resize/extent.c

   1 /*
   2  * extent.c --- ext2 extent abstraction
   3  *
   4  * This abstraction is used to provide a compact way of representing a
   5  * translation table, for moving multiple contiguous ranges (extents)
   6  * of blocks or inodes.
   7  *
   8  * Copyright (C) 1997, 1998 by Theodore Ts'o and
   9  *      PowerQuest, Inc.
  10  *
  11  * Copyright (C) 1999, 2000 by Theosore Ts'o
  12  *
  13  * %Begin-Header%
  14  * This file may be redistributed under the terms of the GNU Public
  15  * License.
  16  * %End-Header%
  17  */
  18
  19 #include "config.h"
  20 #include "resize2fs.h"
  21
  22 struct ext2_extent_entry {
  23         __u64   old_loc, new_loc;
  24         __u64   size;
  25 };
  26
  27 struct _ext2_extent {
  28         struct ext2_extent_entry *list;
  29         __u64   cursor;
  30         __u64   size;
  31         __u64   num;
  32         __u64   sorted;
  33 };
  34
  35 /*
  36  * Create an extent table
  37  */
  38 errcode_t ext2fs_create_extent_table(ext2_extent *ret_extent, __u64 size)
  39 {
  40         ext2_extent     extent;
  41         errcode_t       retval;
  42
  43         retval = ext2fs_get_mem(sizeof(struct _ext2_extent), &extent);
  44         if (retval)
  45                 return retval;
  46         memset(extent, 0, sizeof(struct _ext2_extent));
  47
  48         extent->size = size ? size : 50;
  49         extent->cursor = 0;
  50         extent->num = 0;
  51         extent->sorted = 1;
  52
  53         retval = ext2fs_get_array(sizeof(struct ext2_extent_entry),
  54                                 extent->size, &extent->list);
  55         if (retval) {
  56                 ext2fs_free_mem(&extent);
  57                 return retval;
  58         }
  59         memset(extent->list, 0,
  60                sizeof(struct ext2_extent_entry) * extent->size);
  61         *ret_extent = extent;
  62         return 0;
  63 }
  64
  65 /*
  66  * Free an extent table
  67  */
  68 void ext2fs_free_extent_table(ext2_extent extent)
  69 {
  70         if (extent->list)
  71                 ext2fs_free_mem(&extent->list);
  72         extent->list = 0;
  73         extent->size = 0;
  74         extent->num = 0;
  75         ext2fs_free_mem(&extent);
  76 }
  77
  78 /*
  79  * Add an entry to the extent table
  80  */
  81 errcode_t ext2fs_add_extent_entry(ext2_extent extent, __u64 old_loc, __u64 new_loc)
  82 {
  83         struct  ext2_extent_entry       *ent;
  84         errcode_t                       retval;
  85         __u64                           newsize;
  86         __u64                           curr;
  87
  88         if (extent->num >= extent->size) {
  89                 newsize = extent->size + 100;
  90                 retval = ext2fs_resize_mem(sizeof(struct ext2_extent_entry) *
  91                                            extent->size,
  92                                            sizeof(struct ext2_extent_entry) *
  93                                            newsize, &extent->list);
  94                 if (retval)
  95                         return retval;
  96                 extent->size = newsize;
  97         }
  98         curr = extent->num;
  99         ent = extent->list + curr;
 100         if (curr) {
 101                 /*
 102                  * Check to see if this can be coalesced with the last
 103                  * extent
 104                  */
 105                 ent--;
 106                 if ((ent->old_loc + ent->size == old_loc) &&
 107                     (ent->new_loc + ent->size == new_loc)) {
 108                         ent->size++;
 109                         return 0;
 110                 }
 111                 /*
 112                  * Now see if we're going to ruin the sorting
 113                  */
 114                 if (ent->old_loc + ent->size > old_loc)
 115                         extent->sorted = 0;
 116                 ent++;
 117         }
 118         ent->old_loc = old_loc;
 119         ent->new_loc = new_loc;
 120         ent->size = 1;
 121         extent->num++;
 122         return 0;
 123 }
 124
 125 /*
 126  * Helper function for qsort
 127  */
 128 static EXT2_QSORT_TYPE extent_cmp(const void *a, const void *b)
 129 {
 130         const struct ext2_extent_entry *db_a;
 131         const struct ext2_extent_entry *db_b;
 132
 133         db_a = (const struct ext2_extent_entry *) a;
 134         db_b = (const struct ext2_extent_entry *) b;
 135
 136         return (db_a->old_loc - db_b->old_loc);
 137 }
 138
 139 /*
 140  * Given an inode map and inode number, look up the old inode number
 141  * and return the new inode number.
 142  */
 143 __u64 ext2fs_extent_translate(ext2_extent extent, __u64 old_loc)
 144 {
 145         __s64   low, high, mid;
 146         __u64   lowval, highval;
 147         float   range;
 148
 149         if (!extent->sorted) {
 150                 qsort(extent->list, extent->num,
 151                       sizeof(struct ext2_extent_entry), extent_cmp);
 152                 extent->sorted = 1;
 153         }
 154         low = 0;
 155         high = extent->num-1;
 156         while (low <= high) {
 157 #if 0
 158                 mid = (low+high)/2;
 159 #else
 160                 if (low == high)
 161                         mid = low;
 162                 else {
 163                         /* Interpolate for efficiency */
 164                         lowval = extent->list[low].old_loc;
 165                         highval = extent->list[high].old_loc;
 166
 167                         if (old_loc < lowval)
 168                                 range = 0;
 169                         else if (old_loc > highval)
 170                                 range = 1;
 171                         else {
 172                                 range = ((float) (old_loc - lowval)) /
 173                                         (highval - lowval);
 174                                 if (range > 0.9)
 175                                         range = 0.9;
 176                                 if (range < 0.1)
 177                                         range = 0.1;
 178                         }
 179                         mid = low + ((__u64) (range * (high-low)));
 180                 }
 181 #endif
 182                 if ((old_loc >= extent->list[mid].old_loc) &&
 183                     (old_loc < extent->list[mid].old_loc + extent->list[mid].size))
 184                         return (extent->list[mid].new_loc +
 185                                 (old_loc - extent->list[mid].old_loc));
 186                 if (old_loc < extent->list[mid].old_loc)
 187                         high = mid-1;
 188                 else
 189                         low = mid+1;
 190         }
 191         return 0;
 192 }
 193
 194 /*
 195  * For debugging only
 196  */
 197 void ext2fs_extent_dump(ext2_extent extent, FILE *out)
 198 {
 199         __u64   i;
 200         struct ext2_extent_entry *ent;
 201
 202         fputs(_("# Extent dump:\n"), out);
 203         fprintf(out, _("#\tNum=%llu, Size=%llu, Cursor=%llu, Sorted=%llu\n"),
 204                extent->num, extent->size, extent->cursor, extent->sorted);
 205         for (i=0, ent=extent->list; i < extent->num; i++, ent++) {
 206                 fprintf(out, "#\t\t %llu -> %llu (%llu)\n", ent->old_loc,
 207                         ent->new_loc, ent->size);
 208         }
 209 }
 210
 211 /*
 212  * Iterate over the contents of the extent table
 213  */
 214 errcode_t ext2fs_iterate_extent(ext2_extent extent, __u64 *old_loc,
 215                                 __u64 *new_loc, __u64 *size)
 216 {
 217         struct ext2_extent_entry *ent;
 218
 219         if (!old_loc) {
 220                 extent->cursor = 0;
 221                 return 0;
 222         }
 223
 224         if (extent->cursor >= extent->num) {
 225                 *old_loc = 0;
 226                 *new_loc = 0;
 227                 *size = 0;
 228                 return 0;
 229         }
 230
 231         ent = extent->list + extent->cursor++;
 232
 233         *old_loc = ent->old_loc;
 234         *new_loc = ent->new_loc;
 235         *size = ent->size;
 236         return 0;
 237 }
 238
 239
 240
 241