Re: high speed data to usb disk makes the kernel think that is has been unmounted

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Aug 11, 2020 at 07:19:00PM +0200, Patrik Nilsson wrote:
> Hi!
> 
> I have an issue with a usb to sata adapter when much high speed data is
> sent. If I erase my 4Tb SSD disk connected to the usb to sata interface with
> a "slower" /dev/urandom it works, but if I exchanges this to /dev/zero the
> disk is after a while disconnected.
> 
> For logs from udev and more debug attempts see:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1886172
> 
> Description:
> 
> When the speed of data with a usb disk device is too high, the probes that
> check if the disk still exists is missed. This makes the disk to be
> unmounted and is remounted with an other drive letter (/dev/sdX). If this
> disk is the root ("/"), the computer hangs.
> 
> A usb SSD-disk (4 TB) connected to a USB port reproduce this bug easily.
> This has never happened with a mechanical USB-drive.
> 
> Symptoms and how to reproduce:
> 
> 1) (Disk mounted as root) Computer hangs. Only way to get started again is a
> hard reset.
> 
> 2) (Erasing disk, not mounted as root) If you erase a disk with dd ("dd
> if=/dev/zero of=/dev/sdX"), the disk disappears from the mounted list and
> reappears as an other drive letter. In my case the data is redirected to
> /dev/null and the fans speed up. The apparent data transfer speed is also
> increased. Usually this happens after about 45 to 60 minutes.

Can you provide kernel logs?  Odds are the disk disconnects itself as it
takes too much power or something.

> 3) Fill RAM with programs and make sure the swap to this disk is used.
> 
> Bug found in:
> 
> $ uname -a
> Linux pb-189b1884 5.4.0-40-generic #44-Ubuntu SMP Tue Jun 23 00:01:04 UTC
> 2020 x86_64 x86_64 x86_64 GNU/Linux
> 
> $ cat /proc/version_signature
> Ubuntu 5.4.0-40.44-generic 5.4.44

That's a really old kernel, any chance you can try 5.8?

thanks,

greg k-h