fs/ext4/ext4_extents.h

   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