From patchwork Tue Nov 17 14:07:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Satya Tangirala X-Patchwork-Id: 1401567 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20161025 header.b=CRCbMwpu; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4Cb77q2YsGz9sWg for ; Wed, 18 Nov 2020 01:08:07 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387947AbgKQOHq (ORCPT ); Tue, 17 Nov 2020 09:07:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387935AbgKQOHl (ORCPT ); Tue, 17 Nov 2020 09:07:41 -0500 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25EB6C061A48 for ; Tue, 17 Nov 2020 06:07:42 -0800 (PST) Received: by mail-qv1-xf4a.google.com with SMTP id bn4so13093462qvb.9 for ; Tue, 17 Nov 2020 06:07:42 -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=yJkkPo7d0J6NtmBv7rzIbrBkhqskC5NsYDTAoyAGSwU=; b=CRCbMwpu14Qny/Fey+w65l3KTXcgMu/wKgUqWyt7la+sSuhY3Qh3bSLfvbmNmy2ohN d6CLetvPjrxg9HdcLQrwcUJI/t7E3dhAItIG3xDBSGqno0iPXS+Up8TqksLE2sx9De7b RnDWU7ZU+TwovEWzFLtOxWOaWhir5AxQO2FAkbTw00c9UXWqh58duX34o1osKQfPEqVH kKqjD9fQyxlm+X97TMmYjnC8FTr0DpcoshYQpZMqrkZkd8QOZGD/NcSiuteoNG9hyOLX 0VnfOnPnKTkbYUbPzPkiA75vd3hEs8SLeW/KWNERv36yx+7UQx03bI8wWQFRjgua6eps yiDg== 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=yJkkPo7d0J6NtmBv7rzIbrBkhqskC5NsYDTAoyAGSwU=; b=OOFwv4+811ydVIU2Xh4J4E19eRFpcR/snbVpyv2yuPHb2epabYNF7KPcc/LU8voRxZ TJZXqf6iJ6naod5FSczMfQxrjnKHjRjy+JlZ2wWlpFWninK21qixnvHbSvQ9uouijc9M oOXfWMkIU0DA3clkDnZ6W5vCi6LlVgo8Uu6SJXB1VWqpBjlf6+7QSmijijtyGl9GKMH+ 1S1c86k0pmObuw8Dcx1Tn7uWUvcBOfd0W8mvUl7hoAZih63YeQnXDJ5SKyNOzQMcUASb 7vUfR19OKcuUI2ezQUAgQBg9rJFnqkMj467WujEtP2eZEIU2ktgYjCOq1EfUVfGTi09G aEhw== X-Gm-Message-State: AOAM5336sosic4bY9A3CRnMrQ12eX59rk0OB9c3RO8i/4UeiS/CAA7XF 7P50dGScCIM4bbuMoXeB5QEo//3rf3g= X-Google-Smtp-Source: ABdhPJxEG4c+F9yJyuTls+kfuLbDaGW8pmeOfu1t4VEHHtaVEi94dVbJaunxNyEQ37dnM4o0k+oO8Td4NSk= 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:a05:6214:386:: with SMTP id l6mr21357187qvy.49.1605622061201; Tue, 17 Nov 2020 06:07:41 -0800 (PST) Date: Tue, 17 Nov 2020 14:07:08 +0000 In-Reply-To: <20201117140708.1068688-1-satyat@google.com> Message-Id: <20201117140708.1068688-9-satyat@google.com> Mime-Version: 1.0 References: <20201117140708.1068688-1-satyat@google.com> X-Mailer: git-send-email 2.29.2.299.gdc1121823c-goog Subject: [PATCH v7 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-ext4@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..757b8aa2af9b 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 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 =============================