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References: <20240326021656.202649-1-rick.p.edgecombe@intel.com> <20240326021656.202649-3-rick.p.edgecombe@intel.com>
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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date: Mon, 25 Mar 2024 20:32:40 -0700
Message-ID: <CAADnVQKHtRX2WS9c2qcMUJTmNNda+attkXoiNurFyMKvHNfa=A@mail.gmail.com>
Subject: Re: [PATCH v4 02/14] mm: Switch mm->get_unmapped_area() to a flag
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Liam.Howlett@oracle.com, Andrew Morton <akpm@linux-foundation.org>, 
	Borislav Petkov <bp@alien8.de>, Mark Brown <broonie@kernel.org>, 
	Christophe Leroy <christophe.leroy@csgroup.eu>, Dave Hansen <dave.hansen@linux.intel.com>, 
	debug@rivosinc.com, "H. Peter Anvin" <hpa@zytor.com>, Kees Cook <keescook@chromium.org>, 
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, 
	Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, 
	Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>, 
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	sparclinux@vger.kernel.org, linux-sgx@vger.kernel.org, nvdimm@lists.linux.dev, 
	linux-cxl@vger.kernel.org, Linux-Fsdevel <linux-fsdevel@vger.kernel.org>, 
	io-uring@vger.kernel.org, bpf <bpf@vger.kernel.org>
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On Mon, Mar 25, 2024 at 7:17=E2=80=AFPM Rick Edgecombe
<rick.p.edgecombe@intel.com> wrote:
>
>
> diff --git a/mm/util.c b/mm/util.c
> index 669397235787..8619d353a1aa 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -469,17 +469,17 @@ void arch_pick_mmap_layout(struct mm_struct *mm, st=
ruct rlimit *rlim_stack)
>
>         if (mmap_is_legacy(rlim_stack)) {
>                 mm->mmap_base =3D TASK_UNMAPPED_BASE + random_factor;
> -               mm->get_unmapped_area =3D arch_get_unmapped_area;
> +               clear_bit(MMF_TOPDOWN, &mm->flags);
>         } else {
>                 mm->mmap_base =3D mmap_base(random_factor, rlim_stack);
> -               mm->get_unmapped_area =3D arch_get_unmapped_area_topdown;
> +               set_bit(MMF_TOPDOWN, &mm->flags);
>         }
>  }
>  #elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
>  void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_sta=
ck)
>  {
>         mm->mmap_base =3D TASK_UNMAPPED_BASE;
> -       mm->get_unmapped_area =3D arch_get_unmapped_area;
> +       clear_bit(MMF_TOPDOWN, &mm->flags);
>  }
>  #endif

Makes sense to me.
Acked-by: Alexei Starovoitov <ast@kernel.org>
for the idea and for bpf bits.