fs/sysv/itree.c

   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 };