#!/usr/bin/python2
# Lets a user loopback-mount a private fs of a given type.
# To use, configure the following vsys-attributes in addition to setting the vsys tag for the slice
# - vsys_privatefs_list -> comma-separated list of desired filesystems, e.g. xfs,btrfs
# - vsys_privatefs_size -> desired size in megabytes

import sys
import os
import string

vsys_config_dir = "/etc/planetlab/vsys-attributes"
slicename=sys.argv[1]
sliceroot='/vservers/%s'%slicename

private_fs_config=os.path.join(vsys_config_dir,slicename,"vsys_privatefs_list")
private_fs_size_config=os.path.join(vsys_config_dir,slicename,"vsys_privatefs_size")

private_fs_str = open(private_fs_config).read().rstrip()

nonamespace_path = '/etc/vservers/%s/nonamespace'%slicename
if (not os.path.isfile(nonamespace_path)):
	# Touch
	open(nonamespace_path,'w').close()

	os.system('vserver %s stop'%slicename)
	os.system('vserver %s start'%slicename)
	print 'Reconfiguring slice for private mounts'
	exit(1)

fs_lst = private_fs_str.split(',')
try:
	private_fs_size_str = open(private_fs_size_config).read().rstrip()
	fs_size = int(private_fs_size_str)
except:
	fs_size = 100

num_fs = len(fs_lst)
if num_fs==0:
    print >>sys.stderr, "Please configure your private filesystems at PLC."
    sys.exit(1)

for fs in fs_lst:
	# XXX There's a race condition here. You could 
	# intervene between the creation of the image
	# and the mount operation to replace the empty image
	# with a rogue volume.

	fs_file = '%s/pvtfs-%s'%(sliceroot,fs)
	os.system('umount %s 2>&1>/dev/null'%fs_file)

	sanity_check_cmd = 'cat /proc/mounts | grep %s | wc -l'%fs_file
	sanity_check = os.popen(sanity_check_cmd).read().rstrip()
	if int(sanity_check)!=0:
		print 'Private fs could not be remounted. Please contact support.'
		exit(1)
	os.system('mkdir -p %s'%fs_file)
	
	# This is the critical step
	if (os.system('dd if=/dev/zero of=%s.img bs=1000000 count=%d'%(fs_file,fs_size))):
		print 'Could not recycle private fs. Please contact support.'
		exit(1)

	os.system('mkfs.%s %s.img'%(fs,fs_file))
	os.system('mount -o loop -t %s %s.img %s'%(fs, fs_file, fs_file))