summaryrefslogblamecommitdiff
path: root/fs/ext3/balloc.c
blob: 0213db4911a2adfcd19bb92d33dfc5b0936a192b (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412














































































































































































































































































































































































































































































































































































































































































































































































                                                                                        
   
                                       
                                                                             

                                                                         




                                                    
                                         


                                                                         
                          

                          
                          














                                                                             
                                                          


                                               
                                                                                

























                                                                            


















                                                                              




































                                                                               
  







                                                                         

                                                                      

                                                               










                                                                                
 
































                                                                                      

                            












                                                                           









                                                                              










                                                                            
                              
                                                           
                                                              






                                                                            




                                                       
         
 


                                                           
                                      
           

                                                                              

                                                                        
                                                     


                                                                    

                             
                   




























                                                                               



























                                                                                     
























                                                                                

                                                                                        

                                                                          


                                                                    
                                                                                          

                                          

                                                                                        

                                                                              
                                                                




























































































































































































































































































































                                                                                 
                                                            









                                             

                                       




















                                                                               
















































































































































                                                                                
/*
 *  linux/fs/ext3/balloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/config.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/ext3_fs.h>
#include <linux/ext3_jbd.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>

/*
 * balloc.c contains the blocks allocation and deallocation routines
 */

/*
 * The free blocks are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.  The descriptors are loaded in memory
 * when a file system is mounted (see ext3_read_super).
 */


#define in_range(b, first, len)	((b) >= (first) && (b) <= (first) + (len) - 1)

struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
					     unsigned int block_group,
					     struct buffer_head ** bh)
{
	unsigned long group_desc;
	unsigned long offset;
	struct ext3_group_desc * desc;
	struct ext3_sb_info *sbi = EXT3_SB(sb);

	if (block_group >= sbi->s_groups_count) {
		ext3_error (sb, "ext3_get_group_desc",
			    "block_group >= groups_count - "
			    "block_group = %d, groups_count = %lu",
			    block_group, sbi->s_groups_count);

		return NULL;
	}
	smp_rmb();

	group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(sb);
	offset = block_group & (EXT3_DESC_PER_BLOCK(sb) - 1);
	if (!sbi->s_group_desc[group_desc]) {
		ext3_error (sb, "ext3_get_group_desc",
			    "Group descriptor not loaded - "
			    "block_group = %d, group_desc = %lu, desc = %lu",
			     block_group, group_desc, offset);
		return NULL;
	}

	desc = (struct ext3_group_desc *) sbi->s_group_desc[group_desc]->b_data;
	if (bh)
		*bh = sbi->s_group_desc[group_desc];
	return desc + offset;
}

/*
 * Read the bitmap for a given block_group, reading into the specified 
 * slot in the superblock's bitmap cache.
 *
 * Return buffer_head on success or NULL in case of failure.
 */
static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
	struct ext3_group_desc * desc;
	struct buffer_head * bh = NULL;

	desc = ext3_get_group_desc (sb, block_group, NULL);
	if (!desc)
		goto error_out;
	bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
	if (!bh)
		ext3_error (sb, "read_block_bitmap",
			    "Cannot read block bitmap - "
			    "block_group = %d, block_bitmap = %u",
			    block_group, le32_to_cpu(desc->bg_block_bitmap));
error_out:
	return bh;
}
/*
 * The reservation window structure operations
 * --------------------------------------------
 * Operations include:
 * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
 *
 * We use sorted double linked list for the per-filesystem reservation
 * window list. (like in vm_region).
 *
 * Initially, we keep those small operations in the abstract functions,
 * so later if we need a better searching tree than double linked-list,
 * we could easily switch to that without changing too much
 * code.
 */
#if 0
static void __rsv_window_dump(struct rb_root *root, int verbose,
			      const char *fn)
{
	struct rb_node *n;
	struct ext3_reserve_window_node *rsv, *prev;
	int bad;

restart:
	n = rb_first(root);
	bad = 0;
	prev = NULL;

	printk("Block Allocation Reservation Windows Map (%s):\n", fn);
	while (n) {
		rsv = list_entry(n, struct ext3_reserve_window_node, rsv_node);
		if (verbose)
			printk("reservation window 0x%p "
			       "start:  %d, end:  %d\n",
			       rsv, rsv->rsv_start, rsv->rsv_end);
		if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
			printk("Bad reservation %p (start >= end)\n",
			       rsv);
			bad = 1;
		}
		if (prev && prev->rsv_end >= rsv->rsv_start) {
			printk("Bad reservation %p (prev->end >= start)\n",
			       rsv);
			bad = 1;
		}
		if (bad) {
			if (!verbose) {
				printk("Restarting reservation walk in verbose mode\n");
				verbose = 1;
				goto restart;
			}
		}
		n = rb_next(n);
		prev = rsv;
	}
	printk("Window map complete.\n");
	if (bad)
		BUG();
}
#define rsv_window_dump(root, verbose) \
	__rsv_window_dump((root), (verbose), __FUNCTION__)
#else
#define rsv_window_dump(root, verbose) do {} while (0)
#endif

static int
goal_in_my_reservation(struct ext3_reserve_window *rsv, int goal,
			unsigned int group, struct super_block * sb)
{
	unsigned long group_first_block, group_last_block;

	group_first_block = le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block) +
				group * EXT3_BLOCKS_PER_GROUP(sb);
	group_last_block = group_first_block + EXT3_BLOCKS_PER_GROUP(sb) - 1;

	if ((rsv->_rsv_start > group_last_block) ||
	    (rsv->_rsv_end < group_first_block))
		return 0;
	if ((goal >= 0) && ((goal + group_first_block < rsv->_rsv_start)
		|| (goal + group_first_block > rsv->_rsv_end)))
		return 0;
	return 1;
}

/*
 * Find the reserved window which includes the goal, or the previous one
 * if the goal is not in any window.
 * Returns NULL if there are no windows or if all windows start after the goal.
 */
static struct ext3_reserve_window_node *
search_reserve_window(struct rb_root *root, unsigned long goal)
{
	struct rb_node *n = root->rb_node;
	struct ext3_reserve_window_node *rsv;

	if (!n)
		return NULL;

	do {
		rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);

		if (goal < rsv->rsv_start)
			n = n->rb_left;
		else if (goal > rsv->rsv_end)
			n = n->rb_right;
		else
			return rsv;
	} while (n);
	/*
	 * We've fallen off the end of the tree: the goal wasn't inside
	 * any particular node.  OK, the previous node must be to one
	 * side of the interval containing the goal.  If it's the RHS,
	 * we need to back up one.
	 */
	if (rsv->rsv_start > goal) {
		n = rb_prev(&rsv->rsv_node);
		rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
	}
	return rsv;
}

void ext3_rsv_window_add(struct super_block *sb,
		    struct ext3_reserve_window_node *rsv)
{
	struct rb_root *root = &EXT3_SB(sb)->s_rsv_window_root;
	struct rb_node *node = &rsv->rsv_node;
	unsigned int start = rsv->rsv_start;

	struct rb_node ** p = &root->rb_node;
	struct rb_node * parent = NULL;
	struct ext3_reserve_window_node *this;

	while (*p)
	{
		parent = *p;
		this = rb_entry(parent, struct ext3_reserve_window_node, rsv_node);

		if (start < this->rsv_start)
			p = &(*p)->rb_left;
		else if (start > this->rsv_end)
			p = &(*p)->rb_right;
		else
			BUG();
	}

	rb_link_node(node, parent, p);
	rb_insert_color(node, root);
}

static void rsv_window_remove(struct super_block *sb,
			      struct ext3_reserve_window_node *rsv)
{
	rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
	rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
	rsv->rsv_alloc_hit = 0;
	rb_erase(&rsv->rsv_node, &EXT3_SB(sb)->s_rsv_window_root);
}

static inline int rsv_is_empty(struct ext3_reserve_window *rsv)
{
	/* a valid reservation end block could not be 0 */
	return (rsv->_rsv_end == EXT3_RESERVE_WINDOW_NOT_ALLOCATED);
}
void ext3_init_block_alloc_info(struct inode *inode)
{
	struct ext3_inode_info *ei = EXT3_I(inode);
	struct ext3_block_alloc_info *block_i = ei->i_block_alloc_info;
	struct super_block *sb = inode->i_sb;

	block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
	if (block_i) {
		struct ext3_reserve_window_node *rsv = &block_i->rsv_window_node;

		rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
		rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;

	 	/*
		 * if filesystem is mounted with NORESERVATION, the goal
		 * reservation window size is set to zero to indicate
		 * block reservation is off
		 */
		if (!test_opt(sb, RESERVATION))
			rsv->rsv_goal_size = 0;
		else
			rsv->rsv_goal_size = EXT3_DEFAULT_RESERVE_BLOCKS;
		rsv->rsv_alloc_hit = 0;
		block_i->last_alloc_logical_block = 0;
		block_i->last_alloc_physical_block = 0;
	}
	ei->i_block_alloc_info = block_i;
}

void ext3_discard_reservation(struct inode *inode)
{
	struct ext3_inode_info *ei = EXT3_I(inode);
	struct ext3_block_alloc_info *block_i = ei->i_block_alloc_info;
	struct ext3_reserve_window_node *rsv;
	spinlock_t *rsv_lock = &EXT3_SB(inode->i_sb)->s_rsv_window_lock;

	if (!block_i)
		return;

	rsv = &block_i->rsv_window_node;
	if (!rsv_is_empty(&rsv->rsv_window)) {
		spin_lock(rsv_lock);
		if (!rsv_is_empty(&rsv->rsv_window))
			rsv_window_remove(inode->i_sb, rsv);
		spin_unlock(rsv_lock);
	}
}

/* Free given blocks, update quota and i_blocks field */
void ext3_free_blocks_sb(handle_t *handle, struct super_block *sb,
			 unsigned long block, unsigned long count,
			 int *pdquot_freed_blocks)
{
	struct buffer_head *bitmap_bh = NULL;
	struct buffer_head *gd_bh;
	unsigned long block_group;
	unsigned long bit;
	unsigned long i;
	unsigned long overflow;
	struct ext3_group_desc * desc;
	struct ext3_super_block * es;
	struct ext3_sb_info *sbi;
	int err = 0, ret;
	unsigned group_freed;

	*pdquot_freed_blocks = 0;
	sbi = EXT3_SB(sb);
	es = sbi->s_es;
	if (block < le32_to_cpu(es->s_first_data_block) ||
	    block + count < block ||
	    block + count > le32_to_cpu(es->s_blocks_count)) {
		ext3_error (sb, "ext3_free_blocks",
			    "Freeing blocks not in datazone - "
			    "block = %lu, count = %lu", block, count);
		goto error_return;
	}

	ext3_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);

do_more:
	overflow = 0;
	block_group = (block - le32_to_cpu(es->s_first_data_block)) /
		      EXT3_BLOCKS_PER_GROUP(sb);
	bit = (block - le32_to_cpu(es->s_first_data_block)) %
		      EXT3_BLOCKS_PER_GROUP(sb);
	/*
	 * Check to see if we are freeing blocks across a group
	 * boundary.
	 */
	if (bit + count > EXT3_BLOCKS_PER_GROUP(sb)) {
		overflow = bit + count - EXT3_BLOCKS_PER_GROUP(sb);
		count -= overflow;
	}
	brelse(bitmap_bh);
	bitmap_bh = read_block_bitmap(sb, block_group);
	if (!bitmap_bh)
		goto error_return;
	desc = ext3_get_group_desc (sb, block_group, &gd_bh);
	if (!desc)
		goto error_return;

	if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
	    in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
	    in_range (block, le32_to_cpu(desc->bg_inode_table),
		      sbi->s_itb_per_group) ||
	    in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
		      sbi->s_itb_per_group))
		ext3_error (sb, "ext3_free_blocks",
			    "Freeing blocks in system zones - "
			    "Block = %lu, count = %lu",
			    block, count);

	/*
	 * We are about to start releasing blocks in the bitmap,
	 * so we need undo access.
	 */
	/* @@@ check errors */
	BUFFER_TRACE(bitmap_bh, "getting undo access");
	err = ext3_journal_get_undo_access(handle, bitmap_bh);
	if (err)
		goto error_return;

	/*
	 * We are about to modify some metadata.  Call the journal APIs
	 * to unshare ->b_data if a currently-committing transaction is
	 * using it
	 */
	BUFFER_TRACE(gd_bh, "get_write_access");
	err = ext3_journal_get_write_access(handle, gd_bh);
	if (err)
		goto error_return;

	jbd_lock_bh_state(bitmap_bh);

	for (i = 0, group_freed = 0; i < count; i++) {
		/*
		 * An HJ special.  This is expensive...
		 */
#ifdef CONFIG_JBD_DEBUG
		jbd_unlock_bh_state(bitmap_bh);
		{
			struct buffer_head *debug_bh;
			debug_bh = sb_find_get_block(sb, block + i);
			if (debug_bh) {
				BUFFER_TRACE(debug_bh, "Deleted!");
				if (!bh2jh(bitmap_bh)->b_committed_data)
					BUFFER_TRACE(debug_bh,
						"No commited data in bitmap");
				BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
				__brelse(debug_bh);
			}
		}
		jbd_lock_bh_state(bitmap_bh);
#endif
		if (need_resched()) {
			jbd_unlock_bh_state(bitmap_bh);
			cond_resched();
			jbd_lock_bh_state(bitmap_bh);
		}
		/* @@@ This prevents newly-allocated data from being
		 * freed and then reallocated within the same
		 * transaction. 
		 * 
		 * Ideally we would want to allow that to happen, but to
		 * do so requires making journal_forget() capable of
		 * revoking the queued write of a data block, which
		 * implies blocking on the journal lock.  *forget()
		 * cannot block due to truncate races.
		 *
		 * Eventually we can fix this by making journal_forget()
		 * return a status indicating whether or not it was able
		 * to revoke the buffer.  On successful revoke, it is
		 * safe not to set the allocation bit in the committed
		 * bitmap, because we know that there is no outstanding
		 * activity on the buffer any more and so it is safe to
		 * reallocate it.  
		 */
		BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
		J_ASSERT_BH(bitmap_bh,
				bh2jh(bitmap_bh)->b_committed_data != NULL);
		ext3_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
				bh2jh(bitmap_bh)->b_committed_data);

		/*
		 * We clear the bit in the bitmap after setting the committed
		 * data bit, because this is the reverse order to that which
		 * the allocator uses.
		 */
		BUFFER_TRACE(bitmap_bh, "clear bit");
		if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
						bit + i, bitmap_bh->b_data)) {
			jbd_unlock_bh_state(bitmap_bh);
			ext3_error(sb, __FUNCTION__,
				"bit already cleared for block %lu", block + i);
			jbd_lock_bh_state(bitmap_bh);
			BUFFER_TRACE(bitmap_bh, "bit already cleared");
		} else {
			group_freed++;
		}
	}
	jbd_unlock_bh_state(bitmap_bh);

	spin_lock(sb_bgl_lock(sbi, block_group));
	desc->bg_free_blocks_count =
		cpu_to_le16(le16_to_cpu(desc->bg_free_blocks_count) +
			group_freed);
	spin_unlock(sb_bgl_lock(sbi, block_group));
	percpu_counter_mod(&sbi->s_freeblocks_counter, count);

	/* We dirtied the bitmap block */
	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
	err = ext3_journal_dirty_metadata(handle, bitmap_bh);

	/* And the group descriptor block */
	BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
	ret = ext3_journal_dirty_metadata(handle, gd_bh);
	if (!err) err = ret;
	*pdquot_freed_blocks += group_freed;

	if (overflow && !err) {
		block += count;
		count = overflow;
		goto do_more;
	}
	sb->s_dirt = 1;
error_return:
	brelse(bitmap_bh);
	ext3_std_error(sb, err);
	return;
}

/* Free given blocks, update quota and i_blocks field */
void ext3_free_blocks(handle_t *handle, struct inode *inode,
			unsigned long block, unsigned long count)
{
	struct super_block * sb;
	int dquot_freed_blocks;

	sb = inode->i_sb;
	if (!sb) {
		printk ("ext3_free_blocks: nonexistent device");
		return;
	}
	ext3_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
	if (dquot_freed_blocks)
		DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
	return;
}

/*
 * For ext3 allocations, we must not reuse any blocks which are
 * allocated in the bitmap buffer's "last committed data" copy.  This
 * prevents deletes from freeing up the page for reuse until we have
 * committed the delete transaction.
 *
 * If we didn't do this, then deleting something and reallocating it as
 * data would allow the old block to be overwritten before the
 * transaction committed (because we force data to disk before commit).
 * This would lead to corruption if we crashed between overwriting the
 * data and committing the delete. 
 *
 * @@@ We may want to make this allocation behaviour conditional on
 * data-writes at some point, and disable it for metadata allocations or
 * sync-data inodes.
 */
static int ext3_test_allocatable(int nr, struct buffer_head *bh)
{
	int ret;
	struct journal_head *jh = bh2jh(bh);

	if (ext3_test_bit(nr, bh->b_data))
		return 0;

	jbd_lock_bh_state(bh);
	if (!jh->b_committed_data)
		ret = 1;
	else
		ret = !ext3_test_bit(nr, jh->b_committed_data);
	jbd_unlock_bh_state(bh);
	return ret;
}

static int
bitmap_search_next_usable_block(int start, struct buffer_head *bh,
					int maxblocks)
{
	int next;
	struct journal_head *jh = bh2jh(bh);

	/*
	 * The bitmap search --- search forward alternately through the actual
	 * bitmap and the last-committed copy until we find a bit free in
	 * both
	 */
	while (start < maxblocks) {
		next = ext3_find_next_zero_bit(bh->b_data, maxblocks, start);
		if (next >= maxblocks)
			return -1;
		if (ext3_test_allocatable(next, bh))
			return next;
		jbd_lock_bh_state(bh);
		if (jh->b_committed_data)
			start = ext3_find_next_zero_bit(jh->b_committed_data,
						 	maxblocks, next);
		jbd_unlock_bh_state(bh);
	}
	return -1;
}

/*
 * Find an allocatable block in a bitmap.  We honour both the bitmap and
 * its last-committed copy (if that exists), and perform the "most
 * appropriate allocation" algorithm of looking for a free block near
 * the initial goal; then for a free byte somewhere in the bitmap; then
 * for any free bit in the bitmap.
 */
static int
find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
{
	int here, next;
	char *p, *r;

	if (start > 0) {
		/*
		 * The goal was occupied; search forward for a free 
		 * block within the next XX blocks.
		 *
		 * end_goal is more or less random, but it has to be
		 * less than EXT3_BLOCKS_PER_GROUP. Aligning up to the
		 * next 64-bit boundary is simple..
		 */
		int end_goal = (start + 63) & ~63;
		if (end_goal > maxblocks)
			end_goal = maxblocks;
		here = ext3_find_next_zero_bit(bh->b_data, end_goal, start);
		if (here < end_goal && ext3_test_allocatable(here, bh))
			return here;
		ext3_debug("Bit not found near goal\n");
	}

	here = start;
	if (here < 0)
		here = 0;

	p = ((char *)bh->b_data) + (here >> 3);
	r = memscan(p, 0, (maxblocks - here + 7) >> 3);
	next = (r - ((char *)bh->b_data)) << 3;

	if (next < maxblocks && next >= start && ext3_test_allocatable(next, bh))
		return next;

	/*
	 * The bitmap search --- search forward alternately through the actual
	 * bitmap and the last-committed copy until we find a bit free in
	 * both
	 */
	here = bitmap_search_next_usable_block(here, bh, maxblocks);
	return here;
}

/*
 * We think we can allocate this block in this bitmap.  Try to set the bit.
 * If that succeeds then check that nobody has allocated and then freed the
 * block since we saw that is was not marked in b_committed_data.  If it _was_
 * allocated and freed then clear the bit in the bitmap again and return
 * zero (failure).
 */
static inline int
claim_block(spinlock_t *lock, int block, struct buffer_head *bh)
{
	struct journal_head *jh = bh2jh(bh);
	int ret;

	if (ext3_set_bit_atomic(lock, block, bh->b_data))
		return 0;
	jbd_lock_bh_state(bh);
	if (jh->b_committed_data && ext3_test_bit(block,jh->b_committed_data)) {
		ext3_clear_bit_atomic(lock, block, bh->b_data);
		ret = 0;
	} else {
		ret = 1;
	}
	jbd_unlock_bh_state(bh);
	return ret;
}

/*
 * If we failed to allocate the desired block then we may end up crossing to a
 * new bitmap.  In that case we must release write access to the old one via
 * ext3_journal_release_buffer(), else we'll run out of credits.
 */
static int
ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
	struct buffer_head *bitmap_bh, int goal, struct ext3_reserve_window *my_rsv)
{
	int group_first_block, start, end;

	/* we do allocation within the reservation window if we have a window */
	if (my_rsv) {
		group_first_block =
			le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block) +
			group * EXT3_BLOCKS_PER_GROUP(sb);
		if (my_rsv->_rsv_start >= group_first_block)
			start = my_rsv->_rsv_start - group_first_block;
		else
			/* reservation window cross group boundary */
			start = 0;
		end = my_rsv->_rsv_end - group_first_block + 1;
		if (end > EXT3_BLOCKS_PER_GROUP(sb))
			/* reservation window crosses group boundary */
			end = EXT3_BLOCKS_PER_GROUP(sb);
		if ((start <= goal) && (goal < end))
			start = goal;
		else
			goal = -1;
	} else {
		if (goal > 0)
			start = goal;
		else
			start = 0;
		end = EXT3_BLOCKS_PER_GROUP(sb);
	}

	BUG_ON(start > EXT3_BLOCKS_PER_GROUP(sb));

repeat:
	if (goal < 0 || !ext3_test_allocatable(goal, bitmap_bh)) {
		goal = find_next_usable_block(start, bitmap_bh, end);
		if (goal < 0)
			goto fail_access;
		if (!my_rsv) {
			int i;

			for (i = 0; i < 7 && goal > start &&
					ext3_test_allocatable(goal - 1,
								bitmap_bh);
					i++, goal--)
				;
		}
	}
	start = goal;

	if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group), goal, bitmap_bh)) {
		/*
		 * The block was allocated by another thread, or it was
		 * allocated and then freed by another thread
		 */
		start++;
		goal++;
		if (start >= end)
			goto fail_access;
		goto repeat;
	}
	return goal;
fail_access:
	return -1;
}

/**
 * 	find_next_reservable_window():
 *		find a reservable space within the given range.
 *		It does not allocate the reservation window for now:
 *		alloc_new_reservation() will do the work later.
 *
 * 	@search_head: the head of the searching list;
 *		This is not necessarily the list head of the whole filesystem
 *
 *		We have both head and start_block to assist the search
 *		for the reservable space. The list starts from head,
 *		but we will shift to the place where start_block is,
 *		then start from there, when looking for a reservable space.
 *
 * 	@size: the target new reservation window size
 *
 * 	@group_first_block: the first block we consider to start
 *			the real search from
 *
 * 	@last_block:
 *		the maximum block number that our goal reservable space
 *		could start from. This is normally the last block in this
 *		group. The search will end when we found the start of next
 *		possible reservable space is out of this boundary.
 *		This could handle the cross boundary reservation window
 *		request.
 *
 * 	basically we search from the given range, rather than the whole
 * 	reservation double linked list, (start_block, last_block)
 * 	to find a free region that is of my size and has not
 * 	been reserved.
 *
 */
static int find_next_reservable_window(
				struct ext3_reserve_window_node *search_head,
				struct ext3_reserve_window_node *my_rsv,
				struct super_block * sb, int start_block,
				int last_block)
{
	struct rb_node *next;
	struct ext3_reserve_window_node *rsv, *prev;
	int cur;
	int size = my_rsv->rsv_goal_size;

	/* TODO: make the start of the reservation window byte-aligned */
	/* cur = *start_block & ~7;*/
	cur = start_block;
	rsv = search_head;
	if (!rsv)
		return -1;

	while (1) {
		if (cur <= rsv->rsv_end)
			cur = rsv->rsv_end + 1;

		/* TODO?
		 * in the case we could not find a reservable space
		 * that is what is expected, during the re-search, we could
		 * remember what's the largest reservable space we could have
		 * and return that one.
		 *
		 * For now it will fail if we could not find the reservable
		 * space with expected-size (or more)...
		 */
		if (cur > last_block)
			return -1;		/* fail */

		prev = rsv;
		next = rb_next(&rsv->rsv_node);
		rsv = list_entry(next,struct ext3_reserve_window_node,rsv_node);

		/*
		 * Reached the last reservation, we can just append to the
		 * previous one.
		 */
		if (!next)
			break;

		if (cur + size <= rsv->rsv_start) {
			/*
			 * Found a reserveable space big enough.  We could
			 * have a reservation across the group boundary here
		 	 */
			break;
		}
	}
	/*
	 * we come here either :
	 * when we reach the end of the whole list,
	 * and there is empty reservable space after last entry in the list.
	 * append it to the end of the list.
	 *
	 * or we found one reservable space in the middle of the list,
	 * return the reservation window that we could append to.
	 * succeed.
	 */

	if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
		rsv_window_remove(sb, my_rsv);

	/*
	 * Let's book the whole avaliable window for now.  We will check the
	 * disk bitmap later and then, if there are free blocks then we adjust
	 * the window size if it's larger than requested.
	 * Otherwise, we will remove this node from the tree next time
	 * call find_next_reservable_window.
	 */
	my_rsv->rsv_start = cur;
	my_rsv->rsv_end = cur + size - 1;
	my_rsv->rsv_alloc_hit = 0;

	if (prev != my_rsv)
		ext3_rsv_window_add(sb, my_rsv);

	return 0;
}

/**
 * 	alloc_new_reservation()--allocate a new reservation window
 *
 *		To make a new reservation, we search part of the filesystem
 *		reservation list (the list that inside the group). We try to
 *		allocate a new reservation window near the allocation goal,
 *		or the beginning of the group, if there is no goal.
 *
 *		We first find a reservable space after the goal, then from
 *		there, we check the bitmap for the first free block after
 *		it. If there is no free block until the end of group, then the
 *		whole group is full, we failed. Otherwise, check if the free
 *		block is inside the expected reservable space, if so, we
 *		succeed.
 *		If the first free block is outside the reservable space, then
 *		start from the first free block, we search for next available
 *		space, and go on.
 *
 *	on succeed, a new reservation will be found and inserted into the list
 *	It contains at least one free block, and it does not overlap with other
 *	reservation windows.
 *
 *	failed: we failed to find a reservation window in this group
 *
 *	@rsv: the reservation
 *
 *	@goal: The goal (group-relative).  It is where the search for a
 *		free reservable space should start from.
 *		if we have a goal(goal >0 ), then start from there,
 *		no goal(goal = -1), we start from the first block
 *		of the group.
 *
 *	@sb: the super block
 *	@group: the group we are trying to allocate in
 *	@bitmap_bh: the block group block bitmap
 *
 */
static int alloc_new_reservation(struct ext3_reserve_window_node *my_rsv,
		int goal, struct super_block *sb,
		unsigned int group, struct buffer_head *bitmap_bh)
{
	struct ext3_reserve_window_node *search_head;
	int group_first_block, group_end_block, start_block;
	int first_free_block;
	struct rb_root *fs_rsv_root = &EXT3_SB(sb)->s_rsv_window_root;
	unsigned long size;
	int ret;
	spinlock_t *rsv_lock = &EXT3_SB(sb)->s_rsv_window_lock;

	group_first_block = le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block) +
				group * EXT3_BLOCKS_PER_GROUP(sb);
	group_end_block = group_first_block + EXT3_BLOCKS_PER_GROUP(sb) - 1;

	if (goal < 0)
		start_block = group_first_block;
	else
		start_block = goal + group_first_block;

	size = my_rsv->rsv_goal_size;

	if (!rsv_is_empty(&my_rsv->rsv_window)) {
		/*
		 * if the old reservation is cross group boundary
		 * and if the goal is inside the old reservation window,
		 * we will come here when we just failed to allocate from
		 * the first part of the window. We still have another part
		 * that belongs to the next group. In this case, there is no
		 * point to discard our window and try to allocate a new one
		 * in this group(which will fail). we should
		 * keep the reservation window, just simply move on.
		 *
		 * Maybe we could shift the start block of the reservation
		 * window to the first block of next group.
		 */

		if ((my_rsv->rsv_start <= group_end_block) &&
				(my_rsv->rsv_end > group_end_block) &&
				(start_block >= my_rsv->rsv_start))
			return -1;

		if ((my_rsv->rsv_alloc_hit >
		     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
			/*
			 * if we previously allocation hit ration is greater than half
			 * we double the size of reservation window next time
			 * otherwise keep the same
			 */
			size = size * 2;
			if (size > EXT3_MAX_RESERVE_BLOCKS)
				size = EXT3_MAX_RESERVE_BLOCKS;
			my_rsv->rsv_goal_size= size;
		}
	}

	spin_lock(rsv_lock);
	/*
	 * shift the search start to the window near the goal block
	 */
	search_head = search_reserve_window(fs_rsv_root, start_block);

	/*
	 * find_next_reservable_window() simply finds a reservable window
	 * inside the given range(start_block, group_end_block).
	 *
	 * To make sure the reservation window has a free bit inside it, we
	 * need to check the bitmap after we found a reservable window.
	 */
retry:
	ret = find_next_reservable_window(search_head, my_rsv, sb,
						start_block, group_end_block);

	if (ret == -1) {
		if (!rsv_is_empty(&my_rsv->rsv_window))
			rsv_window_remove(sb, my_rsv);
		spin_unlock(rsv_lock);
		return -1;
	}

	/*
	 * On success, find_next_reservable_window() returns the
	 * reservation window where there is a reservable space after it.
	 * Before we reserve this reservable space, we need
	 * to make sure there is at least a free block inside this region.
	 *
	 * searching the first free bit on the block bitmap and copy of
	 * last committed bitmap alternatively, until we found a allocatable
	 * block. Search start from the start block of the reservable space
	 * we just found.
	 */
	spin_unlock(rsv_lock);
	first_free_block = bitmap_search_next_usable_block(
			my_rsv->rsv_start - group_first_block,
			bitmap_bh, group_end_block - group_first_block + 1);

	if (first_free_block < 0) {
		/*
		 * no free block left on the bitmap, no point
		 * to reserve the space. return failed.
		 */
		spin_lock(rsv_lock);
		if (!rsv_is_empty(&my_rsv->rsv_window))
			rsv_window_remove(sb, my_rsv);
		spin_unlock(rsv_lock);
		return -1;		/* failed */
	}

	start_block = first_free_block + group_first_block;
	/*
	 * check if the first free block is within the
	 * free space we just reserved
	 */
	if (start_block >= my_rsv->rsv_start && start_block < my_rsv->rsv_end)
		return 0;		/* success */
	/*
	 * if the first free bit we found is out of the reservable space
	 * continue search for next reservable space,
	 * start from where the free block is,
	 * we also shift the list head to where we stopped last time
	 */
	search_head = my_rsv;
	spin_lock(rsv_lock);
	goto retry;
}

/*
 * This is the main function used to allocate a new block and its reservation
 * window.
 *
 * Each time when a new block allocation is need, first try to allocate from
 * its own reservation.  If it does not have a reservation window, instead of
 * looking for a free bit on bitmap first, then look up the reservation list to
 * see if it is inside somebody else's reservation window, we try to allocate a
 * reservation window for it starting from the goal first. Then do the block
 * allocation within the reservation window.
 *
 * This will avoid keeping on searching the reservation list again and
 * again when someboday is looking for a free block (without
 * reservation), and there are lots of free blocks, but they are all
 * being reserved.
 *
 * We use a sorted double linked list for the per-filesystem reservation list.
 * The insert, remove and find a free space(non-reserved) operations for the
 * sorted double linked list should be fast.
 *
 */
static int
ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
			unsigned int group, struct buffer_head *bitmap_bh,
			int goal, struct ext3_reserve_window_node * my_rsv,
			int *errp)
{
	unsigned long group_first_block;
	int ret = 0;
	int fatal;

	*errp = 0;

	/*
	 * Make sure we use undo access for the bitmap, because it is critical
	 * that we do the frozen_data COW on bitmap buffers in all cases even
	 * if the buffer is in BJ_Forget state in the committing transaction.
	 */
	BUFFER_TRACE(bitmap_bh, "get undo access for new block");
	fatal = ext3_journal_get_undo_access(handle, bitmap_bh);
	if (fatal) {
		*errp = fatal;
		return -1;
	}

	/*
	 * we don't deal with reservation when
	 * filesystem is mounted without reservation
	 * or the file is not a regular file
	 * or last attempt to allocate a block with reservation turned on failed
	 */
	if (my_rsv == NULL ) {
		ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, goal, NULL);
		goto out;
	}
	/*
	 * goal is a group relative block number (if there is a goal)
	 * 0 < goal < EXT3_BLOCKS_PER_GROUP(sb)
	 * first block is a filesystem wide block number
	 * first block is the block number of the first block in this group
	 */
	group_first_block = le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block) +
			group * EXT3_BLOCKS_PER_GROUP(sb);

	/*
	 * Basically we will allocate a new block from inode's reservation
	 * window.
	 *
	 * We need to allocate a new reservation window, if:
	 * a) inode does not have a reservation window; or
	 * b) last attempt to allocate a block from existing reservation
	 *    failed; or
	 * c) we come here with a goal and with a reservation window
	 *
	 * We do not need to allocate a new reservation window if we come here
	 * at the beginning with a goal and the goal is inside the window, or
	 * we don't have a goal but already have a reservation window.
	 * then we could go to allocate from the reservation window directly.
	 */
	while (1) {
		if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
			!goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb)) {
			ret = alloc_new_reservation(my_rsv, goal, sb,
							group, bitmap_bh);
			if (ret < 0)
				break;			/* failed */

			if (!goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb))
				goal = -1;
		}
		if ((my_rsv->rsv_start >= group_first_block + EXT3_BLOCKS_PER_GROUP(sb))
		    || (my_rsv->rsv_end < group_first_block))
			BUG();
		ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh, goal,
					   &my_rsv->rsv_window);
		if (ret >= 0) {
			my_rsv->rsv_alloc_hit++;
			break;				/* succeed */
		}
	}
out:
	if (ret >= 0) {
		BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
					"bitmap block");
		fatal = ext3_journal_dirty_metadata(handle, bitmap_bh);
		if (fatal) {
			*errp = fatal;
			return -1;
		}
		return ret;
	}

	BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
	ext3_journal_release_buffer(handle, bitmap_bh);
	return ret;
}

static int ext3_has_free_blocks(struct ext3_sb_info *sbi)
{
	int free_blocks, root_blocks;

	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
		sbi->s_resuid != current->fsuid &&
		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
		return 0;
	}
	return 1;
}

/*
 * ext3_should_retry_alloc() is called when ENOSPC is returned, and if
 * it is profitable to retry the operation, this function will wait
 * for the current or commiting transaction to complete, and then
 * return TRUE.
 */
int ext3_should_retry_alloc(struct super_block *sb, int *retries)
{
	if (!ext3_has_free_blocks(EXT3_SB(sb)) || (*retries)++ > 3)
		return 0;

	jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);

	return journal_force_commit_nested(EXT3_SB(sb)->s_journal);
}

/*
 * ext3_new_block uses a goal block to assist allocation.  If the goal is
 * free, or there is a free block within 32 blocks of the goal, that block
 * is allocated.  Otherwise a forward search is made for a free block; within 
 * each block group the search first looks for an entire free byte in the block
 * bitmap, and then for any free bit if that fails.
 * This function also updates quota and i_blocks field.
 */
int ext3_new_block(handle_t *handle, struct inode *inode,
			unsigned long goal, int *errp)
{
	struct buffer_head *bitmap_bh = NULL;
	struct buffer_head *gdp_bh;
	int group_no;
	int goal_group;
	int ret_block;
	int bgi;			/* blockgroup iteration index */
	int target_block;
	int fatal = 0, err;
	int performed_allocation = 0;
	int free_blocks;
	struct super_block *sb;
	struct ext3_group_desc *gdp;
	struct ext3_super_block *es;
	struct ext3_sb_info *sbi;
	struct ext3_reserve_window_node *my_rsv = NULL;
	struct ext3_block_alloc_info *block_i;
	unsigned short windowsz = 0;
#ifdef EXT3FS_DEBUG
	static int goal_hits, goal_attempts;
#endif
	unsigned long ngroups;

	*errp = -ENOSPC;
	sb = inode->i_sb;
	if (!sb) {
		printk("ext3_new_block: nonexistent device");
		return 0;
	}

	/*
	 * Check quota for allocation of this block.
	 */
	if (DQUOT_ALLOC_BLOCK(inode, 1)) {
		*errp = -EDQUOT;
		return 0;
	}

	sbi = EXT3_SB(sb);
	es = EXT3_SB(sb)->s_es;
	ext3_debug("goal=%lu.\n", goal);
	/*
	 * Allocate a block from reservation only when
	 * filesystem is mounted with reservation(default,-o reservation), and
	 * it's a regular file, and
	 * the desired window size is greater than 0 (One could use ioctl
	 * command EXT3_IOC_SETRSVSZ to set the window size to 0 to turn off
	 * reservation on that particular file)
	 */
	block_i = EXT3_I(inode)->i_block_alloc_info;
	if (block_i && ((windowsz = block_i->rsv_window_node.rsv_goal_size) > 0))
		my_rsv = &block_i->rsv_window_node;

	if (!ext3_has_free_blocks(sbi)) {
		*errp = -ENOSPC;
		goto out;
	}

	/*
	 * First, test whether the goal block is free.
	 */
	if (goal < le32_to_cpu(es->s_first_data_block) ||
	    goal >= le32_to_cpu(es->s_blocks_count))
		goal = le32_to_cpu(es->s_first_data_block);
	group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
			EXT3_BLOCKS_PER_GROUP(sb);
	gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
	if (!gdp)
		goto io_error;

	goal_group = group_no;
retry:
	free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
	/*
	 * if there is not enough free blocks to make a new resevation
	 * turn off reservation for this allocation
	 */
	if (my_rsv && (free_blocks < windowsz)
		&& (rsv_is_empty(&my_rsv->rsv_window)))
		my_rsv = NULL;

	if (free_blocks > 0) {
		ret_block = ((goal - le32_to_cpu(es->s_first_data_block)) %
				EXT3_BLOCKS_PER_GROUP(sb));
		bitmap_bh = read_block_bitmap(sb, group_no);
		if (!bitmap_bh)
			goto io_error;
		ret_block = ext3_try_to_allocate_with_rsv(sb, handle, group_no,
					bitmap_bh, ret_block, my_rsv, &fatal);
		if (fatal)
			goto out;
		if (ret_block >= 0)
			goto allocated;
	}

	ngroups = EXT3_SB(sb)->s_groups_count;
	smp_rmb();

	/*
	 * Now search the rest of the groups.  We assume that 
	 * i and gdp correctly point to the last group visited.
	 */
	for (bgi = 0; bgi < ngroups; bgi++) {
		group_no++;
		if (group_no >= ngroups)
			group_no = 0;
		gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
		if (!gdp) {
			*errp = -EIO;
			goto out;
		}
		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
		/*
		 * skip this group if the number of
		 * free blocks is less than half of the reservation
		 * window size.
		 */
		if (free_blocks <= (windowsz/2))
			continue;

		brelse(bitmap_bh);
		bitmap_bh = read_block_bitmap(sb, group_no);
		if (!bitmap_bh)
			goto io_error;
		ret_block = ext3_try_to_allocate_with_rsv(sb, handle, group_no,
					bitmap_bh, -1, my_rsv, &fatal);
		if (fatal)
			goto out;
		if (ret_block >= 0) 
			goto allocated;
	}
	/*
	 * We may end up a bogus ealier ENOSPC error due to
	 * filesystem is "full" of reservations, but
	 * there maybe indeed free blocks avaliable on disk
	 * In this case, we just forget about the reservations
	 * just do block allocation as without reservations.
	 */
	if (my_rsv) {
		my_rsv = NULL;
		group_no = goal_group;
		goto retry;
	}
	/* No space left on the device */
	*errp = -ENOSPC;
	goto out;

allocated:

	ext3_debug("using block group %d(%d)\n",
			group_no, gdp->bg_free_blocks_count);

	BUFFER_TRACE(gdp_bh, "get_write_access");
	fatal = ext3_journal_get_write_access(handle, gdp_bh);
	if (fatal)
		goto out;

	target_block = ret_block + group_no * EXT3_BLOCKS_PER_GROUP(sb)
				+ le32_to_cpu(es->s_first_data_block);

	if (target_block == le32_to_cpu(gdp->bg_block_bitmap) ||
	    target_block == le32_to_cpu(gdp->bg_inode_bitmap) ||
	    in_range(target_block, le32_to_cpu(gdp->bg_inode_table),
		      EXT3_SB(sb)->s_itb_per_group))
		ext3_error(sb, "ext3_new_block",
			    "Allocating block in system zone - "
			    "block = %u", target_block);

	performed_allocation = 1;

#ifdef CONFIG_JBD_DEBUG
	{
		struct buffer_head *debug_bh;

		/* Record bitmap buffer state in the newly allocated block */
		debug_bh = sb_find_get_block(sb, target_block);
		if (debug_bh) {
			BUFFER_TRACE(debug_bh, "state when allocated");
			BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
			brelse(debug_bh);
		}
	}
	jbd_lock_bh_state(bitmap_bh);
	spin_lock(sb_bgl_lock(sbi, group_no));
	if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
		if (ext3_test_bit(ret_block,
				bh2jh(bitmap_bh)->b_committed_data)) {
			printk("%s: block was unexpectedly set in "
				"b_committed_data\n", __FUNCTION__);
		}
	}
	ext3_debug("found bit %d\n", ret_block);
	spin_unlock(sb_bgl_lock(sbi, group_no));
	jbd_unlock_bh_state(bitmap_bh);
#endif

	/* ret_block was blockgroup-relative.  Now it becomes fs-relative */
	ret_block = target_block;

	if (ret_block >= le32_to_cpu(es->s_blocks_count)) {
		ext3_error(sb, "ext3_new_block",
			    "block(%d) >= blocks count(%d) - "
			    "block_group = %d, es == %p ", ret_block,
			le32_to_cpu(es->s_blocks_count), group_no, es);
		goto out;
	}

	/*
	 * It is up to the caller to add the new buffer to a journal
	 * list of some description.  We don't know in advance whether
	 * the caller wants to use it as metadata or data.
	 */
	ext3_debug("allocating block %d. Goal hits %d of %d.\n",
			ret_block, goal_hits, goal_attempts);

	spin_lock(sb_bgl_lock(sbi, group_no));
	gdp->bg_free_blocks_count =
			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - 1);
	spin_unlock(sb_bgl_lock(sbi, group_no));
	percpu_counter_mod(&sbi->s_freeblocks_counter, -1);

	BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
	err = ext3_journal_dirty_metadata(handle, gdp_bh);
	if (!fatal)
		fatal = err;

	sb->s_dirt = 1;
	if (fatal)
		goto out;

	*errp = 0;
	brelse(bitmap_bh);
	return ret_block;

io_error:
	*errp = -EIO;
out:
	if (fatal) {
		*errp = fatal;
		ext3_std_error(sb, fatal);
	}
	/*
	 * Undo the block allocation
	 */
	if (!performed_allocation)
		DQUOT_FREE_BLOCK(inode, 1);
	brelse(bitmap_bh);
	return 0;
}

unsigned long ext3_count_free_blocks(struct super_block *sb)
{
	unsigned long desc_count;
	struct ext3_group_desc *gdp;
	int i;
	unsigned long ngroups = EXT3_SB(sb)->s_groups_count;
#ifdef EXT3FS_DEBUG
	struct ext3_super_block *es;
	unsigned long bitmap_count, x;
	struct buffer_head *bitmap_bh = NULL;

	lock_super(sb);
	es = EXT3_SB(sb)->s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;

	for (i = 0; i < ngroups; i++) {
		gdp = ext3_get_group_desc(sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
		brelse(bitmap_bh);
		bitmap_bh = read_block_bitmap(sb, i);
		if (bitmap_bh == NULL)
			continue;

		x = ext3_count_free(bitmap_bh, sb->s_blocksize);
		printk("group %d: stored = %d, counted = %lu\n",
			i, le16_to_cpu(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	brelse(bitmap_bh);
	printk("ext3_count_free_blocks: stored = %u, computed = %lu, %lu\n",
	       le32_to_cpu(es->s_free_blocks_count), desc_count, bitmap_count);
	unlock_super(sb);
	return bitmap_count;
#else
	desc_count = 0;
	smp_rmb();
	for (i = 0; i < ngroups; i++) {
		gdp = ext3_get_group_desc(sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
	}

	return desc_count;
#endif
}

static inline int
block_in_use(unsigned long block, struct super_block *sb, unsigned char *map)
{
	return ext3_test_bit ((block -
		le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block)) %
			 EXT3_BLOCKS_PER_GROUP(sb), map);
}

static inline int test_root(int a, int b)
{
	int num = b;

	while (a > num)
		num *= b;
	return num == a;
}

static int ext3_group_sparse(int group)
{
	if (group <= 1)
		return 1;
	if (!(group & 1))
		return 0;
	return (test_root(group, 7) || test_root(group, 5) ||
		test_root(group, 3));
}

/**
 *	ext3_bg_has_super - number of blocks used by the superblock in group
 *	@sb: superblock for filesystem
 *	@group: group number to check
 *
 *	Return the number of blocks used by the superblock (primary or backup)
 *	in this group.  Currently this will be only 0 or 1.
 */
int ext3_bg_has_super(struct super_block *sb, int group)
{
	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
	    !ext3_group_sparse(group))
		return 0;
	return 1;
}

/**
 *	ext3_bg_num_gdb - number of blocks used by the group table in group
 *	@sb: superblock for filesystem
 *	@group: group number to check
 *
 *	Return the number of blocks used by the group descriptor table
 *	(primary or backup) in this group.  In the future there may be a
 *	different number of descriptor blocks in each group.
 */
unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
{
	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
	    !ext3_group_sparse(group))
		return 0;
	return EXT3_SB(sb)->s_gdb_count;
}

#ifdef CONFIG_EXT3_CHECK
/* Called at mount-time, super-block is locked */
void ext3_check_blocks_bitmap (struct super_block * sb)
{
	struct ext3_super_block *es;
	unsigned long desc_count, bitmap_count, x, j;
	unsigned long desc_blocks;
	struct buffer_head *bitmap_bh = NULL;
	struct ext3_group_desc *gdp;
	int i;

	es = EXT3_SB(sb)->s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < EXT3_SB(sb)->s_groups_count; i++) {
		gdp = ext3_get_group_desc (sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
		brelse(bitmap_bh);
		bitmap_bh = read_block_bitmap(sb, i);
		if (bitmap_bh == NULL)
			continue;

		if (ext3_bg_has_super(sb, i) &&
				!ext3_test_bit(0, bitmap_bh->b_data))
			ext3_error(sb, __FUNCTION__,
				   "Superblock in group %d is marked free", i);

		desc_blocks = ext3_bg_num_gdb(sb, i);
		for (j = 0; j < desc_blocks; j++)
			if (!ext3_test_bit(j + 1, bitmap_bh->b_data))
				ext3_error(sb, __FUNCTION__,
					   "Descriptor block #%ld in group "
					   "%d is marked free", j, i);

		if (!block_in_use (le32_to_cpu(gdp->bg_block_bitmap),
						sb, bitmap_bh->b_data))
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Block bitmap for group %d is marked free",
				    i);

		if (!block_in_use (le32_to_cpu(gdp->bg_inode_bitmap),
						sb, bitmap_bh->b_data))
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Inode bitmap for group %d is marked free",
				    i);

		for (j = 0; j < EXT3_SB(sb)->s_itb_per_group; j++)
			if (!block_in_use (le32_to_cpu(gdp->bg_inode_table) + j,
							sb, bitmap_bh->b_data))
				ext3_error (sb, "ext3_check_blocks_bitmap",
					    "Block #%d of the inode table in "
					    "group %d is marked free", j, i);

		x = ext3_count_free(bitmap_bh, sb->s_blocksize);
		if (le16_to_cpu(gdp->bg_free_blocks_count) != x)
			ext3_error (sb, "ext3_check_blocks_bitmap",
				    "Wrong free blocks count for group %d, "
				    "stored = %d, counted = %lu", i,
				    le16_to_cpu(gdp->bg_free_blocks_count), x);
		bitmap_count += x;
	}
	brelse(bitmap_bh);
	if (le32_to_cpu(es->s_free_blocks_count) != bitmap_count)
		ext3_error (sb, "ext3_check_blocks_bitmap",
			"Wrong free blocks count in super block, "
			"stored = %lu, counted = %lu",
			(unsigned long)le32_to_cpu(es->s_free_blocks_count),
			bitmap_count);
}
#endif