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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 86589FB44C4 for ; Fri, 24 Apr 2026 08:20:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C924F6B0005; Fri, 24 Apr 2026 04:20:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C43CF6B008A; Fri, 24 Apr 2026 04:20:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B58FA6B008C; Fri, 24 Apr 2026 04:20:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id A33FF6B0005 for ; Fri, 24 Apr 2026 04:20:33 -0400 (EDT) Received: from smtpin12.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 2636A1408A5 for ; Fri, 24 Apr 2026 08:20:33 +0000 (UTC) X-FDA: 84692752746.12.0F5385F Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf30.hostedemail.com (Postfix) with ESMTP id 90A6C80006 for ; Fri, 24 Apr 2026 08:20:31 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=mOMKksAU; spf=pass (imf30.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777018831; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IEwVWEzE2Dj0wHkg3NnVA6TubIBJog0kwGg5D1sN2jg=; b=ITdYNn0xArAHfV2Z/YrqDddA7zn5JR3JNSB3XpZ7ZR1lN/nY5qQVW0ZNUKv4v13ih1rFLE sJAcJB7AbXNPF/ITnCU8rVmkC2BcXR9U8Z+qpNI0CNpm0XZLrdE3VJpJy7WAZdEkR5sEgk fvs44K6dwUk5Ere1CaXasiYHzK0o2Mo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777018831; a=rsa-sha256; cv=none; b=rhZjawEsviNhwZp0zMK04re5vwojHa0azlJZ2WsuCRFC3KCPgZ8m1DtgPcV+45oDWqBhW1 eI6AFF38kBjTIjZkqV2F+DIdI7flxDq2zJOq13dwQtpbnTnqTXkr5gdGyG1oKgi/4277DV x0N/O9G9d/b4vVPohrTM0egwnh111aM= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=mOMKksAU; spf=pass (imf30.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id E24046001A; Fri, 24 Apr 2026 08:20:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68013C19425; Fri, 24 Apr 2026 08:20:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777018830; bh=Rv6jBW9C6+YIR0iVvSndpiy1+KRdv3tYvLeHDMmVn0c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mOMKksAUWZvCKb8Ojm6kYghsEM28I/Mztw1a92GaD+6XofYQMD1pQHKguAWOCnWjB mTCyWZ3OkABdRLM9eSm+SbbPUvMy2otzMEK1ea5pHoNTIwmN90fPnX4+fAc41Z7+g8 QjLLsZLJEJfajKQorsSixJXC+QFFbdXKzmcVZXz68mssOqhvNN/+zrqCUrmfPet45f Q7yhOOr6zoUcXl7tErxPsUGjWtZ5bDM/D/3/qNHD/2j09YrukMF1PMHi8WLDddOZgk jGqxoyyzGn8vdvAf3mgz3hXtt5u+ISYKkrx106+Dc9WhXMb5NeUdq+P491a72duOd0 kyqvtA1rMJUCg== Date: Fri, 24 Apr 2026 11:20:20 +0300 From: Mike Rapoport To: Muchun Song Cc: Andrew Morton , David Hildenbrand , Muchun Song , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v6 6/7] mm/mm_init: Fix uninitialized struct pages for ZONE_DEVICE Message-ID: References: <20260424025547.3806072-1-songmuchun@bytedance.com> <20260424025547.3806072-7-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260424025547.3806072-7-songmuchun@bytedance.com> X-Stat-Signature: bjb49pwitrwhkmuijqmdxgpuqtgj5iuw X-Rspam-User: X-Rspamd-Queue-Id: 90A6C80006 X-Rspamd-Server: rspam05 X-HE-Tag: 1777018831-917689 X-HE-Meta: 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 FWX95g7U RMr6SQenLALetSaEujjYk6D3vk9bzjPwrxlxRYaqWeB9nozIGfCUMWghpWF8CZ/ls4k2A553QvrrcJJFqeDhrhWV4rFVwDVSTXCnY3dgHlcrjLqyGBPjYGLthrM3K1R6VBjky//3kr9uqspzfQGyshinMYl5Tc/Zqr2TkFWSNDaUvJsBq8Pu4xp1EowqaYyAGrX6JrYY+ssVho/ea5mH3EW8foKm0ibjC3PYS6br2QvT9k7yJyl/VvHPm3jBrp9Bg0tledKpJAVDDiMKAskCcfSR/c+GfFrdyTDMWdZ7WOb0z1MxHzH5hHL61NHjqYgilC9LuKcBrskf5u6D4194bwrhDFUe+VD+IjAre Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 24, 2026 at 10:55:46AM +0800, Muchun Song wrote: > If DAX memory is hotplugged into an unoccupied subsection of an early > section, section_activate() reuses the unoptimized boot memmap. > However, compound_nr_pages() still assumes that vmemmap optimization is > in effect and initializes only the reduced number of struct pages. As a > result, the remaining tail struct pages are left uninitialized, which > can later lead to unexpected behavior or crashes. > > Fix this by treating early sections as unoptimized when calculating how > many struct pages to initialize. > > Fixes: 6fd3620b3428 ("mm/page_alloc: reuse tail struct pages for compound devmaps") > Cc: stable@vger.kernel.org > Signed-off-by: Muchun Song > Acked-by: David Hildenbrand (Arm) Acked-by: Mike Rapoport (Microsoft) > --- > mm/mm_init.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index cfc76953e249..bd466a3c10c8 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1055,10 +1055,17 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, > * of how the sparse_vmemmap internals handle compound pages in the lack > * of an altmap. See vmemmap_populate_compound_pages(). > */ > -static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, > +static inline unsigned long compound_nr_pages(unsigned long pfn, > + struct vmem_altmap *altmap, > struct dev_pagemap *pgmap) > { > - if (!vmemmap_can_optimize(altmap, pgmap)) > + /* > + * If DAX memory is hot-plugged into an unoccupied subsection > + * of an early section, the unoptimized boot memmap is reused. > + * See section_activate(). > + */ > + if (early_section(__pfn_to_section(pfn)) || > + !vmemmap_can_optimize(altmap, pgmap)) > return pgmap_vmemmap_nr(pgmap); > > return VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page)); > @@ -1128,7 +1135,7 @@ void __ref memmap_init_zone_device(struct zone *zone, > continue; > > memmap_init_compound(page, pfn, zone_idx, nid, pgmap, > - compound_nr_pages(altmap, pgmap)); > + compound_nr_pages(pfn, altmap, pgmap)); > } > > pageblock_migratetype_init_range(start_pfn, nr_pages, MIGRATE_MOVABLE); > -- > 2.20.1 > -- Sincerely yours, Mike.