linux-kernel - Re: [PATCH 2/2] Revert "vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE

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Message-ID: <CAHk-=whao=iosX1s5Z4SF-ZGa-ebAukJoAdUJFk5SPwnofV+Vg@mail.gmail.com>
Date:   Fri, 22 Apr 2022 11:41:38 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Song Liu <songliubraving@...com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 2/2] Revert "vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP"

On Fri, Apr 22, 2022 at 10:08 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Just opt-in with the mappings that matter.

Actually, we could automatically opt-in a few common cases that we
know are fundamentally ok, because they already can't play protection
games.

In particular, kvmalloc().

So I think something like this patch - along with Song's patch to
enable it for alloc_large_system_hash() - would be fairly safe, and
avoid any nasty cases.

And probably catch quite a lot of the cases that matter that can grow large.

               Linus

View attachment "patch.diff" of type "text/x-patch" (740 bytes)