root/fs/sysv/itree.c

DEFINITIONS

1. dirty_indirect
2. block_to_path
3. block_to_cpu
4. add_chain
5. verify_chain
6. block_end
7. get_branch
8. alloc_branch
9. splice_branch
10. get_block
11. all_zeroes
12. find_shared
13. free_data
14. free_branches
15. sysv_truncate
16. sysv_nblocks
17. sysv_getattr
18. sysv_writepage
19. sysv_readpage
20. sysv_prepare_chunk
21. sysv_write_failed
22. sysv_write_begin
23. sysv_bmap

   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(const struct path *path, struct kstat *stat,
 445                  u32 request_mask, unsigned int flags)
 446 {
 447         struct super_block *s = path->dentry->d_sb;
 448         generic_fillattr(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_readpage(struct file *file, struct page *page)
 460 {
 461         return block_read_full_page(page,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, unsigned flags,
 481                         struct page **pagep, void **fsdata)
 482 {
 483         int ret;
 484 
 485         ret = block_write_begin(mapping, pos, len, flags, 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         .readpage = sysv_readpage,
 499         .writepage = sysv_writepage,
 500         .write_begin = sysv_write_begin,
 501         .write_end = generic_write_end,
 502         .bmap = sysv_bmap
 503 };