Re: [PATCH 3/5] mm/mremap: use pmd_addr_end to calculate next in move_page_tables()

[Andrew Morton]

On Sun, 26 Jan 2020 17:47:57 +0300 Dmitry Osipenko <digetx@xxxxxxxxx> wrote:

> 18.01.2020 02:22, Wei Yang ÐÐÑÐÑ:
> > Use the general helper instead of do it by hand.
> > 
> > Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> > ---
> >  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.

Thanks.  I had these tagged for 5.7-rc1 anyway, so I'll drop all five
patches.