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 C1CD0EB64D9 for ; Mon, 19 Jun 2023 08:05:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229473AbjFSIFq (ORCPT ); Mon, 19 Jun 2023 04:05:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230304AbjFSIFA (ORCPT ); Mon, 19 Jun 2023 04:05:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 057CBD3; Mon, 19 Jun 2023 01:04:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9596461574; Mon, 19 Jun 2023 08:04:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 471BBC433C0; Mon, 19 Jun 2023 08:04:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687161882; bh=Jkv3EGzDEoQxhxTQKy7Jh7KLg0vAnB0lxbXiokDwKsg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oFbvYOPv+cOU5MZ/vephP2zLkQnuJcgb/785+006D4R7v9jvYTpkJMWKrt/Stfanz 74abWgx0R2eoRXXICOUzZpKQvxnwrCi01m2Kik8jxH4RH2q0QeiYKCP90rSpTl6nOr 7lk//ALTYrwr58n+B8p2mVAfInm83HL92Uz1pYyA= Date: Mon, 19 Jun 2023 10:04:38 +0200 From: Greg KH To: mawupeng Cc: david@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, richard.weiyang@linux.alibaba.com, mst@redhat.com, jasowang@redhat.com, pankaj.gupta.linux@gmail.com, mhocko@kernel.org, osalvador@suse.de Subject: Re: [PATCH stable 5.10] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block Message-ID: <2023061936-mantra-pancreas-67d4@gregkh> References: <20230619065121.1720912-1-mawupeng1@huawei.com> <2023061926-monoxide-pastor-fa3b@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Jun 19, 2023 at 03:53:40PM +0800, mawupeng wrote: > > > On 2023/6/19 15:41, David Hildenbrand wrote: > > On 19.06.23 09:22, mawupeng wrote: > >> > >> > >> 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 > >> > > > > Makes sense to me. Of course, we could think about a simplified stable fix that only drops the ref. > > Since the new patch does not introduce any kabi change, maybe we can merge this one？ stable kernels never care about "kabi", that is a made up thing that some distros work to enforce only. It has nothing to do with the community. And I will always prefer to take the real commit that is in Linus's tree over any "custom" patch, as 90%+ of the time, custom changes are almost always wrong. thanks, greg k-h