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 * If EXT_STATS is defined then stats numbers are collected. 35 * These number will be displayed at umount time. 36 */ 37 #define EXT_STATS_ 38 39 40 /* 41 * ext4_inode has i_block array (60 bytes total). 42 * The first 12 bytes store ext4_extent_header; 43 * the remainder stores an array of ext4_extent. 44 * For non-inode extent blocks, ext4_extent_tail 45 * follows the array. 46 */ 47 48 /* 49 * This is the extent tail on-disk structure. 50 * All other extent structures are 12 bytes long. It turns out that 51 * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which 52 * covers all valid ext4 block sizes. Therefore, this tail structure can be 53 * crammed into the end of the block without having to rebalance the tree. 54 */ 55 struct ext4_extent_tail { 56 __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */ 57 }; 58 59 /* 60 * This is the extent on-disk structure. 61 * It's used at the bottom of the tree. 62 */ 63 struct ext4_extent { 64 __le32 ee_block; /* first logical block extent covers */ 65 __le16 ee_len; /* number of blocks covered by extent */ 66 __le16 ee_start_hi; /* high 16 bits of physical block */ 67 __le32 ee_start_lo; /* low 32 bits of physical block */ 68 }; 69 70 /* 71 * This is index on-disk structure. 72 * It's used at all the levels except the bottom. 73 */ 74 struct ext4_extent_idx { 75 __le32 ei_block; /* index covers logical blocks from 'block' */ 76 __le32 ei_leaf_lo; /* pointer to the physical block of the next * 77 * level. leaf or next index could be there */ 78 __le16 ei_leaf_hi; /* high 16 bits of physical block */ 79 __u16 ei_unused; 80 }; 81 82 /* 83 * Each block (leaves and indexes), even inode-stored has header. 84 */ 85 struct ext4_extent_header { 86 __le16 eh_magic; /* probably will support different formats */ 87 __le16 eh_entries; /* number of valid entries */ 88 __le16 eh_max; /* capacity of store in entries */ 89 __le16 eh_depth; /* has tree real underlying blocks? */ 90 __le32 eh_generation; /* generation of the tree */ 91 }; 92 93 #define EXT4_EXT_MAGIC cpu_to_le16(0xf30a) 94 #define EXT4_MAX_EXTENT_DEPTH 5 95 96 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \ 97 (sizeof(struct ext4_extent_header) + \ 98 (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max))) 99 100 static inline struct ext4_extent_tail * 101 find_ext4_extent_tail(struct ext4_extent_header *eh) 102 { 103 return (struct ext4_extent_tail *)(((void *)eh) + 104 EXT4_EXTENT_TAIL_OFFSET(eh)); 105 } 106 107 /* 108 * Array of ext4_ext_path contains path to some extent. 109 * Creation/lookup routines use it for traversal/splitting/etc. 110 * Truncate uses it to simulate recursive walking. 111 */ 112 struct ext4_ext_path { 113 ext4_fsblk_t p_block; 114 __u16 p_depth; 115 __u16 p_maxdepth; 116 struct ext4_extent *p_ext; 117 struct ext4_extent_idx *p_idx; 118 struct ext4_extent_header *p_hdr; 119 struct buffer_head *p_bh; 120 }; 121 122 /* 123 * Used to record a portion of a cluster found at the beginning or end 124 * of an extent while traversing the extent tree during space removal. 125 * A partial cluster may be removed if it does not contain blocks shared 126 * with extents that aren't being deleted (tofree state). Otherwise, 127 * it cannot be removed (nofree state). 128 */ 129 struct partial_cluster { 130 ext4_fsblk_t pclu; /* physical cluster number */ 131 ext4_lblk_t lblk; /* logical block number within logical cluster */ 132 enum {initial, tofree, nofree} state; 133 }; 134 135 /* 136 * structure for external API 137 */ 138 139 /* 140 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an 141 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the 142 * MSB of ee_len field in the extent datastructure to signify if this 143 * particular extent is an initialized extent or an unwritten (i.e. 144 * preallocated). 145 * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an 146 * unwritten extent. 147 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an 148 * unwritten one. In other words, if MSB of ee_len is set, it is an 149 * unwritten extent with only one special scenario when ee_len = 0x8000. 150 * In this case we can not have an unwritten extent of zero length and 151 * thus we make it as a special case of initialized extent with 0x8000 length. 152 * This way we get better extent-to-group alignment for initialized extents. 153 * Hence, the maximum number of blocks we can have in an *initialized* 154 * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767). 155 */ 156 #define EXT_INIT_MAX_LEN (1UL << 15) 157 #define EXT_UNWRITTEN_MAX_LEN (EXT_INIT_MAX_LEN - 1) 158 159 160 #define EXT_FIRST_EXTENT(__hdr__) \ 161 ((struct ext4_extent *) (((char *) (__hdr__)) + \ 162 sizeof(struct ext4_extent_header))) 163 #define EXT_FIRST_INDEX(__hdr__) \ 164 ((struct ext4_extent_idx *) (((char *) (__hdr__)) + \ 165 sizeof(struct ext4_extent_header))) 166 #define EXT_HAS_FREE_INDEX(__path__) \ 167 (le16_to_cpu((__path__)->p_hdr->eh_entries) \ 168 < le16_to_cpu((__path__)->p_hdr->eh_max)) 169 #define EXT_LAST_EXTENT(__hdr__) \ 170 (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) 171 #define EXT_LAST_INDEX(__hdr__) \ 172 (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) 173 #define EXT_MAX_EXTENT(__hdr__) \ 174 ((le16_to_cpu((__hdr__)->eh_max)) ? \ 175 ((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \ 176 : 0) 177 #define EXT_MAX_INDEX(__hdr__) \ 178 ((le16_to_cpu((__hdr__)->eh_max)) ? \ 179 ((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) : 0) 180 181 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode) 182 { 183 return (struct ext4_extent_header *) EXT4_I(inode)->i_data; 184 } 185 186 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh) 187 { 188 return (struct ext4_extent_header *) bh->b_data; 189 } 190 191 static inline unsigned short ext_depth(struct inode *inode) 192 { 193 return le16_to_cpu(ext_inode_hdr(inode)->eh_depth); 194 } 195 196 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext) 197 { 198 /* We can not have an unwritten extent of zero length! */ 199 BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0); 200 ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN); 201 } 202 203 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext) 204 { 205 /* Extent with ee_len of 0x8000 is treated as an initialized extent */ 206 return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN); 207 } 208 209 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext) 210 { 211 return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ? 212 le16_to_cpu(ext->ee_len) : 213 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN)); 214 } 215 216 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext) 217 { 218 ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext)); 219 } 220 221 /* 222 * ext4_ext_pblock: 223 * combine low and high parts of physical block number into ext4_fsblk_t 224 */ 225 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex) 226 { 227 ext4_fsblk_t block; 228 229 block = le32_to_cpu(ex->ee_start_lo); 230 block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1; 231 return block; 232 } 233 234 /* 235 * ext4_idx_pblock: 236 * combine low and high parts of a leaf physical block number into ext4_fsblk_t 237 */ 238 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix) 239 { 240 ext4_fsblk_t block; 241 242 block = le32_to_cpu(ix->ei_leaf_lo); 243 block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1; 244 return block; 245 } 246 247 /* 248 * ext4_ext_store_pblock: 249 * stores a large physical block number into an extent struct, 250 * breaking it into parts 251 */ 252 static inline void ext4_ext_store_pblock(struct ext4_extent *ex, 253 ext4_fsblk_t pb) 254 { 255 ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff)); 256 ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 257 0xffff); 258 } 259 260 /* 261 * ext4_idx_store_pblock: 262 * stores a large physical block number into an index struct, 263 * breaking it into parts 264 */ 265 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix, 266 ext4_fsblk_t pb) 267 { 268 ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff)); 269 ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 270 0xffff); 271 } 272 273 #endif /* _EXT4_EXTENTS */ 274 275