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ialloc.c
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1 /*
2  * linux/fs/ext2/ialloc.c
3  *
4  * Copyright (C) 1992, 1993, 1994, 1995
5  * Remy Card ([email protected])
6  * Laboratoire MASI - Institut Blaise Pascal
7  * Universite Pierre et Marie Curie (Paris VI)
8  *
9  * BSD ufs-inspired inode and directory allocation by
10  * Stephen Tweedie ([email protected]), 1993
11  * Big-endian to little-endian byte-swapping/bitmaps by
12  * David S. Miller ([email protected]), 1995
13  */
14 
15 #include <linux/quotaops.h>
16 #include <linux/sched.h>
17 #include <linux/backing-dev.h>
18 #include <linux/buffer_head.h>
19 #include <linux/random.h>
20 #include "ext2.h"
21 #include "xattr.h"
22 #include "acl.h"
23 
24 /*
25  * ialloc.c contains the inodes allocation and deallocation routines
26  */
27 
28 /*
29  * The free inodes are managed by bitmaps. A file system contains several
30  * blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap
31  * block for inodes, N blocks for the inode table and data blocks.
32  *
33  * The file system contains group descriptors which are located after the
34  * super block. Each descriptor contains the number of the bitmap block and
35  * the free blocks count in the block.
36  */
37 
38 
39 /*
40  * Read the inode allocation bitmap for a given block_group, reading
41  * into the specified slot in the superblock's bitmap cache.
42  *
43  * Return buffer_head of bitmap on success or NULL.
44  */
45 static struct buffer_head *
46 read_inode_bitmap(struct super_block * sb, unsigned long block_group)
47 {
48  struct ext2_group_desc *desc;
49  struct buffer_head *bh = NULL;
50 
51  desc = ext2_get_group_desc(sb, block_group, NULL);
52  if (!desc)
53  goto error_out;
54 
55  bh = sb_bread(sb, le32_to_cpu(desc->bg_inode_bitmap));
56  if (!bh)
57  ext2_error(sb, "read_inode_bitmap",
58  "Cannot read inode bitmap - "
59  "block_group = %lu, inode_bitmap = %u",
60  block_group, le32_to_cpu(desc->bg_inode_bitmap));
61 error_out:
62  return bh;
63 }
64 
65 static void ext2_release_inode(struct super_block *sb, int group, int dir)
66 {
67  struct ext2_group_desc * desc;
68  struct buffer_head *bh;
69 
70  desc = ext2_get_group_desc(sb, group, &bh);
71  if (!desc) {
72  ext2_error(sb, "ext2_release_inode",
73  "can't get descriptor for group %d", group);
74  return;
75  }
76 
77  spin_lock(sb_bgl_lock(EXT2_SB(sb), group));
78  le16_add_cpu(&desc->bg_free_inodes_count, 1);
79  if (dir)
80  le16_add_cpu(&desc->bg_used_dirs_count, -1);
81  spin_unlock(sb_bgl_lock(EXT2_SB(sb), group));
82  if (dir)
83  percpu_counter_dec(&EXT2_SB(sb)->s_dirs_counter);
85 }
86 
87 /*
88  * NOTE! When we get the inode, we're the only people
89  * that have access to it, and as such there are no
90  * race conditions we have to worry about. The inode
91  * is not on the hash-lists, and it cannot be reached
92  * through the filesystem because the directory entry
93  * has been deleted earlier.
94  *
95  * HOWEVER: we must make sure that we get no aliases,
96  * which means that we have to call "clear_inode()"
97  * _before_ we mark the inode not in use in the inode
98  * bitmaps. Otherwise a newly created file might use
99  * the same inode number (not actually the same pointer
100  * though), and then we'd have two inodes sharing the
101  * same inode number and space on the harddisk.
102  */
103 void ext2_free_inode (struct inode * inode)
104 {
105  struct super_block * sb = inode->i_sb;
106  int is_directory;
107  unsigned long ino;
108  struct buffer_head *bitmap_bh;
109  unsigned long block_group;
110  unsigned long bit;
111  struct ext2_super_block * es;
112 
113  ino = inode->i_ino;
114  ext2_debug ("freeing inode %lu\n", ino);
115 
116  /*
117  * Note: we must free any quota before locking the superblock,
118  * as writing the quota to disk may need the lock as well.
119  */
120  /* Quota is already initialized in iput() */
122  dquot_free_inode(inode);
123  dquot_drop(inode);
124 
125  es = EXT2_SB(sb)->s_es;
126  is_directory = S_ISDIR(inode->i_mode);
127 
128  if (ino < EXT2_FIRST_INO(sb) ||
129  ino > le32_to_cpu(es->s_inodes_count)) {
130  ext2_error (sb, "ext2_free_inode",
131  "reserved or nonexistent inode %lu", ino);
132  return;
133  }
134  block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
135  bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);
136  bitmap_bh = read_inode_bitmap(sb, block_group);
137  if (!bitmap_bh)
138  return;
139 
140  /* Ok, now we can actually update the inode bitmaps.. */
141  if (!ext2_clear_bit_atomic(sb_bgl_lock(EXT2_SB(sb), block_group),
142  bit, (void *) bitmap_bh->b_data))
143  ext2_error (sb, "ext2_free_inode",
144  "bit already cleared for inode %lu", ino);
145  else
146  ext2_release_inode(sb, block_group, is_directory);
147  mark_buffer_dirty(bitmap_bh);
148  if (sb->s_flags & MS_SYNCHRONOUS)
149  sync_dirty_buffer(bitmap_bh);
150 
151  brelse(bitmap_bh);
152 }
153 
154 /*
155  * We perform asynchronous prereading of the new inode's inode block when
156  * we create the inode, in the expectation that the inode will be written
157  * back soon. There are two reasons:
158  *
159  * - When creating a large number of files, the async prereads will be
160  * nicely merged into large reads
161  * - When writing out a large number of inodes, we don't need to keep on
162  * stalling the writes while we read the inode block.
163  *
164  * FIXME: ext2_get_group_desc() needs to be simplified.
165  */
166 static void ext2_preread_inode(struct inode *inode)
167 {
168  unsigned long block_group;
169  unsigned long offset;
170  unsigned long block;
171  struct ext2_group_desc * gdp;
172  struct backing_dev_info *bdi;
173 
174  bdi = inode->i_mapping->backing_dev_info;
175  if (bdi_read_congested(bdi))
176  return;
177  if (bdi_write_congested(bdi))
178  return;
179 
180  block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
181  gdp = ext2_get_group_desc(inode->i_sb, block_group, NULL);
182  if (gdp == NULL)
183  return;
184 
185  /*
186  * Figure out the offset within the block group inode table
187  */
188  offset = ((inode->i_ino - 1) % EXT2_INODES_PER_GROUP(inode->i_sb)) *
189  EXT2_INODE_SIZE(inode->i_sb);
190  block = le32_to_cpu(gdp->bg_inode_table) +
191  (offset >> EXT2_BLOCK_SIZE_BITS(inode->i_sb));
192  sb_breadahead(inode->i_sb, block);
193 }
194 
195 /*
196  * There are two policies for allocating an inode. If the new inode is
197  * a directory, then a forward search is made for a block group with both
198  * free space and a low directory-to-inode ratio; if that fails, then of
199  * the groups with above-average free space, that group with the fewest
200  * directories already is chosen.
201  *
202  * For other inodes, search forward from the parent directory\'s block
203  * group to find a free inode.
204  */
205 static int find_group_dir(struct super_block *sb, struct inode *parent)
206 {
207  int ngroups = EXT2_SB(sb)->s_groups_count;
208  int avefreei = ext2_count_free_inodes(sb) / ngroups;
209  struct ext2_group_desc *desc, *best_desc = NULL;
210  int group, best_group = -1;
211 
212  for (group = 0; group < ngroups; group++) {
213  desc = ext2_get_group_desc (sb, group, NULL);
214  if (!desc || !desc->bg_free_inodes_count)
215  continue;
216  if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
217  continue;
218  if (!best_desc ||
220  le16_to_cpu(best_desc->bg_free_blocks_count))) {
221  best_group = group;
222  best_desc = desc;
223  }
224  }
225  if (!best_desc)
226  return -1;
227 
228  return best_group;
229 }
230 
231 /*
232  * Orlov's allocator for directories.
233  *
234  * We always try to spread first-level directories.
235  *
236  * If there are blockgroups with both free inodes and free blocks counts
237  * not worse than average we return one with smallest directory count.
238  * Otherwise we simply return a random group.
239  *
240  * For the rest rules look so:
241  *
242  * It's OK to put directory into a group unless
243  * it has too many directories already (max_dirs) or
244  * it has too few free inodes left (min_inodes) or
245  * it has too few free blocks left (min_blocks) or
246  * it's already running too large debt (max_debt).
247  * Parent's group is preferred, if it doesn't satisfy these
248  * conditions we search cyclically through the rest. If none
249  * of the groups look good we just look for a group with more
250  * free inodes than average (starting at parent's group).
251  *
252  * Debt is incremented each time we allocate a directory and decremented
253  * when we allocate an inode, within 0--255.
254  */
255 
256 #define INODE_COST 64
257 #define BLOCK_COST 256
258 
259 static int find_group_orlov(struct super_block *sb, struct inode *parent)
260 {
261  int parent_group = EXT2_I(parent)->i_block_group;
262  struct ext2_sb_info *sbi = EXT2_SB(sb);
263  struct ext2_super_block *es = sbi->s_es;
264  int ngroups = sbi->s_groups_count;
265  int inodes_per_group = EXT2_INODES_PER_GROUP(sb);
266  int freei;
267  int avefreei;
268  int free_blocks;
269  int avefreeb;
270  int blocks_per_dir;
271  int ndirs;
272  int max_debt, max_dirs, min_blocks, min_inodes;
273  int group = -1, i;
274  struct ext2_group_desc *desc;
275 
276  freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
277  avefreei = freei / ngroups;
278  free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
279  avefreeb = free_blocks / ngroups;
280  ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);
281 
282  if ((parent == sb->s_root->d_inode) ||
283  (EXT2_I(parent)->i_flags & EXT2_TOPDIR_FL)) {
284  struct ext2_group_desc *best_desc = NULL;
285  int best_ndir = inodes_per_group;
286  int best_group = -1;
287 
288  get_random_bytes(&group, sizeof(group));
289  parent_group = (unsigned)group % ngroups;
290  for (i = 0; i < ngroups; i++) {
291  group = (parent_group + i) % ngroups;
292  desc = ext2_get_group_desc (sb, group, NULL);
293  if (!desc || !desc->bg_free_inodes_count)
294  continue;
295  if (le16_to_cpu(desc->bg_used_dirs_count) >= best_ndir)
296  continue;
297  if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
298  continue;
299  if (le16_to_cpu(desc->bg_free_blocks_count) < avefreeb)
300  continue;
301  best_group = group;
302  best_ndir = le16_to_cpu(desc->bg_used_dirs_count);
303  best_desc = desc;
304  }
305  if (best_group >= 0) {
306  desc = best_desc;
307  group = best_group;
308  goto found;
309  }
310  goto fallback;
311  }
312 
313  if (ndirs == 0)
314  ndirs = 1; /* percpu_counters are approximate... */
315 
316  blocks_per_dir = (le32_to_cpu(es->s_blocks_count)-free_blocks) / ndirs;
317 
318  max_dirs = ndirs / ngroups + inodes_per_group / 16;
319  min_inodes = avefreei - inodes_per_group / 4;
320  min_blocks = avefreeb - EXT2_BLOCKS_PER_GROUP(sb) / 4;
321 
322  max_debt = EXT2_BLOCKS_PER_GROUP(sb) / max(blocks_per_dir, BLOCK_COST);
323  if (max_debt * INODE_COST > inodes_per_group)
324  max_debt = inodes_per_group / INODE_COST;
325  if (max_debt > 255)
326  max_debt = 255;
327  if (max_debt == 0)
328  max_debt = 1;
329 
330  for (i = 0; i < ngroups; i++) {
331  group = (parent_group + i) % ngroups;
332  desc = ext2_get_group_desc (sb, group, NULL);
333  if (!desc || !desc->bg_free_inodes_count)
334  continue;
335  if (sbi->s_debts[group] >= max_debt)
336  continue;
337  if (le16_to_cpu(desc->bg_used_dirs_count) >= max_dirs)
338  continue;
339  if (le16_to_cpu(desc->bg_free_inodes_count) < min_inodes)
340  continue;
341  if (le16_to_cpu(desc->bg_free_blocks_count) < min_blocks)
342  continue;
343  goto found;
344  }
345 
346 fallback:
347  for (i = 0; i < ngroups; i++) {
348  group = (parent_group + i) % ngroups;
349  desc = ext2_get_group_desc (sb, group, NULL);
350  if (!desc || !desc->bg_free_inodes_count)
351  continue;
352  if (le16_to_cpu(desc->bg_free_inodes_count) >= avefreei)
353  goto found;
354  }
355 
356  if (avefreei) {
357  /*
358  * The free-inodes counter is approximate, and for really small
359  * filesystems the above test can fail to find any blockgroups
360  */
361  avefreei = 0;
362  goto fallback;
363  }
364 
365  return -1;
366 
367 found:
368  return group;
369 }
370 
371 static int find_group_other(struct super_block *sb, struct inode *parent)
372 {
373  int parent_group = EXT2_I(parent)->i_block_group;
374  int ngroups = EXT2_SB(sb)->s_groups_count;
375  struct ext2_group_desc *desc;
376  int group, i;
377 
378  /*
379  * Try to place the inode in its parent directory
380  */
381  group = parent_group;
382  desc = ext2_get_group_desc (sb, group, NULL);
383  if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
385  goto found;
386 
387  /*
388  * We're going to place this inode in a different blockgroup from its
389  * parent. We want to cause files in a common directory to all land in
390  * the same blockgroup. But we want files which are in a different
391  * directory which shares a blockgroup with our parent to land in a
392  * different blockgroup.
393  *
394  * So add our directory's i_ino into the starting point for the hash.
395  */
396  group = (group + parent->i_ino) % ngroups;
397 
398  /*
399  * Use a quadratic hash to find a group with a free inode and some
400  * free blocks.
401  */
402  for (i = 1; i < ngroups; i <<= 1) {
403  group += i;
404  if (group >= ngroups)
405  group -= ngroups;
406  desc = ext2_get_group_desc (sb, group, NULL);
407  if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
409  goto found;
410  }
411 
412  /*
413  * That failed: try linear search for a free inode, even if that group
414  * has no free blocks.
415  */
416  group = parent_group;
417  for (i = 0; i < ngroups; i++) {
418  if (++group >= ngroups)
419  group = 0;
420  desc = ext2_get_group_desc (sb, group, NULL);
421  if (desc && le16_to_cpu(desc->bg_free_inodes_count))
422  goto found;
423  }
424 
425  return -1;
426 
427 found:
428  return group;
429 }
430 
431 struct inode *ext2_new_inode(struct inode *dir, umode_t mode,
432  const struct qstr *qstr)
433 {
434  struct super_block *sb;
435  struct buffer_head *bitmap_bh = NULL;
436  struct buffer_head *bh2;
437  int group, i;
438  ino_t ino = 0;
439  struct inode * inode;
440  struct ext2_group_desc *gdp;
441  struct ext2_super_block *es;
442  struct ext2_inode_info *ei;
443  struct ext2_sb_info *sbi;
444  int err;
445 
446  sb = dir->i_sb;
447  inode = new_inode(sb);
448  if (!inode)
449  return ERR_PTR(-ENOMEM);
450 
451  ei = EXT2_I(inode);
452  sbi = EXT2_SB(sb);
453  es = sbi->s_es;
454  if (S_ISDIR(mode)) {
455  if (test_opt(sb, OLDALLOC))
456  group = find_group_dir(sb, dir);
457  else
458  group = find_group_orlov(sb, dir);
459  } else
460  group = find_group_other(sb, dir);
461 
462  if (group == -1) {
463  err = -ENOSPC;
464  goto fail;
465  }
466 
467  for (i = 0; i < sbi->s_groups_count; i++) {
468  gdp = ext2_get_group_desc(sb, group, &bh2);
469  brelse(bitmap_bh);
470  bitmap_bh = read_inode_bitmap(sb, group);
471  if (!bitmap_bh) {
472  err = -EIO;
473  goto fail;
474  }
475  ino = 0;
476 
477 repeat_in_this_group:
478  ino = ext2_find_next_zero_bit((unsigned long *)bitmap_bh->b_data,
479  EXT2_INODES_PER_GROUP(sb), ino);
480  if (ino >= EXT2_INODES_PER_GROUP(sb)) {
481  /*
482  * Rare race: find_group_xx() decided that there were
483  * free inodes in this group, but by the time we tried
484  * to allocate one, they're all gone. This can also
485  * occur because the counters which find_group_orlov()
486  * uses are approximate. So just go and search the
487  * next block group.
488  */
489  if (++group == sbi->s_groups_count)
490  group = 0;
491  continue;
492  }
493  if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group),
494  ino, bitmap_bh->b_data)) {
495  /* we lost this inode */
496  if (++ino >= EXT2_INODES_PER_GROUP(sb)) {
497  /* this group is exhausted, try next group */
498  if (++group == sbi->s_groups_count)
499  group = 0;
500  continue;
501  }
502  /* try to find free inode in the same group */
503  goto repeat_in_this_group;
504  }
505  goto got;
506  }
507 
508  /*
509  * Scanned all blockgroups.
510  */
511  err = -ENOSPC;
512  goto fail;
513 got:
514  mark_buffer_dirty(bitmap_bh);
515  if (sb->s_flags & MS_SYNCHRONOUS)
516  sync_dirty_buffer(bitmap_bh);
517  brelse(bitmap_bh);
518 
519  ino += group * EXT2_INODES_PER_GROUP(sb) + 1;
520  if (ino < EXT2_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
521  ext2_error (sb, "ext2_new_inode",
522  "reserved inode or inode > inodes count - "
523  "block_group = %d,inode=%lu", group,
524  (unsigned long) ino);
525  err = -EIO;
526  goto fail;
527  }
528 
529  percpu_counter_add(&sbi->s_freeinodes_counter, -1);
530  if (S_ISDIR(mode))
531  percpu_counter_inc(&sbi->s_dirs_counter);
532 
533  spin_lock(sb_bgl_lock(sbi, group));
534  le16_add_cpu(&gdp->bg_free_inodes_count, -1);
535  if (S_ISDIR(mode)) {
536  if (sbi->s_debts[group] < 255)
537  sbi->s_debts[group]++;
538  le16_add_cpu(&gdp->bg_used_dirs_count, 1);
539  } else {
540  if (sbi->s_debts[group])
541  sbi->s_debts[group]--;
542  }
543  spin_unlock(sb_bgl_lock(sbi, group));
544 
545  mark_buffer_dirty(bh2);
546  if (test_opt(sb, GRPID)) {
547  inode->i_mode = mode;
548  inode->i_uid = current_fsuid();
549  inode->i_gid = dir->i_gid;
550  } else
551  inode_init_owner(inode, dir, mode);
552 
553  inode->i_ino = ino;
554  inode->i_blocks = 0;
555  inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
556  memset(ei->i_data, 0, sizeof(ei->i_data));
557  ei->i_flags =
558  ext2_mask_flags(mode, EXT2_I(dir)->i_flags & EXT2_FL_INHERITED);
559  ei->i_faddr = 0;
560  ei->i_frag_no = 0;
561  ei->i_frag_size = 0;
562  ei->i_file_acl = 0;
563  ei->i_dir_acl = 0;
564  ei->i_dtime = 0;
565  ei->i_block_alloc_info = NULL;
566  ei->i_block_group = group;
567  ei->i_dir_start_lookup = 0;
568  ei->i_state = EXT2_STATE_NEW;
569  ext2_set_inode_flags(inode);
570  spin_lock(&sbi->s_next_gen_lock);
571  inode->i_generation = sbi->s_next_generation++;
572  spin_unlock(&sbi->s_next_gen_lock);
573  if (insert_inode_locked(inode) < 0) {
574  ext2_error(sb, "ext2_new_inode",
575  "inode number already in use - inode=%lu",
576  (unsigned long) ino);
577  err = -EIO;
578  goto fail;
579  }
580 
581  dquot_initialize(inode);
582  err = dquot_alloc_inode(inode);
583  if (err)
584  goto fail_drop;
585 
586  err = ext2_init_acl(inode, dir);
587  if (err)
588  goto fail_free_drop;
589 
590  err = ext2_init_security(inode, dir, qstr);
591  if (err)
592  goto fail_free_drop;
593 
594  mark_inode_dirty(inode);
595  ext2_debug("allocating inode %lu\n", inode->i_ino);
596  ext2_preread_inode(inode);
597  return inode;
598 
599 fail_free_drop:
600  dquot_free_inode(inode);
601 
602 fail_drop:
603  dquot_drop(inode);
604  inode->i_flags |= S_NOQUOTA;
605  clear_nlink(inode);
606  unlock_new_inode(inode);
607  iput(inode);
608  return ERR_PTR(err);
609 
610 fail:
611  make_bad_inode(inode);
612  iput(inode);
613  return ERR_PTR(err);
614 }
615 
616 unsigned long ext2_count_free_inodes (struct super_block * sb)
617 {
618  struct ext2_group_desc *desc;
619  unsigned long desc_count = 0;
620  int i;
621 
622 #ifdef EXT2FS_DEBUG
623  struct ext2_super_block *es;
624  unsigned long bitmap_count = 0;
625  struct buffer_head *bitmap_bh = NULL;
626 
627  es = EXT2_SB(sb)->s_es;
628  for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
629  unsigned x;
630 
631  desc = ext2_get_group_desc (sb, i, NULL);
632  if (!desc)
633  continue;
634  desc_count += le16_to_cpu(desc->bg_free_inodes_count);
635  brelse(bitmap_bh);
636  bitmap_bh = read_inode_bitmap(sb, i);
637  if (!bitmap_bh)
638  continue;
639 
640  x = ext2_count_free(bitmap_bh, EXT2_INODES_PER_GROUP(sb) / 8);
641  printk("group %d: stored = %d, counted = %u\n",
642  i, le16_to_cpu(desc->bg_free_inodes_count), x);
643  bitmap_count += x;
644  }
645  brelse(bitmap_bh);
646  printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
647  (unsigned long)
648  percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
649  desc_count, bitmap_count);
650  return desc_count;
651 #else
652  for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
653  desc = ext2_get_group_desc (sb, i, NULL);
654  if (!desc)
655  continue;
656  desc_count += le16_to_cpu(desc->bg_free_inodes_count);
657  }
658  return desc_count;
659 #endif
660 }
661 
662 /* Called at mount-time, super-block is locked */
663 unsigned long ext2_count_dirs (struct super_block * sb)
664 {
665  unsigned long count = 0;
666  int i;
667 
668  for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
669  struct ext2_group_desc *gdp = ext2_get_group_desc (sb, i, NULL);
670  if (!gdp)
671  continue;
672  count += le16_to_cpu(gdp->bg_used_dirs_count);
673  }
674  return count;
675 }
676