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 DEFINE_RWLOCK(pointers_lock);
  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 + bh->b_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         int err = -ENOSPC;
  78
  79         branch[0].key = cpu_to_block(parent);
  80         if (parent) for (n = 1; n < num; n++) {
  81                 struct buffer_head *bh;
  82                 /* Allocate the next block */
  83                 int nr = minix_new_block(inode);
  84                 if (!nr)
  85                         break;
  86                 branch[n].key = cpu_to_block(nr);
  87                 bh = sb_getblk(inode->i_sb, parent);
  88                 if (!bh) {
  89                         minix_free_block(inode, nr);
  90                         err = -ENOMEM;
  91                         break;
  92                 }
  93                 lock_buffer(bh);
  94                 memset(bh->b_data, 0, bh->b_size);
  95                 branch[n].bh = bh;
  96                 branch[n].p = (block_t*) bh->b_data + offsets[n];
  97                 *branch[n].p = branch[n].key;
  98                 set_buffer_uptodate(bh);
  99                 unlock_buffer(bh);
 100                 mark_buffer_dirty_inode(bh, inode);
 101                 parent = nr;
 102         }
 103         if (n == num)
 104                 return 0;
 105
 106         /* Allocation failed, free what we already allocated */
 107         for (i = 1; i < n; i++)
 108                 bforget(branch[i].bh);
 109         for (i = 0; i < n; i++)
 110                 minix_free_block(inode, block_to_cpu(branch[i].key));
 111         return err;
 112 }
 113
 114 static inline int splice_branch(struct inode *inode,
 115                                      Indirect chain[DEPTH],
 116                                      Indirect *where,
 117                                      int num)
 118 {
 119         int i;
 120
 121         write_lock(&pointers_lock);
 122
 123         /* Verify that place we are splicing to is still there and vacant */
 124         if (!verify_chain(chain, where-1) || *where->p)
 125                 goto changed;
 126
 127         *where->p = where->key;
 128
 129         write_unlock(&pointers_lock);
 130
 131         /* We are done with atomic stuff, now do the rest of housekeeping */
 132
 133         inode->i_ctime = current_time(inode);
 134
 135         /* had we spliced it onto indirect block? */
 136         if (where->bh)
 137                 mark_buffer_dirty_inode(where->bh, inode);
 138
 139         mark_inode_dirty(inode);
 140         return 0;
 141
 142 changed:
 143         write_unlock(&pointers_lock);
 144         for (i = 1; i < num; i++)
 145                 bforget(where[i].bh);
 146         for (i = 0; i < num; i++)
 147                 minix_free_block(inode, block_to_cpu(where[i].key));
 148         return -EAGAIN;
 149 }
 150
 151 static inline int get_block(struct inode * inode, sector_t block,
 152                         struct buffer_head *bh, int create)
 153 {
 154         int err = -EIO;
 155         int offsets[DEPTH];
 156         Indirect chain[DEPTH];
 157         Indirect *partial;
 158         int left;
 159         int depth = block_to_path(inode, block, offsets);
 160
 161         if (depth == 0)
 162                 goto out;
 163
 164 reread:
 165         partial = get_branch(inode, depth, offsets, chain, &err);
 166
 167         /* Simplest case - block found, no allocation needed */
 168         if (!partial) {
 169 got_it:
 170                 map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
 171                 /* Clean up and exit */
 172                 partial = chain+depth-1; /* the whole chain */
 173                 goto cleanup;
 174         }
 175
 176         /* Next simple case - plain lookup or failed read of indirect block */
 177         if (!create || err == -EIO) {
 178 cleanup:
 179                 while (partial > chain) {
 180                         brelse(partial->bh);
 181                         partial--;
 182                 }
 183 out:
 184                 return err;
 185         }
 186
 187         /*
 188          * Indirect block might be removed by truncate while we were
 189          * reading it. Handling of that case (forget what we've got and
 190          * reread) is taken out of the main path.
 191          */
 192         if (err == -EAGAIN)
 193                 goto changed;
 194
 195         left = (chain + depth) - partial;
 196         err = alloc_branch(inode, left, offsets+(partial-chain), partial);
 197         if (err)
 198                 goto cleanup;
 199
 200         if (splice_branch(inode, chain, partial, left) < 0)
 201                 goto changed;
 202
 203         set_buffer_new(bh);
 204         goto got_it;
 205
 206 changed:
 207         while (partial > chain) {
 208                 brelse(partial->bh);
 209                 partial--;
 210         }
 211         goto reread;
 212 }
 213
 214 static inline int all_zeroes(block_t *p, block_t *q)
 215 {
 216         while (p < q)
 217                 if (*p++)
 218                         return 0;
 219         return 1;
 220 }
 221
 222 static Indirect *find_shared(struct inode *inode,
 223                                 int depth,
 224                                 int offsets[DEPTH],
 225                                 Indirect chain[DEPTH],
 226                                 block_t *top)
 227 {
 228         Indirect *partial, *p;
 229         int k, err;
 230
 231         *top = 0;
 232         for (k = depth; k > 1 && !offsets[k-1]; k--)
 233                 ;
 234         partial = get_branch(inode, k, offsets, chain, &err);
 235
 236         write_lock(&pointers_lock);
 237         if (!partial)
 238                 partial = chain + k-1;
 239         if (!partial->key && *partial->p) {
 240                 write_unlock(&pointers_lock);
 241                 goto no_top;
 242         }
 243         for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
 244                 ;
 245         if (p == chain + k - 1 && p > chain) {
 246                 p->p--;
 247         } else {
 248                 *top = *p->p;
 249                 *p->p = 0;
 250         }
 251         write_unlock(&pointers_lock);
 252
 253         while(partial > p)
 254         {
 255                 brelse(partial->bh);
 256                 partial--;
 257         }
 258 no_top:
 259         return partial;
 260 }
 261
 262 static inline void free_data(struct inode *inode, block_t *p, block_t *q)
 263 {
 264         unsigned long nr;
 265
 266         for ( ; p < q ; p++) {
 267                 nr = block_to_cpu(*p);
 268                 if (nr) {
 269                         *p = 0;
 270                         minix_free_block(inode, nr);
 271                 }
 272         }
 273 }
 274
 275 static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
 276 {
 277         struct buffer_head * bh;
 278         unsigned long nr;
 279
 280         if (depth--) {
 281                 for ( ; p < q ; p++) {
 282                         nr = block_to_cpu(*p);
 283                         if (!nr)
 284                                 continue;
 285                         *p = 0;
 286                         bh = sb_bread(inode->i_sb, nr);
 287                         if (!bh)
 288                                 continue;
 289                         free_branches(inode, (block_t*)bh->b_data,
 290                                       block_end(bh), depth);
 291                         bforget(bh);
 292                         minix_free_block(inode, nr);
 293                         mark_inode_dirty(inode);
 294                 }
 295         } else
 296                 free_data(inode, p, q);
 297 }
 298
 299 static inline void truncate (struct inode * inode)
 300 {
 301         struct super_block *sb = inode->i_sb;
 302         block_t *idata = i_data(inode);
 303         int offsets[DEPTH];
 304         Indirect chain[DEPTH];
 305         Indirect *partial;
 306         block_t nr = 0;
 307         int n;
 308         int first_whole;
 309         long iblock;
 310
 311         iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
 312         block_truncate_page(inode->i_mapping, inode->i_size, get_block);
 313
 314         n = block_to_path(inode, iblock, offsets);
 315         if (!n)
 316                 return;
 317
 318         if (n == 1) {
 319                 free_data(inode, idata+offsets[0], idata + DIRECT);
 320                 first_whole = 0;
 321                 goto do_indirects;
 322         }
 323
 324         first_whole = offsets[0] + 1 - DIRECT;
 325         partial = find_shared(inode, n, offsets, chain, &nr);
 326         if (nr) {
 327                 if (partial == chain)
 328                         mark_inode_dirty(inode);
 329                 else
 330                         mark_buffer_dirty_inode(partial->bh, inode);
 331                 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
 332         }
 333         /* Clear the ends of indirect blocks on the shared branch */
 334         while (partial > chain) {
 335                 free_branches(inode, partial->p + 1, block_end(partial->bh),
 336                                 (chain+n-1) - partial);
 337                 mark_buffer_dirty_inode(partial->bh, inode);
 338                 brelse (partial->bh);
 339                 partial--;
 340         }
 341 do_indirects:
 342         /* Kill the remaining (whole) subtrees */
 343         while (first_whole < DEPTH-1) {
 344                 nr = idata[DIRECT+first_whole];
 345                 if (nr) {
 346                         idata[DIRECT+first_whole] = 0;
 347                         mark_inode_dirty(inode);
 348                         free_branches(inode, &nr, &nr+1, first_whole+1);
 349                 }
 350                 first_whole++;
 351         }
 352         inode->i_mtime = inode->i_ctime = current_time(inode);
 353         mark_inode_dirty(inode);
 354 }
 355
 356 static inline unsigned nblocks(loff_t size, struct super_block *sb)
 357 {
 358         int k = sb->s_blocksize_bits - 10;
 359         unsigned blocks, res, direct = DIRECT, i = DEPTH;
 360         blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
 361         res = blocks;
 362         while (--i && blocks > direct) {
 363                 blocks -= direct;
 364                 blocks += sb->s_blocksize/sizeof(block_t) - 1;
 365                 blocks /= sb->s_blocksize/sizeof(block_t);
 366                 res += blocks;
 367                 direct = 1;
 368         }
 369         return res;
 370 }