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  * 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(a...)         printk(a)
  51 #else
  52 #define ext_debug(a...)
  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  */
  67
  68 /*
  69  * This is the extent on-disk structure.
  70  * It's used at the bottom of the tree.
  71  */
  72 struct ext4_extent {
  73         __le32  ee_block;       /* first logical block extent covers */
  74         __le16  ee_len;         /* number of blocks covered by extent */
  75         __le16  ee_start_hi;    /* high 16 bits of physical block */
  76         __le32  ee_start_lo;    /* low 32 bits of physical block */
  77 };
  78
  79 /*
  80  * This is index on-disk structure.
  81  * It's used at all the levels except the bottom.
  82  */
  83 struct ext4_extent_idx {
  84         __le32  ei_block;       /* index covers logical blocks from 'block' */
  85         __le32  ei_leaf_lo;     /* pointer to the physical block of the next *
  86                                  * level. leaf or next index could be there */
  87         __le16  ei_leaf_hi;     /* high 16 bits of physical block */
  88         __u16   ei_unused;
  89 };
  90
  91 /*
  92  * Each block (leaves and indexes), even inode-stored has header.
  93  */
  94 struct ext4_extent_header {
  95         __le16  eh_magic;       /* probably will support different formats */
  96         __le16  eh_entries;     /* number of valid entries */
  97         __le16  eh_max;         /* capacity of store in entries */
  98         __le16  eh_depth;       /* has tree real underlying blocks? */
  99         __le32  eh_generation;  /* generation of the tree */
 100 };
 101
 102 #define EXT4_EXT_MAGIC          cpu_to_le16(0xf30a)
 103
 104 /*
 105  * Array of ext4_ext_path contains path to some extent.
 106  * Creation/lookup routines use it for traversal/splitting/etc.
 107  * Truncate uses it to simulate recursive walking.
 108  */
 109 struct ext4_ext_path {
 110         ext4_fsblk_t                    p_block;
 111         __u16                           p_depth;
 112         struct ext4_extent              *p_ext;
 113         struct ext4_extent_idx          *p_idx;
 114         struct ext4_extent_header       *p_hdr;
 115         struct buffer_head              *p_bh;
 116 };
 117
 118 /*
 119  * structure for external API
 120  */
 121
 122 /*
 123  * to be called by ext4_ext_walk_space()
 124  * negative retcode - error
 125  * positive retcode - signal for ext4_ext_walk_space(), see below
 126  * callback must return valid extent (passed or newly created)
 127  */
 128 typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *,
 129                                         struct ext4_ext_cache *,
 130                                         struct ext4_extent *, void *);
 131
 132 #define EXT_CONTINUE   0
 133 #define EXT_BREAK      1
 134 #define EXT_REPEAT     2
 135
 136 /* Maximum logical block in a file; ext4_extent's ee_block is __le32 */
 137 #define EXT_MAX_BLOCK   0xffffffff
 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 uninitialized (i.e.
 144  * preallocated).
 145  * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
 146  * uninitialized extent.
 147  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
 148  * uninitialized one. In other words, if MSB of ee_len is set, it is an
 149  * uninitialized extent with only one special scenario when ee_len = 0x8000.
 150  * In this case we can not have an uninitialized 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 *uninitialized* extent is 2^15-1 (32767).
 155  */
 156 #define EXT_INIT_MAX_LEN        (1UL << 15)
 157 #define EXT_UNINIT_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         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 175 #define EXT_MAX_INDEX(__hdr__) \
 176         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 177
 178 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
 179 {
 180         return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
 181 }
 182
 183 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
 184 {
 185         return (struct ext4_extent_header *) bh->b_data;
 186 }
 187
 188 static inline unsigned short ext_depth(struct inode *inode)
 189 {
 190         return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 191 }
 192
 193 static inline void
 194 ext4_ext_invalidate_cache(struct inode *inode)
 195 {
 196         EXT4_I(inode)->i_cached_extent.ec_len = 0;
 197 }
 198
 199 static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext)
 200 {
 201         /* We can not have an uninitialized extent of zero length! */
 202         BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
 203         ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
 204 }
 205
 206 static inline int ext4_ext_is_uninitialized(struct ext4_extent *ext)
 207 {
 208         /* Extent with ee_len of 0x8000 is treated as an initialized extent */
 209         return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
 210 }
 211
 212 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 213 {
 214         return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
 215                 le16_to_cpu(ext->ee_len) :
 216                 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
 217 }
 218
 219 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
 220 {
 221         ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
 222 }
 223
 224 /*
 225  * ext4_ext_pblock:
 226  * combine low and high parts of physical block number into ext4_fsblk_t
 227  */
 228 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
 229 {
 230         ext4_fsblk_t block;
 231
 232         block = le32_to_cpu(ex->ee_start_lo);
 233         block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
 234         return block;
 235 }
 236
 237 /*
 238  * ext4_idx_pblock:
 239  * combine low and high parts of a leaf physical block number into ext4_fsblk_t
 240  */
 241 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
 242 {
 243         ext4_fsblk_t block;
 244
 245         block = le32_to_cpu(ix->ei_leaf_lo);
 246         block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
 247         return block;
 248 }
 249
 250 /*
 251  * ext4_ext_store_pblock:
 252  * stores a large physical block number into an extent struct,
 253  * breaking it into parts
 254  */
 255 static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
 256                                          ext4_fsblk_t pb)
 257 {
 258         ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 259         ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 260                                       0xffff);
 261 }
 262
 263 /*
 264  * ext4_idx_store_pblock:
 265  * stores a large physical block number into an index struct,
 266  * breaking it into parts
 267  */
 268 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
 269                                          ext4_fsblk_t pb)
 270 {
 271         ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
 272         ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
 273                                      0xffff);
 274 }
 275
 276 extern int ext4_ext_calc_metadata_amount(struct inode *inode,
 277                                          ext4_lblk_t lblocks);
 278 extern int ext4_extent_tree_init(handle_t *, struct inode *);
 279 extern int ext4_ext_calc_credits_for_single_extent(struct inode *inode,
 280                                                    int num,
 281                                                    struct ext4_ext_path *path);
 282 extern int ext4_can_extents_be_merged(struct inode *inode,
 283                                       struct ext4_extent *ex1,
 284                                       struct ext4_extent *ex2);
 285 extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *, int);
 286 extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
 287                                                         struct ext4_ext_path *);
 288 extern void ext4_ext_drop_refs(struct ext4_ext_path *);
 289 extern int ext4_ext_check_inode(struct inode *inode);
 290 #endif /* _EXT4_EXTENTS */
 291