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=-5.8 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 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 B194BC433EF for ; Tue, 14 Sep 2021 17:49:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9106C60E8B for ; Tue, 14 Sep 2021 17:49:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229785AbhINRux (ORCPT ); Tue, 14 Sep 2021 13:50:53 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:44351 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229526AbhINRux (ORCPT ); Tue, 14 Sep 2021 13:50:53 -0400 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 34B4F5C01C4; Tue, 14 Sep 2021 13:49:35 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute3.internal (MEProxy); Tue, 14 Sep 2021 13:49:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bur.io; h=date :from:to:cc:subject:message-id:references:mime-version :content-type:in-reply-to; s=fm1; bh=rPjVKCsD7wTfn7nrkasUNdxNuqH L56Jg5drfN/Ntaos=; b=JXfv2d/TmGy2UhWZ6w5NsFIpZqQBl+po2U5JX3jdzUC 2uM91J+1qXXt9jl8oZkWPf9LjjEngNwka4u7oFnj5wjqTtxBVuSZyNf1mk3QIaT/ oidzhAZ38GGHi550jiFJpkmfIkLp+qo7wBc00jJABe63uH0PEm2t3L+rhkyIBycr TKuZDnJNyjniZyHVV9DWmRcn7cpkf/lh3oOVMTbEm1MyJkguclP4vO+gmM0aMbzN +um36YP6kHIMuMbk6cQTLe6xEkjpQxtOB3LqC1ZtMvBgK9bIh0S2FkpAZLNeyve0 I898mzeU/btusZfPbf0p08qOqmk54voS63nyIQCBMXA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=rPjVKC sD7wTfn7nrkasUNdxNuqHL56Jg5drfN/Ntaos=; b=jgAfg+0gC3vW6Gx7a0iZqF 8wOt7nAEW4+Rhpe/3hvrIANBL2/WzQvU9KSGiD/6wsIpdXeIZcl0hDA33c/YFULO Kb9BVcGMgjVLI3lVG4IZxkHClwdS5fmpnM5hDphPPdNCiqYVFDDwMwI2P8asHotp pQ/hRG+zX9GdbMn4zRj9Hj1C4Yl2WCt4cH/JUZNz5zExEmNr+jI6AMNEBmOxZymr RbbNLYL0LOSozXED2IZdqhX0/TUmHosoALjnDYRCNJqwsgIt/I/TdNpnhXTHUuvi KnfgRt+GdUVPpJg1nNTaSFMVcLvXkP+2QiOtmJxvfXquACH/CipS/bIn9rSlAH4A == X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrudegledguddugecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpeffhffvuffkfhggtggujgesthdtredttddtvdenucfhrhhomhepuehorhhi shcuuehurhhkohhvuceosghorhhishessghurhdrihhoqeenucggtffrrghtthgvrhhnpe ehudevleekieetleevieeuhfduhedtiefgheekfeefgeelvdeuveeggfduueevfeenucev lhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpegsohhrihhsse gsuhhrrdhioh X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 14 Sep 2021 13:49:34 -0400 (EDT) Date: Tue, 14 Sep 2021 10:49:33 -0700 From: Boris Burkov To: Eric Biggers Cc: linux-btrfs@vger.kernel.org, linux-fscrypt@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v6 2/3] btrfs: initial fsverity support Message-ID: References: <797d6524e4e6386fc343cd5d0bcdd53878a6593e.1625083099.git.boris@bur.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org On Tue, Sep 14, 2021 at 10:32:59AM -0700, Eric Biggers wrote: > Hi Boris, > > On Wed, Jun 30, 2021 at 01:01:49PM -0700, Boris Burkov wrote: > > Add support for fsverity in btrfs. To support the generic interface in > > fs/verity, we add two new item types in the fs tree for inodes with > > verity enabled. One stores the per-file verity descriptor and btrfs > > verity item and the other stores the Merkle tree data itself. > > > > Verity checking is done in end_page_read just before a page is marked > > uptodate. This naturally handles a variety of edge cases like holes, > > preallocated extents, and inline extents. Some care needs to be taken to > > not try to verity pages past the end of the file, which are accessed by > > the generic buffered file reading code under some circumstances like > > reading to the end of the last page and trying to read again. Direct IO > > on a verity file falls back to buffered reads. > > > > Verity relies on PageChecked for the Merkle tree data itself to avoid > > re-walking up shared paths in the tree. For this reason, we need to > > cache the Merkle tree data. Since the file is immutable after verity is > > turned on, we can cache it at an index past EOF. > > > > Use the new inode ro_flags to store verity on the inode item, so that we > > can enable verity on a file, then rollback to an older kernel and still > > mount the file system and read the file. Since we can't safely write the > > file anymore without ruining the invariants of the Merkle tree, we mark > > a ro_compat flag on the file system when a file has verity enabled. > > I want to mention the btrfs verity support in > Documentation/filesystems/fsverity.rst, and I have a couple questions: > > 1. Is the ro_compat filesystem flag still a thing? The commit message claims it > is, and BTRFS_FEATURE_COMPAT_RO_VERITY is defined in the code, but it doesn't > seem to actually be used. It's not needed since you found a way to make the > inode flags ro_compat instead, right? I believe it is still being used, unless I messed up the patch I sent in the end. Taking a quick look, I think it's set at fs/btrfs/verity.c:558. btrfs_set_fs_compat_ro(root->fs_info, VERITY); I believe I still needed it because the tree checker doesn't scan every inode on the filesystem when you mount, so it would only freak out about a ro-compat inode later on if the inode didn't happen to be in a leaf that was being checked at mount time. > > 2. Is there a minimum version of btrfs-progs that is required to use btrfs > verity? With ext4 and f2fs, the fsck tools had to be updated, so there were > minimum versions of the userspace tools required. Hmm. I didn't update fsck, but now that you mention it, I think I need to... I'll test it right away and get back to you, but I suspect I need to hurry up and implement it. Boris > > Thanks, > > - Eric