From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailhost.fernuni-hagen.de ([132.176.114.94]:62206 "EHLO mailhost.FernUni-Hagen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756498Ab2GYKy0 (ORCPT ); Wed, 25 Jul 2012 06:54:26 -0400 Received: from mailstore.fernuni-hagen.de ([132.176.114.185]) by mailhost.FernUni-Hagen.de with esmtp (Exim 4.69) (envelope-from ) id 1Stz1o-0000cV-JV for linux-btrfs@vger.kernel.org; Wed, 25 Jul 2012 12:41:16 +0200 Received: from [85.158.138.21] (account q6753817@mailstore.fernuni-hagen.de) by mailstore.fernuni-hagen.de (CommuniGate Pro WebUser 5.0.2) with HTTP id 48902846 for linux-btrfs@vger.kernel.org; Wed, 25 Jul 2012 12:41:15 +0200 From: "Guenther Rasch" Subject: Question about btrfs metadata structure To: linux-btrfs@vger.kernel.org Date: Wed, 25 Jul 2012 12:41:15 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi! I'm writing my bsc thesis about btrfs and I'm analyzing the btrfs metadata structure at the moment. I'm using fedora 17 with kernel 3.4 and btrfs-prog from your git-repository. For an overview I use "btrfs-debug-tree" and here are my questions: The root tree contains some inode_items, but I don't understand the meaning of them: item 4 key (ROOT_TREE_DIR INODE_ITEM 0) itemoff 3101 itemsize 160 inode generation 3 size 0 block group 0 mode 40555 links 1 item 5 key (ROOT_TREE_DIR INODE_REF 6) itemoff 3089 itemsize 12 inode ref index 0 namelen 2 name: .. The key for an inode_item is objectid=ROOT_TREE_DIR. ROOT-TREE-DIR is the inode-Nr.? What does offset=6 regarding INODE_REF mean? --> item 5 Also placed in the root tree, I've found entries of (FREE_SPACE UNTYPED ....) What does UNTYPED mean in this context and the offset is the logical address of a block group (I guess...)? This item has a pointer to an inode_item, is that right? And last question about this entries: item 2 key (FS_TREE INODE_REF 6) itemoff 3500 itemsize 17 inode ref index 0 namelen 7 name: default ... item 6 key (ROOT_TREE_DIR DIR_ITEM 2378154706) itemoff 3052 itemsize 37 location key (FS_TREE ROOT_ITEM 18446744073709551615) type 2 namelen 7 datalen 0 name: default There is an INODE_REF (again, offset 6...?) pointing to which inode? I cannot find some... What's about that offset in location key (FS_TREE....) Thx in advance for your patience and answers! Regards Guenther