userns: Convert ext4 to user kuid/kgid where appropriate
[linux-3.10.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 #include <trace/events/ext4.h>
25
26 static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
27                                             ext4_group_t block_group);
28 /*
29  * balloc.c contains the blocks allocation and deallocation routines
30  */
31
32 /*
33  * Calculate the block group number and offset into the block/cluster
34  * allocation bitmap, given a block number
35  */
36 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
37                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
38 {
39         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
40         ext4_grpblk_t offset;
41
42         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
43         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >>
44                 EXT4_SB(sb)->s_cluster_bits;
45         if (offsetp)
46                 *offsetp = offset;
47         if (blockgrpp)
48                 *blockgrpp = blocknr;
49
50 }
51
52 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
53                         ext4_group_t block_group)
54 {
55         ext4_group_t actual_group;
56         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
57         if (actual_group == block_group)
58                 return 1;
59         return 0;
60 }
61
62 /* Return the number of clusters used for file system metadata; this
63  * represents the overhead needed by the file system.
64  */
65 unsigned ext4_num_overhead_clusters(struct super_block *sb,
66                                     ext4_group_t block_group,
67                                     struct ext4_group_desc *gdp)
68 {
69         unsigned num_clusters;
70         int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
71         ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
72         ext4_fsblk_t itbl_blk;
73         struct ext4_sb_info *sbi = EXT4_SB(sb);
74
75         /* This is the number of clusters used by the superblock,
76          * block group descriptors, and reserved block group
77          * descriptor blocks */
78         num_clusters = ext4_num_base_meta_clusters(sb, block_group);
79
80         /*
81          * For the allocation bitmaps and inode table, we first need
82          * to check to see if the block is in the block group.  If it
83          * is, then check to see if the cluster is already accounted
84          * for in the clusters used for the base metadata cluster, or
85          * if we can increment the base metadata cluster to include
86          * that block.  Otherwise, we will have to track the cluster
87          * used for the allocation bitmap or inode table explicitly.
88          * Normally all of these blocks are contiguous, so the special
89          * case handling shouldn't be necessary except for *very*
90          * unusual file system layouts.
91          */
92         if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
93                 block_cluster = EXT4_B2C(sbi, (start -
94                                                ext4_block_bitmap(sb, gdp)));
95                 if (block_cluster < num_clusters)
96                         block_cluster = -1;
97                 else if (block_cluster == num_clusters) {
98                         num_clusters++;
99                         block_cluster = -1;
100                 }
101         }
102
103         if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
104                 inode_cluster = EXT4_B2C(sbi,
105                                          start - ext4_inode_bitmap(sb, gdp));
106                 if (inode_cluster < num_clusters)
107                         inode_cluster = -1;
108                 else if (inode_cluster == num_clusters) {
109                         num_clusters++;
110                         inode_cluster = -1;
111                 }
112         }
113
114         itbl_blk = ext4_inode_table(sb, gdp);
115         for (i = 0; i < sbi->s_itb_per_group; i++) {
116                 if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
117                         c = EXT4_B2C(sbi, start - itbl_blk + i);
118                         if ((c < num_clusters) || (c == inode_cluster) ||
119                             (c == block_cluster) || (c == itbl_cluster))
120                                 continue;
121                         if (c == num_clusters) {
122                                 num_clusters++;
123                                 continue;
124                         }
125                         num_clusters++;
126                         itbl_cluster = c;
127                 }
128         }
129
130         if (block_cluster != -1)
131                 num_clusters++;
132         if (inode_cluster != -1)
133                 num_clusters++;
134
135         return num_clusters;
136 }
137
138 static unsigned int num_clusters_in_group(struct super_block *sb,
139                                           ext4_group_t block_group)
140 {
141         unsigned int blocks;
142
143         if (block_group == ext4_get_groups_count(sb) - 1) {
144                 /*
145                  * Even though mke2fs always initializes the first and
146                  * last group, just in case some other tool was used,
147                  * we need to make sure we calculate the right free
148                  * blocks.
149                  */
150                 blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
151                         ext4_group_first_block_no(sb, block_group);
152         } else
153                 blocks = EXT4_BLOCKS_PER_GROUP(sb);
154         return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
155 }
156
157 /* Initializes an uninitialized block bitmap */
158 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
159                             ext4_group_t block_group,
160                             struct ext4_group_desc *gdp)
161 {
162         unsigned int bit, bit_max;
163         struct ext4_sb_info *sbi = EXT4_SB(sb);
164         ext4_fsblk_t start, tmp;
165         int flex_bg = 0;
166
167         J_ASSERT_BH(bh, buffer_locked(bh));
168
169         /* If checksum is bad mark all blocks used to prevent allocation
170          * essentially implementing a per-group read-only flag. */
171         if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
172                 ext4_error(sb, "Checksum bad for group %u", block_group);
173                 ext4_free_group_clusters_set(sb, gdp, 0);
174                 ext4_free_inodes_set(sb, gdp, 0);
175                 ext4_itable_unused_set(sb, gdp, 0);
176                 memset(bh->b_data, 0xff, sb->s_blocksize);
177                 return;
178         }
179         memset(bh->b_data, 0, sb->s_blocksize);
180
181         bit_max = ext4_num_base_meta_clusters(sb, block_group);
182         for (bit = 0; bit < bit_max; bit++)
183                 ext4_set_bit(bit, bh->b_data);
184
185         start = ext4_group_first_block_no(sb, block_group);
186
187         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
188                 flex_bg = 1;
189
190         /* Set bits for block and inode bitmaps, and inode table */
191         tmp = ext4_block_bitmap(sb, gdp);
192         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
193                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
194
195         tmp = ext4_inode_bitmap(sb, gdp);
196         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
197                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
198
199         tmp = ext4_inode_table(sb, gdp);
200         for (; tmp < ext4_inode_table(sb, gdp) +
201                      sbi->s_itb_per_group; tmp++) {
202                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
203                         ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
204         }
205
206         /*
207          * Also if the number of blocks within the group is less than
208          * the blocksize * 8 ( which is the size of bitmap ), set rest
209          * of the block bitmap to 1
210          */
211         ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
212                              sb->s_blocksize * 8, bh->b_data);
213 }
214
215 /* Return the number of free blocks in a block group.  It is used when
216  * the block bitmap is uninitialized, so we can't just count the bits
217  * in the bitmap. */
218 unsigned ext4_free_clusters_after_init(struct super_block *sb,
219                                        ext4_group_t block_group,
220                                        struct ext4_group_desc *gdp)
221 {
222         return num_clusters_in_group(sb, block_group) - 
223                 ext4_num_overhead_clusters(sb, block_group, gdp);
224 }
225
226 /*
227  * The free blocks are managed by bitmaps.  A file system contains several
228  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
229  * block for inodes, N blocks for the inode table and data blocks.
230  *
231  * The file system contains group descriptors which are located after the
232  * super block.  Each descriptor contains the number of the bitmap block and
233  * the free blocks count in the block.  The descriptors are loaded in memory
234  * when a file system is mounted (see ext4_fill_super).
235  */
236
237 /**
238  * ext4_get_group_desc() -- load group descriptor from disk
239  * @sb:                 super block
240  * @block_group:        given block group
241  * @bh:                 pointer to the buffer head to store the block
242  *                      group descriptor
243  */
244 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
245                                              ext4_group_t block_group,
246                                              struct buffer_head **bh)
247 {
248         unsigned int group_desc;
249         unsigned int offset;
250         ext4_group_t ngroups = ext4_get_groups_count(sb);
251         struct ext4_group_desc *desc;
252         struct ext4_sb_info *sbi = EXT4_SB(sb);
253
254         if (block_group >= ngroups) {
255                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
256                            " groups_count = %u", block_group, ngroups);
257
258                 return NULL;
259         }
260
261         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
262         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
263         if (!sbi->s_group_desc[group_desc]) {
264                 ext4_error(sb, "Group descriptor not loaded - "
265                            "block_group = %u, group_desc = %u, desc = %u",
266                            block_group, group_desc, offset);
267                 return NULL;
268         }
269
270         desc = (struct ext4_group_desc *)(
271                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
272                 offset * EXT4_DESC_SIZE(sb));
273         if (bh)
274                 *bh = sbi->s_group_desc[group_desc];
275         return desc;
276 }
277
278 static int ext4_valid_block_bitmap(struct super_block *sb,
279                                         struct ext4_group_desc *desc,
280                                         unsigned int block_group,
281                                         struct buffer_head *bh)
282 {
283         ext4_grpblk_t offset;
284         ext4_grpblk_t next_zero_bit;
285         ext4_fsblk_t bitmap_blk;
286         ext4_fsblk_t group_first_block;
287
288         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
289                 /* with FLEX_BG, the inode/block bitmaps and itable
290                  * blocks may not be in the group at all
291                  * so the bitmap validation will be skipped for those groups
292                  * or it has to also read the block group where the bitmaps
293                  * are located to verify they are set.
294                  */
295                 return 1;
296         }
297         group_first_block = ext4_group_first_block_no(sb, block_group);
298
299         /* check whether block bitmap block number is set */
300         bitmap_blk = ext4_block_bitmap(sb, desc);
301         offset = bitmap_blk - group_first_block;
302         if (!ext4_test_bit(offset, bh->b_data))
303                 /* bad block bitmap */
304                 goto err_out;
305
306         /* check whether the inode bitmap block number is set */
307         bitmap_blk = ext4_inode_bitmap(sb, desc);
308         offset = bitmap_blk - group_first_block;
309         if (!ext4_test_bit(offset, bh->b_data))
310                 /* bad block bitmap */
311                 goto err_out;
312
313         /* check whether the inode table block number is set */
314         bitmap_blk = ext4_inode_table(sb, desc);
315         offset = bitmap_blk - group_first_block;
316         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
317                                 offset + EXT4_SB(sb)->s_itb_per_group,
318                                 offset);
319         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
320                 /* good bitmap for inode tables */
321                 return 1;
322
323 err_out:
324         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
325                         block_group, bitmap_blk);
326         return 0;
327 }
328 /**
329  * ext4_read_block_bitmap()
330  * @sb:                 super block
331  * @block_group:        given block group
332  *
333  * Read the bitmap for a given block_group,and validate the
334  * bits for block/inode/inode tables are set in the bitmaps
335  *
336  * Return buffer_head on success or NULL in case of failure.
337  */
338 struct buffer_head *
339 ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
340 {
341         struct ext4_group_desc *desc;
342         struct buffer_head *bh;
343         ext4_fsblk_t bitmap_blk;
344
345         desc = ext4_get_group_desc(sb, block_group, NULL);
346         if (!desc)
347                 return NULL;
348         bitmap_blk = ext4_block_bitmap(sb, desc);
349         bh = sb_getblk(sb, bitmap_blk);
350         if (unlikely(!bh)) {
351                 ext4_error(sb, "Cannot get buffer for block bitmap - "
352                            "block_group = %u, block_bitmap = %llu",
353                            block_group, bitmap_blk);
354                 return NULL;
355         }
356
357         if (bitmap_uptodate(bh))
358                 return bh;
359
360         lock_buffer(bh);
361         if (bitmap_uptodate(bh)) {
362                 unlock_buffer(bh);
363                 return bh;
364         }
365         ext4_lock_group(sb, block_group);
366         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
367                 ext4_init_block_bitmap(sb, bh, block_group, desc);
368                 set_bitmap_uptodate(bh);
369                 set_buffer_uptodate(bh);
370                 ext4_unlock_group(sb, block_group);
371                 unlock_buffer(bh);
372                 return bh;
373         }
374         ext4_unlock_group(sb, block_group);
375         if (buffer_uptodate(bh)) {
376                 /*
377                  * if not uninit if bh is uptodate,
378                  * bitmap is also uptodate
379                  */
380                 set_bitmap_uptodate(bh);
381                 unlock_buffer(bh);
382                 return bh;
383         }
384         /*
385          * submit the buffer_head for reading
386          */
387         set_buffer_new(bh);
388         trace_ext4_read_block_bitmap_load(sb, block_group);
389         bh->b_end_io = ext4_end_bitmap_read;
390         get_bh(bh);
391         submit_bh(READ, bh);
392         return bh;
393 }
394
395 /* Returns 0 on success, 1 on error */
396 int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
397                            struct buffer_head *bh)
398 {
399         struct ext4_group_desc *desc;
400
401         if (!buffer_new(bh))
402                 return 0;
403         desc = ext4_get_group_desc(sb, block_group, NULL);
404         if (!desc)
405                 return 1;
406         wait_on_buffer(bh);
407         if (!buffer_uptodate(bh)) {
408                 ext4_error(sb, "Cannot read block bitmap - "
409                            "block_group = %u, block_bitmap = %llu",
410                            block_group, (unsigned long long) bh->b_blocknr);
411                 return 1;
412         }
413         clear_buffer_new(bh);
414         /* Panic or remount fs read-only if block bitmap is invalid */
415         ext4_valid_block_bitmap(sb, desc, block_group, bh);
416         return 0;
417 }
418
419 struct buffer_head *
420 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
421 {
422         struct buffer_head *bh;
423
424         bh = ext4_read_block_bitmap_nowait(sb, block_group);
425         if (ext4_wait_block_bitmap(sb, block_group, bh)) {
426                 put_bh(bh);
427                 return NULL;
428         }
429         return bh;
430 }
431
432 /**
433  * ext4_has_free_clusters()
434  * @sbi:        in-core super block structure.
435  * @nclusters:  number of needed blocks
436  * @flags:      flags from ext4_mb_new_blocks()
437  *
438  * Check if filesystem has nclusters free & available for allocation.
439  * On success return 1, return 0 on failure.
440  */
441 static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
442                                   s64 nclusters, unsigned int flags)
443 {
444         s64 free_clusters, dirty_clusters, root_clusters;
445         struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
446         struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
447
448         free_clusters  = percpu_counter_read_positive(fcc);
449         dirty_clusters = percpu_counter_read_positive(dcc);
450         root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
451
452         if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
453                                         EXT4_FREECLUSTERS_WATERMARK) {
454                 free_clusters  = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
455                 dirty_clusters = percpu_counter_sum_positive(dcc);
456         }
457         /* Check whether we have space after accounting for current
458          * dirty clusters & root reserved clusters.
459          */
460         if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
461                 return 1;
462
463         /* Hm, nope.  Are (enough) root reserved clusters available? */
464         if (uid_eq(sbi->s_resuid, current_fsuid()) ||
465             (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) ||
466             capable(CAP_SYS_RESOURCE) ||
467                 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
468
469                 if (free_clusters >= (nclusters + dirty_clusters))
470                         return 1;
471         }
472
473         return 0;
474 }
475
476 int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
477                              s64 nclusters, unsigned int flags)
478 {
479         if (ext4_has_free_clusters(sbi, nclusters, flags)) {
480                 percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
481                 return 0;
482         } else
483                 return -ENOSPC;
484 }
485
486 /**
487  * ext4_should_retry_alloc()
488  * @sb:                 super block
489  * @retries             number of attemps has been made
490  *
491  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
492  * it is profitable to retry the operation, this function will wait
493  * for the current or committing transaction to complete, and then
494  * return TRUE.
495  *
496  * if the total number of retries exceed three times, return FALSE.
497  */
498 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
499 {
500         if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
501             (*retries)++ > 3 ||
502             !EXT4_SB(sb)->s_journal)
503                 return 0;
504
505         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
506
507         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
508 }
509
510 /*
511  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
512  *
513  * @handle:             handle to this transaction
514  * @inode:              file inode
515  * @goal:               given target block(filesystem wide)
516  * @count:              pointer to total number of clusters needed
517  * @errp:               error code
518  *
519  * Return 1st allocated block number on success, *count stores total account
520  * error stores in errp pointer
521  */
522 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
523                                   ext4_fsblk_t goal, unsigned int flags,
524                                   unsigned long *count, int *errp)
525 {
526         struct ext4_allocation_request ar;
527         ext4_fsblk_t ret;
528
529         memset(&ar, 0, sizeof(ar));
530         /* Fill with neighbour allocated blocks */
531         ar.inode = inode;
532         ar.goal = goal;
533         ar.len = count ? *count : 1;
534         ar.flags = flags;
535
536         ret = ext4_mb_new_blocks(handle, &ar, errp);
537         if (count)
538                 *count = ar.len;
539         /*
540          * Account for the allocated meta blocks.  We will never
541          * fail EDQUOT for metdata, but we do account for it.
542          */
543         if (!(*errp) &&
544             ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
545                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
546                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
547                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
548                 dquot_alloc_block_nofail(inode,
549                                 EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
550         }
551         return ret;
552 }
553
554 /**
555  * ext4_count_free_clusters() -- count filesystem free clusters
556  * @sb:         superblock
557  *
558  * Adds up the number of free clusters from each block group.
559  */
560 ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
561 {
562         ext4_fsblk_t desc_count;
563         struct ext4_group_desc *gdp;
564         ext4_group_t i;
565         ext4_group_t ngroups = ext4_get_groups_count(sb);
566 #ifdef EXT4FS_DEBUG
567         struct ext4_super_block *es;
568         ext4_fsblk_t bitmap_count;
569         unsigned int x;
570         struct buffer_head *bitmap_bh = NULL;
571
572         es = EXT4_SB(sb)->s_es;
573         desc_count = 0;
574         bitmap_count = 0;
575         gdp = NULL;
576
577         for (i = 0; i < ngroups; i++) {
578                 gdp = ext4_get_group_desc(sb, i, NULL);
579                 if (!gdp)
580                         continue;
581                 desc_count += ext4_free_group_clusters(sb, gdp);
582                 brelse(bitmap_bh);
583                 bitmap_bh = ext4_read_block_bitmap(sb, i);
584                 if (bitmap_bh == NULL)
585                         continue;
586
587                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
588                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
589                         i, ext4_free_group_clusters(sb, gdp), x);
590                 bitmap_count += x;
591         }
592         brelse(bitmap_bh);
593         printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
594                ", computed = %llu, %llu\n",
595                EXT4_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
596                desc_count, bitmap_count);
597         return bitmap_count;
598 #else
599         desc_count = 0;
600         for (i = 0; i < ngroups; i++) {
601                 gdp = ext4_get_group_desc(sb, i, NULL);
602                 if (!gdp)
603                         continue;
604                 desc_count += ext4_free_group_clusters(sb, gdp);
605         }
606
607         return desc_count;
608 #endif
609 }
610
611 static inline int test_root(ext4_group_t a, int b)
612 {
613         int num = b;
614
615         while (a > num)
616                 num *= b;
617         return num == a;
618 }
619
620 static int ext4_group_sparse(ext4_group_t group)
621 {
622         if (group <= 1)
623                 return 1;
624         if (!(group & 1))
625                 return 0;
626         return (test_root(group, 7) || test_root(group, 5) ||
627                 test_root(group, 3));
628 }
629
630 /**
631  *      ext4_bg_has_super - number of blocks used by the superblock in group
632  *      @sb: superblock for filesystem
633  *      @group: group number to check
634  *
635  *      Return the number of blocks used by the superblock (primary or backup)
636  *      in this group.  Currently this will be only 0 or 1.
637  */
638 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
639 {
640         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
641                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
642                         !ext4_group_sparse(group))
643                 return 0;
644         return 1;
645 }
646
647 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
648                                         ext4_group_t group)
649 {
650         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
651         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
652         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
653
654         if (group == first || group == first + 1 || group == last)
655                 return 1;
656         return 0;
657 }
658
659 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
660                                         ext4_group_t group)
661 {
662         if (!ext4_bg_has_super(sb, group))
663                 return 0;
664
665         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
666                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
667         else
668                 return EXT4_SB(sb)->s_gdb_count;
669 }
670
671 /**
672  *      ext4_bg_num_gdb - number of blocks used by the group table in group
673  *      @sb: superblock for filesystem
674  *      @group: group number to check
675  *
676  *      Return the number of blocks used by the group descriptor table
677  *      (primary or backup) in this group.  In the future there may be a
678  *      different number of descriptor blocks in each group.
679  */
680 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
681 {
682         unsigned long first_meta_bg =
683                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
684         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
685
686         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
687                         metagroup < first_meta_bg)
688                 return ext4_bg_num_gdb_nometa(sb, group);
689
690         return ext4_bg_num_gdb_meta(sb,group);
691
692 }
693
694 /*
695  * This function returns the number of file system metadata clusters at
696  * the beginning of a block group, including the reserved gdt blocks.
697  */
698 static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
699                                      ext4_group_t block_group)
700 {
701         struct ext4_sb_info *sbi = EXT4_SB(sb);
702         unsigned num;
703
704         /* Check for superblock and gdt backups in this group */
705         num = ext4_bg_has_super(sb, block_group);
706
707         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
708             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
709                           sbi->s_desc_per_block) {
710                 if (num) {
711                         num += ext4_bg_num_gdb(sb, block_group);
712                         num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
713                 }
714         } else { /* For META_BG_BLOCK_GROUPS */
715                 num += ext4_bg_num_gdb(sb, block_group);
716         }
717         return EXT4_NUM_B2C(sbi, num);
718 }
719 /**
720  *      ext4_inode_to_goal_block - return a hint for block allocation
721  *      @inode: inode for block allocation
722  *
723  *      Return the ideal location to start allocating blocks for a
724  *      newly created inode.
725  */
726 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
727 {
728         struct ext4_inode_info *ei = EXT4_I(inode);
729         ext4_group_t block_group;
730         ext4_grpblk_t colour;
731         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
732         ext4_fsblk_t bg_start;
733         ext4_fsblk_t last_block;
734
735         block_group = ei->i_block_group;
736         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
737                 /*
738                  * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
739                  * block groups per flexgroup, reserve the first block
740                  * group for directories and special files.  Regular
741                  * files will start at the second block group.  This
742                  * tends to speed up directory access and improves
743                  * fsck times.
744                  */
745                 block_group &= ~(flex_size-1);
746                 if (S_ISREG(inode->i_mode))
747                         block_group++;
748         }
749         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
750         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
751
752         /*
753          * If we are doing delayed allocation, we don't need take
754          * colour into account.
755          */
756         if (test_opt(inode->i_sb, DELALLOC))
757                 return bg_start;
758
759         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
760                 colour = (current->pid % 16) *
761                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
762         else
763                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
764         return bg_start + colour;
765 }
766