1 /* 2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info (at) clusterfs.com 3 * Written by Alex Tomas <alex (at) clusterfs.com> 4 * 5 * %Begin-Header% 6 * This file may be redistributed under the terms of the GNU Library 7 * General Public License, version 2. 8 * %End-Header% 9 */ 10 11 #ifndef _LINUX_EXT3_EXTENTS 12 #define _LINUX_EXT3_EXTENTS 13 14 /* 15 * ext3_inode has i_block array (total 60 bytes) 16 * first 4 bytes are used to store: 17 * - tree depth (0 mean there is no tree yet. all extents in the inode) 18 * - number of alive extents in the inode 19 */ 20 21 /* 22 * this is extent on-disk structure 23 * it's used at the bottom of the tree 24 */ 25 struct ext3_extent { 26 __u32 ee_block; /* first logical block extent covers */ 27 __u16 ee_len; /* number of blocks covered by extent */ 28 __u16 ee_start_hi; /* high 16 bits of physical block */ 29 __u32 ee_start; /* low 32 bigs of physical block */ 30 }; 31 32 /* 33 * this is index on-disk structure 34 * it's used at all the levels, but the bottom 35 */ 36 struct ext3_extent_idx { 37 __u32 ei_block; /* index covers logical blocks from 'block' */ 38 __u32 ei_leaf; /* pointer to the physical block of the next * 39 * level. leaf or next index could bet here */ 40 __u16 ei_leaf_hi; /* high 16 bits of physical block */ 41 __u16 ei_unused; 42 }; 43 44 /* 45 * each block (leaves and indexes), even inode-stored has header 46 */ 47 struct ext3_extent_header { 48 __u16 eh_magic; /* probably will support different formats */ 49 __u16 eh_entries; /* number of valid entries */ 50 __u16 eh_max; /* capacity of store in entries */ 51 __u16 eh_depth; /* has tree real underlaying blocks? */ 52 __u32 eh_generation; /* generation of the tree */ 53 }; 54 55 #define EXT3_EXT_MAGIC 0xf30a 56 57 /* 58 * array of ext3_ext_path contains path to some extent 59 * creation/lookup routines use it for traversal/splitting/etc 60 * truncate uses it to simulate recursive walking 61 */ 62 struct ext3_ext_path { 63 __u32 p_block; 64 __u16 p_depth; 65 struct ext3_extent *p_ext; 66 struct ext3_extent_idx *p_idx; 67 struct ext3_extent_header *p_hdr; 68 struct buffer_head *p_bh; 69 }; 70 71 /* 72 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an 73 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the 74 * MSB of ee_len field in the extent datastructure to signify if this 75 * particular extent is an initialized extent or an uninitialized (i.e. 76 * preallocated). 77 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an 78 * uninitialized extent. 79 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an 80 * uninitialized one. In other words, if MSB of ee_len is set, it is an 81 * uninitialized extent with only one special scenario when ee_len = 0x8000. 82 * In this case we can not have an uninitialized extent of zero length and 83 * thus we make it as a special case of initialized extent with 0x8000 length. 84 * This way we get better extent-to-group alignment for initialized extents. 85 * Hence, the maximum number of blocks we can have in an *initialized* 86 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767). 87 */ 88 #define EXT_INIT_MAX_LEN (1UL << 15) 89 #define EXT_UNINIT_MAX_LEN (EXT_INIT_MAX_LEN - 1) 90 91 #define EXT_FIRST_EXTENT(__hdr__) \ 92 ((struct ext3_extent *) (((char *) (__hdr__)) + \ 93 sizeof(struct ext3_extent_header))) 94 #define EXT_FIRST_INDEX(__hdr__) \ 95 ((struct ext3_extent_idx *) (((char *) (__hdr__)) + \ 96 sizeof(struct ext3_extent_header))) 97 #define EXT_HAS_FREE_INDEX(__path__) \ 98 ((__path__)->p_hdr->eh_entries < (__path__)->p_hdr->eh_max) 99 #define EXT_LAST_EXTENT(__hdr__) \ 100 (EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_entries - 1) 101 #define EXT_LAST_INDEX(__hdr__) \ 102 (EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_entries - 1) 103 #define EXT_MAX_EXTENT(__hdr__) \ 104 (EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_max - 1) 105 #define EXT_MAX_INDEX(__hdr__) \ 106 (EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_max - 1) 107 108 #endif /* _LINUX_EXT3_EXTENTS */ 109 110
