Subject: Re: BUG: Bad page state in process true pfn:a8fed on arm

From: Mike Rapoport <[email-masked]>
Date: Tue, 25 Aug 2020 11:31:19 +0300

On Tue, Aug 25, 2020 at 01:03:53PM +0530, Naresh Kamboju wrote:
> On Mon, 24 Aug 2020 at 16:36, Matthew Wilcox <[email-masked]> wrote:
> >
> > On Mon, Aug 24, 2020 at 03:14:55PM +0530, Naresh Kamboju wrote:
> > > [   67.545247] BUG: Bad page state in process true  pfn:a8fed
> > > [   67.550767] page:9640c0ab refcount:0 mapcount:-1024
> >
> > Somebody freed a page table without calling __ClearPageTable() on it.
> 
> After running git bisect on this problem,
> The first suspecting of this problem on arm architecture this patch.
> 424efe723f7717430bec7c93b4d28bba73e31cf6
> ("mm: account PMD tables like PTE tables ")
> 
> Reported-by: Naresh Kamboju <[email-masked]>
> Reported-by: Anders Roxell <[email-masked]>
 
Can you please check if this fix helps?

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index 9415222b49ad..b8cbe03ad260 100644
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -59,6 +59,7 @@ __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, unsigned long addr)
 #ifdef CONFIG_ARM_LPAE
 	struct page *page = virt_to_page(pmdp);
 
+	pgtable_pmd_page_dtor(page);
 	tlb_remove_table(tlb, page);
 #endif
 }

> Additional information:
> We have tested linux next by reverting this patch and confirmed
> that the reported BUG is not reproduced.
> 
> These configs enabled on the running device,
> 
> CONFIG_TRANSPARENT_HUGEPAGE=y
> CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y
> 
> 
> -- Suspecting patch --
> commit 424efe723f7717430bec7c93b4d28bba73e31cf6
> Author: Matthew Wilcox <[email-masked]>
> Date:   Thu Aug 20 10:01:30 2020 +1000
> 
>     mm: account PMD tables like PTE tables
> 
>     We account the PTE level of the page tables to the process in order to
>     make smarter OOM decisions and help diagnose why memory is fragmented.
>     For these same reasons, we should account pages allocated for PMDs.  With
>     larger process address spaces and ASLR, the number of PMDs in use is
>     higher than it used to be so the inaccuracy is starting to matter.
> 
>     Link: http://lkml.kernel.org/r/[email-masked]
>     Signed-off-by: Matthew Wilcox (Oracle) <[email-masked]>
>     Reviewed-by: Mike Rapoport <[email-masked]>
>     Cc: Abdul Haleem <[email-masked]>
>     Cc: Andy Lutomirski <[email-masked]>
>     Cc: Arnd Bergmann <[email-masked]>
>     Cc: Christophe Leroy <[email-masked]>
>     Cc: Joerg Roedel <[email-masked]>
>     Cc: Max Filippov <[email-masked]>
>     Cc: Peter Zijlstra <[email-masked]>
>     Cc: Satheesh Rajendran <[email-masked]>
>     Cc: Stafford Horne <[email-masked]>
>     Signed-off-by: Andrew Morton <[email-masked]>
>     Signed-off-by: Stephen Rothwell <[email-masked]>
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b0a15ee77b8a..a4e5b806347c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2239,7 +2239,7 @@ static inline spinlock_t *pmd_lockptr(struct
> mm_struct *mm, pmd_t *pmd)
>   return ptlock_ptr(pmd_to_page(pmd));
>  }
> 
> -static inline bool pgtable_pmd_page_ctor(struct page *page)
> +static inline bool pmd_ptlock_init(struct page *page)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>   page->pmd_huge_pte = NULL;
> @@ -2247,7 +2247,7 @@ static inline bool pgtable_pmd_page_ctor(struct
> page *page)
>   return ptlock_init(page);
>  }
> 
> -static inline void pgtable_pmd_page_dtor(struct page *page)
> +static inline void pmd_ptlock_free(struct page *page)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>   VM_BUG_ON_PAGE(page->pmd_huge_pte, page);
> @@ -2264,8 +2264,8 @@ static inline spinlock_t *pmd_lockptr(struct
> mm_struct *mm, pmd_t *pmd)
>   return &mm->page_table_lock;
>  }
> 
> -static inline bool pgtable_pmd_page_ctor(struct page *page) { return true; }
> -static inline void pgtable_pmd_page_dtor(struct page *page) {}
> +static inline bool pmd_ptlock_init(struct page *page) { return true; }
> +static inline void pmd_ptlock_free(struct page *page) {}
> 
>  #define pmd_huge_pte(mm, pmd) ((mm)->pmd_huge_pte)
> 
> @@ -2278,6 +2278,22 @@ static inline spinlock_t *pmd_lock(struct
> mm_struct *mm, pmd_t *pmd)
>   return ptl;
>  }
> 
> +static inline bool pgtable_pmd_page_ctor(struct page *page)
> +{
> + if (!pmd_ptlock_init(page))
> + return false;
> + __SetPageTable(page);
> + inc_zone_page_state(page, NR_PAGETABLE);
> + return true;
> +}
> +
> +static inline void pgtable_pmd_page_dtor(struct page *page)
> +{
> + pmd_ptlock_free(page);
> + __ClearPageTable(page);
> + dec_zone_page_state(page, NR_PAGETABLE);
> +}
> +
>  /*
>   * No scalability reason to split PUD locks yet, but follow the same pattern
>   * as the PMD locks to make it easier if we decide to.  The VM should not be
> 
> 
> 
> 
> - Naresh

-- 
Sincerely yours,
Mike.