punch.c revision 341bc5e368f7a768482f041971fb3c4b156d6ed9
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 */ 28static 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 */ 48static 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 103static 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; 147errout: 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 157static 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 180static 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 ext2fs_extent_goto(handle, start); 196 retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent); 197 if (retval) 198 goto errout; 199 while (1) { 200 op = EXT2_EXTENT_NEXT_LEAF; 201 dbg_print_extent("main loop", &extent); 202 next = extent.e_lblk + extent.e_len; 203 dbg_printf("start %llu, end %llu, next %llu\n", 204 (unsigned long long) start, 205 (unsigned long long) end, 206 (unsigned long long) next); 207 if (start <= extent.e_lblk) { 208 if (end < extent.e_lblk) 209 goto next_extent; 210 dbg_printf("Case #%d\n", 1); 211 /* Start of deleted region before extent; 212 adjust beginning of extent */ 213 free_start = extent.e_pblk; 214 if (next > end) 215 free_count = end - extent.e_lblk + 1; 216 else 217 free_count = extent.e_len; 218 extent.e_len -= free_count; 219 extent.e_lblk += free_count; 220 extent.e_pblk += free_count; 221 } else if (end >= next-1) { 222 if (start >= next) 223 break; 224 /* End of deleted region after extent; 225 adjust end of extent */ 226 dbg_printf("Case #%d\n", 2); 227 newlen = start - extent.e_lblk; 228 free_start = extent.e_pblk + newlen; 229 free_count = extent.e_len - newlen; 230 extent.e_len = newlen; 231 } else { 232 struct ext2fs_extent newex; 233 234 dbg_printf("Case #%d\n", 3); 235 /* The hard case; we need to split the extent */ 236 newex.e_pblk = extent.e_pblk + 237 (end + 1 - extent.e_lblk); 238 newex.e_lblk = end + 1; 239 newex.e_len = next - end - 1; 240 newex.e_flags = extent.e_flags; 241 242 extent.e_len = start - extent.e_lblk; 243 free_start = extent.e_pblk + extent.e_len; 244 free_count = end - start + 1; 245 246 dbg_print_extent("inserting", &newex); 247 retval = ext2fs_extent_insert(handle, 248 EXT2_EXTENT_INSERT_AFTER, &newex); 249 if (retval) 250 goto errout; 251 /* Now pointing at inserted extent; so go back */ 252 retval = ext2fs_extent_get(handle, 253 EXT2_EXTENT_PREV_LEAF, 254 &newex); 255 if (retval) 256 goto errout; 257 } 258 if (extent.e_len) { 259 dbg_print_extent("replacing", &extent); 260 retval = ext2fs_extent_replace(handle, 0, &extent); 261 } else { 262 struct ext2fs_extent newex; 263 dbg_printf("deleting current extent%s\n", ""); 264 retval = ext2fs_extent_delete(handle, 0); 265 if (retval) 266 goto errout; 267 /* 268 * We just moved the next extent into the current 269 * extent's position, so re-read the extent next time. 270 */ 271 retval = ext2fs_extent_get(handle, 272 EXT2_EXTENT_PREV_LEAF, 273 &newex); 274 /* Can't go back? Just reread current. */ 275 if (retval == EXT2_ET_EXTENT_NO_PREV) { 276 retval = 0; 277 op = EXT2_EXTENT_CURRENT; 278 } 279 } 280 if (retval) 281 goto errout; 282 dbg_printf("Free start %llu, free count = %u\n", 283 free_start, free_count); 284 while (free_count-- > 0) { 285 ext2fs_block_alloc_stats2(fs, free_start++, -1); 286 freed++; 287 } 288 next_extent: 289 retval = ext2fs_extent_get(handle, op, 290 &extent); 291 if (retval == EXT2_ET_EXTENT_NO_NEXT || 292 retval == EXT2_ET_NO_CURRENT_NODE) 293 break; 294 if (retval) 295 goto errout; 296 } 297 dbg_printf("Freed %d blocks\n", freed); 298 retval = ext2fs_iblk_sub_blocks(fs, inode, freed); 299errout: 300 ext2fs_extent_free(handle); 301 return retval; 302} 303 304/* 305 * Deallocate all logical blocks starting at start to end, inclusive. 306 * If end is ~0, then this is effectively truncate. 307 */ 308extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino, 309 struct ext2_inode *inode, 310 char *block_buf, blk64_t start, 311 blk64_t end) 312{ 313 errcode_t retval; 314 struct ext2_inode inode_buf; 315 316 if (start > end) 317 return EINVAL; 318 319 /* Read inode structure if necessary */ 320 if (!inode) { 321 retval = ext2fs_read_inode(fs, ino, &inode_buf); 322 if (retval) 323 return retval; 324 inode = &inode_buf; 325 } 326 if (inode->i_flags & EXT4_EXTENTS_FL) 327 retval = ext2fs_punch_extent(fs, ino, inode, start, end); 328 else { 329 blk_t count; 330 331 if (start > ~0U) 332 return 0; 333 count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U; 334 retval = ext2fs_punch_ind(fs, inode, block_buf, 335 (blk_t) start, count); 336 } 337 if (retval) 338 return retval; 339 340 return ext2fs_write_inode(fs, ino, inode); 341} 342