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 8CE25EB64D9 for ; Mon, 19 Jun 2023 07:48:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229538AbjFSHsQ (ORCPT ); Mon, 19 Jun 2023 03:48:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229875AbjFSHsL (ORCPT ); Mon, 19 Jun 2023 03:48:11 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD109E54; Mon, 19 Jun 2023 00:48:09 -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 3836861541; Mon, 19 Jun 2023 07:48:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0D75C433C8; Mon, 19 Jun 2023 07:48:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687160888; bh=+a/ZmnYkb2AqJDdYRdqv7LE893dBIQUn+SESlwMdA9k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dxRKosA64xqAOaG0oGVnfzu8t36uWhDRhUHHvQcfSFFa0m/RWsyanMWADslj3ldLB e0rTVaWx6PxfaO/yj8G1bxvlRe1E17c9WJP7i77YRl6LCh2YymtBd8DVKh4RuzaPLS Gt+qL6BWBVE8NThOt2UZ14SGrT+0O0arYWYNYaHs= Date: Mon, 19 Jun 2023 09:48:05 +0200 From: Greg KH To: mawupeng Cc: akpm@linux-foundation.org, david@redhat.com, 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: <2023061956-unlinked-fossil-ec6a@gregkh> References: <20230619065121.1720912-1-mawupeng1@huawei.com> <2023061926-monoxide-pastor-fa3b@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 19, 2023 at 03:22:20PM +0800, 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 Ok, thanks for the information, now queued up. greg k-h