[PATCHv2] m68k: fix "bad page state" oops on ColdFire boot

[PATCHv2] m68k: fix "bad page state" oops on ColdFire boot

[Greg Ungerer]

Booting a ColdFire m68k core with MMU enabled causes a "bad page state"
oops since commit 1d40a5ea01d5 ("mm: mark pages in use for page tables"):

 BUG: Bad page state in process sh  pfn:01ce2
 page:004fefc8 count:0 mapcount:-1024 mapping:00000000 index:0x0
 flags: 0x0()
 raw: 00000000 00000000 00000000 fffffbff 00000000 00000100 00000200 00000000
 raw: 039c4000
 page dumped because: nonzero mapcount
 Modules linked in:
 CPU: 0 PID: 22 Comm: sh Not tainted 4.17.0-07461-g1d40a5ea01d5 #13

Fix by calling pgtable_page_dtor() in our __pte_free_tlb() code path,
so that the PG_table flag is cleared before we free the pte page.

Note that I had to change the type of pte_free() to be static from
extern. Otherwise you get a lot of warnings like this:

./arch/m68k/include/asm/mcf_pgalloc.h:80:2: warning: ‘pgtable_page_dtor’ is static but used in inline function ‘pte_free’ which is not static
  pgtable_page_dtor(page);
  ^

And making it static is consistent with our use of this in the other
m68k pgalloc definitions of pte_free().

Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
CC: Matthew Wilcox <mawilcox@microsoft.com>
---
 arch/m68k/include/asm/mcf_pgalloc.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

v2: add a call to pgtable_page_dtor() in pte_free() as well

diff --git a/arch/m68k/include/asm/mcf_pgalloc.h b/arch/m68k/include/asm/mcf_pgalloc.h
index 8b707c249026..12fe700632f4 100644
--- a/arch/m68k/include/asm/mcf_pgalloc.h
+++ b/arch/m68k/include/asm/mcf_pgalloc.h
@@ -44,6 +44,7 @@ extern inline pmd_t *pmd_alloc_kernel(pgd_t *pgd, unsigned long address)
 static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t page,
 				  unsigned long address)
 {
+	pgtable_page_dtor(page);
 	__free_page(page);
 }
 
@@ -74,8 +75,9 @@ static inline struct page *pte_alloc_one(struct mm_struct *mm,
 	return page;
 }
 
-extern inline void pte_free(struct mm_struct *mm, struct page *page)
+static inline void pte_free(struct mm_struct *mm, struct page *page)
 {
+	pgtable_page_dtor(page);
 	__free_page(page);
 }
 
-- 
2.17.1

Re: [PATCHv2] m68k: fix "bad page state" oops on ColdFire boot

[Geert Uytterhoeven]

On Tue, Jun 19, 2018 at 2:47 AM Greg Ungerer <gerg@linux-m68k.org> wrote:
>
> Booting a ColdFire m68k core with MMU enabled causes a "bad page state"
> oops since commit 1d40a5ea01d5 ("mm: mark pages in use for page tables"):
>
>  BUG: Bad page state in process sh  pfn:01ce2
>  page:004fefc8 count:0 mapcount:-1024 mapping:00000000 index:0x0
>  flags: 0x0()
>  raw: 00000000 00000000 00000000 fffffbff 00000000 00000100 00000200 00000000
>  raw: 039c4000
>  page dumped because: nonzero mapcount
>  Modules linked in:
>  CPU: 0 PID: 22 Comm: sh Not tainted 4.17.0-07461-g1d40a5ea01d5 #13
>
> Fix by calling pgtable_page_dtor() in our __pte_free_tlb() code path,
> so that the PG_table flag is cleared before we free the pte page.
>
> Note that I had to change the type of pte_free() to be static from
> extern. Otherwise you get a lot of warnings like this:
>
> ./arch/m68k/include/asm/mcf_pgalloc.h:80:2: warning: ‘pgtable_page_dtor’ is static but used in inline function ‘pte_free’ which is not static
>   pgtable_page_dtor(page);
>   ^
>
> And making it static is consistent with our use of this in the other
> m68k pgalloc definitions of pte_free().
>
> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
> CC: Matthew Wilcox <mawilcox@microsoft.com>

CC: Matthew Wilcox <willy@infradead.org>

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds