lib/ext2fs/punch.c

   1 /*
   2  * punch.c --- deallocate blocks allocated to an inode
   3  *
   4  * Copyright (C) 2010 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Library
   8  * General Public License, version 2.
   9  * %End-Header%
  10  */
  11
  12 #include "config.h"
  13 #include <stdio.h>
  14 #include <string.h>
  15 #if HAVE_UNISTD_H
  16 #include <unistd.h>
  17 #endif
  18 #include <errno.h>
  19
  20 #include "ext2_fs.h"
  21 #include "ext2fs.h"
  22
  23 #undef PUNCH_DEBUG
  24
  25 /*
  26  * This function returns 1 if the specified block is all zeros
  27  */
  28 static int check_zero_block(char *buf, int blocksize)
  29 {
  30         char    *cp = buf;
  31         int     left = blocksize;
  32
  33         while (left > 0) {
  34                 if (*cp++)
  35                         return 0;
  36                 left--;
  37         }
  38         return 1;
  39 }
  40
  41 /*
  42  * This clever recursive function handles i_blocks[] as well as
  43  * indirect, double indirect, and triple indirect blocks.  It iterates
  44  * over the entries in the i_blocks array or indirect blocks, and for
  45  * each one, will recursively handle any indirect blocks and then
  46  * frees and deallocates the blocks.
  47  */
  48 static errcode_t ind_punch(ext2_filsys fs, struct ext2_inode *inode,
  49                            char *block_buf, blk_t *p, int level,
  50                            blk_t start, blk_t count, int max)
  51 {
  52         errcode_t       retval;
  53         blk_t           b;
  54         int             i;
  55         blk64_t         offset, incr;
  56         int             freed = 0;
  57
  58 #ifdef PUNCH_DEBUG
  59         printf("Entering ind_punch, level %d, start %u, count %u, "
  60                "max %d\n", level, start, count, max);
  61 #endif
  62         incr = 1ULL << ((EXT2_BLOCK_SIZE_BITS(fs->super)-2)*level);
  63         for (i=0, offset=0; i < max; i++, p++, offset += incr) {
  64                 if (offset >= start + count)
  65                         break;
  66                 if (*p == 0 || (offset+incr) <= start)
  67                         continue;
  68                 b = *p;
  69                 if (level > 0) {
  70                         blk_t start2;
  71 #ifdef PUNCH_DEBUG
  72                         printf("Reading indirect block %u\n", b);
  73 #endif
  74                         retval = ext2fs_read_ind_block(fs, b, block_buf);
  75                         if (retval)
  76                                 return retval;
  77                         start2 = (start > offset) ? start - offset : 0;
  78                         retval = ind_punch(fs, inode, block_buf + fs->blocksize,
  79                                            (blk_t *) block_buf, level - 1,
  80                                            start2, count - offset,
  81                                            fs->blocksize >> 2);
  82                         if (retval)
  83                                 return retval;
  84                         retval = ext2fs_write_ind_block(fs, b, block_buf);
  85                         if (retval)
  86                                 return retval;
  87                         if (!check_zero_block(block_buf, fs->blocksize))
  88                                 continue;
  89                 }
  90 #ifdef PUNCH_DEBUG
  91                 printf("Freeing block %u (offset %llu)\n", b, offset);
  92 #endif
  93                 ext2fs_block_alloc_stats(fs, b, -1);
  94                 *p = 0;
  95                 freed++;
  96         }
  97 #ifdef PUNCH_DEBUG
  98         printf("Freed %d blocks\n", freed);
  99 #endif
 100         return ext2fs_iblk_sub_blocks(fs, inode, freed);
 101 }
 102
 103 static errcode_t ext2fs_punch_ind(ext2_filsys fs, struct ext2_inode *inode,
 104                                   char *block_buf, blk_t start, blk_t count)
 105 {
 106         errcode_t               retval;
 107         char                    *buf = 0;
 108         int                     level;
 109         int                     num = EXT2_NDIR_BLOCKS;
 110         blk_t                   *bp = inode->i_block;
 111         blk_t                   addr_per_block;
 112         blk64_t                 max = EXT2_NDIR_BLOCKS;
 113
 114         if (!block_buf) {
 115                 retval = ext2fs_get_array(3, fs->blocksize, &buf);
 116                 if (retval)
 117                         return retval;
 118                 block_buf = buf;
 119         }
 120
 121         addr_per_block = (blk_t) fs->blocksize >> 2;
 122
 123         for (level = 0; level < 4; level++, max *= (blk64_t)addr_per_block) {
 124 #ifdef PUNCH_DEBUG
 125                 printf("Main loop level %d, start %u count %u "
 126                        "max %llu num %d\n", level, start, count, max, num);
 127 #endif
 128                 if (start < max) {
 129                         retval = ind_punch(fs, inode, block_buf, bp, level,
 130                                            start, count, num);
 131                         if (retval)
 132                                 goto errout;
 133                         if (count > max)
 134                                 count -= max - start;
 135                         else
 136                                 break;
 137                         start = 0;
 138                 } else
 139                         start -= max;
 140                 bp += num;
 141                 if (level == 0) {
 142                         num = 1;
 143                         max = 1;
 144                 }
 145         }
 146         retval = 0;
 147 errout:
 148         if (buf)
 149                 ext2fs_free_mem(&buf);
 150         return retval;
 151 }
 152
 153 #ifdef PUNCH_DEBUG
 154
 155 #define dbg_printf(f, a...)  printf(f, ## a)
 156
 157 static void dbg_print_extent(char *desc, struct ext2fs_extent *extent)
 158 {
 159         if (desc)
 160                 printf("%s: ", desc);
 161         printf("extent: lblk %llu--%llu, len %u, pblk %llu, flags: ",
 162                extent->e_lblk, extent->e_lblk + extent->e_len - 1,
 163                extent->e_len, extent->e_pblk);
 164         if (extent->e_flags & EXT2_EXTENT_FLAGS_LEAF)
 165                 fputs("LEAF ", stdout);
 166         if (extent->e_flags & EXT2_EXTENT_FLAGS_UNINIT)
 167                 fputs("UNINIT ", stdout);
 168         if (extent->e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT)
 169                 fputs("2ND_VISIT ", stdout);
 170         if (!extent->e_flags)
 171                 fputs("(none)", stdout);
 172         fputc('\n', stdout);
 173
 174 }
 175 #else
 176 #define dbg_print_extent(desc, ex)      do { } while (0)
 177 #define dbg_printf(f, a...)             do { } while (0)
 178 #endif
 179
 180 static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
 181                                      struct ext2_inode *inode,
 182                                      blk64_t start, blk64_t end)
 183 {
 184         ext2_extent_handle_t    handle = 0;
 185         struct ext2fs_extent    extent;
 186         errcode_t               retval;
 187         blk64_t                 free_start, next;
 188         __u32                   free_count, newlen;
 189         int                     freed = 0;
 190         int                     op;
 191
 192         retval = ext2fs_extent_open2(fs, ino, inode, &handle);
 193         if (retval)
 194                 return retval;
 195         /*
 196          * Find the extent closest to the start of the punch range.  We don't
 197          * check the return value because _goto() sets the current node to the
 198          * next-lowest extent if 'start' is in a hole, and doesn't set a
 199          * current node if there was a real error reading the extent tree.
 200          * In that case, _get() will error out.
 201          */
 202         ext2fs_extent_goto(handle, start);
 203         retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent);
 204         if (retval)
 205                 goto errout;
 206         while (1) {
 207                 op = EXT2_EXTENT_NEXT_LEAF;
 208                 dbg_print_extent("main loop", &extent);
 209                 next = extent.e_lblk + extent.e_len;
 210                 dbg_printf("start %llu, end %llu, next %llu\n",
 211                            (unsigned long long) start,
 212                            (unsigned long long) end,
 213                            (unsigned long long) next);
 214                 if (start <= extent.e_lblk) {
 215                         if (end < extent.e_lblk)
 216                                 goto next_extent;
 217                         dbg_printf("Case #%d\n", 1);
 218                         /* Start of deleted region before extent;
 219                            adjust beginning of extent */
 220                         free_start = extent.e_pblk;
 221                         if (next > end)
 222                                 free_count = end - extent.e_lblk + 1;
 223                         else
 224                                 free_count = extent.e_len;
 225                         extent.e_len -= free_count;
 226                         extent.e_lblk += free_count;
 227                         extent.e_pblk += free_count;
 228                 } else if (end >= next-1) {
 229                         if (start >= next)
 230                                 break;
 231                         /* End of deleted region after extent;
 232                            adjust end of extent */
 233                         dbg_printf("Case #%d\n", 2);
 234                         newlen = start - extent.e_lblk;
 235                         free_start = extent.e_pblk + newlen;
 236                         free_count = extent.e_len - newlen;
 237                         extent.e_len = newlen;
 238                 } else {
 239                         struct ext2fs_extent    newex;
 240
 241                         dbg_printf("Case #%d\n", 3);
 242                         /* The hard case; we need to split the extent */
 243                         newex.e_pblk = extent.e_pblk +
 244                                 (end + 1 - extent.e_lblk);
 245                         newex.e_lblk = end + 1;
 246                         newex.e_len = next - end - 1;
 247                         newex.e_flags = extent.e_flags;
 248
 249                         extent.e_len = start - extent.e_lblk;
 250                         free_start = extent.e_pblk + extent.e_len;
 251                         free_count = end - start + 1;
 252
 253                         dbg_print_extent("inserting", &newex);
 254                         retval = ext2fs_extent_insert(handle,
 255                                         EXT2_EXTENT_INSERT_AFTER, &newex);
 256                         if (retval)
 257                                 goto errout;
 258                         /* Now pointing at inserted extent; so go back */
 259                         retval = ext2fs_extent_get(handle,
 260                                                    EXT2_EXTENT_PREV_LEAF,
 261                                                    &newex);
 262                         if (retval)
 263                                 goto errout;
 264                 }
 265                 if (extent.e_len) {
 266                         dbg_print_extent("replacing", &extent);
 267                         retval = ext2fs_extent_replace(handle, 0, &extent);
 268                 } else {
 269                         struct ext2fs_extent    newex;
 270                         blk64_t                 old_lblk, next_lblk;
 271                         dbg_printf("deleting current extent%s\n", "");
 272
 273                         /*
 274                          * Save the location of the next leaf, then slip
 275                          * back to the current extent.
 276                          */
 277                         retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT,
 278                                                    &newex);
 279                         if (retval)
 280                                 goto errout;
 281                         old_lblk = newex.e_lblk;
 282
 283                         retval = ext2fs_extent_get(handle,
 284                                                    EXT2_EXTENT_NEXT_LEAF,
 285                                                    &newex);
 286                         if (retval == EXT2_ET_EXTENT_NO_NEXT)
 287                                 next_lblk = old_lblk;
 288                         else if (retval)
 289                                 goto errout;
 290                         else
 291                                 next_lblk = newex.e_lblk;
 292
 293                         retval = ext2fs_extent_goto(handle, old_lblk);
 294                         if (retval)
 295                                 goto errout;
 296
 297                         /* Now delete the extent. */
 298                         retval = ext2fs_extent_delete(handle, 0);
 299                         if (retval)
 300                                 goto errout;
 301
 302                         /* Jump forward to the next extent. */
 303                         ext2fs_extent_goto(handle, next_lblk);
 304                         op = EXT2_EXTENT_CURRENT;
 305                 }
 306                 if (retval)
 307                         goto errout;
 308                 dbg_printf("Free start %llu, free count = %u\n",
 309                        free_start, free_count);
 310                 while (free_count-- > 0) {
 311                         ext2fs_block_alloc_stats2(fs, free_start++, -1);
 312                         freed++;
 313                 }
 314         next_extent:
 315                 retval = ext2fs_extent_get(handle, op,
 316                                            &extent);
 317                 if (retval == EXT2_ET_EXTENT_NO_NEXT ||
 318                     retval == EXT2_ET_NO_CURRENT_NODE)
 319                         break;
 320                 if (retval)
 321                         goto errout;
 322         }
 323         dbg_printf("Freed %d blocks\n", freed);
 324         retval = ext2fs_iblk_sub_blocks(fs, inode, freed);
 325 errout:
 326         ext2fs_extent_free(handle);
 327         return retval;
 328 }
 329
 330 /*
 331  * Deallocate all logical blocks starting at start to end, inclusive.
 332  * If end is ~0, then this is effectively truncate.
 333  */
 334 extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
 335                               struct ext2_inode *inode,
 336                               char *block_buf, blk64_t start,
 337                               blk64_t end)
 338 {
 339         errcode_t               retval;
 340         struct ext2_inode       inode_buf;
 341
 342         if (start > end)
 343                 return EINVAL;
 344
 345         /* Read inode structure if necessary */
 346         if (!inode) {
 347                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
 348                 if (retval)
 349                         return retval;
 350                 inode = &inode_buf;
 351         }
 352         if (inode->i_flags & EXT4_EXTENTS_FL)
 353                 retval = ext2fs_punch_extent(fs, ino, inode, start, end);
 354         else {
 355                 blk_t   count;
 356
 357                 if (start > ~0U)
 358                         return 0;
 359                 count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U;
 360                 retval = ext2fs_punch_ind(fs, inode, block_buf,
 361                                           (blk_t) start, count);
 362         }
 363         if (retval)
 364                 return retval;
 365
 366         return ext2fs_write_inode(fs, ino, inode);
 367 }