Dear list,
I met a problem that looks like systemd-udevd will make a new scsi disk
partition (like /dev/sdb1)
disappear in a few time. This problem makes libvirt cannot lstat the new scsi
disk for a period.
(you can check this link https://bugzilla.redhat.com/show_bug.cgi?id=1264719).
And we wrote a script to verify this problem and finally find if we stop
systemd-udevd, this will not happen.
Could you please give me some help and tell me what systemd-udevd does to a new
scsi disk partition
making scsi disk partition disappear in a few time? Thanks in advance for your
reply.
And the attachment is the script we have used to check if that scsi device will
disappear.
BR,
Luyao
#!/usr/bin/env python
"""
Verify bug https://bugzilla.redhat.com/show_bug.cgi?id=1264719
"""
import glob
import os
import subprocess
import threading
import time
import numpy
def prepare_disk():
"""
Prepare a SCSI disk for debug
"""
subprocess.call(['rmmod', 'scsi_debug'])
pre_disks = glob.glob('/dev/sd?')
subprocess.call(['modprobe', 'scsi_debug'])
new_disks = set(glob.glob('/dev/sd?')) - set(pre_disks)
if len(new_disks) > 1:
raise Exception('Multiple new SCSI disks found: %s' % new_disks)
elif len(new_disks) == 0:
raise Exception("No new SCSI disks found after 'modprobe scsi_debug'")
new_disk = list(new_disks)[0]
subprocess.call(['parted', '-s', new_disk, 'mklabel', 'msdos'])
subprocess.call(['parted', '-s', new_disk, 'mkpart', 'primary', 'ext4',
'8192s', '100%'], stderr=subprocess.STDOUT)
subprocess.call(['sync'])
time.sleep(1)
return new_disk
def monitor_partition(disk, status):
"""
Start a process to monitor change of partitions on given disk.
"""
part = disk + '1'
exists = True
while status['running']:
if os.path.exists(part) != exists:
exists = not exists
status['changes'] += 1
now = time.time()
if exists:
status['durations'].append(now - status['lastchange'])
status['lastchange'] = now
def run():
"""
Main run function
"""
count = 0
results = {}
status = {'running': True, 'changes': 0, 'durations': [], 'lastchange': 0}
disk = prepare_disk()
t_mon = threading.Thread(target=monitor_partition, args=(disk, status))
t_mon.start()
time.sleep(1)
try:
while True:
prepare_disk()
count += 1
if count % 10 == 0:
print "Iteration %8d: part changed %d times" % (
count, status['changes'])
print "\tStats of blackout:"
print "\t\tMean:%s" % numpy.mean(status['durations'])
print "\t\tDeviation:%s" % numpy.std(status['durations'])
for result, result_count in results.items():
result_str = '\n'.join(result[1:]).strip()
if result_str:
result_str = result_str.splitlines()[-1]
print "\t%5.2f%%: %s" % (
float(result_count) * 100 / count, result_str)
finally:
status['running'] = False
if __name__ == '__main__':
run()
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