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
  95 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \
  96         (sizeof(struct ext4_extent_header) + \
  97          (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
  98
  99 static inline struct ext4_extent_tail *
 100 find_ext4_extent_tail(struct ext4_extent_header *eh)
 101 {
 102         return (struct ext4_extent_tail *)(((void *)eh) +
 103                                            EXT4_EXTENT_TAIL_OFFSET(eh));
 104 }
 105
 106 /*
 107  * Array of ext4_ext_path contains path to some extent.
 108  * Creation/lookup routines use it for traversal/splitting/etc.
 109  * Truncate uses it to simulate recursive walking.
 110  */
 111 struct ext4_ext_path {
 112         ext4_fsblk_t                    p_block;
 113         __u16                           p_depth;
 114         __u16                           p_maxdepth;
 115         struct ext4_extent              *p_ext;
 116         struct ext4_extent_idx          *p_idx;
 117         struct ext4_extent_header       *p_hdr;
 118         struct buffer_head              *p_bh;
 119 };
 120
 121 /*
 122  * structure for external API
 123  */
 124
 125 /*
 126  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
 127  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
 128  * MSB of ee_len field in the extent datastructure to signify if this
 129  * particular extent is an initialized extent or an unwritten (i.e.
 130  * preallocated).
 131  * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an
 132  * unwritten extent.
 133  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
 134  * unwritten one. In other words, if MSB of ee_len is set, it is an
 135  * unwritten extent with only one special scenario when ee_len = 0x8000.
 136  * In this case we can not have an unwritten extent of zero length and
 137  * thus we make it as a special case of initialized extent with 0x8000 length.
 138  * This way we get better extent-to-group alignment for initialized extents.
 139  * Hence, the maximum number of blocks we can have in an *initialized*
 140  * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767).
 141  */
 142 #define EXT_INIT_MAX_LEN        (1UL << 15)
 143 #define EXT_UNWRITTEN_MAX_LEN   (EXT_INIT_MAX_LEN - 1)
 144
 145
 146 #define EXT_FIRST_EXTENT(__hdr__) \
 147         ((struct ext4_extent *) (((char *) (__hdr__)) +         \
 148                                  sizeof(struct ext4_extent_header)))
 149 #define EXT_FIRST_INDEX(__hdr__) \
 150         ((struct ext4_extent_idx *) (((char *) (__hdr__)) +     \
 151                                      sizeof(struct ext4_extent_header)))
 152 #define EXT_HAS_FREE_INDEX(__path__) \
 153         (le16_to_cpu((__path__)->p_hdr->eh_entries) \
 154                                      < le16_to_cpu((__path__)->p_hdr->eh_max))
 155 #define EXT_LAST_EXTENT(__hdr__) \
 156         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 157 #define EXT_LAST_INDEX(__hdr__) \
 158         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 159 #define EXT_MAX_EXTENT(__hdr__) \
 160         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 161 #define EXT_MAX_INDEX(__hdr__) \
 162         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 163
 164 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
 165 {
 166         return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
 167 }
 168
 169 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
 170 {
 171         return (struct ext4_extent_header *) bh->b_data;
 172 }
 173
 174 static inline unsigned short ext_depth(struct inode *inode)
 175 {
 176         return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 177 }
 178
 179 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext)
 180 {
 181         /* We can not have an unwritten extent of zero length! */
 182         BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
 183         ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
 184 }
 185
 186 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext)
 187 {
 188         /* Extent with ee_len of 0x8000 is treated as an initialized extent */
 189         return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
 190 }
 191
 192 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 193 {
 194         return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
 195                 le16_to_cpu(ext->ee_len) :
 196                 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
 197 }
 198
 199 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
 200 {
 201         ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
 202 }
 203
 204 /*
 205  * ext4_ext_pblock:
 206  * combine low and high parts of physical block number into ext4_fsblk_t
 207  */
 208 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
 209 {
 210         ext4_fsblk_t block;
 211
 212         block = le32_to_cpu(ex->ee_start_lo);
 213         block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
 214         return block;
 215 }
 216
 217 /*
 218  * ext4_idx_pblock:
 219  * combine low and high parts of a leaf physical block number into ext4_fsblk_t
 220  */
 221 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
 222 {
 223         ext4_fsblk_t block;
 224
 225         block = le32_to_cpu(ix->ei_leaf_lo);
 226         block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
 227         return block;
 228 }
 229
 230 /*
 231  * ext4_ext_store_pblock:
 232  * stores a large physical block number into an extent struct,
 233  * breaking it into parts
 234  */
 235 static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
 236                                          ext4_fsblk_t pb)
 237 {
 238         ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 239         ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 240                                       0xffff);
 241 }
 242
 243 /*
 244  * ext4_idx_store_pblock:
 245  * stores a large physical block number into an index struct,
 246  * breaking it into parts
 247  */
 248 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
 249                                          ext4_fsblk_t pb)
 250 {
 251         ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 252         ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 253                                      0xffff);
 254 }
 255
 256 #define ext4_ext_dirty(handle, inode, path) \
 257                 __ext4_ext_dirty(__func__, __LINE__, (handle), (inode), (path))
 258 int __ext4_ext_dirty(const char *where, unsigned int line, handle_t *handle,
 259                      struct inode *inode, struct ext4_ext_path *path);
 260
 261 #endif /* _EXT4_EXTENTS */
 262