]> err.no Git - linux-2.6/blob - fs/ext4/balloc.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
[linux-2.6] / 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/ext4_fs.h>
19 #include <linux/ext4_jbd2.h>
20 #include <linux/quotaops.h>
21 #include <linux/buffer_head.h>
22
23 #include "group.h"
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                 unsigned long *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 /* Initializes an uninitialized block bitmap if given, and returns the
47  * number of blocks free in the group. */
48 unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
49                                 int block_group, struct ext4_group_desc *gdp)
50 {
51         unsigned long start;
52         int bit, bit_max;
53         unsigned free_blocks, group_blocks;
54         struct ext4_sb_info *sbi = EXT4_SB(sb);
55
56         if (bh) {
57                 J_ASSERT_BH(bh, buffer_locked(bh));
58
59                 /* If checksum is bad mark all blocks used to prevent allocation
60                  * essentially implementing a per-group read-only flag. */
61                 if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
62                         ext4_error(sb, __FUNCTION__,
63                                    "Checksum bad for group %u\n", block_group);
64                         gdp->bg_free_blocks_count = 0;
65                         gdp->bg_free_inodes_count = 0;
66                         gdp->bg_itable_unused = 0;
67                         memset(bh->b_data, 0xff, sb->s_blocksize);
68                         return 0;
69                 }
70                 memset(bh->b_data, 0, sb->s_blocksize);
71         }
72
73         /* Check for superblock and gdt backups in this group */
74         bit_max = ext4_bg_has_super(sb, block_group);
75
76         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
77             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
78                           sbi->s_desc_per_block) {
79                 if (bit_max) {
80                         bit_max += ext4_bg_num_gdb(sb, block_group);
81                         bit_max +=
82                                 le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
83                 }
84         } else { /* For META_BG_BLOCK_GROUPS */
85                 int group_rel = (block_group -
86                                  le32_to_cpu(sbi->s_es->s_first_meta_bg)) %
87                                 EXT4_DESC_PER_BLOCK(sb);
88                 if (group_rel == 0 || group_rel == 1 ||
89                     (group_rel == EXT4_DESC_PER_BLOCK(sb) - 1))
90                         bit_max += 1;
91         }
92
93         if (block_group == sbi->s_groups_count - 1) {
94                 /*
95                  * Even though mke2fs always initialize first and last group
96                  * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
97                  * to make sure we calculate the right free blocks
98                  */
99                 group_blocks = ext4_blocks_count(sbi->s_es) -
100                         le32_to_cpu(sbi->s_es->s_first_data_block) -
101                         (EXT4_BLOCKS_PER_GROUP(sb) * (sbi->s_groups_count -1));
102         } else {
103                 group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
104         }
105
106         free_blocks = group_blocks - bit_max;
107
108         if (bh) {
109                 for (bit = 0; bit < bit_max; bit++)
110                         ext4_set_bit(bit, bh->b_data);
111
112                 start = block_group * EXT4_BLOCKS_PER_GROUP(sb) +
113                         le32_to_cpu(sbi->s_es->s_first_data_block);
114
115                 /* Set bits for block and inode bitmaps, and inode table */
116                 ext4_set_bit(ext4_block_bitmap(sb, gdp) - start, bh->b_data);
117                 ext4_set_bit(ext4_inode_bitmap(sb, gdp) - start, bh->b_data);
118                 for (bit = (ext4_inode_table(sb, gdp) - start),
119                      bit_max = bit + sbi->s_itb_per_group; bit < bit_max; bit++)
120                         ext4_set_bit(bit, bh->b_data);
121
122                 /*
123                  * Also if the number of blocks within the group is
124                  * less than the blocksize * 8 ( which is the size
125                  * of bitmap ), set rest of the block bitmap to 1
126                  */
127                 mark_bitmap_end(group_blocks, sb->s_blocksize * 8, bh->b_data);
128         }
129
130         return free_blocks - sbi->s_itb_per_group - 2;
131 }
132
133
134 /*
135  * The free blocks are managed by bitmaps.  A file system contains several
136  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
137  * block for inodes, N blocks for the inode table and data blocks.
138  *
139  * The file system contains group descriptors which are located after the
140  * super block.  Each descriptor contains the number of the bitmap block and
141  * the free blocks count in the block.  The descriptors are loaded in memory
142  * when a file system is mounted (see ext4_fill_super).
143  */
144
145
146 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
147
148 /**
149  * ext4_get_group_desc() -- load group descriptor from disk
150  * @sb:                 super block
151  * @block_group:        given block group
152  * @bh:                 pointer to the buffer head to store the block
153  *                      group descriptor
154  */
155 struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
156                                              unsigned int block_group,
157                                              struct buffer_head ** bh)
158 {
159         unsigned long group_desc;
160         unsigned long offset;
161         struct ext4_group_desc * desc;
162         struct ext4_sb_info *sbi = EXT4_SB(sb);
163
164         if (block_group >= sbi->s_groups_count) {
165                 ext4_error (sb, "ext4_get_group_desc",
166                             "block_group >= groups_count - "
167                             "block_group = %d, groups_count = %lu",
168                             block_group, sbi->s_groups_count);
169
170                 return NULL;
171         }
172         smp_rmb();
173
174         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
175         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
176         if (!sbi->s_group_desc[group_desc]) {
177                 ext4_error (sb, "ext4_get_group_desc",
178                             "Group descriptor not loaded - "
179                             "block_group = %d, group_desc = %lu, desc = %lu",
180                              block_group, group_desc, offset);
181                 return NULL;
182         }
183
184         desc = (struct ext4_group_desc *)(
185                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
186                 offset * EXT4_DESC_SIZE(sb));
187         if (bh)
188                 *bh = sbi->s_group_desc[group_desc];
189         return desc;
190 }
191
192 /**
193  * read_block_bitmap()
194  * @sb:                 super block
195  * @block_group:        given block group
196  *
197  * Read the bitmap for a given block_group, reading into the specified
198  * slot in the superblock's bitmap cache.
199  *
200  * Return buffer_head on success or NULL in case of failure.
201  */
202 struct buffer_head *
203 read_block_bitmap(struct super_block *sb, unsigned int block_group)
204 {
205         struct ext4_group_desc * desc;
206         struct buffer_head * bh = NULL;
207         ext4_fsblk_t bitmap_blk;
208
209         desc = ext4_get_group_desc(sb, block_group, NULL);
210         if (!desc)
211                 return NULL;
212         bitmap_blk = ext4_block_bitmap(sb, desc);
213         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
214                 bh = sb_getblk(sb, bitmap_blk);
215                 if (!buffer_uptodate(bh)) {
216                         lock_buffer(bh);
217                         if (!buffer_uptodate(bh)) {
218                                 ext4_init_block_bitmap(sb, bh, block_group,
219                                                        desc);
220                                 set_buffer_uptodate(bh);
221                         }
222                         unlock_buffer(bh);
223                 }
224         } else {
225                 bh = sb_bread(sb, bitmap_blk);
226         }
227         if (!bh)
228                 ext4_error (sb, __FUNCTION__,
229                             "Cannot read block bitmap - "
230                             "block_group = %d, block_bitmap = %llu",
231                             block_group, bitmap_blk);
232         return bh;
233 }
234 /*
235  * The reservation window structure operations
236  * --------------------------------------------
237  * Operations include:
238  * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
239  *
240  * We use a red-black tree to represent per-filesystem reservation
241  * windows.
242  *
243  */
244
245 /**
246  * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
247  * @rb_root:            root of per-filesystem reservation rb tree
248  * @verbose:            verbose mode
249  * @fn:                 function which wishes to dump the reservation map
250  *
251  * If verbose is turned on, it will print the whole block reservation
252  * windows(start, end). Otherwise, it will only print out the "bad" windows,
253  * those windows that overlap with their immediate neighbors.
254  */
255 #if 1
256 static void __rsv_window_dump(struct rb_root *root, int verbose,
257                               const char *fn)
258 {
259         struct rb_node *n;
260         struct ext4_reserve_window_node *rsv, *prev;
261         int bad;
262
263 restart:
264         n = rb_first(root);
265         bad = 0;
266         prev = NULL;
267
268         printk("Block Allocation Reservation Windows Map (%s):\n", fn);
269         while (n) {
270                 rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
271                 if (verbose)
272                         printk("reservation window 0x%p "
273                                "start:  %llu, end:  %llu\n",
274                                rsv, rsv->rsv_start, rsv->rsv_end);
275                 if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
276                         printk("Bad reservation %p (start >= end)\n",
277                                rsv);
278                         bad = 1;
279                 }
280                 if (prev && prev->rsv_end >= rsv->rsv_start) {
281                         printk("Bad reservation %p (prev->end >= start)\n",
282                                rsv);
283                         bad = 1;
284                 }
285                 if (bad) {
286                         if (!verbose) {
287                                 printk("Restarting reservation walk in verbose mode\n");
288                                 verbose = 1;
289                                 goto restart;
290                         }
291                 }
292                 n = rb_next(n);
293                 prev = rsv;
294         }
295         printk("Window map complete.\n");
296         if (bad)
297                 BUG();
298 }
299 #define rsv_window_dump(root, verbose) \
300         __rsv_window_dump((root), (verbose), __FUNCTION__)
301 #else
302 #define rsv_window_dump(root, verbose) do {} while (0)
303 #endif
304
305 /**
306  * goal_in_my_reservation()
307  * @rsv:                inode's reservation window
308  * @grp_goal:           given goal block relative to the allocation block group
309  * @group:              the current allocation block group
310  * @sb:                 filesystem super block
311  *
312  * Test if the given goal block (group relative) is within the file's
313  * own block reservation window range.
314  *
315  * If the reservation window is outside the goal allocation group, return 0;
316  * grp_goal (given goal block) could be -1, which means no specific
317  * goal block. In this case, always return 1.
318  * If the goal block is within the reservation window, return 1;
319  * otherwise, return 0;
320  */
321 static int
322 goal_in_my_reservation(struct ext4_reserve_window *rsv, ext4_grpblk_t grp_goal,
323                         unsigned int group, struct super_block * sb)
324 {
325         ext4_fsblk_t group_first_block, group_last_block;
326
327         group_first_block = ext4_group_first_block_no(sb, group);
328         group_last_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
329
330         if ((rsv->_rsv_start > group_last_block) ||
331             (rsv->_rsv_end < group_first_block))
332                 return 0;
333         if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
334                 || (grp_goal + group_first_block > rsv->_rsv_end)))
335                 return 0;
336         return 1;
337 }
338
339 /**
340  * search_reserve_window()
341  * @rb_root:            root of reservation tree
342  * @goal:               target allocation block
343  *
344  * Find the reserved window which includes the goal, or the previous one
345  * if the goal is not in any window.
346  * Returns NULL if there are no windows or if all windows start after the goal.
347  */
348 static struct ext4_reserve_window_node *
349 search_reserve_window(struct rb_root *root, ext4_fsblk_t goal)
350 {
351         struct rb_node *n = root->rb_node;
352         struct ext4_reserve_window_node *rsv;
353
354         if (!n)
355                 return NULL;
356
357         do {
358                 rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
359
360                 if (goal < rsv->rsv_start)
361                         n = n->rb_left;
362                 else if (goal > rsv->rsv_end)
363                         n = n->rb_right;
364                 else
365                         return rsv;
366         } while (n);
367         /*
368          * We've fallen off the end of the tree: the goal wasn't inside
369          * any particular node.  OK, the previous node must be to one
370          * side of the interval containing the goal.  If it's the RHS,
371          * we need to back up one.
372          */
373         if (rsv->rsv_start > goal) {
374                 n = rb_prev(&rsv->rsv_node);
375                 rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
376         }
377         return rsv;
378 }
379
380 /**
381  * ext4_rsv_window_add() -- Insert a window to the block reservation rb tree.
382  * @sb:                 super block
383  * @rsv:                reservation window to add
384  *
385  * Must be called with rsv_lock hold.
386  */
387 void ext4_rsv_window_add(struct super_block *sb,
388                     struct ext4_reserve_window_node *rsv)
389 {
390         struct rb_root *root = &EXT4_SB(sb)->s_rsv_window_root;
391         struct rb_node *node = &rsv->rsv_node;
392         ext4_fsblk_t start = rsv->rsv_start;
393
394         struct rb_node ** p = &root->rb_node;
395         struct rb_node * parent = NULL;
396         struct ext4_reserve_window_node *this;
397
398         while (*p)
399         {
400                 parent = *p;
401                 this = rb_entry(parent, struct ext4_reserve_window_node, rsv_node);
402
403                 if (start < this->rsv_start)
404                         p = &(*p)->rb_left;
405                 else if (start > this->rsv_end)
406                         p = &(*p)->rb_right;
407                 else {
408                         rsv_window_dump(root, 1);
409                         BUG();
410                 }
411         }
412
413         rb_link_node(node, parent, p);
414         rb_insert_color(node, root);
415 }
416
417 /**
418  * ext4_rsv_window_remove() -- unlink a window from the reservation rb tree
419  * @sb:                 super block
420  * @rsv:                reservation window to remove
421  *
422  * Mark the block reservation window as not allocated, and unlink it
423  * from the filesystem reservation window rb tree. Must be called with
424  * rsv_lock hold.
425  */
426 static void rsv_window_remove(struct super_block *sb,
427                               struct ext4_reserve_window_node *rsv)
428 {
429         rsv->rsv_start = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
430         rsv->rsv_end = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
431         rsv->rsv_alloc_hit = 0;
432         rb_erase(&rsv->rsv_node, &EXT4_SB(sb)->s_rsv_window_root);
433 }
434
435 /*
436  * rsv_is_empty() -- Check if the reservation window is allocated.
437  * @rsv:                given reservation window to check
438  *
439  * returns 1 if the end block is EXT4_RESERVE_WINDOW_NOT_ALLOCATED.
440  */
441 static inline int rsv_is_empty(struct ext4_reserve_window *rsv)
442 {
443         /* a valid reservation end block could not be 0 */
444         return rsv->_rsv_end == EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
445 }
446
447 /**
448  * ext4_init_block_alloc_info()
449  * @inode:              file inode structure
450  *
451  * Allocate and initialize the  reservation window structure, and
452  * link the window to the ext4 inode structure at last
453  *
454  * The reservation window structure is only dynamically allocated
455  * and linked to ext4 inode the first time the open file
456  * needs a new block. So, before every ext4_new_block(s) call, for
457  * regular files, we should check whether the reservation window
458  * structure exists or not. In the latter case, this function is called.
459  * Fail to do so will result in block reservation being turned off for that
460  * open file.
461  *
462  * This function is called from ext4_get_blocks_handle(), also called
463  * when setting the reservation window size through ioctl before the file
464  * is open for write (needs block allocation).
465  *
466  * Needs truncate_mutex protection prior to call this function.
467  */
468 void ext4_init_block_alloc_info(struct inode *inode)
469 {
470         struct ext4_inode_info *ei = EXT4_I(inode);
471         struct ext4_block_alloc_info *block_i = ei->i_block_alloc_info;
472         struct super_block *sb = inode->i_sb;
473
474         block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
475         if (block_i) {
476                 struct ext4_reserve_window_node *rsv = &block_i->rsv_window_node;
477
478                 rsv->rsv_start = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
479                 rsv->rsv_end = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
480
481                 /*
482                  * if filesystem is mounted with NORESERVATION, the goal
483                  * reservation window size is set to zero to indicate
484                  * block reservation is off
485                  */
486                 if (!test_opt(sb, RESERVATION))
487                         rsv->rsv_goal_size = 0;
488                 else
489                         rsv->rsv_goal_size = EXT4_DEFAULT_RESERVE_BLOCKS;
490                 rsv->rsv_alloc_hit = 0;
491                 block_i->last_alloc_logical_block = 0;
492                 block_i->last_alloc_physical_block = 0;
493         }
494         ei->i_block_alloc_info = block_i;
495 }
496
497 /**
498  * ext4_discard_reservation()
499  * @inode:              inode
500  *
501  * Discard(free) block reservation window on last file close, or truncate
502  * or at last iput().
503  *
504  * It is being called in three cases:
505  *      ext4_release_file(): last writer close the file
506  *      ext4_clear_inode(): last iput(), when nobody link to this file.
507  *      ext4_truncate(): when the block indirect map is about to change.
508  *
509  */
510 void ext4_discard_reservation(struct inode *inode)
511 {
512         struct ext4_inode_info *ei = EXT4_I(inode);
513         struct ext4_block_alloc_info *block_i = ei->i_block_alloc_info;
514         struct ext4_reserve_window_node *rsv;
515         spinlock_t *rsv_lock = &EXT4_SB(inode->i_sb)->s_rsv_window_lock;
516
517         if (!block_i)
518                 return;
519
520         rsv = &block_i->rsv_window_node;
521         if (!rsv_is_empty(&rsv->rsv_window)) {
522                 spin_lock(rsv_lock);
523                 if (!rsv_is_empty(&rsv->rsv_window))
524                         rsv_window_remove(inode->i_sb, rsv);
525                 spin_unlock(rsv_lock);
526         }
527 }
528
529 /**
530  * ext4_free_blocks_sb() -- Free given blocks and update quota
531  * @handle:                     handle to this transaction
532  * @sb:                         super block
533  * @block:                      start physcial block to free
534  * @count:                      number of blocks to free
535  * @pdquot_freed_blocks:        pointer to quota
536  */
537 void ext4_free_blocks_sb(handle_t *handle, struct super_block *sb,
538                          ext4_fsblk_t block, unsigned long count,
539                          unsigned long *pdquot_freed_blocks)
540 {
541         struct buffer_head *bitmap_bh = NULL;
542         struct buffer_head *gd_bh;
543         unsigned long block_group;
544         ext4_grpblk_t bit;
545         unsigned long i;
546         unsigned long overflow;
547         struct ext4_group_desc * desc;
548         struct ext4_super_block * es;
549         struct ext4_sb_info *sbi;
550         int err = 0, ret;
551         ext4_grpblk_t group_freed;
552
553         *pdquot_freed_blocks = 0;
554         sbi = EXT4_SB(sb);
555         es = sbi->s_es;
556         if (block < le32_to_cpu(es->s_first_data_block) ||
557             block + count < block ||
558             block + count > ext4_blocks_count(es)) {
559                 ext4_error (sb, "ext4_free_blocks",
560                             "Freeing blocks not in datazone - "
561                             "block = %llu, count = %lu", block, count);
562                 goto error_return;
563         }
564
565         ext4_debug ("freeing block(s) %llu-%llu\n", block, block + count - 1);
566
567 do_more:
568         overflow = 0;
569         ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
570         /*
571          * Check to see if we are freeing blocks across a group
572          * boundary.
573          */
574         if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
575                 overflow = bit + count - EXT4_BLOCKS_PER_GROUP(sb);
576                 count -= overflow;
577         }
578         brelse(bitmap_bh);
579         bitmap_bh = read_block_bitmap(sb, block_group);
580         if (!bitmap_bh)
581                 goto error_return;
582         desc = ext4_get_group_desc (sb, block_group, &gd_bh);
583         if (!desc)
584                 goto error_return;
585
586         if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
587             in_range(ext4_inode_bitmap(sb, desc), block, count) ||
588             in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
589             in_range(block + count - 1, ext4_inode_table(sb, desc),
590                      sbi->s_itb_per_group))
591                 ext4_error (sb, "ext4_free_blocks",
592                             "Freeing blocks in system zones - "
593                             "Block = %llu, count = %lu",
594                             block, count);
595
596         /*
597          * We are about to start releasing blocks in the bitmap,
598          * so we need undo access.
599          */
600         /* @@@ check errors */
601         BUFFER_TRACE(bitmap_bh, "getting undo access");
602         err = ext4_journal_get_undo_access(handle, bitmap_bh);
603         if (err)
604                 goto error_return;
605
606         /*
607          * We are about to modify some metadata.  Call the journal APIs
608          * to unshare ->b_data if a currently-committing transaction is
609          * using it
610          */
611         BUFFER_TRACE(gd_bh, "get_write_access");
612         err = ext4_journal_get_write_access(handle, gd_bh);
613         if (err)
614                 goto error_return;
615
616         jbd_lock_bh_state(bitmap_bh);
617
618         for (i = 0, group_freed = 0; i < count; i++) {
619                 /*
620                  * An HJ special.  This is expensive...
621                  */
622 #ifdef CONFIG_JBD2_DEBUG
623                 jbd_unlock_bh_state(bitmap_bh);
624                 {
625                         struct buffer_head *debug_bh;
626                         debug_bh = sb_find_get_block(sb, block + i);
627                         if (debug_bh) {
628                                 BUFFER_TRACE(debug_bh, "Deleted!");
629                                 if (!bh2jh(bitmap_bh)->b_committed_data)
630                                         BUFFER_TRACE(debug_bh,
631                                                 "No commited data in bitmap");
632                                 BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
633                                 __brelse(debug_bh);
634                         }
635                 }
636                 jbd_lock_bh_state(bitmap_bh);
637 #endif
638                 if (need_resched()) {
639                         jbd_unlock_bh_state(bitmap_bh);
640                         cond_resched();
641                         jbd_lock_bh_state(bitmap_bh);
642                 }
643                 /* @@@ This prevents newly-allocated data from being
644                  * freed and then reallocated within the same
645                  * transaction.
646                  *
647                  * Ideally we would want to allow that to happen, but to
648                  * do so requires making jbd2_journal_forget() capable of
649                  * revoking the queued write of a data block, which
650                  * implies blocking on the journal lock.  *forget()
651                  * cannot block due to truncate races.
652                  *
653                  * Eventually we can fix this by making jbd2_journal_forget()
654                  * return a status indicating whether or not it was able
655                  * to revoke the buffer.  On successful revoke, it is
656                  * safe not to set the allocation bit in the committed
657                  * bitmap, because we know that there is no outstanding
658                  * activity on the buffer any more and so it is safe to
659                  * reallocate it.
660                  */
661                 BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
662                 J_ASSERT_BH(bitmap_bh,
663                                 bh2jh(bitmap_bh)->b_committed_data != NULL);
664                 ext4_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
665                                 bh2jh(bitmap_bh)->b_committed_data);
666
667                 /*
668                  * We clear the bit in the bitmap after setting the committed
669                  * data bit, because this is the reverse order to that which
670                  * the allocator uses.
671                  */
672                 BUFFER_TRACE(bitmap_bh, "clear bit");
673                 if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
674                                                 bit + i, bitmap_bh->b_data)) {
675                         jbd_unlock_bh_state(bitmap_bh);
676                         ext4_error(sb, __FUNCTION__,
677                                    "bit already cleared for block %llu",
678                                    (ext4_fsblk_t)(block + i));
679                         jbd_lock_bh_state(bitmap_bh);
680                         BUFFER_TRACE(bitmap_bh, "bit already cleared");
681                 } else {
682                         group_freed++;
683                 }
684         }
685         jbd_unlock_bh_state(bitmap_bh);
686
687         spin_lock(sb_bgl_lock(sbi, block_group));
688         desc->bg_free_blocks_count =
689                 cpu_to_le16(le16_to_cpu(desc->bg_free_blocks_count) +
690                         group_freed);
691         desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
692         spin_unlock(sb_bgl_lock(sbi, block_group));
693         percpu_counter_add(&sbi->s_freeblocks_counter, count);
694
695         /* We dirtied the bitmap block */
696         BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
697         err = ext4_journal_dirty_metadata(handle, bitmap_bh);
698
699         /* And the group descriptor block */
700         BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
701         ret = ext4_journal_dirty_metadata(handle, gd_bh);
702         if (!err) err = ret;
703         *pdquot_freed_blocks += group_freed;
704
705         if (overflow && !err) {
706                 block += count;
707                 count = overflow;
708                 goto do_more;
709         }
710         sb->s_dirt = 1;
711 error_return:
712         brelse(bitmap_bh);
713         ext4_std_error(sb, err);
714         return;
715 }
716
717 /**
718  * ext4_free_blocks() -- Free given blocks and update quota
719  * @handle:             handle for this transaction
720  * @inode:              inode
721  * @block:              start physical block to free
722  * @count:              number of blocks to count
723  */
724 void ext4_free_blocks(handle_t *handle, struct inode *inode,
725                         ext4_fsblk_t block, unsigned long count)
726 {
727         struct super_block * sb;
728         unsigned long dquot_freed_blocks;
729
730         sb = inode->i_sb;
731         if (!sb) {
732                 printk ("ext4_free_blocks: nonexistent device");
733                 return;
734         }
735         ext4_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
736         if (dquot_freed_blocks)
737                 DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
738         return;
739 }
740
741 /**
742  * ext4_test_allocatable()
743  * @nr:                 given allocation block group
744  * @bh:                 bufferhead contains the bitmap of the given block group
745  *
746  * For ext4 allocations, we must not reuse any blocks which are
747  * allocated in the bitmap buffer's "last committed data" copy.  This
748  * prevents deletes from freeing up the page for reuse until we have
749  * committed the delete transaction.
750  *
751  * If we didn't do this, then deleting something and reallocating it as
752  * data would allow the old block to be overwritten before the
753  * transaction committed (because we force data to disk before commit).
754  * This would lead to corruption if we crashed between overwriting the
755  * data and committing the delete.
756  *
757  * @@@ We may want to make this allocation behaviour conditional on
758  * data-writes at some point, and disable it for metadata allocations or
759  * sync-data inodes.
760  */
761 static int ext4_test_allocatable(ext4_grpblk_t nr, struct buffer_head *bh)
762 {
763         int ret;
764         struct journal_head *jh = bh2jh(bh);
765
766         if (ext4_test_bit(nr, bh->b_data))
767                 return 0;
768
769         jbd_lock_bh_state(bh);
770         if (!jh->b_committed_data)
771                 ret = 1;
772         else
773                 ret = !ext4_test_bit(nr, jh->b_committed_data);
774         jbd_unlock_bh_state(bh);
775         return ret;
776 }
777
778 /**
779  * bitmap_search_next_usable_block()
780  * @start:              the starting block (group relative) of the search
781  * @bh:                 bufferhead contains the block group bitmap
782  * @maxblocks:          the ending block (group relative) of the reservation
783  *
784  * The bitmap search --- search forward alternately through the actual
785  * bitmap on disk and the last-committed copy in journal, until we find a
786  * bit free in both bitmaps.
787  */
788 static ext4_grpblk_t
789 bitmap_search_next_usable_block(ext4_grpblk_t start, struct buffer_head *bh,
790                                         ext4_grpblk_t maxblocks)
791 {
792         ext4_grpblk_t next;
793         struct journal_head *jh = bh2jh(bh);
794
795         while (start < maxblocks) {
796                 next = ext4_find_next_zero_bit(bh->b_data, maxblocks, start);
797                 if (next >= maxblocks)
798                         return -1;
799                 if (ext4_test_allocatable(next, bh))
800                         return next;
801                 jbd_lock_bh_state(bh);
802                 if (jh->b_committed_data)
803                         start = ext4_find_next_zero_bit(jh->b_committed_data,
804                                                         maxblocks, next);
805                 jbd_unlock_bh_state(bh);
806         }
807         return -1;
808 }
809
810 /**
811  * find_next_usable_block()
812  * @start:              the starting block (group relative) to find next
813  *                      allocatable block in bitmap.
814  * @bh:                 bufferhead contains the block group bitmap
815  * @maxblocks:          the ending block (group relative) for the search
816  *
817  * Find an allocatable block in a bitmap.  We honor both the bitmap and
818  * its last-committed copy (if that exists), and perform the "most
819  * appropriate allocation" algorithm of looking for a free block near
820  * the initial goal; then for a free byte somewhere in the bitmap; then
821  * for any free bit in the bitmap.
822  */
823 static ext4_grpblk_t
824 find_next_usable_block(ext4_grpblk_t start, struct buffer_head *bh,
825                         ext4_grpblk_t maxblocks)
826 {
827         ext4_grpblk_t here, next;
828         char *p, *r;
829
830         if (start > 0) {
831                 /*
832                  * The goal was occupied; search forward for a free
833                  * block within the next XX blocks.
834                  *
835                  * end_goal is more or less random, but it has to be
836                  * less than EXT4_BLOCKS_PER_GROUP. Aligning up to the
837                  * next 64-bit boundary is simple..
838                  */
839                 ext4_grpblk_t end_goal = (start + 63) & ~63;
840                 if (end_goal > maxblocks)
841                         end_goal = maxblocks;
842                 here = ext4_find_next_zero_bit(bh->b_data, end_goal, start);
843                 if (here < end_goal && ext4_test_allocatable(here, bh))
844                         return here;
845                 ext4_debug("Bit not found near goal\n");
846         }
847
848         here = start;
849         if (here < 0)
850                 here = 0;
851
852         p = ((char *)bh->b_data) + (here >> 3);
853         r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
854         next = (r - ((char *)bh->b_data)) << 3;
855
856         if (next < maxblocks && next >= start && ext4_test_allocatable(next, bh))
857                 return next;
858
859         /*
860          * The bitmap search --- search forward alternately through the actual
861          * bitmap and the last-committed copy until we find a bit free in
862          * both
863          */
864         here = bitmap_search_next_usable_block(here, bh, maxblocks);
865         return here;
866 }
867
868 /**
869  * claim_block()
870  * @block:              the free block (group relative) to allocate
871  * @bh:                 the bufferhead containts the block group bitmap
872  *
873  * We think we can allocate this block in this bitmap.  Try to set the bit.
874  * If that succeeds then check that nobody has allocated and then freed the
875  * block since we saw that is was not marked in b_committed_data.  If it _was_
876  * allocated and freed then clear the bit in the bitmap again and return
877  * zero (failure).
878  */
879 static inline int
880 claim_block(spinlock_t *lock, ext4_grpblk_t block, struct buffer_head *bh)
881 {
882         struct journal_head *jh = bh2jh(bh);
883         int ret;
884
885         if (ext4_set_bit_atomic(lock, block, bh->b_data))
886                 return 0;
887         jbd_lock_bh_state(bh);
888         if (jh->b_committed_data && ext4_test_bit(block,jh->b_committed_data)) {
889                 ext4_clear_bit_atomic(lock, block, bh->b_data);
890                 ret = 0;
891         } else {
892                 ret = 1;
893         }
894         jbd_unlock_bh_state(bh);
895         return ret;
896 }
897
898 /**
899  * ext4_try_to_allocate()
900  * @sb:                 superblock
901  * @handle:             handle to this transaction
902  * @group:              given allocation block group
903  * @bitmap_bh:          bufferhead holds the block bitmap
904  * @grp_goal:           given target block within the group
905  * @count:              target number of blocks to allocate
906  * @my_rsv:             reservation window
907  *
908  * Attempt to allocate blocks within a give range. Set the range of allocation
909  * first, then find the first free bit(s) from the bitmap (within the range),
910  * and at last, allocate the blocks by claiming the found free bit as allocated.
911  *
912  * To set the range of this allocation:
913  *      if there is a reservation window, only try to allocate block(s) from the
914  *      file's own reservation window;
915  *      Otherwise, the allocation range starts from the give goal block, ends at
916  *      the block group's last block.
917  *
918  * If we failed to allocate the desired block then we may end up crossing to a
919  * new bitmap.  In that case we must release write access to the old one via
920  * ext4_journal_release_buffer(), else we'll run out of credits.
921  */
922 static ext4_grpblk_t
923 ext4_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
924                         struct buffer_head *bitmap_bh, ext4_grpblk_t grp_goal,
925                         unsigned long *count, struct ext4_reserve_window *my_rsv)
926 {
927         ext4_fsblk_t group_first_block;
928         ext4_grpblk_t start, end;
929         unsigned long num = 0;
930
931         /* we do allocation within the reservation window if we have a window */
932         if (my_rsv) {
933                 group_first_block = ext4_group_first_block_no(sb, group);
934                 if (my_rsv->_rsv_start >= group_first_block)
935                         start = my_rsv->_rsv_start - group_first_block;
936                 else
937                         /* reservation window cross group boundary */
938                         start = 0;
939                 end = my_rsv->_rsv_end - group_first_block + 1;
940                 if (end > EXT4_BLOCKS_PER_GROUP(sb))
941                         /* reservation window crosses group boundary */
942                         end = EXT4_BLOCKS_PER_GROUP(sb);
943                 if ((start <= grp_goal) && (grp_goal < end))
944                         start = grp_goal;
945                 else
946                         grp_goal = -1;
947         } else {
948                 if (grp_goal > 0)
949                         start = grp_goal;
950                 else
951                         start = 0;
952                 end = EXT4_BLOCKS_PER_GROUP(sb);
953         }
954
955         BUG_ON(start > EXT4_BLOCKS_PER_GROUP(sb));
956
957 repeat:
958         if (grp_goal < 0 || !ext4_test_allocatable(grp_goal, bitmap_bh)) {
959                 grp_goal = find_next_usable_block(start, bitmap_bh, end);
960                 if (grp_goal < 0)
961                         goto fail_access;
962                 if (!my_rsv) {
963                         int i;
964
965                         for (i = 0; i < 7 && grp_goal > start &&
966                                         ext4_test_allocatable(grp_goal - 1,
967                                                                 bitmap_bh);
968                                         i++, grp_goal--)
969                                 ;
970                 }
971         }
972         start = grp_goal;
973
974         if (!claim_block(sb_bgl_lock(EXT4_SB(sb), group),
975                 grp_goal, bitmap_bh)) {
976                 /*
977                  * The block was allocated by another thread, or it was
978                  * allocated and then freed by another thread
979                  */
980                 start++;
981                 grp_goal++;
982                 if (start >= end)
983                         goto fail_access;
984                 goto repeat;
985         }
986         num++;
987         grp_goal++;
988         while (num < *count && grp_goal < end
989                 && ext4_test_allocatable(grp_goal, bitmap_bh)
990                 && claim_block(sb_bgl_lock(EXT4_SB(sb), group),
991                                 grp_goal, bitmap_bh)) {
992                 num++;
993                 grp_goal++;
994         }
995         *count = num;
996         return grp_goal - num;
997 fail_access:
998         *count = num;
999         return -1;
1000 }
1001
1002 /**
1003  *      find_next_reservable_window():
1004  *              find a reservable space within the given range.
1005  *              It does not allocate the reservation window for now:
1006  *              alloc_new_reservation() will do the work later.
1007  *
1008  *      @search_head: the head of the searching list;
1009  *              This is not necessarily the list head of the whole filesystem
1010  *
1011  *              We have both head and start_block to assist the search
1012  *              for the reservable space. The list starts from head,
1013  *              but we will shift to the place where start_block is,
1014  *              then start from there, when looking for a reservable space.
1015  *
1016  *      @size: the target new reservation window size
1017  *
1018  *      @group_first_block: the first block we consider to start
1019  *                      the real search from
1020  *
1021  *      @last_block:
1022  *              the maximum block number that our goal reservable space
1023  *              could start from. This is normally the last block in this
1024  *              group. The search will end when we found the start of next
1025  *              possible reservable space is out of this boundary.
1026  *              This could handle the cross boundary reservation window
1027  *              request.
1028  *
1029  *      basically we search from the given range, rather than the whole
1030  *      reservation double linked list, (start_block, last_block)
1031  *      to find a free region that is of my size and has not
1032  *      been reserved.
1033  *
1034  */
1035 static int find_next_reservable_window(
1036                                 struct ext4_reserve_window_node *search_head,
1037                                 struct ext4_reserve_window_node *my_rsv,
1038                                 struct super_block * sb,
1039                                 ext4_fsblk_t start_block,
1040                                 ext4_fsblk_t last_block)
1041 {
1042         struct rb_node *next;
1043         struct ext4_reserve_window_node *rsv, *prev;
1044         ext4_fsblk_t cur;
1045         int size = my_rsv->rsv_goal_size;
1046
1047         /* TODO: make the start of the reservation window byte-aligned */
1048         /* cur = *start_block & ~7;*/
1049         cur = start_block;
1050         rsv = search_head;
1051         if (!rsv)
1052                 return -1;
1053
1054         while (1) {
1055                 if (cur <= rsv->rsv_end)
1056                         cur = rsv->rsv_end + 1;
1057
1058                 /* TODO?
1059                  * in the case we could not find a reservable space
1060                  * that is what is expected, during the re-search, we could
1061                  * remember what's the largest reservable space we could have
1062                  * and return that one.
1063                  *
1064                  * For now it will fail if we could not find the reservable
1065                  * space with expected-size (or more)...
1066                  */
1067                 if (cur > last_block)
1068                         return -1;              /* fail */
1069
1070                 prev = rsv;
1071                 next = rb_next(&rsv->rsv_node);
1072                 rsv = rb_entry(next,struct ext4_reserve_window_node,rsv_node);
1073
1074                 /*
1075                  * Reached the last reservation, we can just append to the
1076                  * previous one.
1077                  */
1078                 if (!next)
1079                         break;
1080
1081                 if (cur + size <= rsv->rsv_start) {
1082                         /*
1083                          * Found a reserveable space big enough.  We could
1084                          * have a reservation across the group boundary here
1085                          */
1086                         break;
1087                 }
1088         }
1089         /*
1090          * we come here either :
1091          * when we reach the end of the whole list,
1092          * and there is empty reservable space after last entry in the list.
1093          * append it to the end of the list.
1094          *
1095          * or we found one reservable space in the middle of the list,
1096          * return the reservation window that we could append to.
1097          * succeed.
1098          */
1099
1100         if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
1101                 rsv_window_remove(sb, my_rsv);
1102
1103         /*
1104          * Let's book the whole avaliable window for now.  We will check the
1105          * disk bitmap later and then, if there are free blocks then we adjust
1106          * the window size if it's larger than requested.
1107          * Otherwise, we will remove this node from the tree next time
1108          * call find_next_reservable_window.
1109          */
1110         my_rsv->rsv_start = cur;
1111         my_rsv->rsv_end = cur + size - 1;
1112         my_rsv->rsv_alloc_hit = 0;
1113
1114         if (prev != my_rsv)
1115                 ext4_rsv_window_add(sb, my_rsv);
1116
1117         return 0;
1118 }
1119
1120 /**
1121  *      alloc_new_reservation()--allocate a new reservation window
1122  *
1123  *              To make a new reservation, we search part of the filesystem
1124  *              reservation list (the list that inside the group). We try to
1125  *              allocate a new reservation window near the allocation goal,
1126  *              or the beginning of the group, if there is no goal.
1127  *
1128  *              We first find a reservable space after the goal, then from
1129  *              there, we check the bitmap for the first free block after
1130  *              it. If there is no free block until the end of group, then the
1131  *              whole group is full, we failed. Otherwise, check if the free
1132  *              block is inside the expected reservable space, if so, we
1133  *              succeed.
1134  *              If the first free block is outside the reservable space, then
1135  *              start from the first free block, we search for next available
1136  *              space, and go on.
1137  *
1138  *      on succeed, a new reservation will be found and inserted into the list
1139  *      It contains at least one free block, and it does not overlap with other
1140  *      reservation windows.
1141  *
1142  *      failed: we failed to find a reservation window in this group
1143  *
1144  *      @rsv: the reservation
1145  *
1146  *      @grp_goal: The goal (group-relative).  It is where the search for a
1147  *              free reservable space should start from.
1148  *              if we have a grp_goal(grp_goal >0 ), then start from there,
1149  *              no grp_goal(grp_goal = -1), we start from the first block
1150  *              of the group.
1151  *
1152  *      @sb: the super block
1153  *      @group: the group we are trying to allocate in
1154  *      @bitmap_bh: the block group block bitmap
1155  *
1156  */
1157 static int alloc_new_reservation(struct ext4_reserve_window_node *my_rsv,
1158                 ext4_grpblk_t grp_goal, struct super_block *sb,
1159                 unsigned int group, struct buffer_head *bitmap_bh)
1160 {
1161         struct ext4_reserve_window_node *search_head;
1162         ext4_fsblk_t group_first_block, group_end_block, start_block;
1163         ext4_grpblk_t first_free_block;
1164         struct rb_root *fs_rsv_root = &EXT4_SB(sb)->s_rsv_window_root;
1165         unsigned long size;
1166         int ret;
1167         spinlock_t *rsv_lock = &EXT4_SB(sb)->s_rsv_window_lock;
1168
1169         group_first_block = ext4_group_first_block_no(sb, group);
1170         group_end_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
1171
1172         if (grp_goal < 0)
1173                 start_block = group_first_block;
1174         else
1175                 start_block = grp_goal + group_first_block;
1176
1177         size = my_rsv->rsv_goal_size;
1178
1179         if (!rsv_is_empty(&my_rsv->rsv_window)) {
1180                 /*
1181                  * if the old reservation is cross group boundary
1182                  * and if the goal is inside the old reservation window,
1183                  * we will come here when we just failed to allocate from
1184                  * the first part of the window. We still have another part
1185                  * that belongs to the next group. In this case, there is no
1186                  * point to discard our window and try to allocate a new one
1187                  * in this group(which will fail). we should
1188                  * keep the reservation window, just simply move on.
1189                  *
1190                  * Maybe we could shift the start block of the reservation
1191                  * window to the first block of next group.
1192                  */
1193
1194                 if ((my_rsv->rsv_start <= group_end_block) &&
1195                                 (my_rsv->rsv_end > group_end_block) &&
1196                                 (start_block >= my_rsv->rsv_start))
1197                         return -1;
1198
1199                 if ((my_rsv->rsv_alloc_hit >
1200                      (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
1201                         /*
1202                          * if the previously allocation hit ratio is
1203                          * greater than 1/2, then we double the size of
1204                          * the reservation window the next time,
1205                          * otherwise we keep the same size window
1206                          */
1207                         size = size * 2;
1208                         if (size > EXT4_MAX_RESERVE_BLOCKS)
1209                                 size = EXT4_MAX_RESERVE_BLOCKS;
1210                         my_rsv->rsv_goal_size= size;
1211                 }
1212         }
1213
1214         spin_lock(rsv_lock);
1215         /*
1216          * shift the search start to the window near the goal block
1217          */
1218         search_head = search_reserve_window(fs_rsv_root, start_block);
1219
1220         /*
1221          * find_next_reservable_window() simply finds a reservable window
1222          * inside the given range(start_block, group_end_block).
1223          *
1224          * To make sure the reservation window has a free bit inside it, we
1225          * need to check the bitmap after we found a reservable window.
1226          */
1227 retry:
1228         ret = find_next_reservable_window(search_head, my_rsv, sb,
1229                                                 start_block, group_end_block);
1230
1231         if (ret == -1) {
1232                 if (!rsv_is_empty(&my_rsv->rsv_window))
1233                         rsv_window_remove(sb, my_rsv);
1234                 spin_unlock(rsv_lock);
1235                 return -1;
1236         }
1237
1238         /*
1239          * On success, find_next_reservable_window() returns the
1240          * reservation window where there is a reservable space after it.
1241          * Before we reserve this reservable space, we need
1242          * to make sure there is at least a free block inside this region.
1243          *
1244          * searching the first free bit on the block bitmap and copy of
1245          * last committed bitmap alternatively, until we found a allocatable
1246          * block. Search start from the start block of the reservable space
1247          * we just found.
1248          */
1249         spin_unlock(rsv_lock);
1250         first_free_block = bitmap_search_next_usable_block(
1251                         my_rsv->rsv_start - group_first_block,
1252                         bitmap_bh, group_end_block - group_first_block + 1);
1253
1254         if (first_free_block < 0) {
1255                 /*
1256                  * no free block left on the bitmap, no point
1257                  * to reserve the space. return failed.
1258                  */
1259                 spin_lock(rsv_lock);
1260                 if (!rsv_is_empty(&my_rsv->rsv_window))
1261                         rsv_window_remove(sb, my_rsv);
1262                 spin_unlock(rsv_lock);
1263                 return -1;              /* failed */
1264         }
1265
1266         start_block = first_free_block + group_first_block;
1267         /*
1268          * check if the first free block is within the
1269          * free space we just reserved
1270          */
1271         if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
1272                 return 0;               /* success */
1273         /*
1274          * if the first free bit we found is out of the reservable space
1275          * continue search for next reservable space,
1276          * start from where the free block is,
1277          * we also shift the list head to where we stopped last time
1278          */
1279         search_head = my_rsv;
1280         spin_lock(rsv_lock);
1281         goto retry;
1282 }
1283
1284 /**
1285  * try_to_extend_reservation()
1286  * @my_rsv:             given reservation window
1287  * @sb:                 super block
1288  * @size:               the delta to extend
1289  *
1290  * Attempt to expand the reservation window large enough to have
1291  * required number of free blocks
1292  *
1293  * Since ext4_try_to_allocate() will always allocate blocks within
1294  * the reservation window range, if the window size is too small,
1295  * multiple blocks allocation has to stop at the end of the reservation
1296  * window. To make this more efficient, given the total number of
1297  * blocks needed and the current size of the window, we try to
1298  * expand the reservation window size if necessary on a best-effort
1299  * basis before ext4_new_blocks() tries to allocate blocks,
1300  */
1301 static void try_to_extend_reservation(struct ext4_reserve_window_node *my_rsv,
1302                         struct super_block *sb, int size)
1303 {
1304         struct ext4_reserve_window_node *next_rsv;
1305         struct rb_node *next;
1306         spinlock_t *rsv_lock = &EXT4_SB(sb)->s_rsv_window_lock;
1307
1308         if (!spin_trylock(rsv_lock))
1309                 return;
1310
1311         next = rb_next(&my_rsv->rsv_node);
1312
1313         if (!next)
1314                 my_rsv->rsv_end += size;
1315         else {
1316                 next_rsv = rb_entry(next, struct ext4_reserve_window_node, rsv_node);
1317
1318                 if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
1319                         my_rsv->rsv_end += size;
1320                 else
1321                         my_rsv->rsv_end = next_rsv->rsv_start - 1;
1322         }
1323         spin_unlock(rsv_lock);
1324 }
1325
1326 /**
1327  * ext4_try_to_allocate_with_rsv()
1328  * @sb:                 superblock
1329  * @handle:             handle to this transaction
1330  * @group:              given allocation block group
1331  * @bitmap_bh:          bufferhead holds the block bitmap
1332  * @grp_goal:           given target block within the group
1333  * @count:              target number of blocks to allocate
1334  * @my_rsv:             reservation window
1335  * @errp:               pointer to store the error code
1336  *
1337  * This is the main function used to allocate a new block and its reservation
1338  * window.
1339  *
1340  * Each time when a new block allocation is need, first try to allocate from
1341  * its own reservation.  If it does not have a reservation window, instead of
1342  * looking for a free bit on bitmap first, then look up the reservation list to
1343  * see if it is inside somebody else's reservation window, we try to allocate a
1344  * reservation window for it starting from the goal first. Then do the block
1345  * allocation within the reservation window.
1346  *
1347  * This will avoid keeping on searching the reservation list again and
1348  * again when somebody is looking for a free block (without
1349  * reservation), and there are lots of free blocks, but they are all
1350  * being reserved.
1351  *
1352  * We use a red-black tree for the per-filesystem reservation list.
1353  *
1354  */
1355 static ext4_grpblk_t
1356 ext4_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
1357                         unsigned int group, struct buffer_head *bitmap_bh,
1358                         ext4_grpblk_t grp_goal,
1359                         struct ext4_reserve_window_node * my_rsv,
1360                         unsigned long *count, int *errp)
1361 {
1362         ext4_fsblk_t group_first_block, group_last_block;
1363         ext4_grpblk_t ret = 0;
1364         int fatal;
1365         unsigned long num = *count;
1366
1367         *errp = 0;
1368
1369         /*
1370          * Make sure we use undo access for the bitmap, because it is critical
1371          * that we do the frozen_data COW on bitmap buffers in all cases even
1372          * if the buffer is in BJ_Forget state in the committing transaction.
1373          */
1374         BUFFER_TRACE(bitmap_bh, "get undo access for new block");
1375         fatal = ext4_journal_get_undo_access(handle, bitmap_bh);
1376         if (fatal) {
1377                 *errp = fatal;
1378                 return -1;
1379         }
1380
1381         /*
1382          * we don't deal with reservation when
1383          * filesystem is mounted without reservation
1384          * or the file is not a regular file
1385          * or last attempt to allocate a block with reservation turned on failed
1386          */
1387         if (my_rsv == NULL ) {
1388                 ret = ext4_try_to_allocate(sb, handle, group, bitmap_bh,
1389                                                 grp_goal, count, NULL);
1390                 goto out;
1391         }
1392         /*
1393          * grp_goal is a group relative block number (if there is a goal)
1394          * 0 <= grp_goal < EXT4_BLOCKS_PER_GROUP(sb)
1395          * first block is a filesystem wide block number
1396          * first block is the block number of the first block in this group
1397          */
1398         group_first_block = ext4_group_first_block_no(sb, group);
1399         group_last_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
1400
1401         /*
1402          * Basically we will allocate a new block from inode's reservation
1403          * window.
1404          *
1405          * We need to allocate a new reservation window, if:
1406          * a) inode does not have a reservation window; or
1407          * b) last attempt to allocate a block from existing reservation
1408          *    failed; or
1409          * c) we come here with a goal and with a reservation window
1410          *
1411          * We do not need to allocate a new reservation window if we come here
1412          * at the beginning with a goal and the goal is inside the window, or
1413          * we don't have a goal but already have a reservation window.
1414          * then we could go to allocate from the reservation window directly.
1415          */
1416         while (1) {
1417                 if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
1418                         !goal_in_my_reservation(&my_rsv->rsv_window,
1419                                                 grp_goal, group, sb)) {
1420                         if (my_rsv->rsv_goal_size < *count)
1421                                 my_rsv->rsv_goal_size = *count;
1422                         ret = alloc_new_reservation(my_rsv, grp_goal, sb,
1423                                                         group, bitmap_bh);
1424                         if (ret < 0)
1425                                 break;                  /* failed */
1426
1427                         if (!goal_in_my_reservation(&my_rsv->rsv_window,
1428                                                         grp_goal, group, sb))
1429                                 grp_goal = -1;
1430                 } else if (grp_goal >= 0) {
1431                         int curr = my_rsv->rsv_end -
1432                                         (grp_goal + group_first_block) + 1;
1433
1434                         if (curr < *count)
1435                                 try_to_extend_reservation(my_rsv, sb,
1436                                                         *count - curr);
1437                 }
1438
1439                 if ((my_rsv->rsv_start > group_last_block) ||
1440                                 (my_rsv->rsv_end < group_first_block)) {
1441                         rsv_window_dump(&EXT4_SB(sb)->s_rsv_window_root, 1);
1442                         BUG();
1443                 }
1444                 ret = ext4_try_to_allocate(sb, handle, group, bitmap_bh,
1445                                            grp_goal, &num, &my_rsv->rsv_window);
1446                 if (ret >= 0) {
1447                         my_rsv->rsv_alloc_hit += num;
1448                         *count = num;
1449                         break;                          /* succeed */
1450                 }
1451                 num = *count;
1452         }
1453 out:
1454         if (ret >= 0) {
1455                 BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
1456                                         "bitmap block");
1457                 fatal = ext4_journal_dirty_metadata(handle, bitmap_bh);
1458                 if (fatal) {
1459                         *errp = fatal;
1460                         return -1;
1461                 }
1462                 return ret;
1463         }
1464
1465         BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
1466         ext4_journal_release_buffer(handle, bitmap_bh);
1467         return ret;
1468 }
1469
1470 /**
1471  * ext4_has_free_blocks()
1472  * @sbi:                in-core super block structure.
1473  *
1474  * Check if filesystem has at least 1 free block available for allocation.
1475  */
1476 static int ext4_has_free_blocks(struct ext4_sb_info *sbi)
1477 {
1478         ext4_fsblk_t free_blocks, root_blocks;
1479
1480         free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
1481         root_blocks = ext4_r_blocks_count(sbi->s_es);
1482         if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
1483                 sbi->s_resuid != current->fsuid &&
1484                 (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
1485                 return 0;
1486         }
1487         return 1;
1488 }
1489
1490 /**
1491  * ext4_should_retry_alloc()
1492  * @sb:                 super block
1493  * @retries             number of attemps has been made
1494  *
1495  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
1496  * it is profitable to retry the operation, this function will wait
1497  * for the current or commiting transaction to complete, and then
1498  * return TRUE.
1499  *
1500  * if the total number of retries exceed three times, return FALSE.
1501  */
1502 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
1503 {
1504         if (!ext4_has_free_blocks(EXT4_SB(sb)) || (*retries)++ > 3)
1505                 return 0;
1506
1507         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
1508
1509         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
1510 }
1511
1512 /**
1513  * ext4_new_blocks() -- core block(s) allocation function
1514  * @handle:             handle to this transaction
1515  * @inode:              file inode
1516  * @goal:               given target block(filesystem wide)
1517  * @count:              target number of blocks to allocate
1518  * @errp:               error code
1519  *
1520  * ext4_new_blocks uses a goal block to assist allocation.  It tries to
1521  * allocate block(s) from the block group contains the goal block first. If that
1522  * fails, it will try to allocate block(s) from other block groups without
1523  * any specific goal block.
1524  *
1525  */
1526 ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
1527                         ext4_fsblk_t goal, unsigned long *count, int *errp)
1528 {
1529         struct buffer_head *bitmap_bh = NULL;
1530         struct buffer_head *gdp_bh;
1531         unsigned long group_no;
1532         int goal_group;
1533         ext4_grpblk_t grp_target_blk;   /* blockgroup relative goal block */
1534         ext4_grpblk_t grp_alloc_blk;    /* blockgroup-relative allocated block*/
1535         ext4_fsblk_t ret_block;         /* filesyetem-wide allocated block */
1536         int bgi;                        /* blockgroup iteration index */
1537         int fatal = 0, err;
1538         int performed_allocation = 0;
1539         ext4_grpblk_t free_blocks;      /* number of free blocks in a group */
1540         struct super_block *sb;
1541         struct ext4_group_desc *gdp;
1542         struct ext4_super_block *es;
1543         struct ext4_sb_info *sbi;
1544         struct ext4_reserve_window_node *my_rsv = NULL;
1545         struct ext4_block_alloc_info *block_i;
1546         unsigned short windowsz = 0;
1547 #ifdef EXT4FS_DEBUG
1548         static int goal_hits, goal_attempts;
1549 #endif
1550         unsigned long ngroups;
1551         unsigned long num = *count;
1552
1553         *errp = -ENOSPC;
1554         sb = inode->i_sb;
1555         if (!sb) {
1556                 printk("ext4_new_block: nonexistent device");
1557                 return 0;
1558         }
1559
1560         /*
1561          * Check quota for allocation of this block.
1562          */
1563         if (DQUOT_ALLOC_BLOCK(inode, num)) {
1564                 *errp = -EDQUOT;
1565                 return 0;
1566         }
1567
1568         sbi = EXT4_SB(sb);
1569         es = EXT4_SB(sb)->s_es;
1570         ext4_debug("goal=%lu.\n", goal);
1571         /*
1572          * Allocate a block from reservation only when
1573          * filesystem is mounted with reservation(default,-o reservation), and
1574          * it's a regular file, and
1575          * the desired window size is greater than 0 (One could use ioctl
1576          * command EXT4_IOC_SETRSVSZ to set the window size to 0 to turn off
1577          * reservation on that particular file)
1578          */
1579         block_i = EXT4_I(inode)->i_block_alloc_info;
1580         if (block_i && ((windowsz = block_i->rsv_window_node.rsv_goal_size) > 0))
1581                 my_rsv = &block_i->rsv_window_node;
1582
1583         if (!ext4_has_free_blocks(sbi)) {
1584                 *errp = -ENOSPC;
1585                 goto out;
1586         }
1587
1588         /*
1589          * First, test whether the goal block is free.
1590          */
1591         if (goal < le32_to_cpu(es->s_first_data_block) ||
1592             goal >= ext4_blocks_count(es))
1593                 goal = le32_to_cpu(es->s_first_data_block);
1594         ext4_get_group_no_and_offset(sb, goal, &group_no, &grp_target_blk);
1595         goal_group = group_no;
1596 retry_alloc:
1597         gdp = ext4_get_group_desc(sb, group_no, &gdp_bh);
1598         if (!gdp)
1599                 goto io_error;
1600
1601         free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1602         /*
1603          * if there is not enough free blocks to make a new resevation
1604          * turn off reservation for this allocation
1605          */
1606         if (my_rsv && (free_blocks < windowsz)
1607                 && (rsv_is_empty(&my_rsv->rsv_window)))
1608                 my_rsv = NULL;
1609
1610         if (free_blocks > 0) {
1611                 bitmap_bh = read_block_bitmap(sb, group_no);
1612                 if (!bitmap_bh)
1613                         goto io_error;
1614                 grp_alloc_blk = ext4_try_to_allocate_with_rsv(sb, handle,
1615                                         group_no, bitmap_bh, grp_target_blk,
1616                                         my_rsv, &num, &fatal);
1617                 if (fatal)
1618                         goto out;
1619                 if (grp_alloc_blk >= 0)
1620                         goto allocated;
1621         }
1622
1623         ngroups = EXT4_SB(sb)->s_groups_count;
1624         smp_rmb();
1625
1626         /*
1627          * Now search the rest of the groups.  We assume that
1628          * i and gdp correctly point to the last group visited.
1629          */
1630         for (bgi = 0; bgi < ngroups; bgi++) {
1631                 group_no++;
1632                 if (group_no >= ngroups)
1633                         group_no = 0;
1634                 gdp = ext4_get_group_desc(sb, group_no, &gdp_bh);
1635                 if (!gdp)
1636                         goto io_error;
1637                 free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1638                 /*
1639                  * skip this group if the number of
1640                  * free blocks is less than half of the reservation
1641                  * window size.
1642                  */
1643                 if (free_blocks <= (windowsz/2))
1644                         continue;
1645
1646                 brelse(bitmap_bh);
1647                 bitmap_bh = read_block_bitmap(sb, group_no);
1648                 if (!bitmap_bh)
1649                         goto io_error;
1650                 /*
1651                  * try to allocate block(s) from this group, without a goal(-1).
1652                  */
1653                 grp_alloc_blk = ext4_try_to_allocate_with_rsv(sb, handle,
1654                                         group_no, bitmap_bh, -1, my_rsv,
1655                                         &num, &fatal);
1656                 if (fatal)
1657                         goto out;
1658                 if (grp_alloc_blk >= 0)
1659                         goto allocated;
1660         }
1661         /*
1662          * We may end up a bogus ealier ENOSPC error due to
1663          * filesystem is "full" of reservations, but
1664          * there maybe indeed free blocks avaliable on disk
1665          * In this case, we just forget about the reservations
1666          * just do block allocation as without reservations.
1667          */
1668         if (my_rsv) {
1669                 my_rsv = NULL;
1670                 windowsz = 0;
1671                 group_no = goal_group;
1672                 goto retry_alloc;
1673         }
1674         /* No space left on the device */
1675         *errp = -ENOSPC;
1676         goto out;
1677
1678 allocated:
1679
1680         ext4_debug("using block group %d(%d)\n",
1681                         group_no, gdp->bg_free_blocks_count);
1682
1683         BUFFER_TRACE(gdp_bh, "get_write_access");
1684         fatal = ext4_journal_get_write_access(handle, gdp_bh);
1685         if (fatal)
1686                 goto out;
1687
1688         ret_block = grp_alloc_blk + ext4_group_first_block_no(sb, group_no);
1689
1690         if (in_range(ext4_block_bitmap(sb, gdp), ret_block, num) ||
1691             in_range(ext4_inode_bitmap(sb, gdp), ret_block, num) ||
1692             in_range(ret_block, ext4_inode_table(sb, gdp),
1693                      EXT4_SB(sb)->s_itb_per_group) ||
1694             in_range(ret_block + num - 1, ext4_inode_table(sb, gdp),
1695                      EXT4_SB(sb)->s_itb_per_group))
1696                 ext4_error(sb, "ext4_new_block",
1697                             "Allocating block in system zone - "
1698                             "blocks from %llu, length %lu",
1699                              ret_block, num);
1700
1701         performed_allocation = 1;
1702
1703 #ifdef CONFIG_JBD2_DEBUG
1704         {
1705                 struct buffer_head *debug_bh;
1706
1707                 /* Record bitmap buffer state in the newly allocated block */
1708                 debug_bh = sb_find_get_block(sb, ret_block);
1709                 if (debug_bh) {
1710                         BUFFER_TRACE(debug_bh, "state when allocated");
1711                         BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
1712                         brelse(debug_bh);
1713                 }
1714         }
1715         jbd_lock_bh_state(bitmap_bh);
1716         spin_lock(sb_bgl_lock(sbi, group_no));
1717         if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
1718                 int i;
1719
1720                 for (i = 0; i < num; i++) {
1721                         if (ext4_test_bit(grp_alloc_blk+i,
1722                                         bh2jh(bitmap_bh)->b_committed_data)) {
1723                                 printk("%s: block was unexpectedly set in "
1724                                         "b_committed_data\n", __FUNCTION__);
1725                         }
1726                 }
1727         }
1728         ext4_debug("found bit %d\n", grp_alloc_blk);
1729         spin_unlock(sb_bgl_lock(sbi, group_no));
1730         jbd_unlock_bh_state(bitmap_bh);
1731 #endif
1732
1733         if (ret_block + num - 1 >= ext4_blocks_count(es)) {
1734                 ext4_error(sb, "ext4_new_block",
1735                             "block(%llu) >= blocks count(%llu) - "
1736                             "block_group = %lu, es == %p ", ret_block,
1737                         ext4_blocks_count(es), group_no, es);
1738                 goto out;
1739         }
1740
1741         /*
1742          * It is up to the caller to add the new buffer to a journal
1743          * list of some description.  We don't know in advance whether
1744          * the caller wants to use it as metadata or data.
1745          */
1746         ext4_debug("allocating block %lu. Goal hits %d of %d.\n",
1747                         ret_block, goal_hits, goal_attempts);
1748
1749         spin_lock(sb_bgl_lock(sbi, group_no));
1750         if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))
1751                 gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
1752         gdp->bg_free_blocks_count =
1753                         cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)-num);
1754         gdp->bg_checksum = ext4_group_desc_csum(sbi, group_no, gdp);
1755         spin_unlock(sb_bgl_lock(sbi, group_no));
1756         percpu_counter_sub(&sbi->s_freeblocks_counter, num);
1757
1758         BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
1759         err = ext4_journal_dirty_metadata(handle, gdp_bh);
1760         if (!fatal)
1761                 fatal = err;
1762
1763         sb->s_dirt = 1;
1764         if (fatal)
1765                 goto out;
1766
1767         *errp = 0;
1768         brelse(bitmap_bh);
1769         DQUOT_FREE_BLOCK(inode, *count-num);
1770         *count = num;
1771         return ret_block;
1772
1773 io_error:
1774         *errp = -EIO;
1775 out:
1776         if (fatal) {
1777                 *errp = fatal;
1778                 ext4_std_error(sb, fatal);
1779         }
1780         /*
1781          * Undo the block allocation
1782          */
1783         if (!performed_allocation)
1784                 DQUOT_FREE_BLOCK(inode, *count);
1785         brelse(bitmap_bh);
1786         return 0;
1787 }
1788
1789 ext4_fsblk_t ext4_new_block(handle_t *handle, struct inode *inode,
1790                         ext4_fsblk_t goal, int *errp)
1791 {
1792         unsigned long count = 1;
1793
1794         return ext4_new_blocks(handle, inode, goal, &count, errp);
1795 }
1796
1797 /**
1798  * ext4_count_free_blocks() -- count filesystem free blocks
1799  * @sb:         superblock
1800  *
1801  * Adds up the number of free blocks from each block group.
1802  */
1803 ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
1804 {
1805         ext4_fsblk_t desc_count;
1806         struct ext4_group_desc *gdp;
1807         int i;
1808         unsigned long ngroups = EXT4_SB(sb)->s_groups_count;
1809 #ifdef EXT4FS_DEBUG
1810         struct ext4_super_block *es;
1811         ext4_fsblk_t bitmap_count;
1812         unsigned long x;
1813         struct buffer_head *bitmap_bh = NULL;
1814
1815         es = EXT4_SB(sb)->s_es;
1816         desc_count = 0;
1817         bitmap_count = 0;
1818         gdp = NULL;
1819
1820         smp_rmb();
1821         for (i = 0; i < ngroups; i++) {
1822                 gdp = ext4_get_group_desc(sb, i, NULL);
1823                 if (!gdp)
1824                         continue;
1825                 desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
1826                 brelse(bitmap_bh);
1827                 bitmap_bh = read_block_bitmap(sb, i);
1828                 if (bitmap_bh == NULL)
1829                         continue;
1830
1831                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
1832                 printk("group %d: stored = %d, counted = %lu\n",
1833                         i, le16_to_cpu(gdp->bg_free_blocks_count), x);
1834                 bitmap_count += x;
1835         }
1836         brelse(bitmap_bh);
1837         printk("ext4_count_free_blocks: stored = %llu"
1838                 ", computed = %llu, %llu\n",
1839                EXT4_FREE_BLOCKS_COUNT(es),
1840                 desc_count, bitmap_count);
1841         return bitmap_count;
1842 #else
1843         desc_count = 0;
1844         smp_rmb();
1845         for (i = 0; i < ngroups; i++) {
1846                 gdp = ext4_get_group_desc(sb, i, NULL);
1847                 if (!gdp)
1848                         continue;
1849                 desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
1850         }
1851
1852         return desc_count;
1853 #endif
1854 }
1855
1856 static inline int test_root(int a, int b)
1857 {
1858         int num = b;
1859
1860         while (a > num)
1861                 num *= b;
1862         return num == a;
1863 }
1864
1865 static int ext4_group_sparse(int group)
1866 {
1867         if (group <= 1)
1868                 return 1;
1869         if (!(group & 1))
1870                 return 0;
1871         return (test_root(group, 7) || test_root(group, 5) ||
1872                 test_root(group, 3));
1873 }
1874
1875 /**
1876  *      ext4_bg_has_super - number of blocks used by the superblock in group
1877  *      @sb: superblock for filesystem
1878  *      @group: group number to check
1879  *
1880  *      Return the number of blocks used by the superblock (primary or backup)
1881  *      in this group.  Currently this will be only 0 or 1.
1882  */
1883 int ext4_bg_has_super(struct super_block *sb, int group)
1884 {
1885         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
1886                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
1887                         !ext4_group_sparse(group))
1888                 return 0;
1889         return 1;
1890 }
1891
1892 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb, int group)
1893 {
1894         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
1895         unsigned long first = metagroup * EXT4_DESC_PER_BLOCK(sb);
1896         unsigned long last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
1897
1898         if (group == first || group == first + 1 || group == last)
1899                 return 1;
1900         return 0;
1901 }
1902
1903 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb, int group)
1904 {
1905         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
1906                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
1907                         !ext4_group_sparse(group))
1908                 return 0;
1909         return EXT4_SB(sb)->s_gdb_count;
1910 }
1911
1912 /**
1913  *      ext4_bg_num_gdb - number of blocks used by the group table in group
1914  *      @sb: superblock for filesystem
1915  *      @group: group number to check
1916  *
1917  *      Return the number of blocks used by the group descriptor table
1918  *      (primary or backup) in this group.  In the future there may be a
1919  *      different number of descriptor blocks in each group.
1920  */
1921 unsigned long ext4_bg_num_gdb(struct super_block *sb, int group)
1922 {
1923         unsigned long first_meta_bg =
1924                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
1925         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
1926
1927         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
1928                         metagroup < first_meta_bg)
1929                 return ext4_bg_num_gdb_nometa(sb,group);
1930
1931         return ext4_bg_num_gdb_meta(sb,group);
1932
1933 }