linux-kernel - Re: [PATCH v2 bpf 0/3] vmalloc: bpf: introduce VM_ALLOW_HUGE

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Date:   Tue, 12 Apr 2022 17:35:14 -0700
From:   Song Liu <song@...nel.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Kernel Team <kernel-team@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        Christoph Hellwig <hch@...radead.org>, imbrenda@...ux.ibm.com
Subject: Re: [PATCH v2 bpf 0/3] vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP

Hi Luis,

On Tue, Apr 12, 2022 at 8:38 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> On Mon, Apr 11, 2022 at 04:18:05PM -0700, Song Liu wrote:
> > Changes v1 => v2:
> > 1. Add vmalloc_huge(). (Christoph Hellwig)
> > 2. Add module_alloc_huge(). (Christoph Hellwig)
> > 3. Add Fixes tag and Link tag. (Thorsten Leemhuis)
> >
> > Enabling HAVE_ARCH_HUGE_VMALLOC on x86_64 and use it for bpf_prog_pack has
> > caused some issues [1], as many users of vmalloc are not yet ready to
> > handle huge pages. To enable a more smooth transition to use huge page
> > backed vmalloc memory, this set replaces VM_NO_HUGE_VMAP flag with an new
> > opt-in flag, VM_ALLOW_HUGE_VMAP. More discussions about this topic can be
> > found at [2].
> >
> > Patch 1 removes VM_NO_HUGE_VMAP and adds VM_ALLOW_HUGE_VMAP.
> > Patch 2 uses VM_ALLOW_HUGE_VMAP in bpf_prog_pack.
> >
> > [1] https://lore.kernel.org/lkml/20220204185742.271030-1-song@kernel.org/
> > [2] https://lore.kernel.org/linux-mm/20220330225642.1163897-1-song@kernel.org/
> >
> > Song Liu (3):
> >   vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP
> >   module: introduce module_alloc_huge
> >   bpf: use vmalloc with VM_ALLOW_HUGE_VMAP for bpf_prog_pack
> >
> >  arch/Kconfig                 |  6 ++----
> >  arch/powerpc/kernel/module.c |  2 +-
> >  arch/s390/kvm/pv.c           |  2 +-
> >  arch/x86/kernel/module.c     | 21 +++++++++++++++++++
> >  include/linux/moduleloader.h |  5 +++++
> >  include/linux/vmalloc.h      |  4 ++--
> >  kernel/bpf/core.c            |  9 +++++----
> >  kernel/module.c              |  8 ++++++++
>
> Please use modules-next [0] as that has queued up changes which change
> kernel/module.c quite a bit.
>
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=modules-next

We are hoping to ship this set to fix some issues with 5.18. So I guess it
shouldn't go through modules-next branch? Would this work for you?
We are adding a new API module_alloc_huge(), so it shouldn't break
existing features.

Thanks,
Song