fs/ext4/ext4_extents.h

   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  * If EXT_STATS is defined then stats numbers are collected.
  47  * These number will be displayed at umount time.
  48  */
  49 #define EXT_STATS_
  50
  51
  52 /*
  53  * ext4_inode has i_block array (60 bytes total).
  54  * The first 12 bytes store ext4_extent_header;
  55  * the remainder stores an array of ext4_extent.
  56  * For non-inode extent blocks, ext4_extent_tail
  57  * follows the array.
  58  */
  59
  60 /*
  61  * This is the extent tail on-disk structure.
  62  * All other extent structures are 12 bytes long.  It turns out that
  63  * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
  64  * covers all valid ext4 block sizes.  Therefore, this tail structure can be
  65  * crammed into the end of the block without having to rebalance the tree.
  66  */
  67 struct ext4_extent_tail {
  68         __le32  et_checksum;    /* crc32c(uuid+inum+extent_block) */
  69 };
  70
  71 /*
  72  * This is the extent on-disk structure.
  73  * It's used at the bottom of the tree.
  74  */
  75 struct ext4_extent {
  76         __le32  ee_block;       /* first logical block extent covers */
  77         __le16  ee_len;         /* number of blocks covered by extent */
  78         __le16  ee_start_hi;    /* high 16 bits of physical block */
  79         __le32  ee_start_lo;    /* low 32 bits of physical block */
  80 };
  81
  82 /*
  83  * This is index on-disk structure.
  84  * It's used at all the levels except the bottom.
  85  */
  86 struct ext4_extent_idx {
  87         __le32  ei_block;       /* index covers logical blocks from 'block' */
  88         __le32  ei_leaf_lo;     /* pointer to the physical block of the next *
  89                                  * level. leaf or next index could be there */
  90         __le16  ei_leaf_hi;     /* high 16 bits of physical block */
  91         __u16   ei_unused;
  92 };
  93
  94 /*
  95  * Each block (leaves and indexes), even inode-stored has header.
  96  */
  97 struct ext4_extent_header {
  98         __le16  eh_magic;       /* probably will support different formats */
  99         __le16  eh_entries;     /* number of valid entries */
 100         __le16  eh_max;         /* capacity of store in entries */
 101         __le16  eh_depth;       /* has tree real underlying blocks? */
 102         __le32  eh_generation;  /* generation of the tree */
 103 };
 104
 105 #define EXT4_EXT_MAGIC          cpu_to_le16(0xf30a)
 106
 107 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \
 108         (sizeof(struct ext4_extent_header) + \
 109          (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
 110
 111 static inline struct ext4_extent_tail *
 112 find_ext4_extent_tail(struct ext4_extent_header *eh)
 113 {
 114         return (struct ext4_extent_tail *)(((void *)eh) +
 115                                            EXT4_EXTENT_TAIL_OFFSET(eh));
 116 }
 117
 118 /*
 119  * Array of ext4_ext_path contains path to some extent.
 120  * Creation/lookup routines use it for traversal/splitting/etc.
 121  * Truncate uses it to simulate recursive walking.
 122  */
 123 struct ext4_ext_path {
 124         ext4_fsblk_t                    p_block;
 125         __u16                           p_depth;
 126         __u16                           p_maxdepth;
 127         struct ext4_extent              *p_ext;
 128         struct ext4_extent_idx          *p_idx;
 129         struct ext4_extent_header       *p_hdr;
 130         struct buffer_head              *p_bh;
 131 };
 132
 133 /*
 134  * structure for external API
 135  */
 136
 137 /*
 138  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
 139  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
 140  * MSB of ee_len field in the extent datastructure to signify if this
 141  * particular extent is an initialized extent or an unwritten (i.e.
 142  * preallocated).
 143  * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an
 144  * unwritten extent.
 145  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
 146  * unwritten one. In other words, if MSB of ee_len is set, it is an
 147  * unwritten extent with only one special scenario when ee_len = 0x8000.
 148  * In this case we can not have an unwritten extent of zero length and
 149  * thus we make it as a special case of initialized extent with 0x8000 length.
 150  * This way we get better extent-to-group alignment for initialized extents.
 151  * Hence, the maximum number of blocks we can have in an *initialized*
 152  * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767).
 153  */
 154 #define EXT_INIT_MAX_LEN        (1UL << 15)
 155 #define EXT_UNWRITTEN_MAX_LEN   (EXT_INIT_MAX_LEN - 1)
 156
 157
 158 #define EXT_FIRST_EXTENT(__hdr__) \
 159         ((struct ext4_extent *) (((char *) (__hdr__)) +         \
 160                                  sizeof(struct ext4_extent_header)))
 161 #define EXT_FIRST_INDEX(__hdr__) \
 162         ((struct ext4_extent_idx *) (((char *) (__hdr__)) +     \
 163                                      sizeof(struct ext4_extent_header)))
 164 #define EXT_HAS_FREE_INDEX(__path__) \
 165         (le16_to_cpu((__path__)->p_hdr->eh_entries) \
 166                                      < le16_to_cpu((__path__)->p_hdr->eh_max))
 167 #define EXT_LAST_EXTENT(__hdr__) \
 168         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 169 #define EXT_LAST_INDEX(__hdr__) \
 170         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 171 #define EXT_MAX_EXTENT(__hdr__) \
 172         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 173 #define EXT_MAX_INDEX(__hdr__) \
 174         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 175
 176 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
 177 {
 178         return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
 179 }
 180
 181 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
 182 {
 183         return (struct ext4_extent_header *) bh->b_data;
 184 }
 185
 186 static inline unsigned short ext_depth(struct inode *inode)
 187 {
 188         return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 189 }
 190
 191 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext)
 192 {
 193         /* We can not have an unwritten extent of zero length! */
 194         BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
 195         ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
 196 }
 197
 198 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext)
 199 {
 200         /* Extent with ee_len of 0x8000 is treated as an initialized extent */
 201         return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
 202 }
 203
 204 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 205 {
 206         return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
 207                 le16_to_cpu(ext->ee_len) :
 208                 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
 209 }
 210
 211 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
 212 {
 213         ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
 214 }
 215
 216 /*
 217  * ext4_ext_pblock:
 218  * combine low and high parts of physical block number into ext4_fsblk_t
 219  */
 220 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
 221 {
 222         ext4_fsblk_t block;
 223
 224         block = le32_to_cpu(ex->ee_start_lo);
 225         block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
 226         return block;
 227 }
 228
 229 /*
 230  * ext4_idx_pblock:
 231  * combine low and high parts of a leaf physical block number into ext4_fsblk_t
 232  */
 233 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
 234 {
 235         ext4_fsblk_t block;
 236
 237         block = le32_to_cpu(ix->ei_leaf_lo);
 238         block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
 239         return block;
 240 }
 241
 242 /*
 243  * ext4_ext_store_pblock:
 244  * stores a large physical block number into an extent struct,
 245  * breaking it into parts
 246  */
 247 static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
 248                                          ext4_fsblk_t pb)
 249 {
 250         ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 251         ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 252                                       0xffff);
 253 }
 254
 255 /*
 256  * ext4_idx_store_pblock:
 257  * stores a large physical block number into an index struct,
 258  * breaking it into parts
 259  */
 260 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
 261                                          ext4_fsblk_t pb)
 262 {
 263         ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 264         ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 265                                      0xffff);
 266 }
 267
 268 #define ext4_ext_dirty(handle, inode, path) \
 269                 __ext4_ext_dirty(__func__, __LINE__, (handle), (inode), (path))
 270 int __ext4_ext_dirty(const char *where, unsigned int line, handle_t *handle,
 271                      struct inode *inode, struct ext4_ext_path *path);
 272
 273 #endif /* _EXT4_EXTENTS */
 274