Comment 0 for bug 1886172

Description:

When the speed of data with a usb disk device is to 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.

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

Bug not found in:

Linux v4.15 (Ubuntu Bionic)

Hardware:

Tested with slower and faster computers. Tested directly connected to a computer and via a hub. They all reproduce this bug.

Workaround:

None found.