From patchwork Sat Jun 25 09:33:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12895289 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A5CBC43334 for ; Sat, 25 Jun 2022 09:33:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D2FE88E029F; Sat, 25 Jun 2022 05:33:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CDF548E029A; Sat, 25 Jun 2022 05:33:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA75F8E029F; Sat, 25 Jun 2022 05:33:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 9FBB38E029A for ; Sat, 25 Jun 2022 05:33:51 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 80620204ED for ; Sat, 25 Jun 2022 09:33:51 +0000 (UTC) X-FDA: 79616246262.21.C94D466 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf26.hostedemail.com (Postfix) with ESMTP id DA7DD140008 for ; Sat, 25 Jun 2022 09:33:50 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LVTKF74c2zkWNs; Sat, 25 Jun 2022 17:32:01 +0800 (CST) Received: from huawei.com (10.175.124.27) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 25 Jun 2022 17:33:47 +0800 From: Miaohe Lin To: CC: , , , , , , Subject: [PATCH v3 1/2] mm/swapfile: fix possible data races of inuse_pages Date: Sat, 25 Jun 2022 17:33:45 +0800 Message-ID: <20220625093346.48894-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220625093346.48894-1-linmiaohe@huawei.com> References: <20220625093346.48894-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656149631; a=rsa-sha256; cv=none; b=dQBxNeZRWhn1WmMlQVIPSXjwnhJzUHGxUL4FOcOkCrxm4tvb7Gjf/FsuZWqJU+kveWRqzR WVpMVoOqPKqjoDE/RA8gwhNobtta1+DdoeVcH2NNi4742LBkzbsLjfXzk8q/QokbC16/sE mmSs1Q4t/PjoPrBrScUEkaMKl6zNKLU= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656149631; h=from:from:sender: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; bh=nGCa1ZyLJ/feN/RjQYHImnPH8HDpUtyYn5x7/JfCBhk=; b=edrvlzBjZC1KBUxc5ajpK2+48YLMSQ9kvOvATc1fUdfWUVoyQvFumIMlOXPHJpfQh0EEgz 4IctLtzinNm4iOLooU9oWMtMX+pT2krKjzFxZCD0MzoiAHMSfwP7PjQxtLY3FOcHp1eMHM ztSO2PCjgnRsyg3Ky8gDgOKQQhFrY/I= X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: DA7DD140008 Authentication-Results: imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Stat-Signature: zxxrdeyznwwnzaxgdc5brjih38y1nimj X-HE-Tag: 1656149630-857406 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: si->inuse_pages could still be accessed concurrently now. The plain reads outside si->lock critical section, i.e. swap_show and si_swapinfo, which results in data races. READ_ONCE and WRITE_ONCE is used to fix such data races. Note these data races should be ok because they're just used for showing swap info. Signed-off-by: Miaohe Lin Reviewed-by: David Hildenbrand Reviewed-by: "Huang, Ying" --- mm/swapfile.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index edc3420d30e7..5c8681a3f1d9 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -695,7 +695,7 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, si->lowest_bit += nr_entries; if (end == si->highest_bit) WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries); - si->inuse_pages += nr_entries; + WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries); if (si->inuse_pages == si->pages) { si->lowest_bit = si->max; si->highest_bit = 0; @@ -732,7 +732,7 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset, add_to_avail_list(si); } atomic_long_add(nr_entries, &nr_swap_pages); - si->inuse_pages -= nr_entries; + WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); if (si->flags & SWP_BLKDEV) swap_slot_free_notify = si->bdev->bd_disk->fops->swap_slot_free_notify; @@ -2641,7 +2641,7 @@ static int swap_show(struct seq_file *swap, void *v) } bytes = si->pages << (PAGE_SHIFT - 10); - inuse = si->inuse_pages << (PAGE_SHIFT - 10); + inuse = READ_ONCE(si->inuse_pages) << (PAGE_SHIFT - 10); file = si->swap_file; len = seq_file_path(swap, file, " \t\n\\"); @@ -3260,7 +3260,7 @@ void si_swapinfo(struct sysinfo *val) struct swap_info_struct *si = swap_info[type]; if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) - nr_to_be_unused += si->inuse_pages; + nr_to_be_unused += READ_ONCE(si->inuse_pages); } val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused; val->totalswap = total_swap_pages + nr_to_be_unused;