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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Z5W7jjZ5; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9E740606A31D for ; Fri, 30 Oct 2026 09:01:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Z5W7jjZ5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E4161F000C1; Fri, 30 Oct 2026 09:00:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793350860; bh=x9qMcf27LhCCCJBB8Rwt84bdkyoyyl9NUxLsoyq+Ifk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Z5W7jjZ5CHNgkF7jCfE0ZaOHYunaTI4LQaG+EZH2j9fRC+oGHMbSWTcm1ttSiCp1t SOW1jRzY1mB/gLSmMLe1CR6S8BG2H8gpsbHugwymJqUmLtl3nzZlWxhJKHxsws06Yr 7L4WjrVhRTcytnHcAuH5tC3+lr0RmYWw6sjmPzM1YPgUgIdLotSns9nMblv0aJ62YK JPsTZ6sjt9UJGMraJzXiOydmkTyx1O6/S0S9WiSUaXrhd1zeaxic7HhFT60Lj1A1TO S43KTJpl5if86/6JxeCR3njCW4UtLKv0UZ98hYyEhinG1EH90Ay3K5fT9cODSOvOrz RAmJBry2lrlXQ== Message-ID: <19012a9f-7a8d-4eb2-a441-cdb04184890b@kernel.org> Date: Fri, 30 Oct 2026 10:00:53 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2] mm/huge_memory: set the mmu_gather page size in zap_huge_pud() To: "Ritesh Harjani (IBM)" , linux-mm@kvack.org, Andrew Morton Cc: Madhavan Srinivasan , Venkat Rao Bagalkote , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Muchun Song , Zi Yan , Baolin Wang , Pavithra References: <8b853e5f9f16145859407b28af654b0f79e12642.1793318297.git.ritesh.list@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/30/26 01:07, Ritesh Harjani (IBM) wrote: > Unmapping a device-dax mapping with 1G alignment on powerpc radix kernel > built with CONFIG_DEBUG_VM triggers this warning on every munmap: > > WARNING: mm/mmu_gather.c:176 at __tlb_remove_folio_pages_size+0x38/0x230 > NIP [c00000000063d508] __tlb_remove_folio_pages_size+0x38/0x230 > LR [c0000000006fb688] zap_huge_pud+0x1b8/0x2d0 > Call Trace: > zap_huge_pud+0x170/0x2d0 (unreliable) > __zap_vma_range+0x1604/0x1e20 > unmap_vmas+0xa0/0x1f0 > unmap_region+0xb0/0x130 > vms_complete_munmap_vmas+0x120/0x310 > do_vmi_align_munmap+0x1ec/0x240 > __vm_munmap+0x148/0x220 > sys_munmap+0x28/0x40 > > To trigger this - it is enough to mmap() /dev/dax0.0, touch the first > byte so that the whole 1G is mapped by a single PUD and then munmap() > it. > > PowerPC needs MMU_GATHER_PAGE_SIZE in which mmu_gather needs to record > the page size for which tlb flush is needed. zap_huge_pmd(), > zap_pte_range(), change_huge_pud() etc all do this already. However, > since commit: > dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()") > > a device-dax PUD maps a real folio and zap_huge_pud() now hands it to > tlb_remove_page_size(tlb, page, HPAGE_PUD_SIZE). At that point > tlb->page_size is still whatever the previous user left behind, which is > 0 for the fresh gather set up by munmap() and so the check fires. > > Fix this in the same way like how other similar paths do. > > Fixes: dbe54153296d0 ("mm/huge_memory: add vmf_insert_folio_pud()") > Reported-by: Pavithra > Signed-off-by: Ritesh Harjani (IBM) > --- > [v1]->v2: > ========= > - Split the 2 part patch series. Patch-1 is now superseded by a different patch > from Muchun which he already posted [2]. > - No difference in this patch from v1. > > [v1]: https://lore.kernel.org/all/97f85592bb78a273be8519e6897e7f9b9bd31469.1793070429.git.ritesh.list@gmail.com/ > [2]: https://lore.kernel.org/all/20261029063601.1961415-1-songmuchun@bytedance.com/ > > mm/huge_memory.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index bd44d58e8684..7e589a2fb02d 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3040,6 +3040,8 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, > spinlock_t *ptl; > pud_t orig_pud; > > + tlb_change_page_size(tlb, HPAGE_PUD_SIZE); > + > ptl = __pud_trans_huge_lock(pud, vma); > if (!ptl) > return 0; > -- > 2.39.5 > Matches zap_huge_pmd(). I will wait a bit and then queue this shortly. This sounds like stable material? -- Cheers, David