[DragonFlyBSD - Bug #2843] Fails to create dm device via dmsetup

[bugtracker-admin at leaf.dragonflybsd.org]

Issue #2843 has been updated by tkusumi.


dev->uuid is zero-filled whenever dm ioctl is called via dmsetup(8) and that's the reason dm_dev_lookup_uuid() returns non null after the first time.

dm targets with a dedicated high-level command (e.g. cryptsetup(8)) sets an unique non-zero value, so there isn't any issue with lookup, and this is what's expected to happen.

Setting uuid is userspace logic that really has nothing to do with kernel dm code other than it's been used for device lookup, however zero-filled uuid is apparently not a valid one. The patch simply ignores uuid lookup if ioctl received zero-filled uuid.
https://www.dragonflybsd.org/~tkusumi/diff/0001-sys-dev-disk-dm-Ignore-zero-filled-uuid-on-inserting.patch


===== with the existing code
  # kldload dm
  # dmsetup create linear1 --table '0 1000 linear /dev/da3 0'
  # dmsetup create delay1 --table '0 1000 delay /dev/da3 0 10 /dev/da3 0 10' 
  ioctl create call failed: File exists
  
  Command failed
  # dmsetup create zero1 --table '0 100 zero'
  ioctl create call failed: File exists
  
  Command failed
  # dmsetup create error1 --table '0 100 error'
  ioctl create call failed: File exists
  
  Command failed
  # ls /dev/mapper
  control linear1

===== with this commit
  # kldload dm
  # dmsetup create linear1 --table '0 1000 linear /dev/da3 0'
  # dmsetup create delay1 --table '0 1000 delay /dev/da3 0 10 /dev/da3 0 10'
  # dmsetup create zero1 --table '0 100 zero'
  # dmsetup create error1 --table '0 100 error'
  # ls /dev/mapper
  control delay1  error1  linear1 zero1


----------------------------------------
Bug #2843: Fails to create dm device via dmsetup
http://bugs.dragonflybsd.org/issues/2843#change-12711

* Author: tkusumi
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
----------------------------------------
There seems to be an issue with device mapper on dfly.
This happens with dm-error target as well.
I'll try to investigate and fix when possible (since I want dm-flakey on dfly).


----------
# uname
Linux
# dmsetup create zero1 --table '0 100 zero'
# ls -l /dev/mapper/zero*
lrwxrwxrwx 1 root root 7 Sep 29 00:14 /dev/mapper/zero1 -> ../dm-3
# dmsetup create zero2 --table '0 100 zero'
# ls -l /dev/mapper/zero*
lrwxrwxrwx 1 root root 7 Sep 29 00:14 /dev/mapper/zero1 -> ../dm-3
lrwxrwxrwx 1 root root 7 Sep 29 00:14 /dev/mapper/zero2 -> ../dm-4

----------
# uname
DragonFly
# kldload dm
# dmsetup create zero1 --table '0 100 zero'
# ls -l /dev/mapper/zero*
crw-r-----  1 root  operator   66, 0x1e110007 Sep 29 00:01 /dev/mapper/zero1
# dmsetup create zero2 --table '0 100 zero'
ioctl create call failed: File exists

Command failed
# ls -l /dev/mapper/zero*
crw-r-----  1 root  operator   66, 0x1e110007 Sep 29 00:01 /dev/mapper/zero1




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