Description
We spent quite some time debugging a storage test regression in Fedora rawhide which essentially breaks scsi_debug and other devices, but only on RedHat's/Fedora's Testing Farm infrastructure -- which is essentially AWS EC2 machines with an API.
Latest Fedora rawhide instances now have amazon-ec2-utils-2.2.0-2.fc41.noarch (which got introduced into Fedora very recently), which ships /usr/lib/udev/rules.d/70-ec2-nvme-devices.rules with
KERNEL=="nvme[0-9]*n[0-9]*", ENV{DEVTYPE}=="disk", ATTRS{model}=="Amazon Elastic Block Store", PROGRAM="/usr/sbin/ebsnvme-id -u /dev/%k", SYMLINK+="%c"
KERNEL=="nvme[0-9]*n[0-9]*p[0-9]*", ENV{DEVTYPE}=="partition", ATTRS{model}=="Amazon Elastic Block Store", PROGRAM="/usr/sbin/ebsnvme-id -u /dev/%k", SYMLINK+="%c%n"
These instances have an NVME block device, and these rules cause the following symlinks to be created:
lrwxrwxrwx. 1 root root 7 May 29 03:52 /dev/sda1 -> nvme0n1
lrwxrwxrwx. 1 root root 9 May 29 03:52 /dev/sda11 -> nvme0n1p1
lrwxrwxrwx. 1 root root 9 May 29 03:52 /dev/sda12 -> nvme0n1p2
lrwxrwxrwx. 1 root root 9 May 29 03:52 /dev/sda13 -> nvme0n1p3
lrwxrwxrwx. 1 root root 9 May 29 03:52 /dev/sda14 -> nvme0n1p4
This is problematic in multiple ways:
- Pretending that these are SCSI drives tramples on the kernel's namespace. udev symlinks should never create names which the kernel uses.
- "nvme0n1" is the raw block device, not a partition. So it's very confusing to name it "sda1", it should be "sda". Likewise, the first partition should be "sda1", not "sda11".
If then a real sda comes along (e.g. with modprobe scsi_debug), this will create an actual /dev/sda, but then it's impossible to create/see partitions on that, as the sda1 etc. names are already taken.
This is most easily reproduced with
# /usr/sbin/ebsnvme-id -u /dev/nvme0n1
sda1
Curiously, it also does that for a partition:
# /usr/sbin/ebsnvme-id -u /dev/nvme0n1p2
sda1
that explains how the second udev rule can even work -- but this is really hackish!
My recommendation as former udev co-upstream is to just entirely remove these rules. They are not helpful, confusing, and break stuff. You can of course create symlinks in subdirs of /dev all you like, but please don't collide with kernel names.
Thanks!