22bc7435d9134b397f537440faa15ce890b7c44f
[linux-2.6.git] / fs / ext4 / balloc.c
1 /*
2  *  linux/fs/ext4/balloc.c
3  *
4  * Copyright (C) 1992, 1993, 1994, 1995
5  * Remy Card (card@masi.ibp.fr)
6  * Laboratoire MASI - Institut Blaise Pascal
7  * Universite Pierre et Marie Curie (Paris VI)
8  *
9  *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
10  *  Big-endian to little-endian byte-swapping/bitmaps by
11  *        David S. Miller (davem@caip.rutgers.edu), 1995
12  */
13
14 #include <linux/time.h>
15 #include <linux/capability.h>
16 #include <linux/fs.h>
17 #include <linux/jbd2.h>
18 #include <linux/quotaops.h>
19 #include <linux/buffer_head.h>
20 #include "ext4.h"
21 #include "ext4_jbd2.h"
22 #include "mballoc.h"
23
24 /*
25  * balloc.c contains the blocks allocation and deallocation routines
26  */
27
28 /*
29  * Calculate the block group number and offset, given a block number
30  */
31 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
32                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
33 {
34         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
35         ext4_grpblk_t offset;
36
37         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
38         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
39         if (offsetp)
40                 *offsetp = offset;
41         if (blockgrpp)
42                 *blockgrpp = blocknr;
43
44 }
45
46 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
47                         ext4_group_t block_group)
48 {
49         ext4_group_t actual_group;
50         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
51         if (actual_group == block_group)
52                 return 1;
53         return 0;
54 }
55
56 static int ext4_group_used_meta_blocks(struct super_block *sb,
57                                        ext4_group_t block_group,
58                                        struct ext4_group_desc *gdp)
59 {
60         ext4_fsblk_t tmp;
61         struct ext4_sb_info *sbi = EXT4_SB(sb);
62         /* block bitmap, inode bitmap, and inode table blocks */
63         int used_blocks = sbi->s_itb_per_group + 2;
64
65         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
66                 if (!ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp),
67                                         block_group))
68                         used_blocks--;
69
70                 if (!ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp),
71                                         block_group))
72                         used_blocks--;
73
74                 tmp = ext4_inode_table(sb, gdp);
75                 for (; tmp < ext4_inode_table(sb, gdp) +
76                                 sbi->s_itb_per_group; tmp++) {
77                         if (!ext4_block_in_group(sb, tmp, block_group))
78                                 used_blocks -= 1;
79                 }
80         }
81         return used_blocks;
82 }
83
84 /* Initializes an uninitialized block bitmap if given, and returns the
85  * number of blocks free in the group. */
86 unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
87                  ext4_group_t block_group, struct ext4_group_desc *gdp)
88 {
89         int bit, bit_max;
90         ext4_group_t ngroups = ext4_get_groups_count(sb);
91         unsigned free_blocks, group_blocks;
92         struct ext4_sb_info *sbi = EXT4_SB(sb);
93
94         if (bh) {
95                 J_ASSERT_BH(bh, buffer_locked(bh));
96
97                 /* If checksum is bad mark all blocks used to prevent allocation
98                  * essentially implementing a per-group read-only flag. */
99                 if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
100                         ext4_error(sb, __func__,
101                                   "Checksum bad for group %u", block_group);
102                         ext4_free_blks_set(sb, gdp, 0);
103                         ext4_free_inodes_set(sb, gdp, 0);
104                         ext4_itable_unused_set(sb, gdp, 0);
105                         memset(bh->b_data, 0xff, sb->s_blocksize);
106                         return 0;
107                 }
108                 memset(bh->b_data, 0, sb->s_blocksize);
109         }
110
111         /* Check for superblock and gdt backups in this group */
112         bit_max = ext4_bg_has_super(sb, block_group);
113
114         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
115             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
116                           sbi->s_desc_per_block) {
117                 if (bit_max) {
118                         bit_max += ext4_bg_num_gdb(sb, block_group);
119                         bit_max +=
120                                 le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
121                 }
122         } else { /* For META_BG_BLOCK_GROUPS */
123                 bit_max += ext4_bg_num_gdb(sb, block_group);
124         }
125
126         if (block_group == ngroups - 1) {
127                 /*
128                  * Even though mke2fs always initialize first and last group
129                  * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
130                  * to make sure we calculate the right free blocks
131                  */
132                 group_blocks = ext4_blocks_count(sbi->s_es) -
133                         le32_to_cpu(sbi->s_es->s_first_data_block) -
134                         (EXT4_BLOCKS_PER_GROUP(sb) * (ngroups - 1));
135         } else {
136                 group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
137         }
138
139         free_blocks = group_blocks - bit_max;
140
141         if (bh) {
142                 ext4_fsblk_t start, tmp;
143                 int flex_bg = 0;
144
145                 for (bit = 0; bit < bit_max; bit++)
146                         ext4_set_bit(bit, bh->b_data);
147
148                 start = ext4_group_first_block_no(sb, block_group);
149
150                 if (EXT4_HAS_INCOMPAT_FEATURE(sb,
151                                               EXT4_FEATURE_INCOMPAT_FLEX_BG))
152                         flex_bg = 1;
153
154                 /* Set bits for block and inode bitmaps, and inode table */
155                 tmp = ext4_block_bitmap(sb, gdp);
156                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
157                         ext4_set_bit(tmp - start, bh->b_data);
158
159                 tmp = ext4_inode_bitmap(sb, gdp);
160                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
161                         ext4_set_bit(tmp - start, bh->b_data);
162
163                 tmp = ext4_inode_table(sb, gdp);
164                 for (; tmp < ext4_inode_table(sb, gdp) +
165                                 sbi->s_itb_per_group; tmp++) {
166                         if (!flex_bg ||
167                                 ext4_block_in_group(sb, tmp, block_group))
168                                 ext4_set_bit(tmp - start, bh->b_data);
169                 }
170                 /*
171                  * Also if the number of blocks within the group is
172                  * less than the blocksize * 8 ( which is the size
173                  * of bitmap ), set rest of the block bitmap to 1
174                  */
175                 mark_bitmap_end(group_blocks, sb->s_blocksize * 8, bh->b_data);
176         }
177         return free_blocks - ext4_group_used_meta_blocks(sb, block_group, gdp);
178 }
179
180
181 /*
182  * The free blocks are managed by bitmaps.  A file system contains several
183  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
184  * block for inodes, N blocks for the inode table and data blocks.
185  *
186  * The file system contains group descriptors which are located after the
187  * super block.  Each descriptor contains the number of the bitmap block and
188  * the free blocks count in the block.  The descriptors are loaded in memory
189  * when a file system is mounted (see ext4_fill_super).
190  */
191
192
193 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
194
195 /**
196  * ext4_get_group_desc() -- load group descriptor from disk
197  * @sb:                 super block
198  * @block_group:        given block group
199  * @bh:                 pointer to the buffer head to store the block
200  *                      group descriptor
201  */
202 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
203                                              ext4_group_t block_group,
204                                              struct buffer_head **bh)
205 {
206         unsigned int group_desc;
207         unsigned int offset;
208         ext4_group_t ngroups = ext4_get_groups_count(sb);
209         struct ext4_group_desc *desc;
210         struct ext4_sb_info *sbi = EXT4_SB(sb);
211
212         if (block_group >= ngroups) {
213                 ext4_error(sb, "ext4_get_group_desc",
214                            "block_group >= groups_count - "
215                            "block_group = %u, groups_count = %u",
216                            block_group, ngroups);
217
218                 return NULL;
219         }
220
221         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
222         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
223         if (!sbi->s_group_desc[group_desc]) {
224                 ext4_error(sb, "ext4_get_group_desc",
225                            "Group descriptor not loaded - "
226                            "block_group = %u, group_desc = %u, desc = %u",
227                            block_group, group_desc, offset);
228                 return NULL;
229         }
230
231         desc = (struct ext4_group_desc *)(
232                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
233                 offset * EXT4_DESC_SIZE(sb));
234         if (bh)
235                 *bh = sbi->s_group_desc[group_desc];
236         return desc;
237 }
238
239 static int ext4_valid_block_bitmap(struct super_block *sb,
240                                         struct ext4_group_desc *desc,
241                                         unsigned int block_group,
242                                         struct buffer_head *bh)
243 {
244         ext4_grpblk_t offset;
245         ext4_grpblk_t next_zero_bit;
246         ext4_fsblk_t bitmap_blk;
247         ext4_fsblk_t group_first_block;
248
249         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
250                 /* with FLEX_BG, the inode/block bitmaps and itable
251                  * blocks may not be in the group at all
252                  * so the bitmap validation will be skipped for those groups
253                  * or it has to also read the block group where the bitmaps
254                  * are located to verify they are set.
255                  */
256                 return 1;
257         }
258         group_first_block = ext4_group_first_block_no(sb, block_group);
259
260         /* check whether block bitmap block number is set */
261         bitmap_blk = ext4_block_bitmap(sb, desc);
262         offset = bitmap_blk - group_first_block;
263         if (!ext4_test_bit(offset, bh->b_data))
264                 /* bad block bitmap */
265                 goto err_out;
266
267         /* check whether the inode bitmap block number is set */
268         bitmap_blk = ext4_inode_bitmap(sb, desc);
269         offset = bitmap_blk - group_first_block;
270         if (!ext4_test_bit(offset, bh->b_data))
271                 /* bad block bitmap */
272                 goto err_out;
273
274         /* check whether the inode table block number is set */
275         bitmap_blk = ext4_inode_table(sb, desc);
276         offset = bitmap_blk - group_first_block;
277         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
278                                 offset + EXT4_SB(sb)->s_itb_per_group,
279                                 offset);
280         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
281                 /* good bitmap for inode tables */
282                 return 1;
283
284 err_out:
285         ext4_error(sb, __func__,
286                         "Invalid block bitmap - "
287                         "block_group = %d, block = %llu",
288                         block_group, bitmap_blk);
289         return 0;
290 }
291 /**
292  * ext4_read_block_bitmap()
293  * @sb:                 super block
294  * @block_group:        given block group
295  *
296  * Read the bitmap for a given block_group,and validate the
297  * bits for block/inode/inode tables are set in the bitmaps
298  *
299  * Return buffer_head on success or NULL in case of failure.
300  */
301 struct buffer_head *
302 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
303 {
304         struct ext4_group_desc *desc;
305         struct buffer_head *bh = NULL;
306         ext4_fsblk_t bitmap_blk;
307
308         desc = ext4_get_group_desc(sb, block_group, NULL);
309         if (!desc)
310                 return NULL;
311         bitmap_blk = ext4_block_bitmap(sb, desc);
312         bh = sb_getblk(sb, bitmap_blk);
313         if (unlikely(!bh)) {
314                 ext4_error(sb, __func__,
315                             "Cannot read block bitmap - "
316                             "block_group = %u, block_bitmap = %llu",
317                             block_group, bitmap_blk);
318                 return NULL;
319         }
320
321         if (bitmap_uptodate(bh))
322                 return bh;
323
324         lock_buffer(bh);
325         if (bitmap_uptodate(bh)) {
326                 unlock_buffer(bh);
327                 return bh;
328         }
329         ext4_lock_group(sb, block_group);
330         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
331                 ext4_init_block_bitmap(sb, bh, block_group, desc);
332                 set_bitmap_uptodate(bh);
333                 set_buffer_uptodate(bh);
334                 ext4_unlock_group(sb, block_group);
335                 unlock_buffer(bh);
336                 return bh;
337         }
338         ext4_unlock_group(sb, block_group);
339         if (buffer_uptodate(bh)) {
340                 /*
341                  * if not uninit if bh is uptodate,
342                  * bitmap is also uptodate
343                  */
344                 set_bitmap_uptodate(bh);
345                 unlock_buffer(bh);
346                 return bh;
347         }
348         /*
349          * submit the buffer_head for read. We can
350          * safely mark the bitmap as uptodate now.
351          * We do it here so the bitmap uptodate bit
352          * get set with buffer lock held.
353          */
354         set_bitmap_uptodate(bh);
355         if (bh_submit_read(bh) < 0) {
356                 put_bh(bh);
357                 ext4_error(sb, __func__,
358                             "Cannot read block bitmap - "
359                             "block_group = %u, block_bitmap = %llu",
360                             block_group, bitmap_blk);
361                 return NULL;
362         }
363         ext4_valid_block_bitmap(sb, desc, block_group, bh);
364         /*
365          * file system mounted not to panic on error,
366          * continue with corrupt bitmap
367          */
368         return bh;
369 }
370
371 /**
372  * ext4_add_groupblocks() -- Add given blocks to an existing group
373  * @handle:                     handle to this transaction
374  * @sb:                         super block
375  * @block:                      start physcial block to add to the block group
376  * @count:                      number of blocks to free
377  *
378  * This marks the blocks as free in the bitmap. We ask the
379  * mballoc to reload the buddy after this by setting group
380  * EXT4_GROUP_INFO_NEED_INIT_BIT flag
381  */
382 void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
383                          ext4_fsblk_t block, unsigned long count)
384 {
385         struct buffer_head *bitmap_bh = NULL;
386         struct buffer_head *gd_bh;
387         ext4_group_t block_group;
388         ext4_grpblk_t bit;
389         unsigned int i;
390         struct ext4_group_desc *desc;
391         struct ext4_super_block *es;
392         struct ext4_sb_info *sbi;
393         int err = 0, ret, blk_free_count;
394         ext4_grpblk_t blocks_freed;
395         struct ext4_group_info *grp;
396
397         sbi = EXT4_SB(sb);
398         es = sbi->s_es;
399         ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
400
401         ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
402         grp = ext4_get_group_info(sb, block_group);
403         /*
404          * Check to see if we are freeing blocks across a group
405          * boundary.
406          */
407         if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
408                 goto error_return;
409         }
410         bitmap_bh = ext4_read_block_bitmap(sb, block_group);
411         if (!bitmap_bh)
412                 goto error_return;
413         desc = ext4_get_group_desc(sb, block_group, &gd_bh);
414         if (!desc)
415                 goto error_return;
416
417         if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
418             in_range(ext4_inode_bitmap(sb, desc), block, count) ||
419             in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
420             in_range(block + count - 1, ext4_inode_table(sb, desc),
421                      sbi->s_itb_per_group)) {
422                 ext4_error(sb, __func__,
423                            "Adding blocks in system zones - "
424                            "Block = %llu, count = %lu",
425                            block, count);
426                 goto error_return;
427         }
428
429         /*
430          * We are about to add blocks to the bitmap,
431          * so we need undo access.
432          */
433         BUFFER_TRACE(bitmap_bh, "getting undo access");
434         err = ext4_journal_get_undo_access(handle, bitmap_bh);
435         if (err)
436                 goto error_return;
437
438         /*
439          * We are about to modify some metadata.  Call the journal APIs
440          * to unshare ->b_data if a currently-committing transaction is
441          * using it
442          */
443         BUFFER_TRACE(gd_bh, "get_write_access");
444         err = ext4_journal_get_write_access(handle, gd_bh);
445         if (err)
446                 goto error_return;
447         /*
448          * make sure we don't allow a parallel init on other groups in the
449          * same buddy cache
450          */
451         down_write(&grp->alloc_sem);
452         for (i = 0, blocks_freed = 0; i < count; i++) {
453                 BUFFER_TRACE(bitmap_bh, "clear bit");
454                 if (!ext4_clear_bit_atomic(ext4_group_lock_ptr(sb, block_group),
455                                                 bit + i, bitmap_bh->b_data)) {
456                         ext4_error(sb, __func__,
457                                    "bit already cleared for block %llu",
458                                    (ext4_fsblk_t)(block + i));
459                         BUFFER_TRACE(bitmap_bh, "bit already cleared");
460                 } else {
461                         blocks_freed++;
462                 }
463         }
464         ext4_lock_group(sb, block_group);
465         blk_free_count = blocks_freed + ext4_free_blks_count(sb, desc);
466         ext4_free_blks_set(sb, desc, blk_free_count);
467         desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
468         ext4_unlock_group(sb, block_group);
469         percpu_counter_add(&sbi->s_freeblocks_counter, blocks_freed);
470
471         if (sbi->s_log_groups_per_flex) {
472                 ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
473                 atomic_add(blocks_freed,
474                            &sbi->s_flex_groups[flex_group].free_blocks);
475         }
476         /*
477          * request to reload the buddy with the
478          * new bitmap information
479          */
480         set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
481         grp->bb_free += blocks_freed;
482         up_write(&grp->alloc_sem);
483
484         /* We dirtied the bitmap block */
485         BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
486         err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
487
488         /* And the group descriptor block */
489         BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
490         ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
491         if (!err)
492                 err = ret;
493         sb->s_dirt = 1;
494
495 error_return:
496         brelse(bitmap_bh);
497         ext4_std_error(sb, err);
498         return;
499 }
500
501 /**
502  * ext4_has_free_blocks()
503  * @sbi:        in-core super block structure.
504  * @nblocks:    number of needed blocks
505  *
506  * Check if filesystem has nblocks free & available for allocation.
507  * On success return 1, return 0 on failure.
508  */
509 int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
510 {
511         s64 free_blocks, dirty_blocks, root_blocks;
512         struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
513         struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
514
515         free_blocks  = percpu_counter_read_positive(fbc);
516         dirty_blocks = percpu_counter_read_positive(dbc);
517         root_blocks = ext4_r_blocks_count(sbi->s_es);
518
519         if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
520                                                 EXT4_FREEBLOCKS_WATERMARK) {
521                 free_blocks  = percpu_counter_sum_positive(fbc);
522                 dirty_blocks = percpu_counter_sum_positive(dbc);
523                 if (dirty_blocks < 0) {
524                         printk(KERN_CRIT "Dirty block accounting "
525                                         "went wrong %lld\n",
526                                         (long long)dirty_blocks);
527                 }
528         }
529         /* Check whether we have space after
530          * accounting for current dirty blocks & root reserved blocks.
531          */
532         if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
533                 return 1;
534
535         /* Hm, nope.  Are (enough) root reserved blocks available? */
536         if (sbi->s_resuid == current_fsuid() ||
537             ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
538             capable(CAP_SYS_RESOURCE)) {
539                 if (free_blocks >= (nblocks + dirty_blocks))
540                         return 1;
541         }
542
543         return 0;
544 }
545
546 int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
547                                                 s64 nblocks)
548 {
549         if (ext4_has_free_blocks(sbi, nblocks)) {
550                 percpu_counter_add(&sbi->s_dirtyblocks_counter, nblocks);
551                 return 0;
552         } else
553                 return -ENOSPC;
554 }
555
556 /**
557  * ext4_should_retry_alloc()
558  * @sb:                 super block
559  * @retries             number of attemps has been made
560  *
561  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
562  * it is profitable to retry the operation, this function will wait
563  * for the current or commiting transaction to complete, and then
564  * return TRUE.
565  *
566  * if the total number of retries exceed three times, return FALSE.
567  */
568 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
569 {
570         if (!ext4_has_free_blocks(EXT4_SB(sb), 1) ||
571             (*retries)++ > 3 ||
572             !EXT4_SB(sb)->s_journal)
573                 return 0;
574
575         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
576
577         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
578 }
579
580 /*
581  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
582  *
583  * @handle:             handle to this transaction
584  * @inode:              file inode
585  * @goal:               given target block(filesystem wide)
586  * @count:              pointer to total number of blocks needed
587  * @errp:               error code
588  *
589  * Return 1st allocated block number on success, *count stores total account
590  * error stores in errp pointer
591  */
592 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
593                 ext4_fsblk_t goal, unsigned long *count, int *errp)
594 {
595         struct ext4_allocation_request ar;
596         ext4_fsblk_t ret;
597
598         memset(&ar, 0, sizeof(ar));
599         /* Fill with neighbour allocated blocks */
600         ar.inode = inode;
601         ar.goal = goal;
602         ar.len = count ? *count : 1;
603
604         ret = ext4_mb_new_blocks(handle, &ar, errp);
605         if (count)
606                 *count = ar.len;
607
608         /*
609          * Account for the allocated meta blocks
610          */
611         if (!(*errp) && EXT4_I(inode)->i_delalloc_reserved_flag) {
612                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
613                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
614                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
615         }
616         return ret;
617 }
618
619 /**
620  * ext4_count_free_blocks() -- count filesystem free blocks
621  * @sb:         superblock
622  *
623  * Adds up the number of free blocks from each block group.
624  */
625 ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
626 {
627         ext4_fsblk_t desc_count;
628         struct ext4_group_desc *gdp;
629         ext4_group_t i;
630         ext4_group_t ngroups = ext4_get_groups_count(sb);
631 #ifdef EXT4FS_DEBUG
632         struct ext4_super_block *es;
633         ext4_fsblk_t bitmap_count;
634         unsigned int x;
635         struct buffer_head *bitmap_bh = NULL;
636
637         es = EXT4_SB(sb)->s_es;
638         desc_count = 0;
639         bitmap_count = 0;
640         gdp = NULL;
641
642         for (i = 0; i < ngroups; i++) {
643                 gdp = ext4_get_group_desc(sb, i, NULL);
644                 if (!gdp)
645                         continue;
646                 desc_count += ext4_free_blks_count(sb, gdp);
647                 brelse(bitmap_bh);
648                 bitmap_bh = ext4_read_block_bitmap(sb, i);
649                 if (bitmap_bh == NULL)
650                         continue;
651
652                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
653                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
654                         i, ext4_free_blks_count(sb, gdp), x);
655                 bitmap_count += x;
656         }
657         brelse(bitmap_bh);
658         printk(KERN_DEBUG "ext4_count_free_blocks: stored = %llu"
659                 ", computed = %llu, %llu\n", ext4_free_blocks_count(es),
660                desc_count, bitmap_count);
661         return bitmap_count;
662 #else
663         desc_count = 0;
664         for (i = 0; i < ngroups; i++) {
665                 gdp = ext4_get_group_desc(sb, i, NULL);
666                 if (!gdp)
667                         continue;
668                 desc_count += ext4_free_blks_count(sb, gdp);
669         }
670
671         return desc_count;
672 #endif
673 }
674
675 static inline int test_root(ext4_group_t a, int b)
676 {
677         int num = b;
678
679         while (a > num)
680                 num *= b;
681         return num == a;
682 }
683
684 static int ext4_group_sparse(ext4_group_t group)
685 {
686         if (group <= 1)
687                 return 1;
688         if (!(group & 1))
689                 return 0;
690         return (test_root(group, 7) || test_root(group, 5) ||
691                 test_root(group, 3));
692 }
693
694 /**
695  *      ext4_bg_has_super - number of blocks used by the superblock in group
696  *      @sb: superblock for filesystem
697  *      @group: group number to check
698  *
699  *      Return the number of blocks used by the superblock (primary or backup)
700  *      in this group.  Currently this will be only 0 or 1.
701  */
702 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
703 {
704         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
705                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
706                         !ext4_group_sparse(group))
707                 return 0;
708         return 1;
709 }
710
711 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
712                                         ext4_group_t group)
713 {
714         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
715         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
716         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
717
718         if (group == first || group == first + 1 || group == last)
719                 return 1;
720         return 0;
721 }
722
723 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
724                                         ext4_group_t group)
725 {
726         if (!ext4_bg_has_super(sb, group))
727                 return 0;
728
729         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
730                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
731         else
732                 return EXT4_SB(sb)->s_gdb_count;
733 }
734
735 /**
736  *      ext4_bg_num_gdb - number of blocks used by the group table in group
737  *      @sb: superblock for filesystem
738  *      @group: group number to check
739  *
740  *      Return the number of blocks used by the group descriptor table
741  *      (primary or backup) in this group.  In the future there may be a
742  *      different number of descriptor blocks in each group.
743  */
744 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
745 {
746         unsigned long first_meta_bg =
747                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
748         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
749
750         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
751                         metagroup < first_meta_bg)
752                 return ext4_bg_num_gdb_nometa(sb, group);
753
754         return ext4_bg_num_gdb_meta(sb,group);
755
756 }
757