Re: [gentoo-user] cryptsetup close and device in use when it is not

[Ramon Fischer]

Hi Dale,

>   So, something says it is busy but eventually
> releases it if left alone for a while.  I'd like to know what it is and
> if it is really in use or not.  Thing is, I can't find a way to know
> what it is that is using it.  The dmsetup command shows it is in use but
> no way to know what is using it.
I could reproduce this issue by killing my desktop process, unmounting 
the home partition and playing some "kill process" bingo. I could 
backtrace it to one unkillable process "kcryptd":

    1. Kill "awesomewm": <CTRL + ALT> + Backspace
    2. Kill other processes accessing "/home/"
    3. umount /home
    4. cryptsetup close crypthome
    Device crypthome is still in use
    5. dmsetup info /dev/mapper/crypthome
    Name:              crypthome
    State:             ACTIVE
    Read Ahead:        256
    Tables present:    LIVE
    Open count:        1
    Event number:      0
    Major, minor:      253, 1
    Number of targets: 1
    UUID: CRYPT-LUKS2-<some_uuid>-crypthome
    6. Kill any unnecessary process and try "cryptsetup close crypthome"
    7. Search for major, minor: ps aux | grep "253:1"
    root       150  0.2  0.0      0     0 ?        I    15:21   0:02
    [kworker/u16:5-kcryptd/253:1]
    8. Does not work: kill 150
    9. Does not work and could be dangerous: kill -9 150

So, there was still one "kcryptd" process left, accessing the hard 
drive, but I found no way to kill it.

Maybe this could be helpful?

-Ramon


On 02/08/2021 15:33, Dale wrote:
> Ramon Fischer wrote:
>> OK, if it could be "udev", you might want to try to check the following:
>>
>>     $ grep -rF "<part_of_uuid>" /etc/udev/rules.d/
>>     $ grep -rF "<part_of_uuid>" /lib/udev/rules.d/
>>     $ grep -rF "<part_of_uuid>" /etc
>>
>> You could also try to search for the partition device, maybe there
>> will be some interesting configuration files.
>>
>> If you are using "systemd", you might want to check every service unit
>> file as well:
>>
>>     $ systemctl
>>
>> Recently, I had a similar issue with "cryptsetup" on Raspbian, where
>> the "/etc/crypttab" was faulty, which may be applicable here. It had
>> the following entry:
>>
>>     # <accident_paste_with_uuid> # <target name> <source device> [...]
>>     <entry1>
>>     <entry2>
>>
>> Therefore, the systemd service unit
>> "systemd-cryptsetup@dev-disk-by\x2duuid-#<accident_paste_with_uuid> #
>> <target name> <source device> [...]" - if I remember correctly - failed.
>> It seems, that "systemd-cryptsetup-generator" only searches for
>> matching UUIDs in "/etc/crypttab", even, if they are commented and
>> creates service units for each match in "/run/systemd/generator/".
>> I remember, that I had issues to access the hard drive. Nevertheless,
>> I was able to mount it normally, due to the other correct entry(?).
>>
>> By removing the accidentally pasted UUID from "/etc/crypttab" and
>> rebooting, I was able to use the hard drive without issues again.
>>
>> Maybe this is something, where you could poke around? :)
>>
>> -Ramon
> I'm running openrc here.  I don't recall making any udev rules
> recently.  This is a list of what I have.
>
>
> root@fireball / # ls -al /etc/udev/rules.d/
> total 20
> drwxr-xr-x 2 root root 4096 Apr 27 15:07 .
> drwxr-xr-x 3 root root 4096 Jul 27 03:17 ..
> -rw-r--r-- 1 root root 2064 Apr 27 15:07 69-libmtp.rules
> -rw-r--r-- 1 root root 1903 Apr  4  2012 70-persistent-cd.rules
> -rw-r--r-- 1 root root  814 Jan  1  2008 70-persistent-net.rules
> -rw-r--r-- 1 root root    0 Mar 22  2015 80-net-name-slot.rules
> root@fireball / #
>
>
> One is for CD/DVD stuff.  I wonder if I can remove that now.  Two is for
> network cards and top one is something to do with my old Motorola cell
> phone, rest in peace.
>
> All this said, it did it again last night.  I tried a few things and
> went to bed while my updates were compiling.  When I got up a bit ago,
> it closed just fine.  So, something says it is busy but eventually
> releases it if left alone for a while.  I'd like to know what it is and
> if it is really in use or not.  Thing is, I can't find a way to know
> what it is that is using it.  The dmsetup command shows it is in use but
> no way to know what is using it.
>
> Dale
>
> :-)  :-)

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