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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B993C433EF for ; Tue, 8 Feb 2022 01:59:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 072D86B0074; Mon, 7 Feb 2022 20:59:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 022756B0075; Mon, 7 Feb 2022 20:59:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E53C06B0078; Mon, 7 Feb 2022 20:59:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id D6C7C6B0074 for ; Mon, 7 Feb 2022 20:59:27 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 9E96A601A7 for ; Tue, 8 Feb 2022 01:59:27 +0000 (UTC) X-FDA: 79117955574.02.52B792A Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf05.hostedemail.com (Postfix) with ESMTP id AA619100005 for ; Tue, 8 Feb 2022 01:59:23 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Jt5kz3VgHzccpd; Tue, 8 Feb 2022 09:58:19 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 8 Feb 2022 09:59:18 +0800 Subject: Re: [PATCH] mm/memory_hotplug: fix kfree() of bootmem memory To: David Hildenbrand CC: , , , , Andrew Morton References: <20220207135618.17231-1-linmiaohe@huawei.com> <6d4ab70e-b944-5f7d-e9a3-979ac66c70f7@redhat.com> From: Miaohe Lin Message-ID: <828c9b16-6ff0-abb7-3a16-277d2d60de81@huawei.com> Date: Tue, 8 Feb 2022 09:59:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <6d4ab70e-b944-5f7d-e9a3-979ac66c70f7@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Authentication-Results: imf05.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf05.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspam-User: X-Rspamd-Queue-Id: AA619100005 X-Stat-Signature: 6d3sm475uysenfibw7ai9wf1k9kgijoc X-Rspamd-Server: rspam07 X-HE-Tag: 1644285563-700357 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: Hi: On 2022/2/7 22:33, David Hildenbrand wrote: > On 07.02.22 14:56, Miaohe Lin wrote: >> We can't use kfree() to release the resource as it might come from bootmem. >> Use release_mem_region() instead. > > How can this happen? release_mem_region() is called either from > __add_memory() or from add_memory_driver_managed(), where we allocated > the region via register_memory_resource(). Both functions shouldn't ever > be called before the buddy is up an running. > > Do you have a backtrace of an actual instance of this issue? Or was this > identified as possibly broken by code inspection? > This is identified as possibly broken by code inspection. IIUC, alloc_resource is always used to allocate the resource. It has the below logic: if (bootmem_resource_free) { res = bootmem_resource_free; bootmem_resource_free = res->sibling; } where bootmem_resource_free is used to reusing the resource entries allocated by boot mem after the system is up: /* * For memory hotplug, there is no way to free resource entries allocated * by boot mem after the system is up. So for reusing the resource entry * we need to remember the resource. */ static struct resource *bootmem_resource_free; So I think register_memory_resource() can reuse the resource allocated by bootmem. Or am I miss anything? Thanks.