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 X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3FF1C2BB55 for ; Thu, 9 Apr 2020 07:32:12 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6982E206F7 for ; Thu, 9 Apr 2020 07:32:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZU+6gVI7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6982E206F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48yXsQ3lYHzDqSy for ; Thu, 9 Apr 2020 17:32:10 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=205.139.110.61; helo=us-smtp-delivery-1.mimecast.com; envelope-from=david@redhat.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=ZU+6gVI7; dkim-atps=neutral Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [205.139.110.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48yXl41RF0zDqTd for ; Thu, 9 Apr 2020 17:26:38 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1586417195; h=from:from: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:autocrypt:autocrypt; bh=to/0SitJAZRtOGSvrzhYABJpLJM1lhbVLZ/sGmYX698=; b=ZU+6gVI7+hiAZwMEVWP15adAehUAbiAZEx2FqZMHY+RCg9LWadFPe826QAF6ip/0MXUQJA 5ZFXEsQ13Y5w8Ylbl6RNYdoGAFXx0s9+dU2ngoRzpen2CChDh8D+Hc1vFmFel+hwbgGjUj nhpLtzLihYsWbpUTN12zrX7eaEBTW8M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-424-5CD492iRPHyfe7lkOsfKVw-1; Thu, 09 Apr 2020 03:26:31 -0400 X-MC-Unique: 5CD492iRPHyfe7lkOsfKVw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5B1BE800D53; Thu, 9 Apr 2020 07:26:28 +0000 (UTC) Received: from [10.36.113.222] (ovpn-113-222.ams2.redhat.com [10.36.113.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id 45BB85DA7C; Thu, 9 Apr 2020 07:26:23 +0000 (UTC) Subject: Re: [PATCH v1 1/2] powerpc/pseries/hotplug-memory: stop checking is_mem_section_removable() To: piliu , Baoquan He References: <20200407135416.24093-1-david@redhat.com> <20200407135416.24093-2-david@redhat.com> <20200408024630.GQ2402@MiWiFi-R3L-srv> <16187f69-0e5b-c9c2-a31b-8658425758aa@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <85637e60-4d11-2b69-f2a9-1505e0342ce3@redhat.com> Date: Thu, 9 Apr 2020 09:26:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <16187f69-0e5b-c9c2-a31b-8658425758aa@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , linux-kernel@vger.kernel.org, Wei Yang , linux-mm@kvack.org, Paul Mackerras , Nathan Fontenot , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Oscar Salvador Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 09.04.20 04:59, piliu wrote: >=20 >=20 > On 04/08/2020 10:46 AM, Baoquan He wrote: >> Add Pingfan to CC since he usually handles ppc related bugs for RHEL. >> >> On 04/07/20 at 03:54pm, David Hildenbrand wrote: >>> In commit 53cdc1cb29e8 ("drivers/base/memory.c: indicate all memory >>> blocks as removable"), the user space interface to compute whether a = memory >>> block can be offlined (exposed via >>> /sys/devices/system/memory/memoryX/removable) has effectively been >>> deprecated. We want to remove the leftovers of the kernel implementat= ion. >> >> Pingfan, can you have a look at this change on PPC? Please feel free = to >> give comments if any concern, or offer ack if it's OK to you. >> >>> >>> When offlining a memory block (mm/memory_hotplug.c:__offline_pages())= , >>> we'll start by: >>> 1. Testing if it contains any holes, and reject if so >>> 2. Testing if pages belong to different zones, and reject if so >>> 3. Isolating the page range, checking if it contains any unmovable pa= ges >>> >>> Using is_mem_section_removable() before trying to offline is not only= racy, >>> it can easily result in false positives/negatives. Let's stop manuall= y >>> checking is_mem_section_removable(), and let device_offline() handle = it >>> completely instead. We can remove the racy is_mem_section_removable() >>> implementation next. >>> >>> We now take more locks (e.g., memory hotplug lock when offlining and = the >>> zone lock when isolating), but maybe we should optimize that >>> implementation instead if this ever becomes a real problem (after all= , >>> memory unplug is already an expensive operation). We started using >>> is_mem_section_removable() in commit 51925fb3c5c9 ("powerpc/pseries: >>> Implement memory hotplug remove in the kernel"), with the initial >>> hotremove support of lmbs. >>> >>> Cc: Nathan Fontenot >>> Cc: Michael Ellerman >>> Cc: Benjamin Herrenschmidt >>> Cc: Paul Mackerras >>> Cc: Michal Hocko >>> Cc: Andrew Morton >>> Cc: Oscar Salvador >>> Cc: Baoquan He >>> Cc: Wei Yang >>> Signed-off-by: David Hildenbrand >>> --- >>> .../platforms/pseries/hotplug-memory.c | 26 +++--------------= -- >>> 1 file changed, 3 insertions(+), 23 deletions(-) >>> >>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/p= owerpc/platforms/pseries/hotplug-memory.c >>> index b2cde1732301..5ace2f9a277e 100644 >>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c >>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c >>> @@ -337,39 +337,19 @@ static int pseries_remove_mem_node(struct devic= e_node *np) >>> =20 >>> static bool lmb_is_removable(struct drmem_lmb *lmb) >>> { >>> - int i, scns_per_block; >>> - bool rc =3D true; >>> - unsigned long pfn, block_sz; >>> - u64 phys_addr; >>> - >>> if (!(lmb->flags & DRCONF_MEM_ASSIGNED)) >>> return false; >>> =20 >>> - block_sz =3D memory_block_size_bytes(); >>> - scns_per_block =3D block_sz / MIN_MEMORY_BLOCK_SIZE; >>> - phys_addr =3D lmb->base_addr; >>> - >>> #ifdef CONFIG_FA_DUMP >>> /* >>> * Don't hot-remove memory that falls in fadump boot memory area >>> * and memory that is reserved for capturing old kernel memory. >>> */ >>> - if (is_fadump_memory_area(phys_addr, block_sz)) >>> + if (is_fadump_memory_area(lmb->base_addr, memory_block_size_bytes()= )) >>> return false; >>> #endif >>> - >>> - for (i =3D 0; i < scns_per_block; i++) { >>> - pfn =3D PFN_DOWN(phys_addr); >>> - if (!pfn_in_present_section(pfn)) { >>> - phys_addr +=3D MIN_MEMORY_BLOCK_SIZE; >>> - continue; >>> - } >>> - >>> - rc =3D rc && is_mem_section_removable(pfn, PAGES_PER_SECTION); >>> - phys_addr +=3D MIN_MEMORY_BLOCK_SIZE; >>> - } >>> - >>> - return rc; >>> + /* device_offline() will determine if we can actually remove this l= mb */ >>> + return true; > So I think here swaps the check and do sequence. At least it breaks > dlpar_memory_remove_by_count(). It is doable to remove > is_mem_section_removable(), but here should be more effort to re-arrang= e > the code. >=20 Thanks Pingfan, 1. "swaps the check and do sequence": Partially. Any caller of dlpar_remove_lmb() already has to deal with false positives. device_offline() can easily fail after dlpar_remove_lmb() =3D=3D true. It's inherently racy. 2. "breaks dlpar_memory_remove_by_count()" Can you elaborate why it "breaks" it? It will simply try to offline+remove lmbs, detect that it wasn't able to offline+remove as much as it wanted (which could happen before as well easily), and re-add the already offlined+removed ones. 3. "more effort to re-arrange the code" What would be your suggestion? We would rip out that racy check if we can remove as much memory as requested in dlpar_memory_remove_by_count() and simply always try to remove + recover. --=20 Thanks, David / dhildenb