Re: [PATCH 1/6] fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race

[Kiryl Shutsemau <kas@kernel.org>]

On Tue, Nov 10, 2026 at 08:23:11AM -0800, Breno Leitao wrote:
> Hello Kiryl,
> 
> On Fri, May 29, 2026 at 06:23:25PM +0100, Kiryl Shutsemau (Meta) wrote:
> > The non-hugetlb sibling make_uffd_wp_pte() does this correctly via
> > ptep_modify_prot_start() / ptep_modify_prot_commit(). Mirror that
> > pattern for the present-PTE branch. The migration case stays as-is --
> > migration entries are non-present, so there's no hardware update to
> > race against.
> 
> I am  seeing this on next-20261109 (arm64, PAGE_TABLE_CHECK) while the
> pagemap_ioctl kselftest runs next to a workload that migrates pages:
> 
>     WARNING: mm/page_table_check.c:206 at __page_table_check_ptes_set+0x168/0x178, CPU#21: pagemap_ioctl/894691
>     Call trace:
>      __page_table_check_ptes_set+0x168/0x178 (P)
>      __set_ptes_anysz+0x50/0x240
>      make_uffd_wp_pte+0x104/0x1c8
>      pagemap_scan_pmd_entry+0x1b98/0x1df8
>      walk_pgd_range+0x7b4/0xd00
>      __walk_page_range+0x108/0x510
>      walk_page_range_mm_unsafe+0x150/0x3e8
>      do_pagemap_cmd+0x418/0x7d0
>      __arm64_sys_ioctl+0xc08/0x1338
> 
> given you've touched this recently, I am wondering if you've seen it.

I have not. But I think this patch should help:

https://lore.kernel.org/all/20261111-uffd-state-fixes-v1-3-00713d368976@columbia.edu

-- 
  Kiryl Shutsemau / Kirill A. Shutemov