Commit 2d0c8319 authored by Iustin Pop's avatar Iustin Pop
Browse files

drbd: change the semantics of Attach vs. Assemble

Currently, both the Attach and Assemble methods for DRBD8 devices will use and
alter the device state. This is suboptimal, and it has been worked
around in 1.2 via a special cache in the node daemon so that we don't
need to call Attach() again in migration, for example.

Since in 2.0 we have static minors, we can change these functions so
  - Attach() does not affect the device in any way, and only checks if
    the minor is already in use or not
  - Assemble() has two logic paths, one for startup from unused minor
    (the old Assemble, now renamed _FastAssemble) and one for
    re-checking/fixing an in-use minor (the old Attach, now renamed

Basically Attach was renamed to _SlowAttach, Assemble to _FastAssemble,
and we have a new, simple Assemble that calls one or the other based on
the result of the new Attach.

The LUReplaceDisks (with new secondary) is relying on the special
semantics of Attach modifying the device and is broken until the end of
the patch series.

Reviewed-by: ultrotter
parent f87548b5
......@@ -1321,7 +1321,49 @@ class DRBD8(BaseDRBD):
"C", dual_pri=multimaster)
def Attach(self):
"""Find a DRBD device which matches our config and attach to it.
"""Check if our minor is configured.
This doesn't do any device configurations - it only checks if the
minor is in a state different from Unconfigured.
Note that this function will not change the state of the system in
any way (except in case of side-effects caused by reading from
used_devs = self._GetUsedDevs()
if self._aminor in used_devs:
minor = self._aminor
minor = None
return minor is not None
def Assemble(self):
"""Assemble the drbd.
- if we have a configured device, we try to ensure that it matches
our config
- if not, we create it from zero
result = super(DRBD8, self).Assemble()
if not result:
return result
if self.minor is None:
# local device completely unconfigured
return self._FastAssemble()
# we have to recheck the local and network status and try to fix
# the device
return self._SlowAssemble()
def _SlowAssemble(self):
"""Assembles the DRBD device from a (partially) configured device.
In case of partially attached (local device matches but no network
setup), we perform the network attach. If successful, we re-test
......@@ -1382,34 +1424,12 @@ class DRBD8(BaseDRBD):
return minor is not None
def Assemble(self):
"""Assemble the drbd.
def _FastAssemble(self):
"""Assemble the drbd device from zero.
- if we have a local backing device, we bind to it by:
- checking the list of used drbd devices
- check if the local minor use of any of them is our own device
- if yes, abort?
- if not, bind
- if we have a local/remote net info:
- redo the local backing device step for the remote device
- check if any drbd device is using the local port,
if yes abort
- check if any remote drbd device is using the remote
port, if yes abort (for now)
- bind our net port
- bind the remote net port
This is run when in Assemble we detect our minor is unused.
if self.minor is not None:"Already assembled")
return True
result = super(DRBD8, self).Assemble()
if not result:
return result
# TODO: maybe completely tear-down the minor (drbdsetup ... down)
# before attaching our own?
minor = self._aminor
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