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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 E643AC33C8C for ; Sun, 5 Jan 2020 12:00:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6DAA20866 for ; Sun, 5 Jan 2020 12:00:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="L5GcoTDq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726351AbgAEMA2 (ORCPT ); Sun, 5 Jan 2020 07:00:28 -0500 Received: from mail-wm1-f66.google.com ([209.85.128.66]:54662 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725985AbgAEMA2 (ORCPT ); Sun, 5 Jan 2020 07:00:28 -0500 Received: by mail-wm1-f66.google.com with SMTP id b19so12181760wmj.4 for ; Sun, 05 Jan 2020 04:00:26 -0800 (PST) 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; bh=H1hJLNQee379aq3/tU9tTxHeBbBKoIXcCyb5gddw+z0=; b=L5GcoTDqP85Ra89Ye59ARpTSzZ7gnWy21JPPPuYzKAmIAQ4wHEeSQbNDVck2PAtAY7 EmzVCQNNqNWBnCiZZc003gcKlJqV2ioKUakubuUccupOE9u8OG6XsA2Eo3r4hLLTp+So fP5BB0Vsc2VyZmTHpwRU+DrJI+J2yBuxSmqsY= 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; bh=H1hJLNQee379aq3/tU9tTxHeBbBKoIXcCyb5gddw+z0=; b=a/CWidO/D2FNdlUFybbBMGGmyp1olsUOg5YcpuToNMVKgpBOrwltdFB0fx5z6eY5TK tCbyBf9/W9VyLQ8J+wg/HUUiOgNZ4Y/u+aZOLEN//F3xXhHv4IuJw83OGOdjb2tTZS9i aBiPALVUFoKmjN4VVXXqZZxHOGgAI02Hp9QQtJoXqZTz6cepxmvwDzHg63fU13heukjs xoTxY3TR0HfH/gg50XK8SRAtu0t67ooF7GWv5cMPPco6ZKaws7hpwI5viV7tv4EviVBE G8QAoNGmVLGEUe/trVXU3CPzK2Fxke7URolDcZ7hoIgkbgZW+lCaRGhIyq32wahbeGVZ qlyA== X-Gm-Message-State: APjAAAU2VWnS+A9lqPBtizeh4shd776m0B6GDT3f6aBzhVsEWEX0/uup SYbN6qJ5Ch/j3b6dgrkUaSaqpg== X-Google-Smtp-Source: APXvYqw/XcK394/KTqhYIMffQmGHz8RF+wDGNHUwQorEma1YeLD6ubCO1gZEETPUwZ/OyDMO01qA1A== X-Received: by 2002:a1c:67c3:: with SMTP id b186mr28504788wmc.36.1578225626039; Sun, 05 Jan 2020 04:00:26 -0800 (PST) Received: from localhost ([2620:10d:c092:180::1:e1d7]) by smtp.gmail.com with ESMTPSA id a133sm19068415wme.29.2020.01.05.04.00.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Jan 2020 04:00:25 -0800 (PST) Date: Sun, 5 Jan 2020 12:00:24 +0000 From: Chris Down To: linux-mm@vger.kernel.org Cc: Hugh Dickins , Andrew Morton , Al Viro , Matthew Wilcox , Amir Goldstein , Jeff Layton , Johannes Weiner , Tejun Heo , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v4 0/2] fs: inode: shmem: Reduce risk of inum overflow Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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/ Chris Down (2): tmpfs: Add per-superblock i_ino support tmpfs: Support 64-bit inums per-sb Documentation/filesystems/tmpfs.txt | 11 ++++ fs/Kconfig | 15 +++++ include/linux/shmem_fs.h | 2 + mm/shmem.c | 94 ++++++++++++++++++++++++++++- 4 files changed, 121 insertions(+), 1 deletion(-) -- 2.24.1