out = out.split(",")
-    if len(out) != 3:
-      logging.error("Can't parse LVS output, len(%s) != 3", str(out))
+    if len(out) != 5:
+      logging.error("Can't parse LVS output, len(%s) != 5", str(out))
       return False
 
-    status, major, minor = out[:3]
+    status, major, minor, pe_size, stripes = out
     if len(status) != 6:
       logging.error("lvs lv_attr is not 6 characters (%s)", status)
       return False
@@ -434,8 +445,22 @@ class LogicalVolume(BlockDev):
     except ValueError, err:
       logging.error("lvs major/minor cannot be parsed: %s", str(err))
 
+    try:
+      pe_size = int(float(pe_size))
+    except (TypeError, ValueError), err:
+      logging.error("Can't parse vg extent size: %s", err)
+      return False
+
+    try:
+      stripes = int(stripes)
+    except (TypeError, ValueError), err:
+      logging.error("Can't parse the number of stripes: %s", err)
+      return False
+
     self.major = major
     self.minor = minor
+    self.pe_size = pe_size
+    self.stripe_count = stripes
     self._degraded = status[0] == 'v' # virtual volume, i.e. doesn't backing
                                       # storage
     self.attached = True
@@ -554,6 +579,13 @@ class LogicalVolume(BlockDev):
     """Grow the logical volume.
 
     """
+    if self.pe_size is None or self.stripe_count is None:
+      if not self.Attach():
+        _ThrowError("Can't attach to LV during Grow()")
+    full_stripe_size = self.pe_size * self.stripe_count
+    rest = amount % full_stripe_size
+    if rest != 0:
+      amount += full_stripe_size - rest
     # we try multiple algorithms since the 'best' ones might not have
     # space available in the right place, but later ones might (since
     # they have less constraints); also note that only recent LVM
@@ -1609,7 +1641,8 @@ class DRBD8(BaseDRBD):
     if len(self._children) != 2 or None in self._children:
       _ThrowError("drbd%d: cannot grow diskless device", self.minor)
     self._children[0].Grow(amount)
-    result = utils.RunCmd(["drbdsetup", self.dev_path, "resize"])
+    result = utils.RunCmd(["drbdsetup", self.dev_path, "resize", "-s",
+                           "%dm" % (self.size + amount)])
     if result.failed:
       _ThrowError("drbd%d: resize failed: %s", self.minor, result.output)