1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com 4 * Written by Alex Tomas <alex@clusterfs.com> 5 */ 6 7 #ifndef _EXT4_EXTENTS 8 #define _EXT4_EXTENTS 9 10 #include "ext4.h" 11 12 /* 13 * With AGGRESSIVE_TEST defined, the capacity of index/leaf blocks 14 * becomes very small, so index split, in-depth growing and 15 * other hard changes happen much more often. 16 * This is for debug purposes only. 17 */ 18 #define AGGRESSIVE_TEST_ 19 20 /* 21 * With EXTENTS_STATS defined, the number of blocks and extents 22 * are collected in the truncate path. They'll be shown at 23 * umount time. 24 */ 25 #define EXTENTS_STATS__ 26 27 /* 28 * If CHECK_BINSEARCH is defined, then the results of the binary search 29 * will also be checked by linear search. 30 */ 31 #define CHECK_BINSEARCH__ 32 33 /* 34 * ext4_inode has i_block array (60 bytes total). 35 * The first 12 bytes store ext4_extent_header; 36 * the remainder stores an array of ext4_extent. 37 * For non-inode extent blocks, ext4_extent_tail 38 * follows the array. 39 */ 40 41 /* 42 * This is the extent tail on-disk structure. 43 * All other extent structures are 12 bytes long. It turns out that 44 * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which 45 * covers all valid ext4 block sizes. Therefore, this tail structure can be 46 * crammed into the end of the block without having to rebalance the tree. 47 */ 48 struct ext4_extent_tail { 49 __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */ 50 }; 51 52 /* 53 * This is the extent on-disk structure. 54 * It's used at the bottom of the tree. 55 */ 56 struct ext4_extent { 57 __le32 ee_block; /* first logical block extent covers */ 58 __le16 ee_len; /* number of blocks covered by extent */ 59 __le16 ee_start_hi; /* high 16 bits of physical block */ 60 __le32 ee_start_lo; /* low 32 bits of physical block */ 61 }; 62 63 /* 64 * This is index on-disk structure. 65 * It's used at all the levels except the bottom. 66 */ 67 struct ext4_extent_idx { 68 __le32 ei_block; /* index covers logical blocks from 'block' */ 69 __le32 ei_leaf_lo; /* pointer to the physical block of the next * 70 * level. leaf or next index could be there */ 71 __le16 ei_leaf_hi; /* high 16 bits of physical block */ 72 __u16 ei_unused; 73 }; 74 75 /* 76 * Each block (leaves and indexes), even inode-stored has header. 77 */ 78 struct ext4_extent_header { 79 __le16 eh_magic; /* probably will support different formats */ 80 __le16 eh_entries; /* number of valid entries */ 81 __le16 eh_max; /* capacity of store in entries */ 82 __le16 eh_depth; /* has tree real underlying blocks? */ 83 __le32 eh_generation; /* generation of the tree */ 84 }; 85 86 #define EXT4_EXT_MAGIC cpu_to_le16(0xf30a) 87 #define EXT4_MAX_EXTENT_DEPTH 5 88 89 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \ 90 (sizeof(struct ext4_extent_header) + \ 91 (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max))) 92 93 static inline struct ext4_extent_tail * 94 find_ext4_extent_tail(struct ext4_extent_header *eh) 95 { 96 return (struct ext4_extent_tail *)(((void *)eh) + 97 EXT4_EXTENT_TAIL_OFFSET(eh)); 98 } 99 100 /* 101 * Array of ext4_ext_path contains path to some extent. 102 * Creation/lookup routines use it for traversal/splitting/etc. 103 * Truncate uses it to simulate recursive walking. 104 */ 105 struct ext4_ext_path { 106 ext4_fsblk_t p_block; 107 __u16 p_depth; 108 __u16 p_maxdepth; 109 struct ext4_extent *p_ext; 110 struct ext4_extent_idx *p_idx; 111 struct ext4_extent_header *p_hdr; 112 struct buffer_head *p_bh; 113 }; 114 115 /* 116 * Used to record a portion of a cluster found at the beginning or end 117 * of an extent while traversing the extent tree during space removal. 118 * A partial cluster may be removed if it does not contain blocks shared 119 * with extents that aren't being deleted (tofree state). Otherwise, 120 * it cannot be removed (nofree state). 121 */ 122 struct partial_cluster { 123 ext4_fsblk_t pclu; /* physical cluster number */ 124 ext4_lblk_t lblk; /* logical block number within logical cluster */ 125 enum {initial, tofree, nofree} state; 126 }; 127 128 /* 129 * structure for external API 130 */ 131 132 /* 133 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an 134 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the 135 * MSB of ee_len field in the extent datastructure to signify if this 136 * particular extent is an initialized extent or an unwritten (i.e. 137 * preallocated). 138 * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an 139 * unwritten extent. 140 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an 141 * unwritten one. In other words, if MSB of ee_len is set, it is an 142 * unwritten extent with only one special scenario when ee_len = 0x8000. 143 * In this case we can not have an unwritten extent of zero length and 144 * thus we make it as a special case of initialized extent with 0x8000 length. 145 * This way we get better extent-to-group alignment for initialized extents. 146 * Hence, the maximum number of blocks we can have in an *initialized* 147 * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767). 148 */ 149 #define EXT_INIT_MAX_LEN (1UL << 15) 150 #define EXT_UNWRITTEN_MAX_LEN (EXT_INIT_MAX_LEN - 1) 151 152 153 #define EXT_FIRST_EXTENT(__hdr__) \ 154 ((struct ext4_extent *) (((char *) (__hdr__)) + \ 155 sizeof(struct ext4_extent_header))) 156 #define EXT_FIRST_INDEX(__hdr__) \ 157 ((struct ext4_extent_idx *) (((char *) (__hdr__)) + \ 158 sizeof(struct ext4_extent_header))) 159 #define EXT_HAS_FREE_INDEX(__path__) \ 160 (le16_to_cpu((__path__)->p_hdr->eh_entries) \ 161 < le16_to_cpu((__path__)->p_hdr->eh_max)) 162 #define EXT_LAST_EXTENT(__hdr__) \ 163 (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) 164 #define EXT_LAST_INDEX(__hdr__) \ 165 (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) 166 #define EXT_MAX_EXTENT(__hdr__) \ 167 ((le16_to_cpu((__hdr__)->eh_max)) ? \ 168 ((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \ 169 : NULL) 170 #define EXT_MAX_INDEX(__hdr__) \ 171 ((le16_to_cpu((__hdr__)->eh_max)) ? \ 172 ((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \ 173 : NULL) 174 175 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode) 176 { 177 return (struct ext4_extent_header *) EXT4_I(inode)->i_data; 178 } 179 180 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh) 181 { 182 return (struct ext4_extent_header *) bh->b_data; 183 } 184 185 static inline unsigned short ext_depth(struct inode *inode) 186 { 187 return le16_to_cpu(ext_inode_hdr(inode)->eh_depth); 188 } 189 190 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext) 191 { 192 /* We can not have an unwritten extent of zero length! */ 193 BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0); 194 ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN); 195 } 196 197 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext) 198 { 199 /* Extent with ee_len of 0x8000 is treated as an initialized extent */ 200 return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN); 201 } 202 203 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext) 204 { 205 return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ? 206 le16_to_cpu(ext->ee_len) : 207 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN)); 208 } 209 210 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext) 211 { 212 ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext)); 213 } 214 215 /* 216 * ext4_ext_pblock: 217 * combine low and high parts of physical block number into ext4_fsblk_t 218 */ 219 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex) 220 { 221 ext4_fsblk_t block; 222 223 block = le32_to_cpu(ex->ee_start_lo); 224 block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1; 225 return block; 226 } 227 228 /* 229 * ext4_idx_pblock: 230 * combine low and high parts of a leaf physical block number into ext4_fsblk_t 231 */ 232 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix) 233 { 234 ext4_fsblk_t block; 235 236 block = le32_to_cpu(ix->ei_leaf_lo); 237 block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1; 238 return block; 239 } 240 241 /* 242 * ext4_ext_store_pblock: 243 * stores a large physical block number into an extent struct, 244 * breaking it into parts 245 */ 246 static inline void ext4_ext_store_pblock(struct ext4_extent *ex, 247 ext4_fsblk_t pb) 248 { 249 ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff)); 250 ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 251 0xffff); 252 } 253 254 /* 255 * ext4_idx_store_pblock: 256 * stores a large physical block number into an index struct, 257 * breaking it into parts 258 */ 259 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix, 260 ext4_fsblk_t pb) 261 { 262 ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff)); 263 ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 264 0xffff); 265 } 266 267 #endif /* _EXT4_EXTENTS */ 268 269