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, offset;
  54         int             i, incr;
  55         int             freed = 0;
  56
  57 #ifdef PUNCH_DEBUG
  58         printf("Entering ind_punch, level %d, start %u, count %u, "
  59                "max %d\n", level, start, count, max);
  60 #endif
  61         incr = 1 << ((EXT2_BLOCK_SIZE_BITS(fs->super)-2)*level);
  62         for (i=0, offset=0; i < max; i++, p++, offset += incr) {
  63                 if (offset > count)
  64                         break;
  65                 if (*p == 0 || (offset+incr) <= start)
  66                         continue;
  67                 b = *p;
  68                 if (level > 0) {
  69                         blk_t start2;
  70 #ifdef PUNCH_DEBUG
  71                         printf("Reading indirect block %u\n", b);
  72 #endif
  73                         retval = ext2fs_read_ind_block(fs, b, block_buf);
  74                         if (retval)
  75                                 return retval;
  76                         start2 = (start > offset) ? start - offset : 0;
  77                         retval = ind_punch(fs, inode, block_buf + fs->blocksize,
  78                                            (blk_t *) block_buf, level - 1,
  79                                            start2, count - offset,
  80                                            fs->blocksize >> 2);
  81                         if (retval)
  82                                 return retval;
  83                         retval = ext2fs_write_ind_block(fs, b, block_buf);
  84                         if (retval)
  85                                 return retval;
  86                         if (!check_zero_block(block_buf, fs->blocksize))
  87                                 continue;
  88                 }
  89 #ifdef PUNCH_DEBUG
  90                 printf("Freeing block %u (offset %d)\n", b, offset);
  91 #endif
  92                 ext2fs_block_alloc_stats(fs, b, -1);
  93                 *p = 0;
  94                 freed++;
  95         }
  96 #ifdef PUNCH_DEBUG
  97         printf("Freed %d blocks\n", freed);
  98 #endif
  99         return ext2fs_iblk_sub_blocks(fs, inode, freed);
 100 }
 101
 102 static errcode_t ext2fs_punch_ind(ext2_filsys fs, struct ext2_inode *inode,
 103                                   char *block_buf, blk_t start, blk_t count)
 104 {
 105         errcode_t               retval;
 106         char                    *buf = 0;
 107         int                     level;
 108         int                     num = EXT2_NDIR_BLOCKS;
 109         blk_t                   *bp = inode->i_block;
 110         blk_t                   addr_per_block;
 111         blk_t                   max = EXT2_NDIR_BLOCKS;
 112
 113         if (!block_buf) {
 114                 retval = ext2fs_get_array(3, fs->blocksize, &buf);
 115                 if (retval)
 116                         return retval;
 117                 block_buf = buf;
 118         }
 119
 120         addr_per_block = (blk_t) fs->blocksize >> 2;
 121
 122         for (level=0; level < 4; level++, max *= addr_per_block) {
 123 #ifdef PUNCH_DEBUG
 124                 printf("Main loop level %d, start %u count %u "
 125                        "max %d num %d\n", level, start, count, max, num);
 126 #endif
 127                 if (start < max) {
 128                         retval = ind_punch(fs, inode, block_buf, bp, level,
 129                                            start, count, num);
 130                         if (retval)
 131                                 goto errout;
 132                         if (count > max)
 133                                 count -= max - start;
 134                         else
 135                                 break;
 136                         start = 0;
 137                 } else
 138                         start -= max;
 139                 bp += num;
 140                 if (level == 0) {
 141                         num = 1;
 142                         max = 1;
 143                 }
 144         }
 145         retval = 0;
 146 errout:
 147         if (buf)
 148                 ext2fs_free_mem(&buf);
 149         return retval;
 150 }
 151
 152 #ifdef PUNCH_DEBUG
 153
 154 #define dbg_printf(f, a...)  printf(f, ## a)
 155
 156 static void dbg_print_extent(char *desc, struct ext2fs_extent *extent)
 157 {
 158         if (desc)
 159                 printf("%s: ", desc);
 160         printf("extent: lblk %llu--%llu, len %u, pblk %llu, flags: ",
 161                extent->e_lblk, extent->e_lblk + extent->e_len - 1,
 162                extent->e_len, extent->e_pblk);
 163         if (extent->e_flags & EXT2_EXTENT_FLAGS_LEAF)
 164                 fputs("LEAF ", stdout);
 165         if (extent->e_flags & EXT2_EXTENT_FLAGS_UNINIT)
 166                 fputs("UNINIT ", stdout);
 167         if (extent->e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT)
 168                 fputs("2ND_VISIT ", stdout);
 169         if (!extent->e_flags)
 170                 fputs("(none)", stdout);
 171         fputc('\n', stdout);
 172
 173 }
 174 #else
 175 #define dbg_print_extent(desc, ex)      do { } while (0)
 176 #define dbg_printf(f, a...)             do { } while (0)
 177 #endif
 178
 179 static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
 180                                      struct ext2_inode *inode,
 181                                      blk64_t start, blk64_t end)
 182 {
 183         ext2_extent_handle_t    handle = 0;
 184         struct ext2fs_extent    extent;
 185         errcode_t               retval;
 186         blk64_t                 free_start, next;
 187         __u32                   free_count, newlen;
 188         int                     freed = 0;
 189
 190         retval = ext2fs_extent_open2(fs, ino, inode, &handle);
 191         if (retval)
 192                 return retval;
 193         ext2fs_extent_goto(handle, start);
 194         retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent);
 195         if (retval)
 196                 goto errout;
 197         while (1) {
 198                 dbg_print_extent("main loop", &extent);
 199                 next = extent.e_lblk + extent.e_len;
 200                 dbg_printf("start %llu, end %llu, next %llu\n",
 201                            (unsigned long long) start,
 202                            (unsigned long long) end,
 203                            (unsigned long long) next);
 204                 if (start <= extent.e_lblk) {
 205                         if (end < extent.e_lblk)
 206                                 goto next_extent;
 207                         dbg_printf("Case #%d\n", 1);
 208                         /* Start of deleted region before extent;
 209                            adjust beginning of extent */
 210                         free_start = extent.e_pblk;
 211                         if (next > end)
 212                                 free_count = end - extent.e_lblk + 1;
 213                         else
 214                                 free_count = extent.e_len;
 215                         extent.e_len -= free_count;
 216                         extent.e_lblk += free_count;
 217                         extent.e_pblk += free_count;
 218                 } else if (end >= next-1) {
 219                         if (start >= next)
 220                                 break;
 221                         /* End of deleted region after extent;
 222                            adjust end of extent */
 223                         dbg_printf("Case #%d\n", 2);
 224                         newlen = start - extent.e_lblk;
 225                         free_start = extent.e_pblk + newlen;
 226                         free_count = extent.e_len - newlen;
 227                         extent.e_len = newlen;
 228                 } else {
 229                         struct ext2fs_extent    newex;
 230
 231                         dbg_printf("Case #%d\n", 3);
 232                         /* The hard case; we need to split the extent */
 233                         newex.e_pblk = extent.e_pblk +
 234                                 (end + 1 - extent.e_lblk);
 235                         newex.e_lblk = end + 1;
 236                         newex.e_len = next - end - 1;
 237                         newex.e_flags = extent.e_flags;
 238
 239                         extent.e_len = start - extent.e_lblk;
 240                         free_start = extent.e_pblk + extent.e_len;
 241                         free_count = end - start + 1;
 242
 243                         dbg_print_extent("inserting", &newex);
 244                         retval = ext2fs_extent_insert(handle,
 245                                         EXT2_EXTENT_INSERT_AFTER, &newex);
 246                         if (retval)
 247                                 goto errout;
 248                         /* Now pointing at inserted extent; so go back */
 249                         retval = ext2fs_extent_get(handle,
 250                                                    EXT2_EXTENT_PREV_LEAF,
 251                                                    &newex);
 252                         if (retval)
 253                                 goto errout;
 254                 }
 255                 if (extent.e_len) {
 256                         dbg_print_extent("replacing", &extent);
 257                         retval = ext2fs_extent_replace(handle, 0, &extent);
 258                 } else {
 259                         dbg_printf("deleting current extent%s\n", "");
 260                         retval = ext2fs_extent_delete(handle, 0);
 261                 }
 262                 if (retval)
 263                         goto errout;
 264                 dbg_printf("Free start %llu, free count = %u\n",
 265                        free_start, free_count);
 266                 while (free_count-- > 0) {
 267                         ext2fs_block_alloc_stats(fs, free_start++, -1);
 268                         freed++;
 269                 }
 270         next_extent:
 271                 retval = ext2fs_extent_get(handle, EXT2_EXTENT_NEXT_LEAF,
 272                                            &extent);
 273                 if (retval == EXT2_ET_EXTENT_NO_NEXT)
 274                         break;
 275                 if (retval)
 276                         goto errout;
 277         }
 278         dbg_printf("Freed %d blocks\n", freed);
 279         retval = ext2fs_iblk_sub_blocks(fs, inode, freed);
 280 errout:
 281         ext2fs_extent_free(handle);
 282         return retval;
 283 }
 284
 285 /*
 286  * Deallocate all logical blocks starting at start to end, inclusive.
 287  * If end is ~0, then this is effectively truncate.
 288  */
 289 extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
 290                               struct ext2_inode *inode,
 291                               char *block_buf, blk64_t start,
 292                               blk64_t end)
 293 {
 294         errcode_t               retval;
 295         struct ext2_inode       inode_buf;
 296
 297         if (start > end)
 298                 return EINVAL;
 299
 300         if (start == end)
 301                 return 0;
 302
 303         /* Read inode structure if necessary */
 304         if (!inode) {
 305                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
 306                 if (retval)
 307                         return retval;
 308                 inode = &inode_buf;
 309         }
 310         if (inode->i_flags & EXT4_EXTENTS_FL)
 311                 retval = ext2fs_punch_extent(fs, ino, inode, start, end);
 312         else {
 313                 blk_t   count;
 314
 315                 if (start > ~0U)
 316                         return 0;
 317                 count = ((end - start) < ~0U) ? (end - start) : ~0U;
 318                 retval = ext2fs_punch_ind(fs, inode, block_buf,
 319                                           (blk_t) start, count);
 320         }
 321         if (retval)
 322                 return retval;
 323
 324         return ext2fs_write_inode(fs, ino, inode);
 325 }