def remove_block_dev(devpath, scan_timeout=10):
"""Remove a block device from the management partition.
This method causes the operating system of the management partition to
delete the device special files associated with the specified block device.
:param devpath: Any path to the block special file associated with the
device to be removed.
:param scan_timeout: The maximum number of seconds after scanning to wait
for the specified device to disappear.
:raise InvalidDevicePath: If the specified device or its 'delete' special
file cannot be found.
:raise DeviceDeletionException: If the deletion was attempted, but the
device special file is still present
afterward.
"""
# Resolve symlinks, if any, to get to the /dev/sdX path
devpath = os.path.realpath(devpath)
try:
os.stat(devpath)
except OSError:
raise exception.InvalidDevicePath(path=devpath)
devname = devpath.rsplit('/', 1)[-1]
delpath = '/sys/block/%s/device/delete' % devname
try:
os.stat(delpath)
except OSError:
raise exception.InvalidDevicePath(path=delpath)
LOG.debug(
"Deleting block device %(devpath)s from the management "
"partition via special file %(delpath)s.", {
'devpath': devpath,
'delpath': delpath
})
# Writing '1' to this sysfs file deletes the block device and rescans.
priv_path.writefile(delpath, 'a', '1')
# The bus scan is asynchronous. Need to poll, waiting for the device to
# disappear. Stop when stat raises OSError (dev file not found) - which is
# success - or after the specified timeout (which is failure). Sleep 1/4
# second between polls.
@retrying.retry(retry_on_result=lambda result: result,
wait_fixed=250,
stop_max_delay=scan_timeout * 1000)
def _poll_for_del(statpath):
try:
os.stat(statpath)
return True
except OSError:
# Device special file is absent, as expected
return False
try:
_poll_for_del(devpath)
except retrying.RetryError as re:
# stat just kept returning (dev file continued to exist).
raise npvmex.DeviceDeletionException(
devpath=devpath,
polls=re.last_attempt.attempt_number,
timeout=scan_timeout)
def discover_vscsi_disk(mapping, scan_timeout=300):
"""Bring a mapped device into the management partition and find its name.
Based on a VSCSIMapping, scan the appropriate virtual SCSI host bus,
causing the operating system to discover the mapped device. Find and
return the path of the newly-discovered device based on its UDID in the
mapping.
Note: scanning the bus will cause the operating system to discover *all*
devices on that bus. However, this method will only return the path for
the specific device from the input mapping, based on its UDID.
:param mapping: The pypowervm.wrappers.virtual_io_server.VSCSIMapping
representing the mapping of the desired disk to the
management partition.
:param scan_timeout: The maximum number of seconds after scanning to wait
for the specified device to appear.
:return: The udev-generated ("/dev/sdX") name of the discovered disk.
:raise NoDiskDiscoveryException: If the disk did not appear after the
specified timeout.
:raise UniqueDiskDiscoveryException: If more than one disk appears with the
expected UDID.
"""
# Calculate the Linux slot number from the client adapter slot number.
lslot = 0x30000000 | mapping.client_adapter.lpar_slot_num
# We'll match the device ID based on the UDID, which is actually the last
# 32 chars of the field we get from PowerVM.
udid = mapping.backing_storage.udid[-32:]
LOG.debug(
"Trying to discover VSCSI disk with UDID %(udid)s on slot "
"%(slot)x.", {
'udid': udid,
'slot': lslot
})
# Find the special file to scan the bus, and scan it.
# This glob should yield exactly one result, but use the loop just in case.
for scanpath in glob.glob(
'/sys/bus/vio/devices/%x/host*/scsi_host/host*/scan' % lslot):
# Writing '- - -' to this sysfs file triggers bus rescan
priv_path.writefile(scanpath, 'a', '- - -')
# Now see if our device showed up. If so, we can reliably match it based
# on its Linux ID, which ends with the disk's UDID.
dpathpat = '/dev/disk/by-id/*%s' % udid
# The bus scan is asynchronous. Need to poll, waiting for the device to
# spring into existence. Stop when glob finds at least one device, or
# after the specified timeout. Sleep 1/4 second between polls.
@retrying.retry(retry_on_result=lambda result: not result,
wait_fixed=250,
stop_max_delay=scan_timeout * 1000)
def _poll_for_dev(globpat):
return glob.glob(globpat)
try:
disks = _poll_for_dev(dpathpat)
except retrying.RetryError as re:
raise npvmex.NoDiskDiscoveryException(
bus=lslot,
udid=udid,
polls=re.last_attempt.attempt_number,
timeout=scan_timeout)
# If we get here, _poll_for_dev returned a nonempty list. If not exactly
# one entry, this is an error.
if len(disks) != 1:
raise npvmex.UniqueDiskDiscoveryException(path_pattern=dpathpat,
count=len(disks))
# The by-id path is a symlink. Resolve to the /dev/sdX path
dpath = os.path.realpath(disks[0])
LOG.debug(
"Discovered VSCSI disk with UDID %(udid)s on slot %(slot)x at "
"path %(devname)s.", {
'udid': udid,
'slot': lslot,
'devname': dpath
})
return dpath