[blivet:master 2/5] Add new RaidDevice class for handling RAID aspects of devices.

David Lehman dlehman at redhat.com
Mon Oct 6 17:22:40 UTC 2014


On 10/06/2014 08:14 AM, mulhern wrote:
> Signed-off-by: mulhern <amulhern at redhat.com>
> ---
>   blivet/devices/raid.py | 106 +++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 106 insertions(+)
>   create mode 100644 blivet/devices/raid.py

My only comment is that it seems like maybe this should be a subclass of 
ContainerDevice instead of StorageDevice. I see that btrfs having two 
raid level might complicate things, but the general concept is an 
extension of the container concept.

David

>
> diff --git a/blivet/devices/raid.py b/blivet/devices/raid.py
> new file mode 100644
> index 0000000..0f064f9
> --- /dev/null
> +++ b/blivet/devices/raid.py
> @@ -0,0 +1,106 @@
> +# devices/raid.py
> +#
> +# Copyright (C) 2014  Red Hat, Inc.
> +#
> +# This copyrighted material is made available to anyone wishing to use,
> +# modify, copy, or redistribute it subject to the terms and conditions of
> +# the GNU General Public License v.2, or (at your option) any later version.
> +# This program is distributed in the hope that it will be useful, but WITHOUT
> +# ANY WARRANTY expressed or implied, including the implied warranties of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
> +# Public License for more details.  You should have received a copy of the
> +# GNU General Public License along with this program; if not, write to the
> +# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> +# 02110-1301, USA.  Any Red Hat trademarks that are incorporated in the
> +# source code or documentation are not subject to the GNU General Public
> +# License and may only be used or replicated with the express permission of
> +# Red Hat, Inc.
> +#
> +# Red Hat Author(s): Anne Mulhern <amulhern at redhat.com>
> +#
> +
> +import abc
> +
> +from six import add_metaclass
> +
> +from .. import errors
> +from ..i18n import N_, P_
> +
> +from .storage import StorageDevice
> +
> + at add_metaclass(abc.ABCMeta)
> +class RaidDevice(StorageDevice):
> +    """ Metaclass for devices that support RAID in some form. """
> +
> +    def _validateRaidLevel(self, level, parent_diff=0):
> +        """ Returns an error message if the RAID level is invalid for this
> +            device, otherwise None.
> +
> +            :param level: a RAID level
> +            :type level: :class:`~.devicelibs.raid.RAIDLevel`
> +            :param int parent_diff: number of parents being removed or added
> +            :returns: an error message if the RAID level is invalid, else None
> +            :rtype: str or NoneType
> +
> +            The default number of parents being removed or added is 0,
> +            indicating that the level is to be checked against the current
> +            number of parents. The number is positive for added parents,
> +            negative for removed parents.
> +        """
> +        num_parents = len(self.parents) + parent_diff
> +        if not self.exists and num_parents < level.min_members:
> +            message = P_(
> +               "RAID level %(raidLevel)s requires that device have at least %(minMembers)d member.",
> +               "RAID level %(raidLevel)s requires that device have at least %(minMembers)d members.",
> +               level.min_members
> +            )
> +            return message % {"raidLevel": level, "minMembers" : level.min_members}
> +        return None
> +
> +    def _getLevel(self, value, levels):
> +        """ Obtains a valid level for the allowed set of levels.
> +
> +            :param value: a RAID level
> +            :type value: a valid RAID level descriptor
> +            :param levels: a list of valid levels
> +            :type levels: :class:`~.devicelibs.raid.RAIDLevels`
> +            :returns: a valid RAID level
> +            :rtype: :class:`~.devicelibs.raid.RAIDLevel`
> +            :raises: ValueError if invalid RAID level
> +        """
> +        try:
> +            level = levels.raidLevel(value)
> +        except errors.RaidError:
> +            message = N_("RAID level %(raidLevel)s is an invalid value. Must be one of (%(levels)s).")
> +            choices = ", ".join([str(l) for l in levels])
> +            raise ValueError(message % {"raidLevel": value, "levels" : choices})
> +
> +        error_msg = self._validateRaidLevel(level)
> +        if error_msg:
> +            raise ValueError(error_msg)
> +
> +        return level
> +
> +    def _validateParentRemoval(self, level, parent):
> +        """ Check if it is possible to remove a parent from this device.
> +
> +            :param level: a RAID level
> +            :type level: :class:`~.devicelibs.raid.RAIDLevel`
> +            :param parent: the parent to be removed
> +            :type parent: :class:`~.devices.StorageDevice`
> +            :returns: An error message if there is a problem
> +            :rtype: str or None
> +        """
> +        # If this is a raid array that is not actually redundant and it
> +        # appears to have formatting and therefore probably data on it,
> +        # removing one of its devices is a bad idea.
> +        try:
> +            if not level.has_redundancy() and self.exists and parent.format.exists:
> +                return N_("Cannot remove a member from existing %s array") % level
> +        except errors.RaidError:
> +            # If the concept of redundancy is meaningless for this device's
> +            # raid level, then it is OK to remove a parent device.
> +            pass
> +
> +        # Removing a member may invalidate the RAID level
> +        return self._validateRaidLevel(level, -1)
>



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