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=-5.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 AF610C433E2 for ; Mon, 13 Jul 2020 16:15:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F96B207D4 for ; Mon, 13 Jul 2020 16:15:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="dqAuVp/M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729782AbgGMQPe (ORCPT ); Mon, 13 Jul 2020 12:15:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729747AbgGMQPe (ORCPT ); Mon, 13 Jul 2020 12:15:34 -0400 Received: from mail-ed1-x541.google.com (mail-ed1-x541.google.com [IPv6:2a00:1450:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EB8CC061755 for ; Mon, 13 Jul 2020 09:15:34 -0700 (PDT) Received: by mail-ed1-x541.google.com with SMTP id bm28so12176920edb.2 for ; Mon, 13 Jul 2020 09:15:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=qYE0MGzN5oZiWXIC6Rq6ejY3VVjgiXoPpvYjyKeBdiI=; b=dqAuVp/Md6dltU2+wWd9YmXmJl0gjR4sK5zDAvjpTsJSVJFEJFpBOpTEFPSYpZrDap FvgwvNzH7PYXXjZj0kRjjJYnHYbr40UVkpwOFFuDRfDDDHTwKOApy25cUst736JqiSEN 1pXb/1YwmZ1btxsaqDTInRVQlHzc3Smv65CFY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=qYE0MGzN5oZiWXIC6Rq6ejY3VVjgiXoPpvYjyKeBdiI=; b=JeBLISV8n1qfUeh6aU7icvfL7EtDGP8NE0krryUbB8ZMaYdPa03N4wBCSHQwI0OjY7 E/ePhwZqcaJPtYdwd6Y9EdwWWSpeTBU+OgU/bdLunpqN2h1l9Ej0PYy1p4TFictvPlO7 nxTLrgIpaqjbnvoiLtTjxaQ0gcGSe+mEFaIjIp5BxzIyEuKNk1lJYtiMfiTgI7tM8iLr byUjR/vYEzeyBe52ehZiZq8ntzaNLEJWweb35nzqpUAZ0setE5cPSljBnt9EBHWQEYH1 dfVENViwHa8FEl1iVmYFs8hQKCOvpzDcLiin8/aVPQKamBGvSa5JU0OICI0HuQm5YkYk YePg== X-Gm-Message-State: AOAM531R1o7fonY2NUnoyekR/8T/tb+EJxjlsbcIxhjubbFWeJy8txeU E4MP4qD1WDLSrxBe6ZYXkGU43g== X-Google-Smtp-Source: ABdhPJzsRdZY8noRNZwAyszwwF9P9Y/ARLnpJW6z3ijXs5crRBCn6Voi+/JfVOJDz2petEtU+vf66w== X-Received: by 2002:a50:bf09:: with SMTP id f9mr133964edk.249.1594656932825; Mon, 13 Jul 2020 09:15:32 -0700 (PDT) Received: from localhost ([2620:10d:c093:400::5:ef88]) by smtp.gmail.com with ESMTPSA id n9sm12163985edr.46.2020.07.13.09.15.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2020 09:15:32 -0700 (PDT) Date: Mon, 13 Jul 2020 17:15:32 +0100 From: Chris Down To: Andrew Morton Cc: Hugh Dickins , Al Viro , Matthew Wilcox , Amir Goldstein , Jeff Layton , Johannes Weiner , Tejun Heo , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v6 0/2] tmpfs: inode: Reduce risk of inum overflow Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.14.5 (2020-06-23) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org In Facebook production we are seeing heavy i_ino wraparounds on tmpfs. On affected tiers, in excess of 10% of hosts show multiple files with different content and the same inode number, with some servers even having as many as 150 duplicated inode numbers with differing file content. This causes actual, tangible problems in production. For example, we have complaints from those working on remote caches that their application is reporting cache corruptions because it uses (device, inodenum) to establish the identity of a particular cache object, but because it's not unique any more, the application refuses to continue and reports cache corruption. Even worse, sometimes applications may not even detect the corruption but may continue anyway, causing phantom and hard to debug behaviour. In general, userspace applications expect that (device, inodenum) should be enough to be uniquely point to one inode, which seems fair enough. One might also need to check the generation, but in this case: 1. That's not currently exposed to userspace (ioctl(...FS_IOC_GETVERSION...) returns ENOTTY on tmpfs); 2. Even with generation, there shouldn't be two live inodes with the same inode number on one device. In order to mitigate this, we take a two-pronged approach: 1. Moving inum generation from being global to per-sb for tmpfs. This itself allows some reduction in i_ino churn. This works on both 64- and 32- bit machines. 2. Adding inode{64,32} for tmpfs. This fix is supported on machines with 64-bit ino_t only: we allow users to mount tmpfs with a new inode64 option that uses the full width of ino_t, or CONFIG_TMPFS_INODE64. You can see how this compares to previous related patches which didn't implement this per-superblock: - https://patchwork.kernel.org/patch/11254001/ - https://patchwork.kernel.org/patch/11023915/ Changes since v5 (it's been a while, eh?): - Implement percpu batching for SB_KERNMOUNT at Hugh's suggestion. - Hugh also pointed out that user-exposed tmpfs can also now have max_inodes == 0, so we have to account for that. I just use SB_KERNMOUNT to do that in all the places we used to look at max_inodes. Chris Down (2): tmpfs: Per-superblock i_ino support tmpfs: Support 64-bit inums per-sb Documentation/filesystems/tmpfs.rst | 11 +++ fs/Kconfig | 15 ++++ include/linux/fs.h | 15 ++++ include/linux/shmem_fs.h | 3 + mm/shmem.c | 127 ++++++++++++++++++++++++++-- 5 files changed, 166 insertions(+), 5 deletions(-) -- 2.27.0