linux-kernel - Re: [PATCH 3/5] mm/mremap: use pmd_addr_end to calculate next in move_page

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Date:   Sun, 26 Jan 2020 17:47:57 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Wei Yang <richardw.yang@...ux.intel.com>,
        akpm@...ux-foundation.org, dan.j.williams@...el.com,
        aneesh.kumar@...ux.ibm.com, kirill@...temov.name,
        yang.shi@...ux.alibaba.com, thellstrom@...are.com,
        Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>
Subject: Re: [PATCH 3/5] mm/mremap: use pmd_addr_end to calculate next in
 move_page_tables()

18.01.2020 02:22, Wei Yang пишет:
> Use the general helper instead of do it by hand.
> 
> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
> ---
>  mm/mremap.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/mremap.c b/mm/mremap.c
> index c2af8ba4ba43..a258914f3ee1 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -253,11 +253,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>  
>  	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
>  		cond_resched();
> -		next = (old_addr + PMD_SIZE) & PMD_MASK;
> -		/* even if next overflowed, extent below will be ok */
> +		next = pmd_addr_end(old_addr, old_end);
>  		extent = next - old_addr;
> -		if (extent > old_end - old_addr)
> -			extent = old_end - old_addr;
>  		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
>  		if (!old_pmd)
>  			continue;
> @@ -301,7 +298,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>  
>  		if (pte_alloc(new_vma->vm_mm, new_pmd))
>  			break;
> -		next = (new_addr + PMD_SIZE) & PMD_MASK;
> +		next = pmd_addr_end(new_addr, new_addr + len);
>  		if (extent > next - new_addr)
>  			extent = next - new_addr;
>  		move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
> 

Hello Wei,

Starting with next-20200122, I'm seeing the following in KMSG on NVIDIA
Tegra (ARM32):

  BUG: Bad rss-counter state mm:(ptrval) type:MM_ANONPAGES val:190

and eventually kernel hangs.

Git's bisection points to this patch and reverting it helps. Please fix,
thanks in advance.