Created attachment 937243 [details]
Description of problem:
This is a placeholder for the extremely mysterious heisenbug where
the /dev/sda1 device node does not get created, or magically disappears.
Version-Release number of selected component (if applicable):
It started happening in Fedora 21 and above.
Rare, but annoying. Happens a lot more often under Koji than
anywhere else, but can be reproduced in a VM occasionally.
Only appears to happen after we write to the first sector of /dev/sda.
In the attached build log, it happens twice. Search for the
error message "/dev/sda1: No such file or directory"
Turns out to be a stupid udev rule. Whenever you close a device,
the kernel sends a "change" event to udev which fires off a whole
set of rules. It runs at least: scsi_id, path_id, blkid. And these
operations overlap the subsequent mkfs or other operation.
More udev workarounds needed.
Thanks agk for pointing me in the right direction.
Added a workaround: