1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/sysv/itree.c 4 * 5 * Handling of indirect blocks' trees. 6 * AV, Sep--Dec 2000 7 */ 8 9 #include <linux/buffer_head.h> 10 #include <linux/mount.h> 11 #include <linux/mpage.h> 12 #include <linux/string.h> 13 #include "sysv.h" 14 15 enum {DIRECT = 10, DEPTH = 4}; /* Have triple indirect */ 16 17 static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode) 18 { 19 mark_buffer_dirty_inode(bh, inode); 20 if (IS_SYNC(inode)) 21 sync_dirty_buffer(bh); 22 } 23 24 static int block_to_path(struct inode *inode, long block, int offsets[DEPTH]) 25 { 26 struct super_block *sb = inode->i_sb; 27 struct sysv_sb_info *sbi = SYSV_SB(sb); 28 int ptrs_bits = sbi->s_ind_per_block_bits; 29 unsigned long indirect_blocks = sbi->s_ind_per_block, 30 double_blocks = sbi->s_ind_per_block_2; 31 int n = 0; 32 33 if (block < 0) { 34 printk("sysv_block_map: block < 0\n"); 35 } else if (block < DIRECT) { 36 offsets[n++] = block; 37 } else if ( (block -= DIRECT) < indirect_blocks) { 38 offsets[n++] = DIRECT; 39 offsets[n++] = block; 40 } else if ((block -= indirect_blocks) < double_blocks) { 41 offsets[n++] = DIRECT+1; 42 offsets[n++] = block >> ptrs_bits; 43 offsets[n++] = block & (indirect_blocks - 1); 44 } else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) { 45 offsets[n++] = DIRECT+2; 46 offsets[n++] = block >> (ptrs_bits * 2); 47 offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1); 48 offsets[n++] = block & (indirect_blocks - 1); 49 } else { 50 /* nothing */; 51 } 52 return n; 53 } 54 55 static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr) 56 { 57 return sbi->s_block_base + fs32_to_cpu(sbi, nr); 58 } 59 60 typedef struct { 61 sysv_zone_t *p; 62 sysv_zone_t key; 63 struct buffer_head *bh; 64 } Indirect; 65 66 static DEFINE_RWLOCK(pointers_lock); 67 68 static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_t *v) 69 { 70 p->key = *(p->p = v); 71 p->bh = bh; 72 } 73 74 static inline int verify_chain(Indirect *from, Indirect *to) 75 { 76 while (from <= to && from->key == *from->p) 77 from++; 78 return (from > to); 79 } 80 81 static inline sysv_zone_t *block_end(struct buffer_head *bh) 82 { 83 return (sysv_zone_t*)((char*)bh->b_data + bh->b_size); 84 } 85 86 static Indirect *get_branch(struct inode *inode, 87 int depth, 88 int offsets[], 89 Indirect chain[], 90 int *err) 91 { 92 struct super_block *sb = inode->i_sb; 93 Indirect *p = chain; 94 struct buffer_head *bh; 95 96 *err = 0; 97 add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets); 98 if (!p->key) 99 goto no_block; 100 while (--depth) { 101 int block = block_to_cpu(SYSV_SB(sb), p->key); 102 bh = sb_bread(sb, block); 103 if (!bh) 104 goto failure; 105 read_lock(&pointers_lock); 106 if (!verify_chain(chain, p)) 107 goto changed; 108 add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets); 109 read_unlock(&pointers_lock); 110 if (!p->key) 111 goto no_block; 112 } 113 return NULL; 114 115 changed: 116 read_unlock(&pointers_lock); 117 brelse(bh); 118 *err = -EAGAIN; 119 goto no_block; 120 failure: 121 *err = -EIO; 122 no_block: 123 return p; 124 } 125 126 static int alloc_branch(struct inode *inode, 127 int num, 128 int *offsets, 129 Indirect *branch) 130 { 131 int blocksize = inode->i_sb->s_blocksize; 132 int n = 0; 133 int i; 134 135 branch[0].key = sysv_new_block(inode->i_sb); 136 if (branch[0].key) for (n = 1; n < num; n++) { 137 struct buffer_head *bh; 138 int parent; 139 /* Allocate the next block */ 140 branch[n].key = sysv_new_block(inode->i_sb); 141 if (!branch[n].key) 142 break; 143 /* 144 * Get buffer_head for parent block, zero it out and set 145 * the pointer to new one, then send parent to disk. 146 */ 147 parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key); 148 bh = sb_getblk(inode->i_sb, parent); 149 if (!bh) { 150 sysv_free_block(inode->i_sb, branch[n].key); 151 break; 152 } 153 lock_buffer(bh); 154 memset(bh->b_data, 0, blocksize); 155 branch[n].bh = bh; 156 branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n]; 157 *branch[n].p = branch[n].key; 158 set_buffer_uptodate(bh); 159 unlock_buffer(bh); 160 dirty_indirect(bh, inode); 161 } 162 if (n == num) 163 return 0; 164 165 /* Allocation failed, free what we already allocated */ 166 for (i = 1; i < n; i++) 167 bforget(branch[i].bh); 168 for (i = 0; i < n; i++) 169 sysv_free_block(inode->i_sb, branch[i].key); 170 return -ENOSPC; 171 } 172 173 static inline int splice_branch(struct inode *inode, 174 Indirect chain[], 175 Indirect *where, 176 int num) 177 { 178 int i; 179 180 /* Verify that place we are splicing to is still there and vacant */ 181 write_lock(&pointers_lock); 182 if (!verify_chain(chain, where-1) || *where->p) 183 goto changed; 184 *where->p = where->key; 185 write_unlock(&pointers_lock); 186 187 inode_set_ctime_current(inode); 188 189 /* had we spliced it onto indirect block? */ 190 if (where->bh) 191 dirty_indirect(where->bh, inode); 192 193 if (IS_SYNC(inode)) 194 sysv_sync_inode(inode); 195 else 196 mark_inode_dirty(inode); 197 return 0; 198 199 changed: 200 write_unlock(&pointers_lock); 201 for (i = 1; i < num; i++) 202 bforget(where[i].bh); 203 for (i = 0; i < num; i++) 204 sysv_free_block(inode->i_sb, where[i].key); 205 return -EAGAIN; 206 } 207 208 static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) 209 { 210 int err = -EIO; 211 int offsets[DEPTH]; 212 Indirect chain[DEPTH]; 213 struct super_block *sb = inode->i_sb; 214 Indirect *partial; 215 int left; 216 int depth = block_to_path(inode, iblock, offsets); 217 218 if (depth == 0) 219 goto out; 220 221 reread: 222 partial = get_branch(inode, depth, offsets, chain, &err); 223 224 /* Simplest case - block found, no allocation needed */ 225 if (!partial) { 226 got_it: 227 map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb), 228 chain[depth-1].key)); 229 /* Clean up and exit */ 230 partial = chain+depth-1; /* the whole chain */ 231 goto cleanup; 232 } 233 234 /* Next simple case - plain lookup or failed read of indirect block */ 235 if (!create || err == -EIO) { 236 cleanup: 237 while (partial > chain) { 238 brelse(partial->bh); 239 partial--; 240 } 241 out: 242 return err; 243 } 244 245 /* 246 * Indirect block might be removed by truncate while we were 247 * reading it. Handling of that case (forget what we've got and 248 * reread) is taken out of the main path. 249 */ 250 if (err == -EAGAIN) 251 goto changed; 252 253 left = (chain + depth) - partial; 254 err = alloc_branch(inode, left, offsets+(partial-chain), partial); 255 if (err) 256 goto cleanup; 257 258 if (splice_branch(inode, chain, partial, left) < 0) 259 goto changed; 260 261 set_buffer_new(bh_result); 262 goto got_it; 263 264 changed: 265 while (partial > chain) { 266 brelse(partial->bh); 267 partial--; 268 } 269 goto reread; 270 } 271 272 static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q) 273 { 274 while (p < q) 275 if (*p++) 276 return 0; 277 return 1; 278 } 279 280 static Indirect *find_shared(struct inode *inode, 281 int depth, 282 int offsets[], 283 Indirect chain[], 284 sysv_zone_t *top) 285 { 286 Indirect *partial, *p; 287 int k, err; 288 289 *top = 0; 290 for (k = depth; k > 1 && !offsets[k-1]; k--) 291 ; 292 partial = get_branch(inode, k, offsets, chain, &err); 293 294 write_lock(&pointers_lock); 295 if (!partial) 296 partial = chain + k-1; 297 /* 298 * If the branch acquired continuation since we've looked at it - 299 * fine, it should all survive and (new) top doesn't belong to us. 300 */ 301 if (!partial->key && *partial->p) { 302 write_unlock(&pointers_lock); 303 goto no_top; 304 } 305 for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--) 306 ; 307 /* 308 * OK, we've found the last block that must survive. The rest of our 309 * branch should be detached before unlocking. However, if that rest 310 * of branch is all ours and does not grow immediately from the inode 311 * it's easier to cheat and just decrement partial->p. 312 */ 313 if (p == chain + k - 1 && p > chain) { 314 p->p--; 315 } else { 316 *top = *p->p; 317 *p->p = 0; 318 } 319 write_unlock(&pointers_lock); 320 321 while (partial > p) { 322 brelse(partial->bh); 323 partial--; 324 } 325 no_top: 326 return partial; 327 } 328 329 static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q) 330 { 331 for ( ; p < q ; p++) { 332 sysv_zone_t nr = *p; 333 if (nr) { 334 *p = 0; 335 sysv_free_block(inode->i_sb, nr); 336 mark_inode_dirty(inode); 337 } 338 } 339 } 340 341 static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth) 342 { 343 struct buffer_head * bh; 344 struct super_block *sb = inode->i_sb; 345 346 if (depth--) { 347 for ( ; p < q ; p++) { 348 int block; 349 sysv_zone_t nr = *p; 350 if (!nr) 351 continue; 352 *p = 0; 353 block = block_to_cpu(SYSV_SB(sb), nr); 354 bh = sb_bread(sb, block); 355 if (!bh) 356 continue; 357 free_branches(inode, (sysv_zone_t*)bh->b_data, 358 block_end(bh), depth); 359 bforget(bh); 360 sysv_free_block(sb, nr); 361 mark_inode_dirty(inode); 362 } 363 } else 364 free_data(inode, p, q); 365 } 366 367 void sysv_truncate (struct inode * inode) 368 { 369 sysv_zone_t *i_data = SYSV_I(inode)->i_data; 370 int offsets[DEPTH]; 371 Indirect chain[DEPTH]; 372 Indirect *partial; 373 sysv_zone_t nr = 0; 374 int n; 375 long iblock; 376 unsigned blocksize; 377 378 if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) || 379 S_ISLNK(inode->i_mode))) 380 return; 381 382 blocksize = inode->i_sb->s_blocksize; 383 iblock = (inode->i_size + blocksize-1) 384 >> inode->i_sb->s_blocksize_bits; 385 386 block_truncate_page(inode->i_mapping, inode->i_size, get_block); 387 388 n = block_to_path(inode, iblock, offsets); 389 if (n == 0) 390 return; 391 392 if (n == 1) { 393 free_data(inode, i_data+offsets[0], i_data + DIRECT); 394 goto do_indirects; 395 } 396 397 partial = find_shared(inode, n, offsets, chain, &nr); 398 /* Kill the top of shared branch (already detached) */ 399 if (nr) { 400 if (partial == chain) 401 mark_inode_dirty(inode); 402 else 403 dirty_indirect(partial->bh, inode); 404 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial); 405 } 406 /* Clear the ends of indirect blocks on the shared branch */ 407 while (partial > chain) { 408 free_branches(inode, partial->p + 1, block_end(partial->bh), 409 (chain+n-1) - partial); 410 dirty_indirect(partial->bh, inode); 411 brelse (partial->bh); 412 partial--; 413 } 414 do_indirects: 415 /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */ 416 while (n < DEPTH) { 417 nr = i_data[DIRECT + n - 1]; 418 if (nr) { 419 i_data[DIRECT + n - 1] = 0; 420 mark_inode_dirty(inode); 421 free_branches(inode, &nr, &nr+1, n); 422 } 423 n++; 424 } 425 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode)); 426 if (IS_SYNC(inode)) 427 sysv_sync_inode (inode); 428 else 429 mark_inode_dirty(inode); 430 } 431 432 static unsigned sysv_nblocks(struct super_block *s, loff_t size) 433 { 434 struct sysv_sb_info *sbi = SYSV_SB(s); 435 int ptrs_bits = sbi->s_ind_per_block_bits; 436 unsigned blocks, res, direct = DIRECT, i = DEPTH; 437 blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits; 438 res = blocks; 439 while (--i && blocks > direct) { 440 blocks = ((blocks - direct - 1) >> ptrs_bits) + 1; 441 res += blocks; 442 direct = 1; 443 } 444 return res; 445 } 446 447 int sysv_getattr(struct mnt_idmap *idmap, const struct path *path, 448 struct kstat *stat, u32 request_mask, unsigned int flags) 449 { 450 struct super_block *s = path->dentry->d_sb; 451 generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry), 452 stat); 453 stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size); 454 stat->blksize = s->s_blocksize; 455 return 0; 456 } 457 458 static int sysv_writepages(struct address_space *mapping, 459 struct writeback_control *wbc) 460 { 461 return mpage_writepages(mapping, wbc, get_block); 462 } 463 464 static int sysv_read_folio(struct file *file, struct folio *folio) 465 { 466 return block_read_full_folio(folio, get_block); 467 } 468 469 int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len) 470 { 471 return __block_write_begin(page, pos, len, get_block); 472 } 473 474 static void sysv_write_failed(struct address_space *mapping, loff_t to) 475 { 476 struct inode *inode = mapping->host; 477 478 if (to > inode->i_size) { 479 truncate_pagecache(inode, inode->i_size); 480 sysv_truncate(inode); 481 } 482 } 483 484 static int sysv_write_begin(struct file *file, struct address_space *mapping, 485 loff_t pos, unsigned len, 486 struct page **pagep, void **fsdata) 487 { 488 int ret; 489 490 ret = block_write_begin(mapping, pos, len, pagep, get_block); 491 if (unlikely(ret)) 492 sysv_write_failed(mapping, pos + len); 493 494 return ret; 495 } 496 497 static sector_t sysv_bmap(struct address_space *mapping, sector_t block) 498 { 499 return generic_block_bmap(mapping,block,get_block); 500 } 501 502 const struct address_space_operations sysv_aops = { 503 .dirty_folio = block_dirty_folio, 504 .invalidate_folio = block_invalidate_folio, 505 .read_folio = sysv_read_folio, 506 .writepages = sysv_writepages, 507 .write_begin = sysv_write_begin, 508 .write_end = generic_write_end, 509 .migrate_folio = buffer_migrate_folio, 510 .bmap = sysv_bmap 511 }; 512