kern/53217: -current: dumping to wedges on GPT disks broken

[kardel%netbsd.org@localhost]

>Number:         53217
>Category:       kern
>Synopsis:       -current: dumping to wedges on GPT disks broken
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 26 19:10:00 +0000 2018
>Originator:     Frank Kardel
>Release:        NetBSD 8.99.14
>Organization:
	
>Environment:
	
	
System: NetBSD gateway 8.99.14 NetBSD 8.99.14 (GATEWAY) #8: Tue Apr 24 19:32:42 CEST 2018 kardel@xxx:/src/NetBSD/act/src/obj.amd64/sys/arch/amd64/compile/GATEWAY amd64
Architecture: x86_64
Machine: amd64
>Description:
	dumping on a swap wedge from a GPT partitioned disk fails with
	dump: device bad

	caused by: dksubr.c:dk_dump():806
    806         p = &lp->d_partitions[part];
    807         if (p->p_fstype != FS_SWAP) {
    808                 DPRINTF(DKDB_DUMP, ("%s: bad fstype %d\n", __func__,
    809                     p->p_fstype));
    810                 return ENXIO;
    811         }

       fstype is 0 here (FS_UNUSED) as a wedge on a GPT labeled disk references
       the whole disk as underlying structure which usually has FS_UNUSED as type.

>How-To-Repeat:
	create a GPT partitions disk with a swap partition. set dump device to
	the swap wedge. attempt to dump.
>Fix:
	Maybe also accept FS_UNUSED as fstype?

>Unformatted: