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Subject: Re: [PATCH v3 4/5] powerpc/mm: add radix__remove_section_mapping()
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, Reza Arbab
 <arbab@linux.vnet.ibm.com>, Michael Ellerman <mpe@ellerman.id.au>, Paul
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 Alistair Popple <apopple@au1.ibm.com>
Date: Tue, 20 Dec 2016 07:59:22 +1100
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On Mon, 2016-12-19 at 15:18 +0530, Aneesh Kumar K.V wrote:
> > +     pte = pte_start + pte_index(addr);
> > +     for (; addr < end; addr = next, pte++) {
> > +             next = (addr + PAGE_SIZE) & PAGE_MASK;
> > +             if (next > end)
> > +                     next = end;
> > +
> > +             if (!pte_present(*pte))
> > +                     continue;
> > +
> > +             spin_lock(&init_mm.page_table_lock);
> > +             pte_clear(&init_mm, addr, pte);
> > +             spin_unlock(&init_mm.page_table_lock);
> > +     }
> > +
> > +     flush_tlb_mm(&init_mm);
> 
> Why call a flush here. we do that at the end of remove_page_table .
> Isn't that sufficient ?

All those lock/unlock ... what for ? Can't we just do the whole page ?

Also I agree, we can delay the flush of the PTEs to the end.

Ben.