fs/sysv/itree.c

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