From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5CBAECD5BAB for ; Thu, 21 May 2026 22:31:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:Mime-Version:References:In-Reply-To:Message-Id:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=bnv8z/U53fPYRQVRdESTD0xQjxqDX0NyGk7FJvl1zug=; b=Pij8vE6dTz/F0+LbRJ1q80khVS csG9dYDBF+HK0Umz7e98s5M0BtdbOgh+V/TCuCLYvRhdP55qgXIdHcyshu+9Vuqd+eofLZKidHPZ5 vfHK/Ry2N89s9gnVLz7F7USW0NA4Ka6HRwgTvmqVAxk20iI2qz0dKDDp/vYAeuyF2ySBt1LX4xFKz XN4cFV1PirdW09SgoMTONmV77tt9M6aH7neD8FVBjvnWsrJPLGLUK819dQMKPoOS7PRqQhjpfTxgG anXk54NR3UAnXFm2pOkj8vstlrnrsRdZBF6qHE/b01Dgj7ypDG/wsmG/RS1RaInGKGe7cENQ1kYXy k6WXE9Uw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQBvS-00000009EKg-176k; Thu, 21 May 2026 22:31:34 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQBvP-00000009EKD-46TF for linux-arm-kernel@lists.infradead.org; Thu, 21 May 2026 22:31:33 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 553ED41A5C; Thu, 21 May 2026 22:31:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F02621F000E9; Thu, 21 May 2026 22:31:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1779402691; bh=bnv8z/U53fPYRQVRdESTD0xQjxqDX0NyGk7FJvl1zug=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=dgyXsqH67FvyK+9N+RrmIuzBnPicK5E+nVD175qTBrUi/dZfe//hrorWytuL6wRpo g/WQLOOXYW9aoOx0MAwfabDfx6fXjkFvdm7PbfxgdHHnL9fSY4y2XNQ7fJZips1O8Q NBQBE0pdjLnBhjrbbOTs7Jlfa8pXiZwDxcbAiEq0= Date: Thu, 21 May 2026 15:31:30 -0700 From: Andrew Morton To: Alistair Popple Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, catalin.marinas@arm.com, will@kernel.org, david@kernel.org Subject: Re: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables Message-Id: <20260521153130.d7d5cd060f7522f894252333@linux-foundation.org> In-Reply-To: <20260521032730.2104017-1-apopple@nvidia.com> References: <20260521032730.2104017-1-apopple@nvidia.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260521_153132_047330_77E3AC6B X-CRM114-Status: GOOD ( 20.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 21 May 2026 13:27:30 +1000 Alistair Popple wrote: > Since 5e8eb9aeeda3 ("arm64: mm: always call PTE/PMD ctor in > __create_pgd_mapping()") page-table allocation on ARM64 always > calls pagetable_{pte,pmd,pud,p4d}_ctor(). This sets the page_type > to PGTY_table, increments NR_PAGETABLE and possible allocates a PTL. > However the matching pagetable_dtor() calls were never added. > > With DEBUG_VM enabled on kernel versions prior to v6.17 without > 2dfcd1608f3a9 ("mm/page_alloc: let page freeing clear any set page > type") this leads to the following warning when freeing these pages due > to page->page_type sharing page->_mapcount: > > BUG: Bad page state in process ... pfn:284fbb > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x284fbb > flags: 0x17fffc000000000(node=0|zone=2|lastcpupid=0x1ffff) > page_type: f2(table) > page dumped because: nonzero mapcount > Call trace: > bad_page+0x13c/0x160 > __free_frozen_pages+0x6cc/0x860 > ___free_pages+0xf4/0x180 > free_pages+0x54/0x80 > free_hotplug_page_range.part.0+0x58/0x90 > free_empty_tables+0x438/0x500 > __remove_pgd_mapping.constprop.0+0x60/0xa8 > arch_remove_memory+0x48/0x80 > try_remove_memory+0x158/0x1d8 > offline_and_remove_memory+0x138/0x180 > > It can also lead to leaking the ptl allocation if ALLOC_SPLIT_PTLOCKS > is defined and incorrect NR_PAGETABLE stats. Fix this by calling > pagetable_dtor() in free_hotplug_pgtable_page() prior to freeing the > page to undo the effects of calling pagetable_*_ctor(). > > Fixes: 5e8eb9aeeda3 ("arm64: mm: always call PTE/PMD ctor in __create_pgd_mapping()") 6.16+, so I assume we want cc:stable here. > arch/arm64/mm/mmu.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 8e1d80a7033e..0c24fe650e95 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1422,6 +1422,7 @@ static void free_hotplug_page_range(struct page *page, size_t size, > > static void free_hotplug_pgtable_page(struct page *page) > { > + pagetable_dtor(page_ptdesc(page)); > free_hotplug_page_range(page, PAGE_SIZE, NULL); > } I'd of course prefer that arm maintainers handle this. But 5e8eb9aeeda3 came via myself so convention kinda-dictates that I get to fix it.