kernel BUG at mm/swap_slots.c:270

[Linus Torvalds]

Tim at al,
 I got this on my desktop at shutdown:

  ------------[ cut here ]------------
  kernel BUG at mm/swap_slots.c:270!
  invalid opcode: 0000 [#1] SMP
  CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
  Hardware name: System manufacturer System Product Name/Z170-K, BIOS
1803 05/06/2016
  RIP: 0010:free_swap_slot+0xba/0xd0
  Call Trace:
   swap_free+0x36/0x40
   do_swap_page+0x360/0x6d0
   __handle_mm_fault+0x880/0x1080
   handle_mm_fault+0xd0/0x240
   __do_page_fault+0x232/0x4d0
   do_page_fault+0x20/0x70
   page_fault+0x22/0x30
  ---[ end trace aefc9ede53e0ab21 ]---

so there seems to be something screwy in the new swap_slots code.

Any ideas? I'm not finding other reports of this, but I'm also not
seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
much checks whether swap_slot_cache_initialized has been set, so the
BUG_ON() just seems like garbage. But please take a look.

                  Linus