From patchwork Thu Jan 21 23:03:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Satya Tangirala X-Patchwork-Id: 12037991 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 4B0AFC43381 for ; Thu, 21 Jan 2021 23:25:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEDC420769 for ; Thu, 21 Jan 2021 23:25:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726212AbhAUXZI (ORCPT ); Thu, 21 Jan 2021 18:25:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726230AbhAUXGb (ORCPT ); Thu, 21 Jan 2021 18:06:31 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 304DBC061A27 for ; Thu, 21 Jan 2021 15:03:55 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id f127so981519ybf.12 for ; Thu, 21 Jan 2021 15:03:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=CZMyGWlKFZQTRektdrF/slvssAIzMQGtBohXi2xlJZo=; b=rrCQEqKVW1ZDhW4+xC0fjbzkbeY/JM71fiwBKXHsmFH4bwE2GxtDFk+U88/SUhdZrf m7wzzh7s3pqKnNjd10foCZJDNdK/vkuuRpPD69ujIVZe3eifyns8biUA8hZoFwPNKnDb Ba3v3G79vllZnXC34ggan7U2sUksnH545H+f+6bih9NuBbW12SjTSwsWplttdtVyg536 GP0pN9LaqdE82PHlByUSvgve2pSMZuoQ6XfZu6yXARBBw+19h3asuK13j5tmK1ncQkcY r6k+aHDCwUHG8X/Lo9Rh9plI3yOEJxIzYYGPgdsvlhvIGQPysaEunA99fEdDpORoP0Ww T1lg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=CZMyGWlKFZQTRektdrF/slvssAIzMQGtBohXi2xlJZo=; b=rI9PV0QQ9eHHcDmiS1c50hKBOGKbE7/hNBvYefiw7Zo+txc720PvUygNdyYlUSnpcj 9uRaGYAnq7tmGwN2HK1tmabMs/5FE4hMEG5BDkXhoNrqkCWhwpaZZ/oXWhR/YMxCnLBL H6Cfi0SADT2ZOW7Nzk3G9hESx2TEiIIdphDG2+ghkb7RdXPO5zGvkhqVwEVfYSceAORT BAwIzJHxhrk7R0ipwh/0QxqlWQ8cHqSZUcnTOMMzlgMqzq7fmXujTn3bJtJZh0XI3i/1 GhtBf+d/fvrGDkpfwLCBSdBtmRSZ3lUV3rdvWXh2RhraOBDfWpuWBElU1pPoEOzYYDSz KAQQ== X-Gm-Message-State: AOAM532c4uzu0FviLAmwneJYRBPqGh5goKNJu6NJPu5Zac7JR8gd8EVn YasbbOiKjwOmf5ZWtitYrqGH2VY7ge4= X-Google-Smtp-Source: ABdhPJwB0G5OeVzx657WHRwvKU6JZee+AtLxAL7APPuuacdYF8k9c5jXPavHspxiawBp2gvtwJK1mN7H78c= Sender: "satyat via sendgmr" X-Received: from satyaprateek.c.googlers.com ([fda3:e722:ac3:10:24:72f4:c0a8:1092]) (user=satyat job=sendgmr) by 2002:a25:61c2:: with SMTP id v185mr2563181ybb.378.1611270234438; Thu, 21 Jan 2021 15:03:54 -0800 (PST) Date: Thu, 21 Jan 2021 23:03:36 +0000 In-Reply-To: <20210121230336.1373726-1-satyat@google.com> Message-Id: <20210121230336.1373726-9-satyat@google.com> Mime-Version: 1.0 References: <20210121230336.1373726-1-satyat@google.com> X-Mailer: git-send-email 2.30.0.280.ga3ce27912f-goog Subject: [PATCH v8 8/8] fscrypt: update documentation for direct I/O support From: Satya Tangirala To: "Theodore Y . Ts'o" , Jaegeuk Kim , Eric Biggers , Chao Yu , Jens Axboe , "Darrick J . Wong" Cc: linux-kernel@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-block@vger.kernel.org, linux-ext4@vger.kernel.org, Satya Tangirala , Eric Biggers Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Update fscrypt documentation to reflect the addition of direct I/O support and document the necessary conditions for direct I/O on encrypted files. Signed-off-by: Satya Tangirala Reviewed-by: Eric Biggers Reviewed-by: Jaegeuk Kim --- Documentation/filesystems/fscrypt.rst | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 44b67ebd6e40..c0c1747fa2fb 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -1047,8 +1047,10 @@ astute users may notice some differences in behavior: may be used to overwrite the source files but isn't guaranteed to be effective on all filesystems and storage devices. -- Direct I/O is not supported on encrypted files. Attempts to use - direct I/O on such files will fall back to buffered I/O. +- Direct I/O is supported on encrypted files only under some + circumstances (see `Direct I/O support`_ for details). When these + circumstances are not met, attempts to use direct I/O on encrypted + files will fall back to buffered I/O. - The fallocate operations FALLOC_FL_COLLAPSE_RANGE and FALLOC_FL_INSERT_RANGE are not supported on encrypted files and will @@ -1121,6 +1123,21 @@ It is not currently possible to backup and restore encrypted files without the encryption key. This would require special APIs which have not yet been implemented. +Direct I/O support +================== + +Direct I/O on encrypted files is supported through blk-crypto. In +particular, this means the kernel must have CONFIG_BLK_INLINE_ENCRYPTION +enabled, the filesystem must have had the 'inlinecrypt' mount option +specified, and either hardware inline encryption must be present, or +CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK must have been enabled. Further, +the starting position in the file and the length of any I/O must be aligned +to the filesystem block size (*not* necessarily the same as the block +device's block size). If any of these conditions isn't met, attempts to do +direct I/O on an encrypted file will fall back to buffered I/O. However, +there aren't any additional requirements on user buffer alignment (apart +from those already present when using direct I/O on unencrypted files). + Encryption policy enforcement =============================