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=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 65567C2BA1B for ; Tue, 7 Apr 2020 08:09:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38E34206F7 for ; Tue, 7 Apr 2020 08:09:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727868AbgDGIJc (ORCPT ); Tue, 7 Apr 2020 04:09:32 -0400 Received: from relay10.mail.gandi.net ([217.70.178.230]:35125 "EHLO relay10.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726030AbgDGIJc (ORCPT ); Tue, 7 Apr 2020 04:09:32 -0400 Received: from localhost (50-39-163-217.bvtn.or.frontiernet.net [50.39.163.217]) (Authenticated sender: josh@joshtriplett.org) by relay10.mail.gandi.net (Postfix) with ESMTPSA id 681C724000B; Tue, 7 Apr 2020 08:09:27 +0000 (UTC) Date: Tue, 7 Apr 2020 01:09:25 -0700 From: Josh Triplett To: "Theodore Y. Ts'o" Cc: linux-ext4@vger.kernel.org Subject: Re: Use case for EXT4_INODE_HUGE_FILE / EXT4_HUGE_FILE_FL? Message-ID: <20200407080925.GA675720@localhost> References: <20200406224534.GA668050@localhost> <20200407033031.GT45598@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407033031.GT45598@mit.edu> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Mon, Apr 06, 2020 at 11:30:31PM -0400, Theodore Y. Ts'o wrote: > On Mon, Apr 06, 2020 at 03:45:34PM -0700, Josh Triplett wrote: > > Under what circumstances can an inode ever end up with EXT4_HUGE_FILE_FL > > set? (Other than in an artificially constructed filesystem.) > > > > Was EXT4_HUGE_FILE_FL just added for future extensibility, in case a > > future file storage mechanism allows storing files bigger than 2**32 > > blocks? > > Yes. basically. When we added the huge_file feature, which introduced > the i_blocks_hi field, the thinking was to add EXT4_HUGE_FILE_FL so > that we could painlessly upgrade a file system from ext3 (w/o the huge > file feature) to enabling the feature without having to rewrite all of > the inodes. However, we also didn't want to artificially limit > ourselves to 2**57 file sizes, so we also added the EXT4_HUGE_FILE_FL > flag. Thanks for the explanation! That makes sense. > It hasn't gotten a huge amount of testing in a while, but it would be > relatively easy to add debugging code (triggered via a mount option or > a sysfs file) which forces the use of EXT4_HUGE_FILE_FL all the time. That does seem like a good idea. It would also be nice to have an e2fsck option to rewrite all inodes to use EXT4_HUGE_FILE_FL. I think I'll avoid poking that code for now, though, since I don't currently have a need for files anywhere near that large.