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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=WgwvLHrG; 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 B283D606A31C for ; Fri, 30 Oct 2026 11:09:06 +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=WgwvLHrG Received: by smtp.kernel.org (Postfix) with ESMTPSA id D22D71F000C1; Fri, 30 Oct 2026 11:09:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793358546; bh=bkc30PrXE7NoTD9uYcKfNgc6wV2Fj3rIUgm/AIyfBvc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WgwvLHrG1rnaa6zIaTWYYVChMqH+LvTLd0/7d6Sp8KnDUXr6GQ+eOzdfIrIQfGeus /QXwIhlV9z6X9uxq6Y6wUyJ7DVeYBvVsq0OEilMrxYN0TLhswXdKXjp4Ybl5QojXio AXFfWCpUQTqTQcLZIyMMq7x+VWijPcoOe2Tr2QIHtOs4ZaAqbmig8bwwLDbEe2/V5E MQSbYloRwuwX5c2zNxa0KWgEEzNRWqCSvAeCoznLyJoWWKKYD5sLshWPQzwAfD+i3p 80FlJAJRnGTtHZMJHdt1Gd2Mhq3zt+DqkVO3/13tRt0Ms0lWU4j5w1LcMifPXOZmk/ RT3OFbg7E5qPw== Message-ID: <6591722a-d841-46ef-85d4-e7a3243344c2@kernel.org> Date: Fri, 30 Oct 2026 12:09:01 +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> <19012a9f-7a8d-4eb2-a441-cdb04184890b@kernel.org> 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 11:15, Ritesh Harjani (IBM) wrote: > "David Hildenbrand (Arm)" writes: > >> 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. >> > > Thanks David, however, looks like Andrew might have queued this up in > his mm tree [1], right? > > [1]: https://lore.kernel.org/all/20261030021905.2DCA71F000C1@smtp.kernel.org/ No worries, one of us can drop it before sending it upstream. I'm about to send out the MAINTAINTERS update in a bit, so right now it's still confusing. (but also there is no harm in having it in two trees temporarily) > >> This sounds like stable material? >> > > Sorry, my bad. Yes, we should have this Cc: stable@vger.kernel.org. > > Kindly let me know if I should update the tag and send v3, or can it be > taken care? Thanks! I would just apply that when picking, no need to resend. Thanks! -- Cheers, David