1 /* 2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com 3 * Written by Alex Tomas <alex@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 tail on-disk structure. 23 * All other extent structures are 12 bytes long. It turns out that 24 * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which 25 * covers all valid ext4 block sizes. Therefore, this tail structure can be 26 * crammed into the end of the block without having to rebalance the tree. 27 */ 28 struct ext3_extent_tail { 29 __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */ 30 }; 31 32 /* 33 * this is extent on-disk structure 34 * it's used at the bottom of the tree 35 */ 36 struct ext3_extent { 37 __le32 ee_block; /* first logical block extent covers */ 38 __le16 ee_len; /* number of blocks covered by extent */ 39 __le16 ee_start_hi; /* high 16 bits of physical block */ 40 __le32 ee_start; /* low 32 bigs of physical block */ 41 }; 42 43 /* 44 * this is index on-disk structure 45 * it's used at all the levels, but the bottom 46 */ 47 struct ext3_extent_idx { 48 __le32 ei_block; /* index covers logical blocks from 'block' */ 49 __le32 ei_leaf; /* pointer to the physical block of the next * 50 * level. leaf or next index could bet here */ 51 __le16 ei_leaf_hi; /* high 16 bits of physical block */ 52 __le16 ei_unused; 53 }; 54 55 /* 56 * each block (leaves and indexes), even inode-stored has header 57 */ 58 struct ext3_extent_header { 59 __le16 eh_magic; /* probably will support different formats */ 60 __le16 eh_entries; /* number of valid entries */ 61 __le16 eh_max; /* capacity of store in entries */ 62 __le16 eh_depth; /* has tree real underlaying blocks? */ 63 __le32 eh_generation; /* generation of the tree */ 64 }; 65 66 #define EXT3_EXT_MAGIC 0xf30a 67 68 /* 69 * array of ext3_ext_path contains path to some extent 70 * creation/lookup routines use it for traversal/splitting/etc 71 * truncate uses it to simulate recursive walking 72 */ 73 struct ext3_ext_path { 74 __u32 p_block; 75 __u16 p_depth; 76 struct ext3_extent *p_ext; 77 struct ext3_extent_idx *p_idx; 78 struct ext3_extent_header *p_hdr; 79 struct buffer_head *p_bh; 80 }; 81 82 /* 83 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an 84 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the 85 * MSB of ee_len field in the extent datastructure to signify if this 86 * particular extent is an initialized extent or an uninitialized (i.e. 87 * preallocated). 88 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an 89 * uninitialized extent. 90 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an 91 * uninitialized one. In other words, if MSB of ee_len is set, it is an 92 * uninitialized extent with only one special scenario when ee_len = 0x8000. 93 * In this case we can not have an uninitialized extent of zero length and 94 * thus we make it as a special case of initialized extent with 0x8000 length. 95 * This way we get better extent-to-group alignment for initialized extents. 96 * Hence, the maximum number of blocks we can have in an *initialized* 97 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767). 98 */ 99 #define EXT_INIT_MAX_LEN (1UL << 15) 100 #define EXT_UNINIT_MAX_LEN (EXT_INIT_MAX_LEN - 1) 101 #define EXT_MAX_EXTENT_LBLK (((__u64) 1 << 32) - 1) 102 #define EXT_MAX_EXTENT_PBLK (((__u64) 1 << 48) - 1) 103 104 #define EXT_FIRST_EXTENT(__hdr__) \ 105 ((struct ext3_extent *) (((char *) (__hdr__)) + \ 106 sizeof(struct ext3_extent_header))) 107 #define EXT_FIRST_INDEX(__hdr__) \ 108 ((struct ext3_extent_idx *) (((char *) (__hdr__)) + \ 109 sizeof(struct ext3_extent_header))) 110 #define EXT_HAS_FREE_INDEX(__path__) \ 111 (ext2fs_le16_to_cpu((__path__)->p_hdr->eh_entries) < \ 112 ext2fs_le16_to_cpu((__path__)->p_hdr->eh_max)) 113 #define EXT_LAST_EXTENT(__hdr__) \ 114 (EXT_FIRST_EXTENT((__hdr__)) + \ 115 ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1) 116 #define EXT_LAST_INDEX(__hdr__) \ 117 (EXT_FIRST_INDEX((__hdr__)) + \ 118 ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1) 119 #define EXT_MAX_EXTENT(__hdr__) \ 120 (EXT_FIRST_EXTENT((__hdr__)) + \ 121 ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1) 122 #define EXT_MAX_INDEX(__hdr__) \ 123 (EXT_FIRST_INDEX((__hdr__)) + \ 124 ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1) 125 126 #endif /* _LINUX_EXT3_EXTENTS */ 127 128