fs/minix/itree_common.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Generic part */
   3
   4 typedef struct {
   5         block_t *p;
   6         block_t key;
   7         struct buffer_head *bh;
   8 } Indirect;
   9
  10 static DEFINE_RWLOCK(pointers_lock);
  11
  12 static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
  13 {
  14         p->key = *(p->p = v);
  15         p->bh = bh;
  16 }
  17
  18 static inline int verify_chain(Indirect *from, Indirect *to)
  19 {
  20         while (from <= to && from->key == *from->p)
  21                 from++;
  22         return (from > to);
  23 }
  24
  25 static inline block_t *block_end(struct buffer_head *bh)
  26 {
  27         return (block_t *)((char*)bh->b_data + bh->b_size);
  28 }
  29
  30 static inline Indirect *get_branch(struct inode *inode,
  31                                         int depth,
  32                                         int *offsets,
  33                                         Indirect chain[DEPTH],
  34                                         int *err)
  35 {
  36         struct super_block *sb = inode->i_sb;
  37         Indirect *p = chain;
  38         struct buffer_head *bh;
  39
  40         *err = 0;
  41         /* i_data is not going away, no lock needed */
  42         add_chain (chain, NULL, i_data(inode) + *offsets);
  43         if (!p->key)
  44                 goto no_block;
  45         while (--depth) {
  46                 bh = sb_bread(sb, block_to_cpu(p->key));
  47                 if (!bh)
  48                         goto failure;
  49                 read_lock(&pointers_lock);
  50                 if (!verify_chain(chain, p))
  51                         goto changed;
  52                 add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
  53                 read_unlock(&pointers_lock);
  54                 if (!p->key)
  55                         goto no_block;
  56         }
  57         return NULL;
  58
  59 changed:
  60         read_unlock(&pointers_lock);
  61         brelse(bh);
  62         *err = -EAGAIN;
  63         goto no_block;
  64 failure:
  65         *err = -EIO;
  66 no_block:
  67         return p;
  68 }
  69
  70 static int alloc_branch(struct inode *inode,
  71                              int num,
  72                              int *offsets,
  73                              Indirect *branch)
  74 {
  75         int n = 0;
  76         int i;
  77         int parent = minix_new_block(inode);
  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                 lock_buffer(bh);
  89                 memset(bh->b_data, 0, bh->b_size);
  90                 branch[n].bh = bh;
  91                 branch[n].p = (block_t*) bh->b_data + offsets[n];
  92                 *branch[n].p = branch[n].key;
  93                 set_buffer_uptodate(bh);
  94                 unlock_buffer(bh);
  95                 mark_buffer_dirty_inode(bh, inode);
  96                 parent = nr;
  97         }
  98         if (n == num)
  99                 return 0;
 100
 101         /* Allocation failed, free what we already allocated */
 102         for (i = 1; i < n; i++)
 103                 bforget(branch[i].bh);
 104         for (i = 0; i < n; i++)
 105                 minix_free_block(inode, block_to_cpu(branch[i].key));
 106         return -ENOSPC;
 107 }
 108
 109 static inline int splice_branch(struct inode *inode,
 110                                      Indirect chain[DEPTH],
 111                                      Indirect *where,
 112                                      int num)
 113 {
 114         int i;
 115
 116         write_lock(&pointers_lock);
 117
 118         /* Verify that place we are splicing to is still there and vacant */
 119         if (!verify_chain(chain, where-1) || *where->p)
 120                 goto changed;
 121
 122         *where->p = where->key;
 123
 124         write_unlock(&pointers_lock);
 125
 126         /* We are done with atomic stuff, now do the rest of housekeeping */
 127
 128         inode->i_ctime = current_time(inode);
 129
 130         /* had we spliced it onto indirect block? */
 131         if (where->bh)
 132                 mark_buffer_dirty_inode(where->bh, inode);
 133
 134         mark_inode_dirty(inode);
 135         return 0;
 136
 137 changed:
 138         write_unlock(&pointers_lock);
 139         for (i = 1; i < num; i++)
 140                 bforget(where[i].bh);
 141         for (i = 0; i < num; i++)
 142                 minix_free_block(inode, block_to_cpu(where[i].key));
 143         return -EAGAIN;
 144 }
 145
 146 static int get_block(struct inode * inode, sector_t block,
 147                         struct buffer_head *bh, int create)
 148 {
 149         int err = -EIO;
 150         int offsets[DEPTH];
 151         Indirect chain[DEPTH];
 152         Indirect *partial;
 153         int left;
 154         int depth = block_to_path(inode, block, offsets);
 155
 156         if (depth == 0)
 157                 goto out;
 158
 159 reread:
 160         partial = get_branch(inode, depth, offsets, chain, &err);
 161
 162         /* Simplest case - block found, no allocation needed */
 163         if (!partial) {
 164 got_it:
 165                 map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
 166                 /* Clean up and exit */
 167                 partial = chain+depth-1; /* the whole chain */
 168                 goto cleanup;
 169         }
 170
 171         /* Next simple case - plain lookup or failed read of indirect block */
 172         if (!create || err == -EIO) {
 173 cleanup:
 174                 while (partial > chain) {
 175                         brelse(partial->bh);
 176                         partial--;
 177                 }
 178 out:
 179                 return err;
 180         }
 181
 182         /*
 183          * Indirect block might be removed by truncate while we were
 184          * reading it. Handling of that case (forget what we've got and
 185          * reread) is taken out of the main path.
 186          */
 187         if (err == -EAGAIN)
 188                 goto changed;
 189
 190         left = (chain + depth) - partial;
 191         err = alloc_branch(inode, left, offsets+(partial-chain), partial);
 192         if (err)
 193                 goto cleanup;
 194
 195         if (splice_branch(inode, chain, partial, left) < 0)
 196                 goto changed;
 197
 198         set_buffer_new(bh);
 199         goto got_it;
 200
 201 changed:
 202         while (partial > chain) {
 203                 brelse(partial->bh);
 204                 partial--;
 205         }
 206         goto reread;
 207 }
 208
 209 static inline int all_zeroes(block_t *p, block_t *q)
 210 {
 211         while (p < q)
 212                 if (*p++)
 213                         return 0;
 214         return 1;
 215 }
 216
 217 static Indirect *find_shared(struct inode *inode,
 218                                 int depth,
 219                                 int offsets[DEPTH],
 220                                 Indirect chain[DEPTH],
 221                                 block_t *top)
 222 {
 223         Indirect *partial, *p;
 224         int k, err;
 225
 226         *top = 0;
 227         for (k = depth; k > 1 && !offsets[k-1]; k--)
 228                 ;
 229         partial = get_branch(inode, k, offsets, chain, &err);
 230
 231         write_lock(&pointers_lock);
 232         if (!partial)
 233                 partial = chain + k-1;
 234         if (!partial->key && *partial->p) {
 235                 write_unlock(&pointers_lock);
 236                 goto no_top;
 237         }
 238         for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
 239                 ;
 240         if (p == chain + k - 1 && p > chain) {
 241                 p->p--;
 242         } else {
 243                 *top = *p->p;
 244                 *p->p = 0;
 245         }
 246         write_unlock(&pointers_lock);
 247
 248         while(partial > p)
 249         {
 250                 brelse(partial->bh);
 251                 partial--;
 252         }
 253 no_top:
 254         return partial;
 255 }
 256
 257 static inline void free_data(struct inode *inode, block_t *p, block_t *q)
 258 {
 259         unsigned long nr;
 260
 261         for ( ; p < q ; p++) {
 262                 nr = block_to_cpu(*p);
 263                 if (nr) {
 264                         *p = 0;
 265                         minix_free_block(inode, nr);
 266                 }
 267         }
 268 }
 269
 270 static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
 271 {
 272         struct buffer_head * bh;
 273         unsigned long nr;
 274
 275         if (depth--) {
 276                 for ( ; p < q ; p++) {
 277                         nr = block_to_cpu(*p);
 278                         if (!nr)
 279                                 continue;
 280                         *p = 0;
 281                         bh = sb_bread(inode->i_sb, nr);
 282                         if (!bh)
 283                                 continue;
 284                         free_branches(inode, (block_t*)bh->b_data,
 285                                       block_end(bh), depth);
 286                         bforget(bh);
 287                         minix_free_block(inode, nr);
 288                         mark_inode_dirty(inode);
 289                 }
 290         } else
 291                 free_data(inode, p, q);
 292 }
 293
 294 static inline void truncate (struct inode * inode)
 295 {
 296         struct super_block *sb = inode->i_sb;
 297         block_t *idata = i_data(inode);
 298         int offsets[DEPTH];
 299         Indirect chain[DEPTH];
 300         Indirect *partial;
 301         block_t nr = 0;
 302         int n;
 303         int first_whole;
 304         long iblock;
 305
 306         iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
 307         block_truncate_page(inode->i_mapping, inode->i_size, get_block);
 308
 309         n = block_to_path(inode, iblock, offsets);
 310         if (!n)
 311                 return;
 312
 313         if (n == 1) {
 314                 free_data(inode, idata+offsets[0], idata + DIRECT);
 315                 first_whole = 0;
 316                 goto do_indirects;
 317         }
 318
 319         first_whole = offsets[0] + 1 - DIRECT;
 320         partial = find_shared(inode, n, offsets, chain, &nr);
 321         if (nr) {
 322                 if (partial == chain)
 323                         mark_inode_dirty(inode);
 324                 else
 325                         mark_buffer_dirty_inode(partial->bh, inode);
 326                 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
 327         }
 328         /* Clear the ends of indirect blocks on the shared branch */
 329         while (partial > chain) {
 330                 free_branches(inode, partial->p + 1, block_end(partial->bh),
 331                                 (chain+n-1) - partial);
 332                 mark_buffer_dirty_inode(partial->bh, inode);
 333                 brelse (partial->bh);
 334                 partial--;
 335         }
 336 do_indirects:
 337         /* Kill the remaining (whole) subtrees */
 338         while (first_whole < DEPTH-1) {
 339                 nr = idata[DIRECT+first_whole];
 340                 if (nr) {
 341                         idata[DIRECT+first_whole] = 0;
 342                         mark_inode_dirty(inode);
 343                         free_branches(inode, &nr, &nr+1, first_whole+1);
 344                 }
 345                 first_whole++;
 346         }
 347         inode->i_mtime = inode->i_ctime = current_time(inode);
 348         mark_inode_dirty(inode);
 349 }
 350
 351 static inline unsigned nblocks(loff_t size, struct super_block *sb)
 352 {
 353         int k = sb->s_blocksize_bits - 10;
 354         unsigned blocks, res, direct = DIRECT, i = DEPTH;
 355         blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
 356         res = blocks;
 357         while (--i && blocks > direct) {
 358                 blocks -= direct;
 359                 blocks += sb->s_blocksize/sizeof(block_t) - 1;
 360                 blocks /= sb->s_blocksize/sizeof(block_t);
 361                 res += blocks;
 362                 direct = 1;
 363         }
 364         return res;
 365 }