[patch] allow crash dumps to Linux swap partitions

[Don Lewis]

On  9 Jan, Nikos Vassiliadis wrote:
> On 1/9/2012 11:25 AM, Doug Barton wrote:
>> Actually I'm fairly confident that we write dumps backwards from the end
>> of the swap partition. It's done that way on purpose in case fsck'ing
>> causes the system to swap, it may still be possible to save the dump.
> 
> So, dumping core is safe, but not sharing the swap area...
> It would be nice to be able to do that.

According to the mkswap(8) man page (which hasn't been updated
since 2.2 even though the machine is running a 2.6 kernel) on a nearby
Linux machine, the metadata stored in the first page of the swap
partition. It looks like we could safely coexist if we skipped the first
page of the partition. Otherwise Linux will want mkswap to be run on the
partition before it will swap to the partition.

Dunno why it never caused problems for me ...

BTW, partition type 0x82 was also used for Solaris x86 before 2005.
Hopefully nobody will accidentally overwrite their old Solaris partition
with a FreeBSD crash dump ;-)