include/linux/ext4_fs_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 _LINUX_EXT4_EXTENTS
  20 #define _LINUX_EXT4_EXTENTS
  21
  22 #include <linux/ext4_fs.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_DEBUG is defined you can use the 'extdebug' mount option
  47  * to get lots of info about what's going on.
  48  */
  49 #define EXT_DEBUG__
  50 #ifdef EXT_DEBUG
  51 #define ext_debug(a...)         printk(a)
  52 #else
  53 #define ext_debug(a...)
  54 #endif
  55
  56 /*
  57  * If EXT_STATS is defined then stats numbers are collected.
  58  * These number will be displayed at umount time.
  59  */
  60 #define EXT_STATS_
  61
  62
  63 /*
  64  * ext4_inode has i_block array (60 bytes total).
  65  * The first 12 bytes store ext4_extent_header;
  66  * the remainder stores an array of ext4_extent.
  67  */
  68
  69 /*
  70  * This is the extent on-disk structure.
  71  * It's used at the bottom of the tree.
  72  */
  73 struct ext4_extent {
  74         __le32  ee_block;       /* first logical block extent covers */
  75         __le16  ee_len;         /* number of blocks covered by extent */
  76         __le16  ee_start_hi;    /* high 16 bits of physical block */
  77         __le32  ee_start_lo;    /* low 32 bits of physical block */
  78 };
  79
  80 /*
  81  * This is index on-disk structure.
  82  * It's used at all the levels except the bottom.
  83  */
  84 struct ext4_extent_idx {
  85         __le32  ei_block;       /* index covers logical blocks from 'block' */
  86         __le32  ei_leaf_lo;     /* pointer to the physical block of the next *
  87                                  * level. leaf or next index could be there */
  88         __le16  ei_leaf_hi;     /* high 16 bits of physical block */
  89         __u16   ei_unused;
  90 };
  91
  92 /*
  93  * Each block (leaves and indexes), even inode-stored has header.
  94  */
  95 struct ext4_extent_header {
  96         __le16  eh_magic;       /* probably will support different formats */
  97         __le16  eh_entries;     /* number of valid entries */
  98         __le16  eh_max;         /* capacity of store in entries */
  99         __le16  eh_depth;       /* has tree real underlying blocks? */
 100         __le32  eh_generation;  /* generation of the tree */
 101 };
 102
 103 #define EXT4_EXT_MAGIC          cpu_to_le16(0xf30a)
 104
 105 /*
 106  * Array of ext4_ext_path contains path to some extent.
 107  * Creation/lookup routines use it for traversal/splitting/etc.
 108  * Truncate uses it to simulate recursive walking.
 109  */
 110 struct ext4_ext_path {
 111         ext4_fsblk_t                    p_block;
 112         __u16                           p_depth;
 113         struct ext4_extent              *p_ext;
 114         struct ext4_extent_idx          *p_idx;
 115         struct ext4_extent_header       *p_hdr;
 116         struct buffer_head              *p_bh;
 117 };
 118
 119 /*
 120  * structure for external API
 121  */
 122
 123 #define EXT4_EXT_CACHE_NO       0
 124 #define EXT4_EXT_CACHE_GAP      1
 125 #define EXT4_EXT_CACHE_EXTENT   2
 126
 127 /*
 128  * to be called by ext4_ext_walk_space()
 129  * negative retcode - error
 130  * positive retcode - signal for ext4_ext_walk_space(), see below
 131  * callback must return valid extent (passed or newly created)
 132  */
 133 typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *,
 134                                         struct ext4_ext_cache *,
 135                                         void *);
 136
 137 #define EXT_CONTINUE    0
 138 #define EXT_BREAK       1
 139 #define EXT_REPEAT      2
 140
 141
 142 #define EXT_MAX_BLOCK   0xffffffff
 143
 144 /*
 145  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
 146  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
 147  * MSB of ee_len field in the extent datastructure to signify if this
 148  * particular extent is an initialized extent or an uninitialized (i.e.
 149  * preallocated).
 150  * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
 151  * uninitialized extent.
 152  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
 153  * uninitialized one. In other words, if MSB of ee_len is set, it is an
 154  * uninitialized extent with only one special scenario when ee_len = 0x8000.
 155  * In this case we can not have an uninitialized extent of zero length and
 156  * thus we make it as a special case of initialized extent with 0x8000 length.
 157  * This way we get better extent-to-group alignment for initialized extents.
 158  * Hence, the maximum number of blocks we can have in an *initialized*
 159  * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767).
 160  */
 161 #define EXT_INIT_MAX_LEN        (1UL << 15)
 162 #define EXT_UNINIT_MAX_LEN      (EXT_INIT_MAX_LEN - 1)
 163
 164
 165 #define EXT_FIRST_EXTENT(__hdr__) \
 166         ((struct ext4_extent *) (((char *) (__hdr__)) +         \
 167                                  sizeof(struct ext4_extent_header)))
 168 #define EXT_FIRST_INDEX(__hdr__) \
 169         ((struct ext4_extent_idx *) (((char *) (__hdr__)) +     \
 170                                      sizeof(struct ext4_extent_header)))
 171 #define EXT_HAS_FREE_INDEX(__path__) \
 172         (le16_to_cpu((__path__)->p_hdr->eh_entries) \
 173                                      < le16_to_cpu((__path__)->p_hdr->eh_max))
 174 #define EXT_LAST_EXTENT(__hdr__) \
 175         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 176 #define EXT_LAST_INDEX(__hdr__) \
 177         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
 178 #define EXT_MAX_EXTENT(__hdr__) \
 179         (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 180 #define EXT_MAX_INDEX(__hdr__) \
 181         (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)
 182
 183 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
 184 {
 185         return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
 186 }
 187
 188 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
 189 {
 190         return (struct ext4_extent_header *) bh->b_data;
 191 }
 192
 193 static inline unsigned short ext_depth(struct inode *inode)
 194 {
 195         return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 196 }
 197
 198 static inline void ext4_ext_tree_changed(struct inode *inode)
 199 {
 200         EXT4_I(inode)->i_ext_generation++;
 201 }
 202
 203 static inline void
 204 ext4_ext_invalidate_cache(struct inode *inode)
 205 {
 206         EXT4_I(inode)->i_cached_extent.ec_type = EXT4_EXT_CACHE_NO;
 207 }
 208
 209 static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext)
 210 {
 211         /* We can not have an uninitialized extent of zero length! */
 212         BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
 213         ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
 214 }
 215
 216 static inline int ext4_ext_is_uninitialized(struct ext4_extent *ext)
 217 {
 218         /* Extent with ee_len of 0x8000 is treated as an initialized extent */
 219         return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
 220 }
 221
 222 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 223 {
 224         return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
 225                 le16_to_cpu(ext->ee_len) :
 226                 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
 227 }
 228
 229 extern int ext4_extent_tree_init(handle_t *, struct inode *);
 230 extern int ext4_ext_calc_credits_for_insert(struct inode *, struct ext4_ext_path *);
 231 extern int ext4_ext_try_to_merge(struct inode *inode,
 232                                  struct ext4_ext_path *path,
 233                                  struct ext4_extent *);
 234 extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, struct ext4_ext_path *);
 235 extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
 236 extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *);
 237 extern struct ext4_ext_path * ext4_ext_find_extent(struct inode *, int, struct ext4_ext_path *);
 238
 239 #endif /* _LINUX_EXT4_EXTENTS */
 240