linux-kernel - Re: [PATCH] x86/mm/hotplug: fix BUG

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Date:   Tue, 6 Jun 2017 13:50:14 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jérôme Glisse <jglisse@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove

Thanks Jerome! This indeed fixes the bug I reported.

Tested-by: Logan Gunthorpe <logang@...tatee.com>

Logan


On 06/06/17 11:35 AM, Jérôme Glisse wrote:
> With commit af2cf278ef4f we no longer free pud so that we
> do not have synchronize all pgd on hotremove/vfree. But the
> new 5 level page table code re-added that code f2a6a705 and
> thus we now trigger a BUG_ON() l128 in sync_global_pgds()
> 
> This patch remove free_pud() like in af2cf278ef4f
> 
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Logan Gunthorpe <logang@...tatee.com>
> ---
>  arch/x86/mm/init_64.c | 19 -------------------
>  1 file changed, 19 deletions(-)
> 
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index a8a9972..8cf7e99 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -772,24 +772,6 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud)
>  	spin_unlock(&init_mm.page_table_lock);
>  }
>  
> -static void __meminit free_pud_table(pud_t *pud_start, p4d_t *p4d)
> -{
> -	pud_t *pud;
> -	int i;
> -
> -	for (i = 0; i < PTRS_PER_PUD; i++) {
> -		pud = pud_start + i;
> -		if (!pud_none(*pud))
> -			return;
> -	}
> -
> -	/* free a pud talbe */
> -	free_pagetable(p4d_page(*p4d), 0);
> -	spin_lock(&init_mm.page_table_lock);
> -	p4d_clear(p4d);
> -	spin_unlock(&init_mm.page_table_lock);
> -}
> -
>  static void __meminit
>  remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
>  		 bool direct)
> @@ -991,7 +973,6 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end,
>  
>  		pud_base = pud_offset(p4d, 0);
>  		remove_pud_table(pud_base, addr, next, direct);
> -		free_pud_table(pud_base, p4d);
>  	}
>  
>  	if (direct)
>