Re: [PATCH] x86/mm: avoid a reclaiming allocation in pud_free_pmd_page()

[Mikhail Gavrilov]

On 9/23/26 15:53, Dave Hansen wrote:
> I think that means we can do something like the completely untested
> attached patch.
>
> Looks like Mikhail came to basically the same conclusion.

Yes - v2 does the same thing, and also drops the now-stale NOTE about
the page allocation.  It went out about 20 minutes before your mail:

  https://lore.kernel.org/all/20260923223116.20090-1-mikhail.v.gavrilov@xxxxxxxxx/

It was tested on a box that reaches this path at boot without any
instrumentation (from amdgpu_ttm_init()), plus the TTM shrinker
reproducer; the details are below the scissors there.

Two things in the attached sketch, in case it gets picked up as is:

 - The first hunk prepends the patch name to the SPDX line
   ("pud_free_pmd_page-simplify// SPDX-License-Identifier: ..."),
   which will not build.

 - Making it return void conflicts with the prototype in
   include/linux/pgtable.h, and vmap_try_huge_pud() still does
   "if (!pud_free_pmd_page(pud, addr))".  The arm64, riscv and powerpc
   versions also always return 1, so dropping the return value looks
   like a reasonable follow-up across architectures, but I kept v2
   x86-only and returning int so that it stays small for stable.

Your comment above the flush explains it better than the "INVLPG to
clear all paging-structure caches" one-liner.  If you prefer it, I can
send a v3 with it, or feel free to fold it in when applying.