linux-kernel - Re: USB Attached SCSI breakage due no udev involvement

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Message-ID: <3b107771-550f-8ca1-d05a-4f6c2ef1920a@gmail.com>
Date:   Sun, 10 May 2020 20:15:08 +0700
From:   Dio Putra <dioput12@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     oneukum@...e.com, linux-usb@...r.kernel.org,
        linux-scsi@...r.kernel.org, usb-storage@...ts.one-eyed-alien.net,
        stern@...land.harvard.edu, linux-kernel@...r.kernel.org
Subject: Re: USB Attached SCSI breakage due no udev involvement

On 5/10/20 4:48 PM, Dio Putra wrote:
> On 5/10/20 3:48 PM, Greg KH wrote:
>> On Sun, May 10, 2020 at 03:35:34PM +0700, Dio Putra wrote:
>>> On 5/10/20 2:32 PM, Greg KH wrote:
>>>> On Sun, May 10, 2020 at 02:10:04PM +0700, Dio Putra wrote:
>>>>> On 5/10/20 1:54 PM, Greg KH wrote:
>>>>>> On Sun, May 10, 2020 at 01:48:24PM +0700, Dio Putra wrote:
>>>>>>> On 5/10/20 12:47 PM, Greg KH wrote:
>>>>>>>> On Sun, May 10, 2020 at 09:55:57AM +0700, Dio Putra wrote:
>>>>>>>>> Hi, it's first time for me to report user-space breakage in here, so
>>>>>>>>> i'm begging your pardon.
>>>>>>>>>
>>>>>>>>> I want to report that Linux 5.4 breaking my USB mount workflow due
>>>>>>>>> udevadm monitor report here (I'm using vanilla kernel 5.4.39 on
>>>>>>>>> Slackware64 Current and vanilla kernel 4.4.221 on Slackware64 14.2):
>>>>>>>>
>>>>>>>> <snip>
>>>>>>>>
>>>>>>>> Sorry, but what actually changed that you can see in the logs?
>>>>>>> Sorry, what do you mean? The dmesg log or the kernel changelogs?
>>>>>>
>>>>>> Either, your message made them pretty impossible to compare with all of
>>>>>> the line-wrapping :(
>>>>>>
>>>>> I'm so sorry for first message mess, because that message has been sent by
>>>>> Gmail Website. Can I send my logs as attachment? I try to convenient everyone
>>>>> here. ( FYI, I just switched to Thunderbird with these settings:
>>>>> https://www.kernel.org/doc/html/v4.12/process/email-clients.html#thunderbird-gui )
>>>>
>>>> Sure, attachments work, but better yet, if you can show the difference
>>>> in a few lines that is much nicer than having to dig through large
>>>> numbers of log files.
>>>>
>>> Okay, I'll attach long messages and trim it as far as I can.
>>
>> Again, I really do not understand what exactly is "not working".
>>
>> Please explain that when you send the new log messages.
>>
> Okay, here's compilation of "dmesg | grep -i udev && udevadm
> monitor && lsblk" on linux-4.4.221 vs linux-5.4.39. You can check
> my attachment here because I can't explain it by words (I'm not
> english native speaker anyway, which makes it so difficult to
> explain it for me).
> 
>>>>>>>> What functionality broke?  What used to work that no longer does work?
>>>>>>>>
>>>>>>> Yes, it supposed that just work and kernel could talk with udev, not just handled by the kernel.
>>>>>>
>>>>>> I don't understand, what functionality changed?  What exactly used to
>>>>>> work that no longer does?
>>>>> linux-5.4 has been never called the udev dependencies whereas
>>>>> linux-4.4 will call any udev dependencies if necessary, that's the problem.
>>>>
>>>> I do not understand what exactly you mean by "call udev dependencies".
>>>>
>>>> udev is used to create symlinks and set user/group permissions on device
>>>> nodes in /dev/ which is created by devtmpfs.  What exactly is not
>>>> happening in your /dev/ with the move to a newer kernel?
>>>>
>>> Would I send my dmesg log with "udev.log-priority=debug" as attachment then?
>>>
>>>>>> Did you change anything else other than the kernel on your system?  Did
>>>>>> you change to a newer version of udev/systemd or anything else?
>>>>>>
>>>>> I'm using eudev-master from their official mirror github:
>>>>> https://github.com/gentoo/eudev
>>>>
>>>> Have you contacted the eudev developers to see if something different
>>>> needs to be set in your kernel when moving 4 years in kernel development
>>>> forward?  Are you sure you have all the correct config options enabled?
>>>>
>>> It's my bad not to contact the eudev developers first. However I'm not quite
>>> sure to contact the eudev developers would solve the problem, but CMIIW.
>>>
>>>> Why such a huge leap forward all at once, how about going from 4.4.y to
>>>> 4.9.y and then 4.14.y and then 5.4.y?  That might help narrow things
>>>> down a bit easier.
>>>>
>>> Unfortunately I need to think twice due almost ran out of electricity
>>> here every time I power on my laptop for long time. So maybe I can't.
>>>
>>> But if these steps are necessary, I'll think solution later.
>>
>> Why would it take a long time to do this type of change?
>>
> It's a weak machine, it took appropriately 2 hours to just compiling
> linux kernel. I need to think twice too because electricity is expensive here.
>
After deep digging into /dev/ folder, indeed some important file has 
been deleted after restart on Slackware.

On behalf from myself for linux-kernel community, I'm really sorry for 
causing these noise. Thank you Greg and all for the hints.
>> thanks,
>>
>> greg k-h
>>
>