From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Monteiro de Carvalho Subject: Re: Beginner questions about ext4 Date: Mon, 15 Jul 2013 19:55:50 +0200 Message-ID: References: <20130623115953.GA16193@thunk.org> <20130715134357.GA26359@thunk.org> <20130715163720.GC26359@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: linux-ext4@vger.kernel.org To: "Theodore Ts'o" Return-path: Received: from mail-pb0-f54.google.com ([209.85.160.54]:50752 "EHLO mail-pb0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752910Ab3GORzu (ORCPT ); Mon, 15 Jul 2013 13:55:50 -0400 Received: by mail-pb0-f54.google.com with SMTP id ro2so11492896pbb.13 for ; Mon, 15 Jul 2013 10:55:50 -0700 (PDT) In-Reply-To: <20130715163720.GC26359@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Hello, Sorry for my dumb questions, but please, just 1 more =D In another separate case, and a different partition being read too, I have: /usr/ directory with information: inode = 261837 superblock^.s_blocks_per_group = 32768 superblock^.s_inodes_per_group = 8128 superblock^.s_log_block_size = 2 -> so each block has 4k bytes superblock^.s_inodes_per_group = 8128 number of block groups = (superblock^.s_blocks_count + superblock^.s_blocks_per_group-1) div superblock^.s_blocks_per_group = 63 So I calculate (inodenr-1)/(inodes per group)=32 -> so the group nr for inode /usr/ is 32 So next I decide to attempt to read the group descriptor for group 32 But my table of group descriptors read from group nr 0 is all correct between group nr 0 and 31, but group nr 32 to 63 are filled with zeroes. >>From what I had understood, the group descriptor in group zero should contain all group descriptors from all groups, and subsequent occurences of the group descriptor table would be backups. Clearly it is not like that ... so I suppose that in group nr 32 I'll find a table of group descriptors for groups between 32 and 63 or something like that ... or maybe they did not fill in that block and are somewhere else in group 0 .... any ideas? full table of group descriptors read from group 0: memoDebugOut Group Descriptor Nr=0 bg_block_bitmap_lo=501 bg_inode_bitmap_lo=517 bg_inode_table_lo=533 bg_free_blocks_count_lo=21463 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=1232 bg_flags=4 Group Descriptor Nr=1 bg_block_bitmap_lo=503 bg_inode_bitmap_lo=519 bg_inode_table_lo=1549 bg_free_blocks_count_lo=47 bg_free_inodes_count_lo=23 bg_used_dirs_count_lo=633 bg_flags=4 Group Descriptor Nr=2 bg_block_bitmap_lo=505 bg_inode_bitmap_lo=521 bg_inode_table_lo=2565 bg_free_blocks_count_lo=2 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=3 bg_block_bitmap_lo=507 bg_inode_bitmap_lo=523 bg_inode_table_lo=3581 bg_free_blocks_count_lo=3410 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=4 bg_block_bitmap_lo=509 bg_inode_bitmap_lo=525 bg_inode_table_lo=4597 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=5 bg_block_bitmap_lo=511 bg_inode_bitmap_lo=527 bg_inode_table_lo=5613 bg_free_blocks_count_lo=16 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=6 bg_block_bitmap_lo=513 bg_inode_bitmap_lo=529 bg_inode_table_lo=6629 bg_free_blocks_count_lo=26803 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=7 bg_block_bitmap_lo=515 bg_inode_bitmap_lo=531 bg_inode_table_lo=7645 bg_free_blocks_count_lo=27542 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=8 bg_block_bitmap_lo=524288 bg_inode_bitmap_lo=524304 bg_inode_table_lo=524320 bg_free_blocks_count_lo=20867 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=573 bg_flags=4 Group Descriptor Nr=9 bg_block_bitmap_lo=524290 bg_inode_bitmap_lo=524306 bg_inode_table_lo=525336 bg_free_blocks_count_lo=171 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=423 bg_flags=4 Group Descriptor Nr=10 bg_block_bitmap_lo=524292 bg_inode_bitmap_lo=524308 bg_inode_table_lo=526352 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=499 bg_used_dirs_count_lo=1666 bg_flags=4 Group Descriptor Nr=11 bg_block_bitmap_lo=524294 bg_inode_bitmap_lo=524310 bg_inode_table_lo=527368 bg_free_blocks_count_lo=32243 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=12 bg_block_bitmap_lo=524296 bg_inode_bitmap_lo=524312 bg_inode_table_lo=528384 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=13 bg_block_bitmap_lo=524298 bg_inode_bitmap_lo=524314 bg_inode_table_lo=529400 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=14 bg_block_bitmap_lo=524300 bg_inode_bitmap_lo=524316 bg_inode_table_lo=530416 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=15 bg_block_bitmap_lo=524302 bg_inode_bitmap_lo=524318 bg_inode_table_lo=531432 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=16 bg_block_bitmap_lo=1048576 bg_inode_bitmap_lo=1048592 bg_inode_table_lo=1048608 bg_free_blocks_count_lo=20418 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=654 bg_flags=4 Group Descriptor Nr=17 bg_block_bitmap_lo=1048578 bg_inode_bitmap_lo=1048594 bg_inode_table_lo=1049624 bg_free_blocks_count_lo=12 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=2256 bg_flags=4 Group Descriptor Nr=18 bg_block_bitmap_lo=1048580 bg_inode_bitmap_lo=1048596 bg_inode_table_lo=1050640 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=19 bg_block_bitmap_lo=1048582 bg_inode_bitmap_lo=1048598 bg_inode_table_lo=1051656 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=20 bg_block_bitmap_lo=1048584 bg_inode_bitmap_lo=1048600 bg_inode_table_lo=1052672 bg_free_blocks_count_lo=17447 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=21 bg_block_bitmap_lo=1048586 bg_inode_bitmap_lo=1048602 bg_inode_table_lo=1053688 bg_free_blocks_count_lo=7625 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=22 bg_block_bitmap_lo=1048588 bg_inode_bitmap_lo=1048604 bg_inode_table_lo=1054704 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=23 bg_block_bitmap_lo=1048590 bg_inode_bitmap_lo=1048606 bg_inode_table_lo=1055720 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=24 bg_block_bitmap_lo=1572864 bg_inode_bitmap_lo=1572880 bg_inode_table_lo=1572896 bg_free_blocks_count_lo=20845 bg_free_inodes_count_lo=1 bg_used_dirs_count_lo=790 bg_flags=4 Group Descriptor Nr=25 bg_block_bitmap_lo=1572866 bg_inode_bitmap_lo=1572882 bg_inode_table_lo=1573912 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=188 bg_flags=4 Group Descriptor Nr=26 bg_block_bitmap_lo=1572868 bg_inode_bitmap_lo=1572884 bg_inode_table_lo=1574928 bg_free_blocks_count_lo=118 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=1314 bg_flags=4 Group Descriptor Nr=27 bg_block_bitmap_lo=1572870 bg_inode_bitmap_lo=1572886 bg_inode_table_lo=1575944 bg_free_blocks_count_lo=30412 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=28 bg_block_bitmap_lo=1572872 bg_inode_bitmap_lo=1572888 bg_inode_table_lo=1576960 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=29 bg_block_bitmap_lo=1572874 bg_inode_bitmap_lo=1572890 bg_inode_table_lo=1577976 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=30 bg_block_bitmap_lo=1572876 bg_inode_bitmap_lo=1572892 bg_inode_table_lo=1578992 bg_free_blocks_count_lo=32768 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=7 Group Descriptor Nr=31 bg_block_bitmap_lo=1572878 bg_inode_bitmap_lo=1572894 bg_inode_table_lo=1580008 bg_free_blocks_count_lo=14655 bg_free_inodes_count_lo=8128 bg_used_dirs_count_lo=0 bg_flags=5 Group Descriptor Nr=32 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=33 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=34 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=35 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=36 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=37 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=38 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=39 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=40 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=41 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=42 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=43 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=44 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=45 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=46 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=47 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=48 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=49 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=50 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=51 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=52 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=53 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=54 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=55 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=56 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=57 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=58 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=59 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=60 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=61 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 Group Descriptor Nr=62 bg_block_bitmap_lo=0 bg_inode_bitmap_lo=0 bg_inode_table_lo=0 bg_free_blocks_count_lo=0 bg_free_inodes_count_lo=0 bg_used_dirs_count_lo=0 bg_flags=0 thank you very much, -- Felipe Monteiro de Carvalho