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#!/usr/bin/python 

# 

# Copyright (C) Citrix Systems Inc. 

# 

# This program is free software; you can redistribute it and/or modify 

# it under the terms of the GNU Lesser General Public License as published 

# by the Free Software Foundation; version 2.1 only. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU Lesser General Public License for more details. 

# 

# You should have received a copy of the GNU Lesser 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 

# 

# A plugin for enabling trim on LVM based SRs to free up storage space 

# in Storage arrays. 

 

import xml 

import os 

import time 

import util 

import lock 

import lvhdutil 

import vhdutil 

import lvutil 

 

TRIM_LV_TAG = "_trim_lv" 

TRIM_CAP = "SR_TRIM" 

LOCK_RETRY_ATTEMPTS = 3 

LOCK_RETRY_INTERVAL = 1 

ERROR_CODE_KEY = "errcode" 

ERROR_MSG_KEY = "errmsg" 

 

TRIM_LAST_TRIGGERED_KEY = "trim_last_triggered" 

MASTER_LVM_CONF = '/etc/lvm/master' 

 

def _vg_by_sr_uuid(sr_uuid): 

    return lvhdutil.VG_PREFIX + sr_uuid 

 

def _lvpath_by_vg_lv_name(vg_name, lv_name): 

    return os.path.join(lvhdutil.VG_LOCATION, vg_name, lv_name) 

 

def to_xml(d): 

 

    dom = xml.dom.minidom.Document() 

    trim_response = dom.createElement("trim_response") 

    dom.appendChild(trim_response) 

 

    for key, value in sorted(d.items()): 

        key_value_element = dom.createElement("key_value_pair") 

        trim_response.appendChild(key_value_element) 

 

        key_element = dom.createElement("key") 

        key_text_node = dom.createTextNode(key) 

        key_element.appendChild(key_text_node) 

        key_value_element.appendChild(key_element) 

 

        value_element = dom.createElement("value") 

        value_text_mode = dom.createTextNode(value) 

        value_element.appendChild(value_text_mode) 

        key_value_element.appendChild(value_element) 

 

 

    return dom.toxml() 

 

# Note: This function is expected to be called from a context where 

# the SR is locked by the thread calling the function; therefore removing 

# any risk of a race condition updating the LAST_TRIGGERED value. 

def _log_last_triggered(session, sr_uuid): 

    try: 

        sr_ref = session.xenapi.SR.get_by_uuid(sr_uuid) 

        other_config = session.xenapi.SR.get_other_config(sr_ref) 

        if other_config.has_key(TRIM_LAST_TRIGGERED_KEY): 

            session.xenapi.SR.remove_from_other_config(sr_ref, TRIM_LAST_TRIGGERED_KEY) 

        session.xenapi.SR.add_to_other_config(sr_ref, TRIM_LAST_TRIGGERED_KEY, str(time.time())) 

    except: 

        util.logException("Unable to set other-config:%s" % TRIM_LAST_TRIGGERED_KEY) 

 

def do_trim(session, args): 

    """Attempt to trim the given LVHDSR""" 

    util.SMlog("do_trim: %s" % args) 

    sr_uuid = args["sr_uuid"] 

    os.environ['LVM_SYSTEM_DIR'] = MASTER_LVM_CONF 

 

    if TRIM_CAP not in util.sr_get_capability(sr_uuid): 

        util.SMlog("Trim command ignored on unsupported SR %s" % sr_uuid) 

        err_msg = {ERROR_CODE_KEY: 'UnsupportedSRForTrim', 

                   ERROR_MSG_KEY: 'Trim on [%s] not supported' % sr_uuid} 

        return to_xml(err_msg) 

 

    # Lock SR, get vg empty space details 

    sr_lock = lock.Lock(vhdutil.LOCK_TYPE_SR, sr_uuid) 

    got_lock = False 

    for i in range(LOCK_RETRY_ATTEMPTS): 

        got_lock = sr_lock.acquireNoblock() 

        if got_lock: 

            break 

        time.sleep(LOCK_RETRY_INTERVAL) 

 

    if got_lock: 

        try: 

            vg_name = _vg_by_sr_uuid(sr_uuid) 

            lv_name = sr_uuid + TRIM_LV_TAG 

            lv_path = _lvpath_by_vg_lv_name(vg_name, lv_name) 

 

            # Clean trim LV in case the previous trim attemp failed 

            if lvutil.exists(lv_path): 

               lvutil.remove(lv_path) 

 

            #Check if VG limits are enough for creating LV. 

            stats = lvutil._getVGstats(vg_name) 

            if (stats['freespace'] < lvutil.LVM_SIZE_INCREMENT): 

                util.SMlog("No space to claim on a full SR %s" % sr_uuid) 

                err_msg = {ERROR_CODE_KEY: 'Trim failed on full SR', 

                           ERROR_MSG_KEY: 'No space to claim on a full SR'} 

                result = to_xml(err_msg) 

            else: 

                # Perform a lvcreate, blkdiscard and lvremove to 

                # trigger trim on the array 

                lvutil.create(lv_name, 0, vg_name, size_in_percentage="100%F") 

                cmd = ["/usr/sbin/blkdiscard", "-v", lv_path] 

                stdout = util.pread2(cmd) 

                util.SMlog("Stdout is %s" % stdout) 

                util.SMlog("Trim on SR: %s complete. " % sr_uuid) 

                result = str(True) 

        except util.CommandException, e: 

            err_msg = { 

                ERROR_CODE_KEY: 'TrimException', 

                ERROR_MSG_KEY: e.reason 

            } 

            result = to_xml(err_msg) 

        except: 

            err_msg = { 

                ERROR_CODE_KEY: 'UnknownTrimException', 

                ERROR_MSG_KEY: 'Unknown Exception: trim failed on SR [%s]' 

                % sr_uuid 

            } 

            result = to_xml(err_msg) 

        finally: 

            if lvutil.exists(lv_path): 

                lvutil.remove(lv_path) 

 

        _log_last_triggered(session, sr_uuid) 

 

        sr_lock.release() 

        return result 

    else: 

        util.SMlog("Could not complete Trim on %s, Lock unavailable !" \ 

                   % sr_uuid) 

        err_msg = {ERROR_CODE_KEY: 'SRUnavailable', 

                   ERROR_MSG_KEY: 'Unable to get SR lock [%s]' % sr_uuid} 

        return to_xml(err_msg)