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