if one repurposes a FreeBSD swap file system for another file system (e.g. 2nd system) or mistyypes the partition in fstab
and FreeBSD boots with that swap in fstab, swapon -a will nuke that file system even if it is no longer a freebsd-swap in GPT
(no idea about MBR anymore).
It seems to be a good idea to put in a check, warn and let the user fix this rather than simply activating swap and with
that likely nuking a file system there..
It's probably a bit tricky to find all the cases but it should be fairly easy to test in a VM so..
(In reply to Bjoern A. Zeeb from comment #0)
Probably it wasn't an issue when swap lied obligatory on "b" BSD swap partition under FreeBSD slice on MBR partitioned disk.
The proposed check could be also relevant with regard to configuring the dump device.