Re: [REGRESSION][BISECTED] Crash with Bad page state for FUSE/Flatpak related applications since v6.13

[Matthew Wilcox <willy@infradead.org>]

On Fri, Feb 07, 2025 at 10:34:52AM +0100, Miklos Szeredi wrote:
> Seems like page allocation gets an inconsistent page (mapcount != -1)
> in the report below.

I think you're misreading the report.  _mapcount is -1.  Which means
mapcount is 0.

> > Feb 06 08:54:47 archvm kernel: BUG: Bad page state in process rnote  pfn:67587
> > Feb 06 08:54:47 archvm kernel: page: refcount:-1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x67587
> > Feb 06 08:54:47 archvm kernel: flags: 0xfffffc8000020(lru|node=0|zone=1|lastcpupid=0x1fffff)
> > Feb 06 08:54:47 archvm kernel: raw: 000fffffc8000020 dead000000000100 dead000000000122 0000000000000000

flags lru.next lru.prev mapping

> > Feb 06 08:54:47 archvm kernel: raw: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000000

index private mapcount:refcount memcg_data

> > Feb 06 08:54:47 archvm kernel: page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag(s) set

So the problem is the lru flag is set.

> > Feb 06 08:54:47 archvm kernel:  dump_stack_lvl+0x5d/0x80
> > Feb 06 08:54:47 archvm kernel:  bad_page.cold+0x7a/0x91
> > Feb 06 08:54:47 archvm kernel:  __rmqueue_pcplist+0x200/0xc50
> > Feb 06 08:54:47 archvm kernel:  get_page_from_freelist+0x2ae/0x1740
> > Feb 06 08:54:47 archvm kernel:  __alloc_frozen_pages_noprof+0x184/0x330
> > Feb 06 08:54:47 archvm kernel:  alloc_pages_mpol+0x7d/0x160
> > Feb 06 08:54:47 archvm kernel:  folio_alloc_mpol_noprof+0x14/0x40
> > Feb 06 08:54:47 archvm kernel:  vma_alloc_folio_noprof+0x69/0xb0
> > Feb 06 08:54:47 archvm kernel:  do_anonymous_page+0x32a/0x8b0

It's very weird, because PG_lru is also in PAGE_FLAGS_CHECK_AT_FREE.
So it should already have been checked and not be set.  I'm on holiday
until Monday, so I'm not going to dive into this any further.