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 7283CCCD188 for ; Thu, 9 Oct 2025 09:17:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ADEE88E006F; Thu, 9 Oct 2025 05:16:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A88948E0002; Thu, 9 Oct 2025 05:16:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 976F38E006F; Thu, 9 Oct 2025 05:16:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 7F3FB8E0002 for ; Thu, 9 Oct 2025 05:16:59 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 3512114058E for ; Thu, 9 Oct 2025 09:16:59 +0000 (UTC) X-FDA: 83978021358.03.03A2334 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by imf13.hostedemail.com (Postfix) with ESMTP id F11C020004 for ; Thu, 9 Oct 2025 09:16:56 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=none; spf=pass (imf13.hostedemail.com: domain of christophe.leroy@csgroup.eu designates 93.17.235.10 as permitted sender) smtp.mailfrom=christophe.leroy@csgroup.eu; dmarc=pass (policy=quarantine) header.from=csgroup.eu ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760001417; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SjzO/ywmFDyEDpAIYRGFQ4F67Mu4cfU8z7gpJNsGZLg=; b=LrP70ZAeGdYOOFVh5vugPIYJlFmTHXI4WvIUGvaHjdBl22Q1oueDVzx5VqkmRXR+j36wub 22woGQ+dRkOkpDQ8Y+skkq5JyiPkj2pfh+A3YX/iwQObFYtDqgKU6agwjHW9qqfylgOqgn I1q8BKV4h15ntH45Z9ub8YoUdpnu0MY= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=none; spf=pass (imf13.hostedemail.com: domain of christophe.leroy@csgroup.eu designates 93.17.235.10 as permitted sender) smtp.mailfrom=christophe.leroy@csgroup.eu; dmarc=pass (policy=quarantine) header.from=csgroup.eu ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760001417; a=rsa-sha256; cv=none; b=KgUj1+7ksooV7LL4E5/aT9OEPrcyHM/AMWSpEnQsDD53XCy75Gh+8pK/ZVXc9vSzHiT5yK S2ASqnUNjK7sqjEoyX9flOZmtFGcaQVRG65vH9xCeM7FvauHAE4cRsJ+2nT+/I5ZJJ2Zn5 gfkpNvaGV2+8RFhdNZbGvTKLa0UcEXw= Received: from localhost (mailhub4.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4cj4530nVNz9sSY; Thu, 9 Oct 2025 11:16:55 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1xW49BLVjvgf; Thu, 9 Oct 2025 11:16:55 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4cj4526L27z9sSX; Thu, 9 Oct 2025 11:16:54 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BC2658B773; Thu, 9 Oct 2025 11:16:54 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ecZHQXz6ERX1; Thu, 9 Oct 2025 11:16:54 +0200 (CEST) Received: from [192.168.235.99] (unknown [192.168.235.99]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BE4258B770; Thu, 9 Oct 2025 11:16:52 +0200 (CEST) Message-ID: <03671aa8-4276-4707-9c75-83c96968cbb2@csgroup.eu> Date: Thu, 9 Oct 2025 11:16:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: (bisected) [PATCH v2 08/37] mm/hugetlb: check for unreasonable folio sizes when registering hstate To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: Zi Yan , Lorenzo Stoakes , "Liam R. Howlett" , Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, "linuxppc-dev@lists.ozlabs.org" References: <20250901150359.867252-1-david@redhat.com> <20250901150359.867252-9-david@redhat.com> <3e043453-3f27-48ad-b987-cc39f523060a@csgroup.eu> <9361c75a-ab37-4d7f-8680-9833430d93d4@redhat.com> From: Christophe Leroy Content-Language: fr-FR In-Reply-To: <9361c75a-ab37-4d7f-8680-9833430d93d4@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: F11C020004 X-Stat-Signature: 6wb3bifqihbgx3kkpa6puaygqsrinw7d X-Rspam-User: X-HE-Tag: 1760001416-308034 X-HE-Meta: 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 QS4DB21r PagvcSowmzyuSfgjUeXi/18tVnkPuuIwkV5xJ5EDAU54Py3jVYdcE606b8RFor9oW0YtZMnFjQxtvlXEEtnl3i8JrYNTJ3kaYjfETHjfixXUtdSWeOWcKxh5tSamzpGbQL3dbaoK9qyEKnwA+wAJGqqprR+YuEIv+g8qcigRoypA37yWAEH9vTLRtJTnME7nwuAagR/UnMR/47+cfXUgtgF2VHW1W4zx22GeF2u93+/A+YyY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Le 09/10/2025 à 10:14, David Hildenbrand a écrit : > On 09.10.25 10:04, Christophe Leroy wrote: >> >> >> Le 09/10/2025 à 09:22, David Hildenbrand a écrit : >>> On 09.10.25 09:14, Christophe Leroy wrote: >>>> Hi David, >>>> >>>> Le 01/09/2025 à 17:03, David Hildenbrand a écrit : >>>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>>> index 1e777cc51ad04..d3542e92a712e 100644 >>>>> --- a/mm/hugetlb.c >>>>> +++ b/mm/hugetlb.c >>>>> @@ -4657,6 +4657,7 @@ static int __init hugetlb_init(void) >>>>>         BUILD_BUG_ON(sizeof_field(struct page, private) * >>>>> BITS_PER_BYTE < >>>>>                 __NR_HPAGEFLAGS); >>>>> +    BUILD_BUG_ON_INVALID(HUGETLB_PAGE_ORDER > MAX_FOLIO_ORDER); >>>>>         if (!hugepages_supported()) { >>>>>             if (hugetlb_max_hstate || default_hstate_max_huge_pages) >>>>> @@ -4740,6 +4741,7 @@ void __init hugetlb_add_hstate(unsigned int >>>>> order) >>>>>         } >>>>>         BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE); >>>>>         BUG_ON(order < order_base_2(__NR_USED_SUBPAGE)); >>>>> +    WARN_ON(order > MAX_FOLIO_ORDER); >>>>>         h = &hstates[hugetlb_max_hstate++]; >>>>>         __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key); >>>>>         h->order = order; >>> >>> We end up registering hugetlb folios that are bigger than >>> MAX_FOLIO_ORDER. So we have to figure out how a config can trigger that >>> (and if we have to support that). >>> >> >> MAX_FOLIO_ORDER is defined as: >> >> #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE >> #define MAX_FOLIO_ORDER        PUD_ORDER >> #else >> #define MAX_FOLIO_ORDER        MAX_PAGE_ORDER >> #endif >> >> MAX_PAGE_ORDER is the limit for dynamic creation of hugepages via >> /sys/kernel/mm/hugepages/ but bigger pages can be created at boottime >> with kernel boot parameters without CONFIG_ARCH_HAS_GIGANTIC_PAGE: >> >>     hugepagesz=64m hugepages=1 hugepagesz=256m hugepages=1 >> >> Gives: >> >> HugeTLB: registered 1.00 GiB page size, pre-allocated 0 pages >> HugeTLB: 0 KiB vmemmap can be freed for a 1.00 GiB page >> HugeTLB: registered 64.0 MiB page size, pre-allocated 1 pages >> HugeTLB: 0 KiB vmemmap can be freed for a 64.0 MiB page >> HugeTLB: registered 256 MiB page size, pre-allocated 1 pages >> HugeTLB: 0 KiB vmemmap can be freed for a 256 MiB page >> HugeTLB: registered 4.00 MiB page size, pre-allocated 0 pages >> HugeTLB: 0 KiB vmemmap can be freed for a 4.00 MiB page >> HugeTLB: registered 16.0 MiB page size, pre-allocated 0 pages >> HugeTLB: 0 KiB vmemmap can be freed for a 16.0 MiB page > > I think it's a violation of CONFIG_ARCH_HAS_GIGANTIC_PAGE. The existing > folio_dump() code would not handle it correctly as well. I'm trying to dig into history and when looking at commit 4eb0716e868e ("hugetlb: allow to free gigantic pages regardless of the configuration") I understand that CONFIG_ARCH_HAS_GIGANTIC_PAGE is needed to be able to allocate gigantic pages at runtime. It is not needed to reserve gigantic pages at boottime. What am I missing ? > > See how snapshot_page() uses MAX_FOLIO_NR_PAGES. >