linux/fs/ext4/ext4_extents.h
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   1/*
   2 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
   3 * Written by Alex Tomas <alex@clusterfs.com>
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 as
   7 * published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope that it will be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public Licens
  15 * along with this program; if not, write to the Free Software
  16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
  17 */
  18
  19#ifndef _EXT4_EXTENTS
  20#define _EXT4_EXTENTS
  21
  22#include "ext4.h"
  23
  24/*
  25 * With AGGRESSIVE_TEST defined, the capacity of index/leaf blocks
  26 * becomes very small, so index split, in-depth growing and
  27 * other hard changes happen much more often.
  28 * This is for debug purposes only.
  29 */
  30#define AGGRESSIVE_TEST_
  31
  32/*
  33 * With EXTENTS_STATS defined, the number of blocks and extents
  34 * are collected in the truncate path. They'll be shown at
  35 * umount time.
  36 */
  37#define EXTENTS_STATS__
  38
  39/*
  40 * If CHECK_BINSEARCH is defined, then the results of the binary search
  41 * will also be checked by linear search.
  42 */
  43#define CHECK_BINSEARCH__
  44
  45/*
  46 * Turn on EXT_DEBUG to get lots of info about extents operations.
  47 */
  48#define EXT_DEBUG__
  49#ifdef EXT_DEBUG
  50#define ext_debug(fmt, ...)     printk(fmt, ##__VA_ARGS__)
  51#else
  52#define ext_debug(fmt, ...)     no_printk(fmt, ##__VA_ARGS__)
  53#endif
  54
  55/*
  56 * If EXT_STATS is defined then stats numbers are collected.
  57 * These number will be displayed at umount time.
  58 */
  59#define EXT_STATS_
  60
  61
  62/*
  63 * ext4_inode has i_block array (60 bytes total).
  64 * The first 12 bytes store ext4_extent_header;
  65 * the remainder stores an array of ext4_extent.
  66 * For non-inode extent blocks, ext4_extent_tail
  67 * follows the array.
  68 */
  69
  70/*
  71 * This is the extent tail on-disk structure.
  72 * All other extent structures are 12 bytes long.  It turns out that
  73 * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
  74 * covers all valid ext4 block sizes.  Therefore, this tail structure can be
  75 * crammed into the end of the block without having to rebalance the tree.
  76 */
  77struct ext4_extent_tail {
  78        __le32  et_checksum;    /* crc32c(uuid+inum+extent_block) */
  79};
  80
  81/*
  82 * This is the extent on-disk structure.
  83 * It's used at the bottom of the tree.
  84 */
  85struct ext4_extent {
  86        __le32  ee_block;       /* first logical block extent covers */
  87        __le16  ee_len;         /* number of blocks covered by extent */
  88        __le16  ee_start_hi;    /* high 16 bits of physical block */
  89        __le32  ee_start_lo;    /* low 32 bits of physical block */
  90};
  91
  92/*
  93 * This is index on-disk structure.
  94 * It's used at all the levels except the bottom.
  95 */
  96struct ext4_extent_idx {
  97        __le32  ei_block;       /* index covers logical blocks from 'block' */
  98        __le32  ei_leaf_lo;     /* pointer to the physical block of the next *
  99                                 * level. leaf or next index could be there */
 100        __le16  ei_leaf_hi;     /* high 16 bits of physical block */
 101        __u16   ei_unused;
 102};
 103
 104/*
 105 * Each block (leaves and indexes), even inode-stored has header.
 106 */
 107struct ext4_extent_header {
 108        __le16  eh_magic;       /* probably will support different formats */
 109        __le16  eh_entries;     /* number of valid entries */
 110        __le16  eh_max;         /* capacity of store in entries */
 111        __le16  eh_depth;       /* has tree real underlying blocks? */
 112        __le32  eh_generation;  /* generation of the tree */
 113};
 114
 115#define EXT4_EXT_MAGIC          cpu_to_le16(0xf30a)
 116
 117#define EXT4_EXTENT_TAIL_OFFSET(hdr) \
 118        (sizeof(struct ext4_extent_header) + \
 119         (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
 120
 121static inline struct ext4_extent_tail *
 122find_ext4_extent_tail(struct ext4_extent_header *eh)
 123{
 124        return (struct ext4_extent_tail *)(((void *)eh) +
 125                                           EXT4_EXTENT_TAIL_OFFSET(eh));
 126}
 127
 128/*
 129 * Array of ext4_ext_path contains path to some extent.
 130 * Creation/lookup routines use it for traversal/splitting/etc.
 131 * Truncate uses it to simulate recursive walking.
 132 */
 133struct ext4_ext_path {
 134        ext4_fsblk_t                    p_block;
 135        __u16                           p_depth;
 136        struct ext4_extent              *p_ext;
 137        struct ext4_extent_idx          *p_idx;
 138        struct ext4_extent_header       *p_hdr;
 139        struct buffer_head              *p_bh;
 140};
 141
 142/*
 143 * structure for external API
 144 */
 145
 146/*
 147 * to be called by ext4_ext_walk_space()
 148 * negative retcode - error
 149 * positive retcode - signal for ext4_ext_walk_space(), see below
 150 * callback must return valid extent (passed or newly created)
 151 */
 152typedef int (*ext_prepare_callback)(struct inode *, ext4_lblk_t,
 153                                        struct ext4_ext_cache *,
 154                                        struct ext4_extent *, void *);
 155
 156#define EXT_CONTINUE   0
 157#define EXT_BREAK      1
 158#define EXT_REPEAT     2
 159
 160/*
 161 * Maximum number of logical blocks in a file; ext4_extent's ee_block is
 162 * __le32.
 163 */
 164#define EXT_MAX_BLOCKS  0xffffffff
 165
 166/*
 167 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
 168 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
 169 * MSB of ee_len field in the extent datastructure to signify if this
 170 * particular extent is an initialized extent or an uninitialized (i.e.
 171 * preallocated).
 172 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
 173 * uninitialized extent.
 174 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
 175 * uninitialized one. In other words, if MSB of ee_len is set, it is an
 176 * uninitialized extent with only one special scenario when ee_len = 0x8000.
 177 * In this case we can not have an uninitialized extent of zero length and
 178 * thus we make it as a special case of initialized extent with 0x8000 length.
 179 * This way we get better extent-to-group alignment for initialized extents.
 180 * Hence, the maximum number of blocks we can have in an *initialized*
 181 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767).
 182 */
 183#define EXT_INIT_MAX_LEN        (1UL << 15)
 184#define EXT_UNINIT_MAX_LEN      (EXT_INIT_MAX_LEN - 1)
 185
 186
 187#define EXT_FIRST_EXTENT(__hdr__) \
 188        ((struct ext4_extent *) (((char *) (__hdr__)) +         \
 189                                 sizeof(struct ext4_extent_header)))
 190#define EXT_FIRST_INDEX(__hdr__) \
 191        ((struct ext4_extent_idx *) (((char *) (__hdr__)) +     \
 192                                     sizeof(struct ext4_extent_header)))
 193#define EXT_HAS_FREE_INDEX(__path__) \
 194        (le16_to_cpu((__path__)->p_hdr->eh_entries) \
 195                                     < le16_to_cpu((__path__)->p_hdr->eh_max))
 196#define EXT_LAST_EXTENT(__hdr__) \
 197        (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 198#define EXT_LAST_INDEX(__hdr__) \
 199        (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 200#define EXT_MAX_EXTENT(__hdr__) \
 201        (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 202#define EXT_MAX_INDEX(__hdr__) \
 203        (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 204
 205static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
 206{
 207        return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
 208}
 209
 210static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
 211{
 212        return (struct ext4_extent_header *) bh->b_data;
 213}
 214
 215static inline unsigned short ext_depth(struct inode *inode)
 216{
 217        return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 218}
 219
 220static inline void
 221ext4_ext_invalidate_cache(struct inode *inode)
 222{
 223        EXT4_I(inode)->i_cached_extent.ec_len = 0;
 224}
 225
 226static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext)
 227{
 228        /* We can not have an uninitialized extent of zero length! */
 229        BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
 230        ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
 231}
 232
 233static inline int ext4_ext_is_uninitialized(struct ext4_extent *ext)
 234{
 235        /* Extent with ee_len of 0x8000 is treated as an initialized extent */
 236        return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
 237}
 238
 239static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 240{
 241        return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
 242                le16_to_cpu(ext->ee_len) :
 243                (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
 244}
 245
 246static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
 247{
 248        ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
 249}
 250
 251/*
 252 * ext4_ext_pblock:
 253 * combine low and high parts of physical block number into ext4_fsblk_t
 254 */
 255static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
 256{
 257        ext4_fsblk_t block;
 258
 259        block = le32_to_cpu(ex->ee_start_lo);
 260        block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
 261        return block;
 262}
 263
 264/*
 265 * ext4_idx_pblock:
 266 * combine low and high parts of a leaf physical block number into ext4_fsblk_t
 267 */
 268static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
 269{
 270        ext4_fsblk_t block;
 271
 272        block = le32_to_cpu(ix->ei_leaf_lo);
 273        block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
 274        return block;
 275}
 276
 277/*
 278 * ext4_ext_store_pblock:
 279 * stores a large physical block number into an extent struct,
 280 * breaking it into parts
 281 */
 282static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
 283                                         ext4_fsblk_t pb)
 284{
 285        ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 286        ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 287                                      0xffff);
 288}
 289
 290/*
 291 * ext4_idx_store_pblock:
 292 * stores a large physical block number into an index struct,
 293 * breaking it into parts
 294 */
 295static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
 296                                         ext4_fsblk_t pb)
 297{
 298        ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 299        ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 300                                     0xffff);
 301}
 302
 303extern int ext4_ext_calc_metadata_amount(struct inode *inode,
 304                                         ext4_lblk_t lblocks);
 305extern int ext4_extent_tree_init(handle_t *, struct inode *);
 306extern int ext4_ext_calc_credits_for_single_extent(struct inode *inode,
 307                                                   int num,
 308                                                   struct ext4_ext_path *path);
 309extern int ext4_can_extents_be_merged(struct inode *inode,
 310                                      struct ext4_extent *ex1,
 311                                      struct ext4_extent *ex2);
 312extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *, int);
 313extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
 314                                                        struct ext4_ext_path *);
 315extern void ext4_ext_drop_refs(struct ext4_ext_path *);
 316extern int ext4_ext_check_inode(struct inode *inode);
 317extern int ext4_find_delalloc_cluster(struct inode *inode, ext4_lblk_t lblk,
 318                                      int search_hint_reverse);
 319#endif /* _EXT4_EXTENTS */
 320
 321
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