From: Felipe Monteiro de Carvalho Subject: Which features should I implement in my ext4 reader? Date: Mon, 12 Aug 2013 17:38:03 +0200 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: linux-ext4@vger.kernel.org Return-path: Received: from mail-pd0-f175.google.com ([209.85.192.175]:51378 "EHLO mail-pd0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756374Ab3HLPiE (ORCPT ); Mon, 12 Aug 2013 11:38:04 -0400 Received: by mail-pd0-f175.google.com with SMTP id q10so3564019pdj.6 for ; Mon, 12 Aug 2013 08:38:03 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: Hello, Thanks to the help here I have essentially finished my ext4 reader =) At least it can read ext4 filesystems with these features, which is what I found when using Ubuntu and Mageia LInux: EXT4_FEATURE_INCOMPAT_JOURNAL_DEV = $0008; // Journal device */ EXT4_FEATURE_INCOMPAT_META_BG = $0010; EXT4_FEATURE_INCOMPAT_EXTENTS = $0040; // extents support */ EXT4_FEATURE_INCOMPAT_FLEX_BG = $0200; EXT4_FEATURE_INCOMPAT_64BIT = $0080; Some features seam to not require any extra care for my reader: EXT4_FEATURE_INCOMPAT_COMPRESSION = $0001; EXT4_FEATURE_INCOMPAT_FILETYPE = $0002; EXT4_FEATURE_INCOMPAT_RECOVER = $0004; // Needs recovery */ EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM= $2000; // use crc32c for bg */ But I now wonder about these features: EXT4_FEATURE_INCOMPAT_MMP = $0100; EXT4_FEATURE_INCOMPAT_EA_INODE = $0400; // EA in inode */ EXT4_FEATURE_INCOMPAT_DIRDATA = $1000; // data in dirent */ EXT4_FEATURE_INCOMPAT_LARGEDIR = $4000; // >2GB or 3-lvl htree */ EXT4_FEATURE_INCOMPAT_INLINEDATA = $8000; // data in inode */ Could anyone comment how common is the use of those features and if they are already stable and in production usage (I read that they were under development in 2011)? And also which ones require an active work for a reader application to implement. As I already found out that FLEX_BG does not require active work to be supported despite being in the INCOMPAT list... >From the description I'm pretty sure that at least DIRDATA and INLINEDATA would require adjustments in my software. But I wonder if they are already being used and stable, etc, and if it is a good idea to work on supporting them. thanks, =) -- Felipe Monteiro de Carvalho