fs/minix/itree_common.c

   1 /* Generic part */
   2
   3 typedef struct {
   4         block_t *p;
   5         block_t key;
   6         struct buffer_head *bh;
   7 } Indirect;
   8
   9 static rwlock_t pointers_lock = RW_LOCK_UNLOCKED;
  10
  11 static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
  12 {
  13         p->key = *(p->p = v);
  14         p->bh = bh;
  15 }
  16
  17 static inline int verify_chain(Indirect *from, Indirect *to)
  18 {
  19         while (from <= to && from->key == *from->p)
  20                 from++;
  21         return (from > to);
  22 }
  23
  24 static inline block_t *block_end(struct buffer_head *bh)
  25 {
  26         return (block_t *)((char*)bh->b_data + BLOCK_SIZE);
  27 }
  28
  29 static inline Indirect *get_branch(struct inode *inode,
  30                                         int depth,
  31                                         int *offsets,
  32                                         Indirect chain[DEPTH],
  33                                         int *err)
  34 {
  35         struct super_block *sb = inode->i_sb;
  36         Indirect *p = chain;
  37         struct buffer_head *bh;
  38
  39         *err = 0;
  40         /* i_data is not going away, no lock needed */
  41         add_chain (chain, NULL, i_data(inode) + *offsets);
  42         if (!p->key)
  43                 goto no_block;
  44         while (--depth) {
  45                 bh = sb_bread(sb, block_to_cpu(p->key));
  46                 if (!bh)
  47                         goto failure;
  48                 read_lock(&pointers_lock);
  49                 if (!verify_chain(chain, p))
  50                         goto changed;
  51                 add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
  52                 read_unlock(&pointers_lock);
  53                 if (!p->key)
  54                         goto no_block;
  55         }
  56         return NULL;
  57
  58 changed:
  59         read_unlock(&pointers_lock);
  60         brelse(bh);
  61         *err = -EAGAIN;
  62         goto no_block;
  63 failure:
  64         *err = -EIO;
  65 no_block:
  66         return p;
  67 }
  68
  69 static int alloc_branch(struct inode *inode,
  70                              int num,
  71                              int *offsets,
  72                              Indirect *branch)
  73 {
  74         int n = 0;
  75         int i;
  76         int parent = minix_new_block(inode);
  77
  78         branch[0].key = cpu_to_block(parent);
  79         if (parent) for (n = 1; n < num; n++) {
  80                 struct buffer_head *bh;
  81                 /* Allocate the next block */
  82                 int nr = minix_new_block(inode);
  83                 if (!nr)
  84                         break;
  85                 branch[n].key = cpu_to_block(nr);
  86                 bh = sb_getblk(inode->i_sb, parent);
  87                 lock_buffer(bh);
  88                 memset(bh->b_data, 0, BLOCK_SIZE);
  89                 branch[n].bh = bh;
  90                 branch[n].p = (block_t*) bh->b_data + offsets[n];
  91                 *branch[n].p = branch[n].key;
  92                 set_buffer_uptodate(bh);
  93                 unlock_buffer(bh);
  94                 mark_buffer_dirty_inode(bh, inode);
  95                 parent = nr;
  96         }
  97         if (n == num)
  98                 return 0;
  99
 100         /* Allocation failed, free what we already allocated */
 101         for (i = 1; i < n; i++)
 102                 bforget(branch[i].bh);
 103         for (i = 0; i < n; i++)
 104                 minix_free_block(inode, block_to_cpu(branch[i].key));
 105         return -ENOSPC;
 106 }
 107
 108 static inline int splice_branch(struct inode *inode,
 109                                      Indirect chain[DEPTH],
 110                                      Indirect *where,
 111                                      int num)
 112 {
 113         int i;
 114
 115         write_lock(&pointers_lock);
 116
 117         /* Verify that place we are splicing to is still there and vacant */
 118         if (!verify_chain(chain, where-1) || *where->p)
 119                 goto changed;
 120
 121         *where->p = where->key;
 122
 123         write_unlock(&pointers_lock);
 124
 125         /* We are done with atomic stuff, now do the rest of housekeeping */
 126
 127         inode->i_ctime = CURRENT_TIME;
 128
 129         /* had we spliced it onto indirect block? */
 130         if (where->bh)
 131                 mark_buffer_dirty_inode(where->bh, inode);
 132
 133         mark_inode_dirty(inode);
 134         return 0;
 135
 136 changed:
 137         write_unlock(&pointers_lock);
 138         for (i = 1; i < num; i++)
 139                 bforget(where[i].bh);
 140         for (i = 0; i < num; i++)
 141                 minix_free_block(inode, block_to_cpu(where[i].key));
 142         return -EAGAIN;
 143 }
 144
 145 static inline int get_block(struct inode * inode, sector_t block,
 146                         struct buffer_head *bh, int create)
 147 {
 148         int err = -EIO;
 149         int offsets[DEPTH];
 150         Indirect chain[DEPTH];
 151         Indirect *partial;
 152         int left;
 153         int depth = block_to_path(inode, block, offsets);
 154
 155         if (depth == 0)
 156                 goto out;
 157
 158 reread:
 159         partial = get_branch(inode, depth, offsets, chain, &err);
 160
 161         /* Simplest case - block found, no allocation needed */
 162         if (!partial) {
 163 got_it:
 164                 map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
 165                 /* Clean up and exit */
 166                 partial = chain+depth-1; /* the whole chain */
 167                 goto cleanup;
 168         }
 169
 170         /* Next simple case - plain lookup or failed read of indirect block */
 171         if (!create || err == -EIO) {
 172 cleanup:
 173                 while (partial > chain) {
 174                         brelse(partial->bh);
 175                         partial--;
 176                 }
 177 out:
 178                 return err;
 179         }
 180
 181         /*
 182          * Indirect block might be removed by truncate while we were
 183          * reading it. Handling of that case (forget what we've got and
 184          * reread) is taken out of the main path.
 185          */
 186         if (err == -EAGAIN)
 187                 goto changed;
 188
 189         left = (chain + depth) - partial;
 190         err = alloc_branch(inode, left, offsets+(partial-chain), partial);
 191         if (err)
 192                 goto cleanup;
 193
 194         if (splice_branch(inode, chain, partial, left) < 0)
 195                 goto changed;
 196
 197         set_buffer_new(bh);
 198         goto got_it;
 199
 200 changed:
 201         while (partial > chain) {
 202                 brelse(partial->bh);
 203                 partial--;
 204         }
 205         goto reread;
 206 }
 207
 208 static inline int all_zeroes(block_t *p, block_t *q)
 209 {
 210         while (p < q)
 211                 if (*p++)
 212                         return 0;
 213         return 1;
 214 }
 215
 216 static Indirect *find_shared(struct inode *inode,
 217                                 int depth,
 218                                 int offsets[DEPTH],
 219                                 Indirect chain[DEPTH],
 220                                 block_t *top)
 221 {
 222         Indirect *partial, *p;
 223         int k, err;
 224
 225         *top = 0;
 226         for (k = depth; k > 1 && !offsets[k-1]; k--)
 227                 ;
 228         partial = get_branch(inode, k, offsets, chain, &err);
 229
 230         write_lock(&pointers_lock);
 231         if (!partial)
 232                 partial = chain + k-1;
 233         if (!partial->key && *partial->p) {
 234                 write_unlock(&pointers_lock);
 235                 goto no_top;
 236         }
 237         for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
 238                 ;
 239         if (p == chain + k - 1 && p > chain) {
 240                 p->p--;
 241         } else {
 242                 *top = *p->p;
 243                 *p->p = 0;
 244         }
 245         write_unlock(&pointers_lock);
 246
 247         while(partial > p)
 248         {
 249                 brelse(partial->bh);
 250                 partial--;
 251         }
 252 no_top:
 253         return partial;
 254 }
 255
 256 static inline void free_data(struct inode *inode, block_t *p, block_t *q)
 257 {
 258         unsigned long nr;
 259
 260         for ( ; p < q ; p++) {
 261                 nr = block_to_cpu(*p);
 262                 if (nr) {
 263                         *p = 0;
 264                         minix_free_block(inode, nr);
 265                 }
 266         }
 267 }
 268
 269 static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
 270 {
 271         struct buffer_head * bh;
 272         unsigned long nr;
 273
 274         if (depth--) {
 275                 for ( ; p < q ; p++) {
 276                         nr = block_to_cpu(*p);
 277                         if (!nr)
 278                                 continue;
 279                         *p = 0;
 280                         bh = sb_bread(inode->i_sb, nr);
 281                         if (!bh)
 282                                 continue;
 283                         free_branches(inode, (block_t*)bh->b_data,
 284                                       block_end(bh), depth);
 285                         bforget(bh);
 286                         minix_free_block(inode, nr);
 287                         mark_inode_dirty(inode);
 288                 }
 289         } else
 290                 free_data(inode, p, q);
 291 }
 292
 293 static inline void truncate (struct inode * inode)
 294 {
 295         block_t *idata = i_data(inode);
 296         int offsets[DEPTH];
 297         Indirect chain[DEPTH];
 298         Indirect *partial;
 299         block_t nr = 0;
 300         int n;
 301         int first_whole;
 302         long iblock;
 303
 304         iblock = (inode->i_size + BLOCK_SIZE-1) >> 10;
 305         block_truncate_page(inode->i_mapping, inode->i_size, get_block);
 306
 307         n = block_to_path(inode, iblock, offsets);
 308         if (!n)
 309                 return;
 310
 311         if (n == 1) {
 312                 free_data(inode, idata+offsets[0], idata + DIRECT);
 313                 first_whole = 0;
 314                 goto do_indirects;
 315         }
 316
 317         first_whole = offsets[0] + 1 - DIRECT;
 318         partial = find_shared(inode, n, offsets, chain, &nr);
 319         if (nr) {
 320                 if (partial == chain)
 321                         mark_inode_dirty(inode);
 322                 else
 323                         mark_buffer_dirty_inode(partial->bh, inode);
 324                 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
 325         }
 326         /* Clear the ends of indirect blocks on the shared branch */
 327         while (partial > chain) {
 328                 free_branches(inode, partial->p + 1, block_end(partial->bh),
 329                                 (chain+n-1) - partial);
 330                 mark_buffer_dirty_inode(partial->bh, inode);
 331                 brelse (partial->bh);
 332                 partial--;
 333         }
 334 do_indirects:
 335         /* Kill the remaining (whole) subtrees */
 336         while (first_whole < DEPTH-1) {
 337                 nr = idata[DIRECT+first_whole];
 338                 if (nr) {
 339                         idata[DIRECT+first_whole] = 0;
 340                         mark_inode_dirty(inode);
 341                         free_branches(inode, &nr, &nr+1, first_whole+1);
 342                 }
 343                 first_whole++;
 344         }
 345         inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 346         mark_inode_dirty(inode);
 347 }
 348
 349 static inline unsigned nblocks(loff_t size)
 350 {
 351         unsigned blocks, res, direct = DIRECT, i = DEPTH;
 352         blocks = (size + BLOCK_SIZE - 1) >> BLOCK_SIZE_BITS;
 353         res = blocks;
 354         while (--i && blocks > direct) {
 355                 blocks -= direct;
 356                 blocks += BLOCK_SIZE/sizeof(block_t) - 1;
 357                 blocks /= BLOCK_SIZE/sizeof(block_t);
 358                 res += blocks;
 359                 direct = 1;
 360         }
 361         return res;
 362 }