linux-kernel - Re: [PATCH v4 02/14] mm: Switch mm->get_unmapped

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Date: Mon, 25 Mar 2024 20:32:40 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: Liam.Howlett@...cle.com, Andrew Morton <akpm@...ux-foundation.org>, 
	Borislav Petkov <bp@...en8.de>, Mark Brown <broonie@...nel.org>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	debug@...osinc.com, "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, 
	Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	linux-mm <linux-mm@...ck.org>, linux-s390 <linux-s390@...r.kernel.org>, 
	sparclinux@...r.kernel.org, linux-sgx@...r.kernel.org, nvdimm@...ts.linux.dev, 
	linux-cxl@...r.kernel.org, Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, 
	io-uring@...r.kernel.org, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v4 02/14] mm: Switch mm->get_unmapped_area() to a flag

On Mon, Mar 25, 2024 at 7:17 PM Rick Edgecombe
<rick.p.edgecombe@...el.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, struct rlimit *rlim_stack)
>
>         if (mmap_is_legacy(rlim_stack)) {
>                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
> -               mm->get_unmapped_area = arch_get_unmapped_area;
> +               clear_bit(MMF_TOPDOWN, &mm->flags);
>         } else {
>                 mm->mmap_base = mmap_base(random_factor, rlim_stack);
> -               mm->get_unmapped_area = 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_stack)
>  {
>         mm->mmap_base = TASK_UNMAPPED_BASE;
> -       mm->get_unmapped_area = arch_get_unmapped_area;
> +       clear_bit(MMF_TOPDOWN, &mm->flags);
>  }
>  #endif

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