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=-2.2 required=3.0 tests=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 93A98CA9EB3 for ; Fri, 18 Oct 2019 01:57:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C3AD21D7D for ; Fri, 18 Oct 2019 01:57:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2409526AbfJRB5A (ORCPT ); Thu, 17 Oct 2019 21:57:00 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:44860 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2409223AbfJRB47 (ORCPT ); Thu, 17 Oct 2019 21:56:59 -0400 Received: from callcc.thunk.org (pool-72-93-95-157.bstnma.fios.verizon.net [72.93.95.157]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x9I1utmt016701 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Oct 2019 21:56:56 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 58DD0420458; Thu, 17 Oct 2019 21:56:55 -0400 (EDT) Date: Thu, 17 Oct 2019 21:56:55 -0400 From: "Theodore Y. Ts'o" To: Harshad Shirwadkar Cc: linux-ext4@vger.kernel.org Subject: Re: [PATCH v3 12/13] docs: Add fast commit documentation Message-ID: <20191018015655.GB21137@mit.edu> References: <20191001074101.256523-1-harshadshirwadkar@gmail.com> <20191001074101.256523-13-harshadshirwadkar@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191001074101.256523-13-harshadshirwadkar@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Tue, Oct 01, 2019 at 12:41:01AM -0700, Harshad Shirwadkar wrote: > + > +Multiple fast commit blocks are a part of one sub-transaction. To > +indicate the last block in a fast commit transaction, fc_flags field > +in the last block in every subtransaction is marked with "LAST" (0x1) > +flag. A subtransaction is valid only if all the following conditions > +are met: > + > +1) SUBTID of all blocks is either equal to or greater than SUBTID of > + the previous fast commit block. > +2) For every sub-transaction, last block is marked with LAST flag. > +3) There are no invalid blocks in between. I'm wondering why we need to support multiple inodes being modified in a single transaction. As we currently have defined what can be done, all updates to an inode should be free standing and not dependent on a change to another inode, right? And today, one block only modifies one inode. The only reason why we might want to define a sub-transaction as being composed of multiple inodes, which must all be updated in an all-or-nothing fashion, is the swap boot inode ioctl, and if that's the only one, I wonder if it's worth the extra complexity. Am I missing anything? - Ted