[Bug 585027] Re: Race condition with dmsetup causes 'map already present' messages

Peter Petrakis peter.petrakis at canonical.com
Mon Jul 9 15:31:30 UTC 2012 

Should really be won't fix but I apparently can't set it.

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Title:
  Race condition with dmsetup causes 'map already present' messages

Status in “multipath-tools” package in Ubuntu:
  Invalid

Bug description:
  Binary package hint: multipath-tools

  Environment:

  njones at fantail:~$ lsb_release -rd
  Description:	Ubuntu 10.04 LTS
  Release:	10.04
  njones at fantail:~$ apt-cache policy multipath-tools
  multipath-tools:
    Installed: 0.4.8-14ubuntu4
    Candidate: 0.4.8-14ubuntu4
    Version table:
   *** 0.4.8-14ubuntu4 0
          500 http://nz.archive.ubuntu.com/ubuntu/ lucid/main Packages
          100 /var/lib/dpkg/status

  Issue:

  While reproducing
  https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/571093 both
  myself and Dustin Kirkland encountered an apparent race condition in
  multipath and dmsetup.

  We were attempting variants of 'while true; do sudo multipath -F; sudo
  multipath -v4 ; done' to create a set of udev add/remove events and
  noticed that shortly after starting, no output appeared within the
  'udevadm monitor' command.

  We observed that the output from a: multipath -v4 was similar to:

  root at fantail:~# multipath -v4
  Discover device /sys/block/ram0
  ram0: device node name blacklisted
  Discover device /sys/block/ram1
  ram1: device node name blacklisted
  Discover device /sys/block/ram2
  ram2: device node name blacklisted
  Discover device /sys/block/ram3
  ram3: device node name blacklisted
  Discover device /sys/block/ram4
  ram4: device node name blacklisted
  Discover device /sys/block/ram5
  ram5: device node name blacklisted
  Discover device /sys/block/ram6
  ram6: device node name blacklisted
  Discover device /sys/block/ram7
  ram7: device node name blacklisted
  Discover device /sys/block/ram8
  ram8: device node name blacklisted
  Discover device /sys/block/ram9
  ram9: device node name blacklisted
  Discover device /sys/block/ram10
  ram10: device node name blacklisted
  Discover device /sys/block/ram11
  ram11: device node name blacklisted
  Discover device /sys/block/ram12
  ram12: device node name blacklisted
  Discover device /sys/block/ram13
  ram13: device node name blacklisted
  Discover device /sys/block/ram14
  ram14: device node name blacklisted
  Discover device /sys/block/ram15
  ram15: device node name blacklisted
  Discover device /sys/block/loop0
  loop0: device node name blacklisted
  Discover device /sys/block/loop1
  loop1: device node name blacklisted
  Discover device /sys/block/loop2
  loop2: device node name blacklisted
  Discover device /sys/block/loop3
  loop3: device node name blacklisted
  Discover device /sys/block/loop4
  loop4: device node name blacklisted
  Discover device /sys/block/loop5
  loop5: device node name blacklisted
  Discover device /sys/block/loop6
  loop6: device node name blacklisted
  Discover device /sys/block/loop7
  loop7: device node name blacklisted
  Discover device /sys/block/sda
  sda: not found in pathvec
  sda: mask = 0x1f
  sda: dev_t = 8:0
  sda: size = 625142448
  sda: subsystem = scsi
  sda: vendor = ATA
  sda: product = WDC WD3200AAKS-0
  sda: rev = 12.0
  sda: h:b:t:l = 0:0:0:0
  sda: serial = WD-WCAS70000070
  sda: getprio = NULL (internal default)
  sda: prio = 1
  sda: getuid = /lib/udev/scsi_id -g -u -d /dev/%n (config file default)
  sda: uid = 1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070 (callout)
  Discover device /sys/block/sr0
  sr0: device node name blacklisted
  Discover device /sys/block/sdb
  sdb: not found in pathvec
  sdb: mask = 0x1f
  sdb: dev_t = 8:16
  sdb: size = 15679488
  sdb: subsystem = scsi
  sdb: vendor = Kingston
  sdb: product = DataTraveler G2
  sdb: rev = PMAP
  sdb: h:b:t:l = 6:0:0:0
  sdb: serial =
  sdb: getprio = NULL (internal default)
  sdb: prio = 1
  sdb: getuid = /lib/udev/scsi_id -g -u -d /dev/%n (config file default)
  error calling out /lib/udev/scsi_id -g -u -d /dev/sdb
  Discover device /sys/block/sdc
  sdc: not found in pathvec
  sdc: mask = 0x1f
  sdc: dev_t = 8:32
  sdc: size = 41943040
  sdc: subsystem = scsi
  sdc: vendor = IET
  sdc: product = VIRTUAL-DISK
  sdc: rev = 0
  sdc: h:b:t:l = 7:0:0:0
  sdc: serial =
  sdc: getprio = NULL (internal default)
  sdc: prio = 1
  sdc: getuid = /lib/udev/scsi_id -g -u -d /dev/%n (config file default)
  error calling out /lib/udev/scsi_id -g -u -d /dev/sdc
  Discover device /sys/block/dm-0
  dm-0: device node name blacklisted
  Discovery status 0
  ===== paths list =====
  uuid                                       hcil    dev dev_t pri dm_st  chk_st
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070 0:0:0:0 sda 8:0   1   [undef][undef
                                             6:0:0:0 sdb 8:16  1   [undef][undef
                                             7:0:0:0 sdc 8:32  1   [undef][undef
  sda: ownership set to 1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070
  sda: not found in pathvec
  sda: mask = 0xc
  sda: path checker = directio (config file default)
  directio: called for 800
  directio: called in synchronous mode
  directio: starting new request
  directio: async io getevents returns 1 (errno=No such file or directory)
  directio: io finished 4096/0
  sda: state = 2
  sda: prio = 1
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: pgfailover = -1 (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: pgpolicy = failover (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: selector = round-robin 0 (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: features = 0 (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: hwhandler = 0 (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: rr_weight = 1 (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: minio = 1000 (config file default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: no_path_retry = NONE (internal default)
  pg_timeout = NONE (internal default)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: set ACT_CREATE (map does not exist)
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: map already present
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: domap (0) failure for create/reload map
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070: remove multipath map
  sda: orphaned

  And a device was left behind in /dev/mapper:

  njones at fantail:~$ ll /dev/mapper/
  total 0
  drwxr-xr-x  2 root root      80 2010-05-25 04:25 ./
  drwxr-xr-x 18 root root    4080 2010-05-25 04:25 ../
  brw-rw----  1 root disk 252,  0 2010-05-25 04:25 1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070
  crw-rw----  1 root root  10, 59 2010-05-22 10:35 control

  $ sudo dmsetup ls
  1ATA_WDC_WD3200AAKS-00TMA0_WD-WCAS70000070	(252, 0)

  We had to perform 'dmsetup remove <id>' to clear the 'map already
  present' message.

  While I admit that this is a very specific case, it is still a race
  condition and does warrant a bug report.

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