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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Muhammad Usama Anjum , Stephen Rothwell , Arnd Bergmann , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/6] fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race Message-ID: References: <20260529172331.356655-1-kas@kernel.org> <20260529172331.356655-2-kas@kernel.org> X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260529172331.356655-2-kas@kernel.org> 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. --breno