From patchwork Mon Apr 24 13:45:39 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baolin Wang X-Patchwork-Id: 87060 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2774088vqo; Mon, 24 Apr 2023 07:11:01 -0700 (PDT) X-Google-Smtp-Source: AKy350YDQpcO2DhRzbUSxAmD5ppx8Ll9/F5KjLyzxiasR2h2+I4e//LEMpxTx8TZbHVHqiU69Jey X-Received: by 2002:a17:903:230d:b0:1a8:5083:21ed with SMTP id d13-20020a170903230d00b001a8508321edmr17548193plh.51.1682345460733; Mon, 24 Apr 2023 07:11:00 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1682345460; cv=none; d=google.com; s=arc-20160816; b=wH5yCCA3MuCoXksrZ3kPYjEo295iC+1EQd/vLmIB9FW1pvIW6H6XUENuOJeiQkVCad bTJ/w2EkUPpThy/M7KxTy/qUEZwtR7Wfk6Faqq/4DxeJU/hLwJ/IfoOfdBS9taNPsW85 EtOJFWh+a5pR2Zr8fL+83+rLtMvOs3RnhfM1vel57INKB8b7qGfT58xHRw4U6HGw1XBc NftFt9SmfIbOmDbziYvMusBdvbfsB2pfYYJOqSz6Qq33cg6GntUUY/mFm4sOJtH1C/D/ xRo51B3cZfpyrG2kke8HKW9wW3OibcKFugpsN0Q0wwDYCd9Qu2lxJjSehHo8PAI/eYD9 7Usg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :message-id:date:subject:cc:to:from; bh=of4y4r11HnMBjpqe6J5ROFKicQ684iyvaOjw+qGJf5k=; b=A6CTm01S+j+n7LGCivgEkzGniL79zGJKuHS6wJc4uf04SMfIDLSiDboXdxHyYTdzww QsvPlkm6bwrQ6edDL4fxMQh3+d6nD2PN+ryfDSq6SSmdsept1WW9M82aNtkXichLCpD5 rHLLAUVMYncW54WtoK4wcJfRFpJmqbXJP/KyE5Uqj6SGBJv3uoUJWeIVQv5vBjP1L3U/ 9r6dNbcsWg9HwMHCX/K0Dyc7VhE6Mvgd3dX3L88xGi5RY5EY7HchaedPpyMRNDVKynR0 XG99poTKrEU+xzDn/yfdSWXWdNVdjLxmkdZwWP1BD2DzSG5Q2qV8waMBqd7dBG4QHRJr IAEg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id d4-20020a170902654400b001a5089fe47fsi10603891pln.326.2023.04.24.07.10.47; Mon, 24 Apr 2023 07:11:00 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231824AbjDXNqJ (ORCPT + 99 others); Mon, 24 Apr 2023 09:46:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231766AbjDXNqH (ORCPT ); Mon, 24 Apr 2023 09:46:07 -0400 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B32367A8A for ; Mon, 24 Apr 2023 06:45:55 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0Vgw4CI-_1682343948; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Vgw4CI-_1682343948) by smtp.aliyun-inc.com; Mon, 24 Apr 2023 21:45:49 +0800 From: Baolin Wang To: akpm@linux-foundation.org Cc: rppt@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, vbabka@suse.cz, mhocko@suse.com, david@redhat.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 1/2] mm/page_alloc: drop the unnecessary pfn_valid() for start pfn Date: Mon, 24 Apr 2023 21:45:39 +0800 Message-Id: X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1763964727027523520?= X-GMAIL-MSGID: =?utf-8?q?1764067073349144369?= __pageblock_pfn_to_page() currently performs both pfn_valid check and pfn_to_online_page(). The former one is redundant because the latter is a stronger check. Drop pfn_valid(). Signed-off-by: Baolin Wang Reviewed-by: David Hildenbrand Reviewed-by: "Huang, Ying" Acked-by: Michal Hocko --- Changes from v2: - Update the commit message per Michal. Thanks. - Add acked tag from Michal. Changes from v1: - Collect reviewed tags. Thanks David and Ying. --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9de2a18519a1..6457b64fe562 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, /* end_pfn is one past the range we are checking */ end_pfn--; - if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) + if (!pfn_valid(end_pfn)) return NULL; start_page = pfn_to_online_page(start_pfn); From patchwork Mon Apr 24 13:45:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baolin Wang X-Patchwork-Id: 87041 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2761878vqo; Mon, 24 Apr 2023 06:55:51 -0700 (PDT) X-Google-Smtp-Source: AKy350Y0PGRy7Sr398jOn2xWqyo0dEsPu9g2O9M3BAoXuTBHwrisP9S14fhDenZYatIyw9zxhMvZ X-Received: by 2002:a05:6a21:339a:b0:f2:5a2:c058 with SMTP id yy26-20020a056a21339a00b000f205a2c058mr16677451pzb.61.1682344551200; Mon, 24 Apr 2023 06:55:51 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1682344551; cv=none; d=google.com; s=arc-20160816; b=t2yxql1hjZyY8DGKKYQWHULkqwHZloXBqIljeaK6QuPxKXPTxM42v75NNJrS9xrsaB fodDMc26nB1Q1oqjcbozBQefgmIpJKWu2rZRz5vAQpvbyT46xC1mX1OgMPtQKOzDBqJ4 WPVDHEC8JsVdSb3Ndf2x7sU7ICx2hmpWyMg9ffoeJRZO834Kmi4N0V8qjb8Q6F58qUUL TQOEAVSVCKQrxP6tjODIUcxANxE2TkwAaIJqeauz8pjIaZh4McnjTYKWM0rnfTkq++Hd nE0iQgJN3VzMVIZsENDly7E37PvuDeiMvsXQkB4IC6+mIB4EnU4qlCc6y0f1F6FFxwuN RyeA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=UBWDO8RCzgEr8K6oHfsOpzVH+9c5LYLiXMC+yOgcIZY=; b=Ix/ONVGM6CqTPZtv0xad+M8R+ncGP1oYizyvPuoM4piAEdRZPXvQTIYNEgNXRFml5+ ix8iCiiFZc8YXDfs5j7MUH8CLP5yH5IP8Ccov4BSQrFCqv7PypRlQrNcPaxUlzFiMdMN DaZJBnW/7yqlAgjxIJyhQQP51h9Y0DXYoGV7lb1naSWmTcwcX9BHP93QCylqM8Ayf8wZ udgBT7faKPlYAXgFVXD13japw+KVGnXcNrd3+m2vCqe7Hx5zY1aGDG/5IX3YvTvyroI9 PLkLbxhDsBkJOhGXFJcKykhGcsPXjpZt906y/kxtPomGC+okYbmywl6LbgL09KilkW+i ZRfg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id u11-20020a63470b000000b004ff6f80f6c5si11113640pga.410.2023.04.24.06.55.37; Mon, 24 Apr 2023 06:55:51 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231826AbjDXNqM (ORCPT + 99 others); Mon, 24 Apr 2023 09:46:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52388 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231889AbjDXNqH (ORCPT ); Mon, 24 Apr 2023 09:46:07 -0400 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6692C7DA9 for ; Mon, 24 Apr 2023 06:45:54 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0Vgw4CIR_1682343949; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Vgw4CIR_1682343949) by smtp.aliyun-inc.com; Mon, 24 Apr 2023 21:45:50 +0800 From: Baolin Wang To: akpm@linux-foundation.org Cc: rppt@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, vbabka@suse.cz, mhocko@suse.com, david@redhat.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/2] mm/page_alloc: add some comments to explain the possible hole in __pageblock_pfn_to_page() Date: Mon, 24 Apr 2023 21:45:40 +0800 Message-Id: <50b5e05dbb007e3a969ac946bc9ee0b2b77b185f.1682342634.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY, USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1764066120246552453?= X-GMAIL-MSGID: =?utf-8?q?1764066120246552453?= Now the __pageblock_pfn_to_page() is used by set_zone_contiguous(), which checks whether the given zone contains holes, and uses pfn_to_online_page() to validate if the start pfn is online and valid, as well as using pfn_valid() to validate the end pfn. However, the __pageblock_pfn_to_page() function may return non-NULL even if the end pfn of a pageblock is in a memory hole in some situations. For example, if the pageblock order is MAX_ORDER, which will fall into 2 sub-sections, and the end pfn of the pageblock may be hole even though the start pfn is online and valid. See below memory layout as an example and suppose the pageblock order is MAX_ORDER. [ 0.000000] Zone ranges: [ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff] [ 0.000000] DMA32 empty [ 0.000000] Normal [mem 0x0000000100000000-0x0000001fa7ffffff] [ 0.000000] Movable zone start for each node [ 0.000000] Early memory node ranges [ 0.000000] node 0: [mem 0x0000000040000000-0x0000001fa3c7ffff] [ 0.000000] node 0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff] [ 0.000000] node 0: [mem 0x0000001fa4000000-0x0000001fa402ffff] [ 0.000000] node 0: [mem 0x0000001fa4030000-0x0000001fa40effff] [ 0.000000] node 0: [mem 0x0000001fa40f0000-0x0000001fa73cffff] [ 0.000000] node 0: [mem 0x0000001fa73d0000-0x0000001fa745ffff] [ 0.000000] node 0: [mem 0x0000001fa7460000-0x0000001fa746ffff] [ 0.000000] node 0: [mem 0x0000001fa7470000-0x0000001fa758ffff] [ 0.000000] node 0: [mem 0x0000001fa7590000-0x0000001fa7dfffff] Focus on the last memory range, and there is a hole for the range [mem 0x0000001fa7590000-0x0000001fa7dfffff]. That means the last pageblock will contain the range from 0x1fa7c00000 to 0x1fa7ffffff, since the pageblock must be 4M aligned. And in this pageblock, these pfns will fall into 2 sub-section (the sub-section size is 2M aligned). So, the 1st sub-section (indicates pfn range: 0x1fa7c00000 - 0x1fa7dfffff ) in this pageblock is valid by calling subsection_map_init() in free_area_init(), but the 2nd sub-section (indicates pfn range: 0x1fa7e00000 - 0x1fa7ffffff ) in this pageblock is not valid. This did not break anything until now, but the zone continuous is fragile in this possible scenario. So as previous discussion[1], it is better to add some comments to explain this possible issue in case there are some future pfn walkers that rely on this. [1] https://lore.kernel.org/all/87r0sdsmr6.fsf@yhuang6-desk2.ccr.corp.intel.com/ Signed-off-by: Baolin Wang Acked-by: Michal Hocko --- Changes from v2: - Update the commit log and comments per Michal, thanks. Changes from v1: - Update the comments per Ying and Mike, thanks. Note, I did not add Huang Ying's reviewed tag, since there are some updates per Michal's suggestion. Ying, please review the v3. Thanks. --- mm/page_alloc.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6457b64fe562..bd124390c79b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1502,6 +1502,15 @@ void __free_pages_core(struct page *page, unsigned int order) * interleaving within a single pageblock. It is therefore sufficient to check * the first and last page of a pageblock and avoid checking each individual * page in a pageblock. + * + * Note: the function may return non-NULL struct page even for a page block + * which contains a memory hole (i.e. there is no physical memory for a subset + * of the pfn range). For example, if the pageblock order is MAX_ORDER, which + * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole + * even though the start pfn is online and valid. This should be safe most of + * the time because struct pages are still zero pre-filled and pfn walkers + * shouldn't touch any physical memory range for which they do not recognize + * any specific metadata in struct pages. */ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, unsigned long end_pfn, struct zone *zone)