[Bug 1655779] Re: parted/libparted disables the read only status during the probe

[Phillip Susi]

I could not reproduce this at first using a loop device, but then I
tried scsi_debug.  This can be reproduced with a simple dd if=/dev/zero
count=0 of=/dev/sda.  Parted takes care to not needlessly delete and
recreate partition dev nodes when they are not modified, but it appears
that there has been a regression in udev/systemd that deletes and
recreates all partitions on the disk any time the disk is opened for RW
access, thus resetting the RO flag, and also triggering needless update
events that cause unity to re-add removed drive icons to the launcher.


** Package changed: parted (Ubuntu) => udev (Ubuntu)

** Summary changed:

- parted/libparted disables the read only status during the probe
+ udev deletes and recreates partition devices when the disk is opened r/w

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to parted in Ubuntu.
https://bugs.launchpad.net/bugs/1655779

Title:
  udev deletes and recreates partition devices when the disk is opened
  r/w

Status in udev package in Ubuntu:
  New

Bug description:
  Description:	Ubuntu 16.04.1 LTS
  Release:	16.04

  parted:  3.2-15
  gparted:  0.25.0-1

  
  Applications that utilized parted/libparted to probe for block device information disable the read only status during the probe.

  Example:

  Set a block device read only using either hdparm -r1 /dev/sdc* or blockdev --setro /dev/sdc*:
  # hdparm -r1 /dev/sdc*

  /dev/sdc:
   readonly      =  1 (on)

  /dev/sdc1:
   readonly      =  1 (on)

  
  Run gparted

  
  Check the readonly status with hdparm:
  # hdparm -r /dev/sdc*

  /dev/sdc:
   readonly      =  0 (off)

  /dev/sdc1:
   readonly      =  0 (off)

  
  The read only status has changed to off.  This can be replicated using partprobe:

  Set a block device read only using either hdparm -r1 /dev/sdc*:
  # hdparm -r1 /dev/sdc*

  /dev/sdc:
   readonly      =  1 (on)

  /dev/sdc1:
   readonly      =  1 (on)

  
  Probe the devices using partprobe -s:
  # partprobe -s
  /dev/sda: msdos partitions 1 2 3
  /dev/sdb: gpt partitions 1 2 3 5 4
  /dev/sdc: msdos partitions 1

  
  Recheck the read only status:
  # hdparm -r /dev/sdc*

  /dev/sdc:
   readonly      =  0 (off)

  /dev/sdc1:
   readonly      =  0 (off)

  
  As before the read only status has been switched off.  Again, this can be replicated using parted:

  Set a block device read only using either hdparm -r1 /dev/sdc*:
  # hdparm -r1 /dev/sdc*

  /dev/sdc:
   readonly      =  1 (on)

  /dev/sdc1:
   readonly      =  1 (on)

  
  List the partition layout using parted -l:
  # parted -l
  .
  .
  Model: WDC WD10 EFRX-68JCSN0 (scsi)
  Disk /dev/sdc: 1000GB
  Sector size (logical/physical): 512B/512B
  Partition Table: msdos
  Disk Flags: 

  Number  Start   End     Size    Type     File system  Flags
   1      1049kB  1000GB  1000GB  primary  ntfs

  
  Recheck the read only status:
  # hdparm -r /dev/sdc*

  /dev/sdc:
   readonly      =  0 (off)

  /dev/sdc1:
   readonly      =  0 (off)

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/udev/+bug/1655779/+subscriptions