1 /* 2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com 3 * Written by Alex Tomas <alex@clusterfs.com> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public Licens 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111- 17 */ 18 19 #ifndef _LINUX_EXT3_EXTENTS 20 #define _LINUX_EXT3_EXTENTS 21 22 /* 23 * ext3_inode has i_block array (total 60 bytes) 24 * first 4 bytes are used to store: 25 * - tree depth (0 mean there is no tree yet. all extents in the inode) 26 * - number of alive extents in the inode 27 */ 28 29 /* 30 * this is extent on-disk structure 31 * it's used at the bottom of the tree 32 */ 33 struct ext3_extent { 34 __u32 ee_block; /* first logical block extent covers */ 35 __u16 ee_len; /* number of blocks covered by extent */ 36 __u16 ee_start_hi; /* high 16 bits of physical block */ 37 __u32 ee_start; /* low 32 bigs of physical block */ 38 }; 39 40 /* 41 * this is index on-disk structure 42 * it's used at all the levels, but the bottom 43 */ 44 struct ext3_extent_idx { 45 __u32 ei_block; /* index covers logical blocks from 'block' */ 46 __u32 ei_leaf; /* pointer to the physical block of the next * 47 * level. leaf or next index could bet here */ 48 __u16 ei_leaf_hi; /* high 16 bits of physical block */ 49 __u16 ei_unused; 50 }; 51 52 /* 53 * each block (leaves and indexes), even inode-stored has header 54 */ 55 struct ext3_extent_header { 56 __u16 eh_magic; /* probably will support different formats */ 57 __u16 eh_entries; /* number of valid entries */ 58 __u16 eh_max; /* capacity of store in entries */ 59 __u16 eh_depth; /* has tree real underlaying blocks? */ 60 __u32 eh_generation; /* generation of the tree */ 61 }; 62 63 #define EXT3_EXT_MAGIC 0xf30a 64 65 /* 66 * array of ext3_ext_path contains path to some extent 67 * creation/lookup routines use it for traversal/splitting/etc 68 * truncate uses it to simulate recursive walking 69 */ 70 struct ext3_ext_path { 71 __u32 p_block; 72 __u16 p_depth; 73 struct ext3_extent *p_ext; 74 struct ext3_extent_idx *p_idx; 75 struct ext3_extent_header *p_hdr; 76 struct buffer_head *p_bh; 77 }; 78 79 /* 80 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an 81 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the 82 * MSB of ee_len field in the extent datastructure to signify if this 83 * particular extent is an initialized extent or an uninitialized (i.e. 84 * preallocated). 85 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an 86 * uninitialized extent. 87 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an 88 * uninitialized one. In other words, if MSB of ee_len is set, it is an 89 * uninitialized extent with only one special scenario when ee_len = 0x8000. 90 * In this case we can not have an uninitialized extent of zero length and 91 * thus we make it as a special case of initialized extent with 0x8000 length. 92 * This way we get better extent-to-group alignment for initialized extents. 93 * Hence, the maximum number of blocks we can have in an *initialized* 94 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767). 95 */ 96 #define EXT_INIT_MAX_LEN (1UL << 15) 97 #define EXT_UNINIT_MAX_LEN (EXT_INIT_MAX_LEN - 1) 98 99 #define EXT_FIRST_EXTENT(__hdr__) \ 100 ((struct ext3_extent *) (((char *) (__hdr__)) + \ 101 sizeof(struct ext3_extent_header))) 102 #define EXT_FIRST_INDEX(__hdr__) \ 103 ((struct ext3_extent_idx *) (((char *) (__hdr__)) + \ 104 sizeof(struct ext3_extent_header))) 105 #define EXT_HAS_FREE_INDEX(__path__) \ 106 ((__path__)->p_hdr->eh_entries < (__path__)->p_hdr->eh_max) 107 #define EXT_LAST_EXTENT(__hdr__) \ 108 (EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_entries - 1) 109 #define EXT_LAST_INDEX(__hdr__) \ 110 (EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_entries - 1) 111 #define EXT_MAX_EXTENT(__hdr__) \ 112 (EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_max - 1) 113 #define EXT_MAX_INDEX(__hdr__) \ 114 (EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_max - 1) 115 116 #endif /* _LINUX_EXT3_EXTENTS */ 117 118