linux-kernel - Re: [RFC PATCH] mm/rmap: do not call mmu_notifier_invalidate

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Date:   Tue, 29 Aug 2017 12:09:45 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Jérôme Glisse <jglisse@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Bernhard Held <berny156@....de>,
        Adam Borowski <kilobyte@...band.pl>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Takashi Iwai <tiwai@...e.de>,
        Nadav Amit <nadav.amit@...il.com>,
        Mike Galbraith <efault@....de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        axie <axie@....com>, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH] mm/rmap: do not call mmu_notifier_invalidate_page() v3

On Tue, Aug 29, 2017 at 12:05 PM, Jérôme Glisse <jglisse@...hat.com> wrote:
> Some MMU notifier need to be able to sleep during callback. This was
> broken by c7ab0d2fdc84 ("mm: convert try_to_unmap_one() to use
> page_vma_mapped_walk()").

No. No no no.

Didn't you learn *anything* from the bug?

You cannot replace "mmu_notifier_invalidate_page()" with
"mmu_notifier_invalidate_range()".

KVM implements mmu_notifier_invalidate_page().

IT DOES NOT IMPLEMENT THAT RANGE CRAP AT ALL.

So any approach like this is fundamentally garbage. Really. Stop
sending crap. This is exactly tehe same thing that we already reverted
because it was broken shit. Why do you re-send it without actually
fixing the fundamental problems that were pointed out?

               Linus