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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0EBBEB64D9 for ; Mon, 19 Jun 2023 07:22:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229519AbjFSHW0 (ORCPT ); Mon, 19 Jun 2023 03:22:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229454AbjFSHWZ (ORCPT ); Mon, 19 Jun 2023 03:22:25 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6F69E4; Mon, 19 Jun 2023 00:22:23 -0700 (PDT) Received: from dggpemm500014.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Ql1NL1P6NzMpZ8; Mon, 19 Jun 2023 15:19:14 +0800 (CST) Received: from [10.174.178.120] (10.174.178.120) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Mon, 19 Jun 2023 15:22:20 +0800 Message-ID: Date: Mon, 19 Jun 2023 15:22:20 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 CC: , , , , , , , , , , , Subject: Re: [PATCH stable 5.10] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block Content-Language: en-US To: References: <20230619065121.1720912-1-mawupeng1@huawei.com> <2023061926-monoxide-pastor-fa3b@gregkh> From: mawupeng In-Reply-To: <2023061926-monoxide-pastor-fa3b@gregkh> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 2023/6/19 15:16, Greg KH wrote: > On Mon, Jun 19, 2023 at 02:51:21PM +0800, Wupeng Ma wrote: >> From: David Hildenbrand >> >> commit 8dc4bb58a146655eb057247d7c9d19e73928715b upstream. >> >> virtio-mem soon wants to use offline_and_remove_memory() memory that >> exceeds a single Linux memory block (memory_block_size_bytes()). Let's >> remove that restriction. >> >> Let's remember the old state and try to restore that if anything goes >> wrong. While re-onlining can, in general, fail, it's highly unlikely to >> happen (usually only when a notifier fails to allocate memory, and these >> are rather rare). >> >> This will be used by virtio-mem to offline+remove memory ranges that are >> bigger than a single memory block - for example, with a device block >> size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory >> block size of 128MB. >> >> While we could compress the state into 2 bit, using 8 bit is much >> easier. >> >> This handling is similar, but different to acpi_scan_try_to_offline(): >> >> a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG >> optimization is still relevant - it should only apply to ZONE_NORMAL >> (where we have no guarantees). If relevant, we can always add it. >> >> b) acpi_scan_try_to_offline() simply onlines all memory in case >> something goes wrong. It doesn't restore previous online type. Let's do >> that, so we won't overwrite what e.g., user space configured. >> >> Reviewed-by: Wei Yang >> Cc: "Michael S. Tsirkin" >> Cc: Jason Wang >> Cc: Pankaj Gupta >> Cc: Michal Hocko >> Cc: Oscar Salvador >> Cc: Wei Yang >> Cc: Andrew Morton >> Signed-off-by: David Hildenbrand >> Link: https://lore.kernel.org/r/20201112133815.13332-28-david@redhat.com >> Signed-off-by: Michael S. Tsirkin >> Acked-by: Andrew Morton >> Signed-off-by: Ma Wupeng >> --- >> mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++------- >> 1 file changed, 89 insertions(+), 16 deletions(-) >> > > Why is this needed in 5.10.y? Looks like a new feature to me, what > problem does it solve there? > > thanks, > > greg k-h It do introduce a new feature. But at the same time, it fix a memleak introduced in Commit 08b3acd7a68f ("mm/memory_hotplug: Introduce offline_and_remove_memory()" Our test find a memleak in init_memory_block, it is clear that mem is never been released due to wrong refcount. Commit 08b3acd7a68f ("mm/memory_hotplug: Introduce offline_and_remove_memory()") failed to dec refcount after find_memory_block which fail to dec refcount to zero in remove memory causing the leak. Commit 8dc4bb58a146 ("mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block") introduce walk_memory_blocks to replace find_memory_block which dec refcount by calling put_device after find_memory_block_by_id. In the way, the memleak is fixed. Here is the simplified calltrace: kmem_cache_alloc_trace+0x664/0xed0 init_memory_block+0x8c/0x170 create_memory_block_devices+0xa4/0x150 add_memory_resource+0x188/0x530 __add_memory+0x78/0x104 add_memory+0x6c/0xb0