summaryrefslogtreecommitdiffstats
path: root/fs/xfs/linux-2.6/xfs_buf.c
blob: e2bea6a661f07462f92d82d71a54cfd459a0ce45 (plain)
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
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
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
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/bio.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/workqueue.h>
#include <linux/percpu.h>
#include <linux/blkdev.h>
#include <linux/hash.h>
#include <linux/kthread.h>
#include <linux/migrate.h>
#include <linux/backing-dev.h>
#include <linux/freezer.h>

static kmem_zone_t *xfs_buf_zone;
static kmem_shaker_t xfs_buf_shake;
STATIC int xfsbufd(void *);
STATIC int xfsbufd_wakeup(int, gfp_t);
STATIC void xfs_buf_delwri_queue(xfs_buf_t *, int);

static struct workqueue_struct *xfslogd_workqueue;
struct workqueue_struct *xfsdatad_workqueue;

#ifdef XFS_BUF_TRACE
void
xfs_buf_trace(
	xfs_buf_t	*bp,
	char		*id,
	void		*data,
	void		*ra)
{
	ktrace_enter(xfs_buf_trace_buf,
		bp, id,
		(void *)(unsigned long)bp->b_flags,
		(void *)(unsigned long)bp->b_hold.counter,
		(void *)(unsigned long)bp->b_sema.count.counter,
		(void *)current,
		data, ra,
		(void *)(unsigned long)((bp->b_file_offset>>32) & 0xffffffff),
		(void *)(unsigned long)(bp->b_file_offset & 0xffffffff),
		(void *)(unsigned long)bp->b_buffer_length,
		NULL, NULL, NULL, NULL, NULL);
}
ktrace_t *xfs_buf_trace_buf;
#define XFS_BUF_TRACE_SIZE	4096
#define XB_TRACE(bp, id, data)	\
	xfs_buf_trace(bp, id, (void *)data, (void *)__builtin_return_address(0))
#else
#define XB_TRACE(bp, id, data)	do { } while (0)
#endif

#ifdef XFS_BUF_LOCK_TRACKING
# define XB_SET_OWNER(bp)	((bp)->b_last_holder = current->pid)
# define XB_CLEAR_OWNER(bp)	((bp)->b_last_holder = -1)
# define XB_GET_OWNER(bp)	((bp)->b_last_holder)
#else
# define XB_SET_OWNER(bp)	do { } while (0)
# define XB_CLEAR_OWNER(bp)	do { } while (0)
# define XB_GET_OWNER(bp)	do { } while (0)
#endif

#define xb_to_gfp(flags) \
	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : \
	  ((flags) & XBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)

#define xb_to_km(flags) \
	 (((flags) & XBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)

#define xfs_buf_allocate(flags) \
	kmem_zone_alloc(xfs_buf_zone, xb_to_km(flags))
#define xfs_buf_deallocate(bp) \
	kmem_zone_free(xfs_buf_zone, (bp));

/*
 *	Page Region interfaces.
 *
 *	For pages in filesystems where the blocksize is smaller than the
 *	pagesize, we use the page->private field (long) to hold a bitmap
 * 	of uptodate regions within the page.
 *
 *	Each such region is "bytes per page / bits per long" bytes long.
 *
 *	NBPPR == number-of-bytes-per-page-region
 *	BTOPR == bytes-to-page-region (rounded up)
 *	BTOPRT == bytes-to-page-region-truncated (rounded down)
 */
#if (BITS_PER_LONG == 32)
#define PRSHIFT		(PAGE_CACHE_SHIFT - 5)	/* (32 == 1<<5) */
#elif (BITS_PER_LONG == 64)
#define PRSHIFT		(PAGE_CACHE_SHIFT - 6)	/* (64 == 1<<6) */
#else
#error BITS_PER_LONG must be 32 or 64
#endif
#define NBPPR		(PAGE_CACHE_SIZE/BITS_PER_LONG)
#define BTOPR(b)	(((unsigned int)(b) + (NBPPR - 1)) >> PRSHIFT)
#define BTOPRT(b)	(((unsigned int)(b) >> PRSHIFT))

STATIC unsigned long
page_region_mask(
	size_t		offset,
	size_t		length)
{
	unsigned long	mask;
	int		first, final;

	first = BTOPR(offset);
	final = BTOPRT(offset + length - 1);
	first = min(first, final);

	mask = ~0UL;
	mask <<= BITS_PER_LONG - (final - first);
	mask >>= BITS_PER_LONG - (final);

	ASSERT(offset + length <= PAGE_CACHE_SIZE);
	ASSERT((final - first) < BITS_PER_LONG && (final - first) >= 0);

	return mask;
}

STATIC_INLINE void
set_page_region(
	struct page	*page,
	size_t		offset,
	size_t		length)
{
	set_page_private(page,
		page_private(page) | page_region_mask(offset, length));
	if (page_private(page) == ~0UL)
		SetPageUptodate(page);
}

STATIC_INLINE int
test_page_region(
	struct page	*page,
	size_t		offset,
	size_t		length)
{
	unsigned long	mask = page_region_mask(offset, length);

	return (mask && (page_private(page) & mask) == mask);
}

/*
 *	Mapping of multi-page buffers into contiguous virtual space
 */

typedef struct a_list {
	void		*vm_addr;
	struct a_list	*next;
} a_list_t;

static a_list_t		*as_free_head;
static int		as_list_len;
static DEFINE_SPINLOCK(as_lock);

/*
 *	Try to batch vunmaps because they are costly.
 */
STATIC void
free_address(
	void		*addr)
{
	a_list_t	*aentry;

	aentry = kmalloc(sizeof(a_list_t), GFP_NOWAIT);
	if (likely(aentry)) {
		spin_lock(&as_lock);
		aentry->next = as_free_head;
		aentry->vm_addr = addr;
		as_free_head = aentry;
		as_list_len++;
		spin_unlock(&as_lock);
	} else {
		vunmap(addr);
	}
}

STATIC void
purge_addresses(void)
{
	a_list_t	*aentry, *old;

	if (as_free_head == NULL)
		return;

	spin_lock(&as_lock);
	aentry = as_free_head;
	as_free_head = NULL;
	as_list_len = 0;
	spin_unlock(&as_lock);

	while ((old = aentry) != NULL) {
		vunmap(aentry->vm_addr);
		aentry = aentry->next;
		kfree(old);
	}
}

/*
 *	Internal xfs_buf_t object manipulation
 */

STATIC void
_xfs_buf_initialize(
	xfs_buf_t		*bp,
	xfs_buftarg_t		*target,
	xfs_off_t		range_base,
	size_t			range_length,
	xfs_buf_flags_t		flags)
{
	/*
	 * We don't want certain flags to appear in b_flags.
	 */
	flags &= ~(XBF_LOCK|XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);

	memset(bp, 0, sizeof(xfs_buf_t));
	atomic_set(&bp->b_hold, 1);
	init_MUTEX_LOCKED(&bp->b_iodonesema);
	INIT_LIST_HEAD(&bp->b_list);
	INIT_LIST_HEAD(&bp->b_hash_list);
	init_MUTEX_LOCKED(&bp->b_sema); /* held, no waiters */
	XB_SET_OWNER(bp);
	bp->b_target = target;
	bp->b_file_offset = range_base;
	/*
	 * Set buffer_length and count_desired to the same value initially.
	 * I/O routines should use count_desired, which will be the same in
	 * most cases but may be reset (e.g. XFS recovery).
	 */
	bp->b_buffer_length = bp->b_count_desired = range_length;
	bp->b_flags = flags;
	bp->b_bn = XFS_BUF_DADDR_NULL;
	atomic_set(&bp->b_pin_count, 0);
	init_waitqueue_head(&bp->b_waiters);

	XFS_STATS_INC(xb_create);
	XB_TRACE(bp, "initialize", target);
}

/*
 *	Allocate a page array capable of holding a specified number
 *	of pages, and point the page buf at it.
 */
STATIC int
_xfs_buf_get_pages(
	xfs_buf_t		*bp,
	int			page_count,
	xfs_buf_flags_t		flags)
{
	/* Make sure that we have a page list */
	if (bp->b_pages == NULL) {
		bp->b_offset = xfs_buf_poff(bp->b_file_offset);
		bp->b_page_count = page_count;
		if (page_count <= XB_PAGES) {
			bp->b_pages = bp->b_page_array;
		} else {
			bp->b_pages = kmem_alloc(sizeof(struct page *) *
					page_count, xb_to_km(flags));
			if (bp->b_pages == NULL)
				return -ENOMEM;
		}
		memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
	}
	return 0;
}

/*
 *	Frees b_pages if it was allocated.
 */
STATIC void
_xfs_buf_free_pages(
	xfs_buf_t	*bp)
{
	if (bp->b_pages != bp->b_page_array) {
		kmem_free(bp->b_pages,
			  bp->b_page_count * sizeof(struct page *));
	}
}

/*
 *	Releases the specified buffer.
 *
 * 	The modification state of any associated pages is left unchanged.
 * 	The buffer most not be on any hash - use xfs_buf_rele instead for
 * 	hashed and refcounted buffers
 */
void
xfs_buf_free(
	xfs_buf_t		*bp)
{
	XB_TRACE(bp, "free", 0);

	ASSERT(list_empty(&bp->b_hash_list));

	if (bp->b_flags & _XBF_PAGE_CACHE) {
		uint		i;

		if ((bp->b_flags & XBF_MAPPED) && (bp->b_page_count > 1))
			free_address(bp->b_addr - bp->b_offset);

		for (i = 0; i < bp->b_page_count; i++) {
			struct page	*page = bp->b_pages[i];

			ASSERT(!PagePrivate(page));
			page_cache_release(page);
		}
		_xfs_buf_free_pages(bp);
	} else if (bp->b_flags & _XBF_KMEM_ALLOC) {
		 /*
		  * XXX(hch): bp->b_count_desired might be incorrect (see
		  * xfs_buf_associate_memory for details), but fortunately
		  * the Linux version of kmem_free ignores the len argument..
		  */
		kmem_free(bp->b_addr, bp->b_count_desired);
		_xfs_buf_free_pages(bp);
	}

	xfs_buf_deallocate(bp);
}

/*
 *	Finds all pages for buffer in question and builds it's page list.
 */
STATIC int
_xfs_buf_lookup_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	struct address_space	*mapping = bp->b_target->bt_mapping;
	size_t			blocksize = bp->b_target->bt_bsize;
	size_t			size = bp->b_count_desired;
	size_t			nbytes, offset;
	gfp_t			gfp_mask = xb_to_gfp(flags);
	unsigned short		page_count, i;
	pgoff_t			first;
	xfs_off_t		end;
	int			error;

	end = bp->b_file_offset + bp->b_buffer_length;
	page_count = xfs_buf_btoc(end) - xfs_buf_btoct(bp->b_file_offset);

	error = _xfs_buf_get_pages(bp, page_count, flags);
	if (unlikely(error))
		return error;
	bp->b_flags |= _XBF_PAGE_CACHE;

	offset = bp->b_offset;
	first = bp->b_file_offset >> PAGE_CACHE_SHIFT;

	for (i = 0; i < bp->b_page_count; i++) {
		struct page	*page;
		uint		retries = 0;

	      retry:
		page = find_or_create_page(mapping, first + i, gfp_mask);
		if (unlikely(page == NULL)) {
			if (flags & XBF_READ_AHEAD) {
				bp->b_page_count = i;
				for (i = 0; i < bp->b_page_count; i++)
					unlock_page(bp->b_pages[i]);
				return -ENOMEM;
			}

			/*
			 * This could deadlock.
			 *
			 * But until all the XFS lowlevel code is revamped to
			 * handle buffer allocation failures we can't do much.
			 */
			if (!(++retries % 100))
				printk(KERN_ERR
					"XFS: possible memory allocation "
					"deadlock in %s (mode:0x%x)\n",
					__FUNCTION__, gfp_mask);

			XFS_STATS_INC(xb_page_retries);
			xfsbufd_wakeup(0, gfp_mask);
			congestion_wait(WRITE, HZ/50);
			goto retry;
		}

		XFS_STATS_INC(xb_page_found);

		nbytes = min_t(size_t, size, PAGE_CACHE_SIZE - offset);
		size -= nbytes;

		ASSERT(!PagePrivate(page));
		if (!PageUptodate(page)) {
			page_count--;
			if (blocksize >= PAGE_CACHE_SIZE) {
				if (flags & XBF_READ)
					bp->b_locked = 1;
			} else if (!PagePrivate(page)) {
				if (test_page_region(page, offset, nbytes))
					page_count++;
			}
		}

		bp->b_pages[i] = page;
		offset = 0;
	}

	if (!bp->b_locked) {
		for (i = 0; i < bp->b_page_count; i++)
			unlock_page(bp->b_pages[i]);
	}

	if (page_count == bp->b_page_count)
		bp->b_flags |= XBF_DONE;

	XB_TRACE(bp, "lookup_pages", (long)page_count);
	return error;
}

/*
 *	Map buffer into kernel address-space if nessecary.
 */
STATIC int
_xfs_buf_map_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	/* A single page buffer is always mappable */
	if (bp->b_page_count == 1) {
		bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
		bp->b_flags |= XBF_MAPPED;
	} else if (flags & XBF_MAPPED) {
		if (as_list_len > 64)
			purge_addresses();
		bp->b_addr = vmap(bp->b_pages, bp->b_page_count,
					VM_MAP, PAGE_KERNEL);
		if (unlikely(bp->b_addr == NULL))
			return -ENOMEM;
		bp->b_addr += bp->b_offset;
		bp->b_flags |= XBF_MAPPED;
	}

	return 0;
}

/*
 *	Finding and Reading Buffers
 */

/*
 *	Look up, and creates if absent, a lockable buffer for
 *	a given range of an inode.  The buffer is returned
 *	locked.	 If other overlapping buffers exist, they are
 *	released before the new buffer is created and locked,
 *	which may imply that this call will block until those buffers
 *	are unlocked.  No I/O is implied by this call.
 */
xfs_buf_t *
_xfs_buf_find(
	xfs_buftarg_t		*btp,	/* block device target		*/
	xfs_off_t		ioff,	/* starting offset of range	*/
	size_t			isize,	/* length of range		*/
	xfs_buf_flags_t		flags,
	xfs_buf_t		*new_bp)
{
	xfs_off_t		range_base;
	size_t			range_length;
	xfs_bufhash_t		*hash;
	xfs_buf_t		*bp, *n;

	range_base = (ioff << BBSHIFT);
	range_length = (isize << BBSHIFT);

	/* Check for IOs smaller than the sector size / not sector aligned */
	ASSERT(!(range_length < (1 << btp->bt_sshift)));
	ASSERT(!(range_base & (xfs_off_t)btp->bt_smask));

	hash = &btp->bt_hash[hash_long((unsigned long)ioff, btp->bt_hashshift)];

	spin_lock(&hash->bh_lock);

	list_for_each_entry_safe(bp, n, &hash->bh_list, b_hash_list) {
		ASSERT(btp == bp->b_target);
		if (bp->b_file_offset == range_base &&
		    bp->b_buffer_length == range_length) {
			/*
			 * If we look at something, bring it to the
			 * front of the list for next time.
			 */
			atomic_inc(&bp->b_hold);
			list_move(&bp->b_hash_list, &hash->bh_list);
			goto found;
		}
	}

	/* No match found */
	if (new_bp) {
		_xfs_buf_initialize(new_bp, btp, range_base,
				range_length, flags);
		new_bp->b_hash = hash;
		list_add(&new_bp->b_hash_list, &hash->bh_list);
	} else {
		XFS_STATS_INC(xb_miss_locked);
	}

	spin_unlock(&hash->bh_lock);
	return new_bp;

found:
	spin_unlock(&hash->bh_lock);

	/* Attempt to get the semaphore without sleeping,
	 * if this does not work then we need to drop the
	 * spinlock and do a hard attempt on the semaphore.
	 */
	if (down_trylock(&bp->b_sema)) {
		if (!(flags & XBF_TRYLOCK)) {
			/* wait for buffer ownership */
			XB_TRACE(bp, "get_lock", 0);
			xfs_buf_lock(bp);
			XFS_STATS_INC(xb_get_locked_waited);
		} else {
			/* We asked for a trylock and failed, no need
			 * to look at file offset and length here, we
			 * know that this buffer at least overlaps our
			 * buffer and is locked, therefore our buffer
			 * either does not exist, or is this buffer.
			 */
			xfs_buf_rele(bp);
			XFS_STATS_INC(xb_busy_locked);
			return NULL;
		}
	} else {
		/* trylock worked */
		XB_SET_OWNER(bp);
	}

	if (bp->b_flags & XBF_STALE) {
		ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
		bp->b_flags &= XBF_MAPPED;
	}
	XB_TRACE(bp, "got_lock", 0);
	XFS_STATS_INC(xb_get_locked);
	return bp;
}

/*
 *	Assembles a buffer covering the specified range.
 *	Storage in memory for all portions of the buffer will be allocated,
 *	although backing storage may not be.
 */
xfs_buf_t *
xfs_buf_get_flags(
	xfs_buftarg_t		*target,/* target for buffer		*/
	xfs_off_t		ioff,	/* starting offset of range	*/
	size_t			isize,	/* length of range		*/
	xfs_buf_flags_t		flags)
{
	xfs_buf_t		*bp, *new_bp;
	int			error = 0, i;

	new_bp = xfs_buf_allocate(flags);
	if (unlikely(!new_bp))
		return NULL;

	bp = _xfs_buf_find(target, ioff, isize, flags, new_bp);
	if (bp == new_bp) {
		error = _xfs_buf_lookup_pages(bp, flags);
		if (error)
			goto no_buffer;
	} else {
		xfs_buf_deallocate(new_bp);
		if (unlikely(bp == NULL))
			return NULL;
	}

	for (i = 0; i < bp->b_page_count; i++)
		mark_page_accessed(bp->b_pages[i]);

	if (!(bp->b_flags & XBF_MAPPED)) {
		error = _xfs_buf_map_pages(bp, flags);
		if (unlikely(error)) {
			printk(KERN_WARNING "%s: failed to map pages\n",
					__FUNCTION__);
			goto no_buffer;
		}
	}

	XFS_STATS_INC(xb_get);

	/*
	 * Always fill in the block number now, the mapped cases can do
	 * their own overlay of this later.
	 */
	bp->b_bn = ioff;
	bp->b_count_desired = bp->b_buffer_length;

	XB_TRACE(bp, "get", (unsigned long)flags);
	return bp;

 no_buffer:
	if (flags & (XBF_LOCK | XBF_TRYLOCK))
		xfs_buf_unlock(bp);
	xfs_buf_rele(bp);
	return NULL;
}

xfs_buf_t *
xfs_buf_read_flags(
	xfs_buftarg_t		*target,
	xfs_off_t		ioff,
	size_t			isize,
	xfs_buf_flags_t		flags)
{
	xfs_buf_t		*bp;

	flags |= XBF_READ;

	bp = xfs_buf_get_flags(target, ioff, isize, flags);
	if (bp) {
		if (!XFS_BUF_ISDONE(bp)) {
			XB_TRACE(bp, "read", (unsigned long)flags);
			XFS_STATS_INC(xb_get_read);
			xfs_buf_iostart(bp, flags);
		} else if (flags & XBF_ASYNC) {
			XB_TRACE(bp, "read_async", (unsigned long)flags);
			/*
			 * Read ahead call which is already satisfied,
			 * drop the buffer
			 */
			goto no_buffer;
		} else {
			XB_TRACE(bp, "read_done", (unsigned long)flags);
			/* We do not want read in the flags */
			bp->b_flags &= ~XBF_READ;
		}
	}

	return bp;

 no_buffer:
	if (flags & (XBF_LOCK | XBF_TRYLOCK))
		xfs_buf_unlock(bp);
	xfs_buf_rele(bp);
	return NULL;
}

/*
 *	If we are not low on memory then do the readahead in a deadlock
 *	safe manner.
 */
void
xfs_buf_readahead(
	xfs_buftarg_t		*target,
	xfs_off_t		ioff,
	size_t			isize,
	xfs_buf_flags_t		flags)
{
	struct backing_dev_info *bdi;

	bdi = target->bt_mapping->backing_dev_info;
	if (bdi_read_congested(bdi))
		return;

	flags |= (XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD);
	xfs_buf_read_flags(target, ioff, isize, flags);
}

xfs_buf_t *
xfs_buf_get_empty(
	size_t			len,
	xfs_buftarg_t		*target)
{
	xfs_buf_t		*bp;

	bp = xfs_buf_allocate(0);
	if (bp)
		_xfs_buf_initialize(bp, target, 0, len, 0);
	return bp;
}

static inline struct page *
mem_to_page(
	void			*addr)
{
	if (((unsigned long)addr < VMALLOC_START) ||
	    ((unsigned long)addr >= VMALLOC_END)) {
		return virt_to_page(addr);
	} else {
		return vmalloc_to_page(addr);
	}
}

int
xfs_buf_associate_memory(
	xfs_buf_t		*bp,
	void			*mem,
	size_t			len)
{
	int			rval;
	int			i = 0;
	size_t			ptr;
	size_t			end, end_cur;
	off_t			offset;
	int			page_count;

	page_count = PAGE_CACHE_ALIGN(len) >> PAGE_CACHE_SHIFT;
	offset = (off_t) mem - ((off_t)mem & PAGE_CACHE_MASK);
	if (offset && (len > PAGE_CACHE_SIZE))
		page_count++;

	/* Free any previous set of page pointers */
	if (bp->b_pages)
		_xfs_buf_free_pages(bp);

	bp->b_pages = NULL;
	bp->b_addr = mem;

	rval = _xfs_buf_get_pages(bp, page_count, 0);
	if (rval)
		return rval;

	bp->b_offset = offset;
	ptr = (size_t) mem & PAGE_CACHE_MASK;
	end = PAGE_CACHE_ALIGN((size_t) mem + len);
	end_cur = end;
	/* set up first page */
	bp->b_pages[0] = mem_to_page(mem);

	ptr += PAGE_CACHE_SIZE;
	bp->b_page_count = ++i;
	while (ptr < end) {
		bp->b_pages[i] = mem_to_page((void *)ptr);
		bp->b_page_count = ++i;
		ptr += PAGE_CACHE_SIZE;
	}
	bp->b_locked = 0;

	bp->b_count_desired = bp->b_buffer_length = len;
	bp->b_flags |= XBF_MAPPED;

	return 0;
}

xfs_buf_t *
xfs_buf_get_noaddr(
	size_t			len,
	xfs_buftarg_t		*target)
{
	size_t			malloc_len = len;
	xfs_buf_t		*bp;
	void			*data;
	int			error;

	bp = xfs_buf_allocate(0);
	if (unlikely(bp == NULL))
		goto fail;
	_xfs_buf_initialize(bp, target, 0, len, 0);

 try_again:
	data = kmem_alloc(malloc_len, KM_SLEEP | KM_MAYFAIL | KM_LARGE);
	if (unlikely(data == NULL))
		goto fail_free_buf;

	/* check whether alignment matches.. */
	if ((__psunsigned_t)data !=
	    ((__psunsigned_t)data & ~target->bt_smask)) {
		/* .. else double the size and try again */
		kmem_free(data, malloc_len);
		malloc_len <<= 1;
		goto try_again;
	}

	error = xfs_buf_associate_memory(bp, data, len);
	if (error)
		goto fail_free_mem;
	bp->b_flags |= _XBF_KMEM_ALLOC;

	xfs_buf_unlock(bp);

	XB_TRACE(bp, "no_daddr", data);
	return bp;
 fail_free_mem:
	kmem_free(data, malloc_len);
 fail_free_buf:
	xfs_buf_free(bp);
 fail:
	return NULL;
}

/*
 *	Increment reference count on buffer, to hold the buffer concurrently
 *	with another thread which may release (free) the buffer asynchronously.
 *	Must hold the buffer already to call this function.
 */
void
xfs_buf_hold(
	xfs_buf_t		*bp)
{
	atomic_inc(&bp->b_hold);
	XB_TRACE(bp, "hold", 0);
}

/*
 *	Releases a hold on the specified buffer.  If the
 *	the hold count is 1, calls xfs_buf_free.
 */
void
xfs_buf_rele(
	xfs_buf_t		*bp)
{
	xfs_bufhash_t		*hash = bp->b_hash;

	XB_TRACE(bp, "rele", bp->b_relse);

	if (unlikely(!hash)) {
		ASSERT(!bp->b_relse);
		if (atomic_dec_and_test(&bp->b_hold))
			xfs_buf_free(bp);
		return;
	}

	if (atomic_dec_and_lock(&bp->b_hold, &hash->bh_lock)) {
		if (bp->b_relse) {
			atomic_inc(&bp->b_hold);
			spin_unlock(&hash->bh_lock);
			(*(bp->b_relse)) (bp);
		} else if (bp->b_flags & XBF_FS_MANAGED) {
			spin_unlock(&hash->bh_lock);
		} else {
			ASSERT(!(bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)));
			list_del_init(&bp->b_hash_list);
			spin_unlock(&hash->bh_lock);
			xfs_buf_free(bp);
		}
	} else {
		/*
		 * Catch reference count leaks
		 */
		ASSERT(atomic_read(&bp->b_hold) >= 0);
	}
}


/*
 *	Mutual exclusion on buffers.  Locking model:
 *
 *	Buffers associated with inodes for which buffer locking
 *	is not enabled are not protected by semaphores, and are
 *	assumed to be exclusively owned by the caller.  There is a
 *	spinlock in the buffer, used by the caller when concurrent
 *	access is possible.
 */

/*
 *	Locks a buffer object, if it is not already locked.
 *	Note that this in no way locks the underlying pages, so it is only
 *	useful for synchronizing concurrent use of buffer objects, not for
 *	synchronizing independent access to the underlying pages.
 */
int
xfs_buf_cond_lock(
	xfs_buf_t		*bp)
{
	int			locked;

	locked = down_trylock(&bp->b_sema) == 0;
	if (locked) {
		XB_SET_OWNER(bp);
	}
	XB_TRACE(bp, "cond_lock", (long)locked);
	return locked ? 0 : -EBUSY;
}

#if defined(DEBUG) || defined(XFS_BLI_TRACE)
int
xfs_buf_lock_value(
	xfs_buf_t		*bp)
{
	return atomic_read(&bp->b_sema.count);
}
#endif

/*
 *	Locks a buffer object.
 *	Note that this in no way locks the underlying pages, so it is only
 *	useful for synchronizing concurrent use of buffer objects, not for
 *	synchronizing independent access to the underlying pages.
 */
void
xfs_buf_lock(
	xfs_buf_t		*bp)
{
	XB_TRACE(bp, "lock", 0);
	if (atomic_read(&bp->b_io_remaining))
		blk_run_address_space(bp->b_target->bt_mapping);
	down(&bp->b_sema);
	XB_SET_OWNER(bp);
	XB_TRACE(bp, "locked", 0);
}

/*
 *	Releases the lock on the buffer object.
 *	If the buffer is marked delwri but is not queued, do so before we
 *	unlock the buffer as we need to set flags correctly.  We also need to
 *	take a reference for the delwri queue because the unlocker is going to
 *	drop their's and they don't know we just queued it.
 */
void
xfs_buf_unlock(
	xfs_buf_t		*bp)
{
	if ((bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)) == XBF_DELWRI) {
		atomic_inc(&bp->b_hold);
		bp->b_flags |= XBF_ASYNC;
		xfs_buf_delwri_queue(bp, 0);
	}

	XB_CLEAR_OWNER(bp);
	up(&bp->b_sema);
	XB_TRACE(bp, "unlock", 0);
}


/*
 *	Pinning Buffer Storage in Memory
 *	Ensure that no attempt to force a buffer to disk will succeed.
 */
void
xfs_buf_pin(
	xfs_buf_t		*bp)
{
	atomic_inc(&bp->b_pin_count);
	XB_TRACE(bp, "pin", (long)bp->b_pin_count.counter);
}

void
xfs_buf_unpin(
	xfs_buf_t		*bp)
{
	if (atomic_dec_and_test(&bp->b_pin_count))
		wake_up_all(&bp->b_waiters);
	XB_TRACE(bp, "unpin", (long)bp->b_pin_count.counter);
}

int
xfs_buf_ispin(
	xfs_buf_t		*bp)
{
	return atomic_read(&bp->b_pin_count);
}

STATIC void
xfs_buf_wait_unpin(
	xfs_buf_t		*bp)
{
	DECLARE_WAITQUEUE	(wait, current);

	if (atomic_read(&bp->b_pin_count) == 0)
		return;

	add_wait_queue(&bp->b_waiters, &wait);
	for (;;) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (atomic_read(&bp->b_pin_count) == 0)
			break;
		if (atomic_read(&bp->b_io_remaining))
			blk_run_address_space(bp->b_target->bt_mapping);
		schedule();
	}
	remove_wait_queue(&bp->b_waiters, &wait);
	set_current_state(TASK_RUNNING);
}

/*
 *	Buffer Utility Routines
 */

STATIC void
xfs_buf_iodone_work(
	struct work_struct	*work)
{
	xfs_buf_t		*bp =
		container_of(work, xfs_buf_t, b_iodone_work);

	if (bp->b_iodone)
		(*(bp->b_iodone))(bp);
	else if (bp->b_flags & XBF_ASYNC)
		xfs_buf_relse(bp);
}

void
xfs_buf_ioend(
	xfs_buf_t		*bp,
	int			schedule)
{
	bp->b_flags &= ~(XBF_READ | XBF_WRITE);
	if (bp->b_error == 0)
		bp->b_flags |= XBF_DONE;

	XB_TRACE(bp, "iodone", bp->b_iodone);

	if ((bp->b_iodone) || (bp->b_flags & XBF_ASYNC)) {
		if (schedule) {
			INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
			queue_work(xfslogd_workqueue, &bp->b_iodone_work);
		} else {
			xfs_buf_iodone_work(&bp->b_iodone_work);
		}
	} else {
		up(&bp->b_iodonesema);
	}
}

void
xfs_buf_ioerror(
	xfs_buf_t		*bp,
	int			error)
{
	ASSERT(error >= 0 && error <= 0xffff);
	bp->b_error = (unsigned short)error;
	XB_TRACE(bp, "ioerror", (unsigned long)error);
}

/*
 *	Initiate I/O on a buffer, based on the flags supplied.
 *	The b_iodone routine in the buffer supplied will only be called
 *	when all of the subsidiary I/O requests, if any, have been completed.
 */
int
xfs_buf_iostart(
	xfs_buf_t		*bp,
	xfs_buf_flags_t		flags)
{
	int			status = 0;

	XB_TRACE(bp, "iostart", (unsigned long)flags);

	if (flags & XBF_DELWRI) {
		bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_ASYNC);
		bp->b_flags |= flags & (XBF_DELWRI | XBF_ASYNC);
		xfs_buf_delwri_queue(bp, 1);
		return status;
	}

	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_ASYNC | XBF_DELWRI | \
			XBF_READ_AHEAD | _XBF_RUN_QUEUES);
	bp->b_flags |= flags & (XBF_READ | XBF_WRITE | XBF_ASYNC | \
			XBF_READ_AHEAD | _XBF_RUN_QUEUES);

	BUG_ON(bp->b_bn == XFS_BUF_DADDR_NULL);

	/* For writes allow an alternate strategy routine to precede
	 * the actual I/O request (which may not be issued at all in
	 * a shutdown situation, for example).
	 */
	status = (flags & XBF_WRITE) ?
		xfs_buf_iostrategy(bp) : xfs_buf_iorequest(bp);

	/* Wait for I/O if we are not an async request.
	 * Note: async I/O request completion will release the buffer,
	 * and that can already be done by this point.  So using the
	 * buffer pointer from here on, after async I/O, is invalid.
	 */
	if (!status && !(flags & XBF_ASYNC))
		status = xfs_buf_iowait(bp);

	return status;
}

STATIC_INLINE int
_xfs_buf_iolocked(
	xfs_buf_t		*bp)
{
	ASSERT(bp->b_flags & (XBF_READ | XBF_WRITE));
	if (bp->b_flags & XBF_READ)
		return bp->b_locked;
	return 0;
}

STATIC_INLINE void
_xfs_buf_ioend(
	xfs_buf_t		*bp,
	int			schedule)
{
	if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
		bp->b_locked = 0;
		xfs_buf_ioend(bp, schedule);
	}
}

STATIC int
xfs_buf_bio_end_io(
	struct bio		*bio,
	unsigned int		bytes_done,
	int			error)
{
	xfs_buf_t		*bp = (xfs_buf_t *)bio->bi_private;
	unsigned int		blocksize = bp->b_target->bt_bsize;
	struct bio_vec		*bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

	if (bio->bi_size)
		return 1;

	if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
		bp->b_error = EIO;

	do {
		struct page	*page = bvec->bv_page;

		ASSERT(!PagePrivate(page));
		if (unlikely(bp->b_error)) {
			if (bp->b_flags & XBF_READ)
				ClearPageUptodate(page);
		} else if (blocksize >= PAGE_CACHE_SIZE) {
			SetPageUptodate(page);
		} else if (!PagePrivate(page) &&
				(bp->b_flags & _XBF_PAGE_CACHE)) {
			set_page_region(page, bvec->bv_offset, bvec->bv_len);
		}

		if (--bvec >= bio->bi_io_vec)
			prefetchw(&bvec->bv_page->flags);

		if (_xfs_buf_iolocked(bp)) {
			unlock_page(page);
		}
	} while (bvec >= bio->bi_io_vec);

	_xfs_buf_ioend(bp, 1);
	bio_put(bio);
	return 0;
}

STATIC void
_xfs_buf_ioapply(
	xfs_buf_t		*bp)
{
	int			i, rw, map_i, total_nr_pages, nr_pages;
	struct bio		*bio;
	int			offset = bp->b_offset;
	int			size = bp->b_count_desired;
	sector_t		sector = bp->b_bn;
	unsigned int		blocksize = bp->b_target->bt_bsize;
	int			locking = _xfs_buf_iolocked(bp);

	total_nr_pages = bp->b_page_count;
	map_i = 0;

	if (bp->b_flags & XBF_ORDERED) {
		ASSERT(!(bp->b_flags & XBF_READ));
		rw = WRITE_BARRIER;
	} else if (bp->b_flags & _XBF_RUN_QUEUES) {
		ASSERT(!(bp->b_flags & XBF_READ_AHEAD));
		bp->b_flags &= ~_XBF_RUN_QUEUES;
		rw = (bp->b_flags & XBF_WRITE) ? WRITE_SYNC : READ_SYNC;
	} else {
		rw = (bp->b_flags & XBF_WRITE) ? WRITE :
		     (bp->b_flags & XBF_READ_AHEAD) ? READA : READ;
	}

	/* Special code path for reading a sub page size buffer in --
	 * we populate up the whole page, and hence the other metadata
	 * in the same page.  This optimization is only valid when the
	 * filesystem block size is not smaller than the page size.
	 */
	if ((bp->b_buffer_length < PAGE_CACHE_SIZE) &&
	    (bp->b_flags & XBF_READ) && locking &&
	    (blocksize >= PAGE_CACHE_SIZE)) {
		bio = bio_alloc(GFP_NOIO, 1);

		bio->bi_bdev = bp->b_target->bt_bdev;
		bio->bi_sector = sector - (offset >> BBSHIFT);
		bio->bi_end_io = xfs_buf_bio_end_io;
		bio->bi_private = bp;

		bio_add_page(bio, bp->b_pages[0], PAGE_CACHE_SIZE, 0);
		size = 0;

		atomic_inc(&bp->b_io_remaining);

		goto submit_io;
	}

	/* Lock down the pages which we need to for the request */
	if (locking && (bp->b_flags & XBF_WRITE) && (bp->b_locked == 0)) {
		for (i = 0; size; i++) {
			int		nbytes = PAGE_CACHE_SIZE - offset;
			struct page	*page = bp->b_pages[i];

			if (nbytes > size)
				nbytes = size;

			lock_page(page);

			size -= nbytes;
			offset = 0;
		}
		offset = bp->b_offset;
		size = bp->b_count_desired;
	}

next_chunk:
	atomic_inc(&bp->b_io_remaining);
	nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
	if (nr_pages > total_nr_pages)
		nr_pages = total_nr_pages;

	bio = bio_alloc(GFP_NOIO, nr_pages);
	bio->bi_bdev = bp->b_target->bt_bdev;
	bio->bi_sector = sector;
	bio->bi_end_io = xfs_buf_bio_end_io;
	bio->bi_private = bp;

	for (; size && nr_pages; nr_pages--, map_i++) {
		int	rbytes, nbytes = PAGE_CACHE_SIZE - offset;

		if (nbytes > size)
			nbytes = size;

		rbytes = bio_add_page(bio, bp->b_pages[map_i], nbytes, offset);
		if (rbytes < nbytes)
			break;

		offset = 0;
		sector += nbytes >> BBSHIFT;
		size -= nbytes;
		total_nr_pages--;
	}

submit_io:
	if (likely(bio->bi_size)) {
		submit_bio(rw, bio);
		if (size)
			goto next_chunk;
	} else {
		bio_put(bio);
		xfs_buf_ioerror(bp, EIO);
	}
}

int
xfs_buf_iorequest(
	xfs_buf_t		*bp)
{
	XB_TRACE(bp, "iorequest", 0);

	if (bp->b_flags & XBF_DELWRI) {
		xfs_buf_delwri_queue(bp, 1);
		return 0;
	}

	if (bp->b_flags & XBF_WRITE) {
		xfs_buf_wait_unpin(bp);
	}

	xfs_buf_hold(bp);

	/* Set the count to 1 initially, this will stop an I/O
	 * completion callout which happens before we have started
	 * all the I/O from calling xfs_buf_ioend too early.
	 */
	atomic_set(&bp->b_io_remaining, 1);
	_xfs_buf_ioapply(bp);
	_xfs_buf_ioend(bp, 0);

	xfs_buf_rele(bp);
	return 0;
}

/*
 *	Waits for I/O to complete on the buffer supplied.
 *	It returns immediately if no I/O is pending.
 *	It returns the I/O error code, if any, or 0 if there was no error.
 */
int
xfs_buf_iowait(
	xfs_buf_t		*bp)
{
	XB_TRACE(bp, "iowait", 0);
	if (atomic_read(&bp->b_io_remaining))
		blk_run_address_space(bp->b_target->bt_mapping);
	down(&bp->b_iodonesema);
	XB_TRACE(bp, "iowaited", (long)bp->b_error);
	return bp->b_error;
}

xfs_caddr_t
xfs_buf_offset(
	xfs_buf_t		*bp,
	size_t			offset)
{
	struct page		*page;

	if (bp->b_flags & XBF_MAPPED)
		return XFS_BUF_PTR(bp) + offset;

	offset += bp->b_offset;
	page = bp->b_pages[offset >> PAGE_CACHE_SHIFT];
	return (xfs_caddr_t)page_address(page) + (offset & (PAGE_CACHE_SIZE-1));
}

/*
 *	Move data into or out of a buffer.
 */
void
xfs_buf_iomove(
	xfs_buf_t		*bp,	/* buffer to process		*/
	size_t			boff,	/* starting buffer offset	*/
	size_t			bsize,	/* length to copy		*/
	caddr_t			data,	/* data address			*/
	xfs_buf_rw_t		mode)	/* read/write/zero flag		*/
{
	size_t			bend, cpoff, csize;
	struct page		*page;

	bend = boff + bsize;
	while (boff < bend) {
		page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
		cpoff = xfs_buf_poff(boff + bp->b_offset);
		csize = min_t(size_t,
			      PAGE_CACHE_SIZE-cpoff, bp->b_count_desired-boff);

		ASSERT(((csize + cpoff) <= PAGE_CACHE_SIZE));

		switch (mode) {
		case XBRW_ZERO:
			memset(page_address(page) + cpoff, 0, csize);
			break;
		case XBRW_READ:
			memcpy(data, page_address(page) + cpoff, csize);
			break;
		case XBRW_WRITE:
			memcpy(page_address(page) + cpoff, data, csize);
		}

		boff += csize;
		data += csize;
	}
}

/*
 *	Handling of buffer targets (buftargs).
 */

/*
 *	Wait for any bufs with callbacks that have been submitted but
 *	have not yet returned... walk the hash list for the target.
 */
void
xfs_wait_buftarg(
	xfs_buftarg_t	*btp)
{
	xfs_buf_t	*bp, *n;
	xfs_bufhash_t	*hash;
	uint		i;

	for (i = 0; i < (1 << btp->bt_hashshift); i++) {
		hash = &btp->bt_hash[i];
again:
		spin_lock(&hash->bh_lock);
		list_for_each_entry_safe(bp, n, &hash->bh_list, b_hash_list) {
			ASSERT(btp == bp->b_target);
			if (!(bp->b_flags & XBF_FS_MANAGED)) {
				spin_unlock(&hash->bh_lock);
				/*
				 * Catch superblock reference count leaks
				 * immediately
				 */
				BUG_ON(bp->b_bn == 0);
				delay(100);
				goto again;
			}
		}
		spin_unlock(&hash->bh_lock);
	}
}

/*
 *	Allocate buffer hash table for a given target.
 *	For devices containing metadata (i.e. not the log/realtime devices)
 *	we need to allocate a much larger hash table.
 */
STATIC void
xfs_alloc_bufhash(
	xfs_buftarg_t		*btp,
	int			external)
{
	unsigned int		i;

	btp->bt_hashshift = external ? 3 : 8;	/* 8 or 256 buckets */
	btp->bt_hashmask = (1 << btp->bt_hashshift) - 1;
	btp->bt_hash = kmem_zalloc((1 << btp->bt_hashshift) *
					sizeof(xfs_bufhash_t), KM_SLEEP | KM_LARGE);
	for (i = 0; i < (1 << btp->bt_hashshift); i++) {
		spin_lock_init(&btp->bt_hash[i].bh_lock);
		INIT_LIST_HEAD(&btp->bt_hash[i].bh_list);
	}
}

STATIC void
xfs_free_bufhash(
	xfs_buftarg_t		*btp)
{
	kmem_free(btp->bt_hash, (1<<btp->bt_hashshift) * sizeof(xfs_bufhash_t));
	btp->bt_hash = NULL;
}

/*
 *	buftarg list for delwrite queue processing
 */
LIST_HEAD(xfs_buftarg_list);
static DEFINE_SPINLOCK(xfs_buftarg_lock);

STATIC void
xfs_register_buftarg(
	xfs_buftarg_t           *btp)
{
	spin_lock(&xfs_buftarg_lock);
	list_add(&btp->bt_list, &xfs_buftarg_list);
	spin_unlock(&xfs_buftarg_lock);
}

STATIC void
xfs_unregister_buftarg(
	xfs_buftarg_t           *btp)
{
	spin_lock(&xfs_buftarg_lock);
	list_del(&btp->bt_list);
	spin_unlock(&xfs_buftarg_lock);
}

void
xfs_free_buftarg(
	xfs_buftarg_t		*btp,
	int			external)
{
	xfs_flush_buftarg(btp, 1);
	if (external)
		xfs_blkdev_put(btp->bt_bdev);
	xfs_free_bufhash(btp);
	iput(btp->bt_mapping->host);

	/* Unregister the buftarg first so that we don't get a
	 * wakeup finding a non-existent task
	 */
	xfs_unregister_buftarg(btp);
	kthread_stop(btp->bt_task);

	kmem_free(btp, sizeof(*btp));
}

STATIC int
xfs_setsize_buftarg_flags(
	xfs_buftarg_t		*btp,
	unsigned int		blocksize,
	unsigned int		sectorsize,
	int			verbose)
{
	btp->bt_bsize = blocksize;
	btp->bt_sshift = ffs(sectorsize) - 1;
	btp->bt_smask = sectorsize - 1;

	if (set_blocksize(btp->bt_bdev, sectorsize)) {
		printk(KERN_WARNING
			"XFS: Cannot set_blocksize to %u on device %s\n",
			sectorsize, XFS_BUFTARG_NAME(btp));
		return EINVAL;
	}

	if (verbose &&
	    (PAGE_CACHE_SIZE / BITS_PER_LONG) > sectorsize) {
		printk(KERN_WARNING
			"XFS: %u byte sectors in use on device %s.  "
			"This is suboptimal; %u or greater is ideal.\n",
			sectorsize, XFS_BUFTARG_NAME(btp),
			(unsigned int)PAGE_CACHE_SIZE / BITS_PER_LONG);
	}

	return 0;
}

/*
 *	When allocating the initial buffer target we have not yet
 *	read in the superblock, so don't know what sized sectors
 *	are being used is at this early stage.  Play safe.
 */
STATIC int
xfs_setsize_buftarg_early(
	xfs_buftarg_t		*btp,
	struct block_device	*bdev)
{
	return xfs_setsize_buftarg_flags(btp,
			PAGE_CACHE_SIZE, bdev_hardsect_size(bdev), 0);
}

int
xfs_setsize_buftarg(
	xfs_buftarg_t		*btp,
	unsigned int		blocksize,
	unsigned int		sectorsize)
{
	return xfs_setsize_buftarg_flags(btp, blocksize, sectorsize, 1);
}

STATIC int
xfs_mapping_buftarg(
	xfs_buftarg_t		*btp,
	struct block_device	*bdev)
{
	struct backing_dev_info	*bdi;
	struct inode		*inode;
	struct address_space	*mapping;
	static const struct address_space_operations mapping_aops = {
		.sync_page = block_sync_page,
		.migratepage = fail_migrate_page,
	};

	inode = new_inode(bdev->bd_inode->i_sb);
	if (!inode) {
		printk(KERN_WARNING
			"XFS: Cannot allocate mapping inode for device %s\n",
			XFS_BUFTARG_NAME(btp));
		return ENOMEM;
	}
	inode->i_mode = S_IFBLK;
	inode->i_bdev = bdev;
	inode->i_rdev = bdev->bd_dev;
	bdi = blk_get_backing_dev_info(bdev);
	if (!bdi)
		bdi = &default_backing_dev_info;
	mapping = &inode->i_data;
	mapping->a_ops = &mapping_aops;
	mapping->backing_dev_info = bdi;
	mapping_set_gfp_mask(mapping, GFP_NOFS);
	btp->bt_mapping = mapping;
	return 0;
}

STATIC int
xfs_alloc_delwrite_queue(
	xfs_buftarg_t		*btp)
{
	int	error = 0;

	INIT_LIST_HEAD(&btp->bt_list);
	INIT_LIST_HEAD(&btp->bt_delwrite_queue);
	spinlock_init(&btp->bt_delwrite_lock, "delwri_lock");
	btp->bt_flags = 0;
	btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd");
	if (IS_ERR(btp->bt_task)) {
		error = PTR_ERR(btp->bt_task);
		goto out_error;
	}
	xfs_register_buftarg(btp);
out_error:
	return error;
}

xfs_buftarg_t *
xfs_alloc_buftarg(
	struct block_device	*bdev,
	int			external)
{
	xfs_buftarg_t		*btp;

	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);

	btp->bt_dev =  bdev->bd_dev;
	btp->bt_bdev = bdev;
	if (xfs_setsize_buftarg_early(btp, bdev))
		goto error;
	if (xfs_mapping_buftarg(btp, bdev))
		goto error;
	if (xfs_alloc_delwrite_queue(btp))
		goto error;
	xfs_alloc_bufhash(btp, external);
	return btp;

error:
	kmem_free(btp, sizeof(*btp));
	return NULL;
}


/*
 *	Delayed write buffer handling
 */
STATIC void
xfs_buf_delwri_queue(
	xfs_buf_t		*bp,
	int			unlock)
{
	struct list_head	*dwq = &bp->b_target->bt_delwrite_queue;
	spinlock_t		*dwlk = &bp->b_target->bt_delwrite_lock;

	XB_TRACE(bp, "delwri_q", (long)unlock);
	ASSERT((bp->b_flags&(XBF_DELWRI|XBF_ASYNC)) == (XBF_DELWRI|XBF_ASYNC));

	spin_lock(dwlk);
	/* If already in the queue, dequeue and place at tail */
	if (!list_empty(&bp->b_list)) {
		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
		if (unlock)
			atomic_dec(&bp->b_hold);
		list_del(&bp->b_list);
	}

	bp->b_flags |= _XBF_DELWRI_Q;
	list_add_tail(&bp->b_list, dwq);
	bp->b_queuetime = jiffies;
	spin_unlock(dwlk);

	if (unlock)
		xfs_buf_unlock(bp);
}

void
xfs_buf_delwri_dequeue(
	xfs_buf_t		*bp)
{
	spinlock_t		*dwlk = &bp->b_target->bt_delwrite_lock;
	int			dequeued = 0;

	spin_lock(dwlk);
	if ((bp->b_flags & XBF_DELWRI) && !list_empty(&bp->b_list)) {
		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
		list_del_init(&bp->b_list);
		dequeued = 1;
	}
	bp->b_flags &= ~(XBF_DELWRI|_XBF_DELWRI_Q);
	spin_unlock(dwlk);

	if (dequeued)
		xfs_buf_rele(bp);

	XB_TRACE(bp, "delwri_dq", (long)dequeued);
}

STATIC void
xfs_buf_runall_queues(
	struct workqueue_struct	*queue)
{
	flush_workqueue(queue);
}

STATIC int
xfsbufd_wakeup(
	int			priority,
	gfp_t			mask)
{
	xfs_buftarg_t		*btp;

	spin_lock(&xfs_buftarg_lock);
	list_for_each_entry(btp, &xfs_buftarg_list, bt_list) {
		if (test_bit(XBT_FORCE_SLEEP, &btp->bt_flags))
			continue;
		set_bit(XBT_FORCE_FLUSH, &btp->bt_flags);
		wake_up_process(btp->bt_task);
	}
	spin_unlock(&xfs_buftarg_lock);
	return 0;
}

/*
 * Move as many buffers as specified to the supplied list
 * idicating if we skipped any buffers to prevent deadlocks.
 */
STATIC int
xfs_buf_delwri_split(
	xfs_buftarg_t	*target,
	struct list_head *list,
	unsigned long	age)
{
	xfs_buf_t	*bp, *n;
	struct list_head *dwq = &target->bt_delwrite_queue;
	spinlock_t	*dwlk = &target->bt_delwrite_lock;
	int		skipped = 0;
	int		force;

	force = test_and_clear_bit(XBT_FORCE_FLUSH, &target->bt_flags);
	INIT_LIST_HEAD(list);
	spin_lock(dwlk);
	list_for_each_entry_safe(bp, n, dwq, b_list) {
		XB_TRACE(bp, "walkq1", (long)xfs_buf_ispin(bp));
		ASSERT(bp->b_flags & XBF_DELWRI);

		if (!xfs_buf_ispin(bp) && !xfs_buf_cond_lock(bp)) {
			if (!force &&
			    time_before(jiffies, bp->b_queuetime + age)) {
				xfs_buf_unlock(bp);
				break;
			}

			bp->b_flags &= ~(XBF_DELWRI|_XBF_DELWRI_Q|
					 _XBF_RUN_QUEUES);
			bp->b_flags |= XBF_WRITE;
			list_move_tail(&bp->b_list, list);
		} else
			skipped++;
	}
	spin_unlock(dwlk);

	return skipped;

}

STATIC int
xfsbufd(
	void		*data)
{
	struct list_head tmp;
	xfs_buftarg_t	*target = (xfs_buftarg_t *)data;
	int		count;
	xfs_buf_t	*bp;

	current->flags |= PF_MEMALLOC;

	do {
		if (unlikely(freezing(current))) {
			set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
			refrigerator();
		} else {
			clear_bit(XBT_FORCE_SLEEP, &target->bt_flags);
		}

		schedule_timeout_interruptible(
			xfs_buf_timer_centisecs * msecs_to_jiffies(10));

		xfs_buf_delwri_split(target, &tmp,
				xfs_buf_age_centisecs * msecs_to_jiffies(10));

		count = 0;
		while (!list_empty(&tmp)) {
			bp = list_entry(tmp.next, xfs_buf_t, b_list);
			ASSERT(target == bp->b_target);

			list_del_init(&bp->b_list);
			xfs_buf_iostrategy(bp);
			count++;
		}

		if (as_list_len > 0)
			purge_addresses();
		if (count)
			blk_run_address_space(target->bt_mapping);

	} while (!kthread_should_stop());

	return 0;
}

/*
 *	Go through all incore buffers, and release buffers if they belong to
 *	the given device. This is used in filesystem error handling to
 *	preserve the consistency of its metadata.
 */
int
xfs_flush_buftarg(
	xfs_buftarg_t	*target,
	int		wait)
{
	struct list_head tmp;
	xfs_buf_t	*bp, *n;
	int		pincount = 0;

	xfs_buf_runall_queues(xfsdatad_workqueue);
	xfs_buf_runall_queues(xfslogd_workqueue);

	set_bit(XBT_FORCE_FLUSH, &target->bt_flags);
	pincount = xfs_buf_delwri_split(target, &tmp, 0);

	/*
	 * Dropped the delayed write list lock, now walk the temporary list
	 */
	list_for_each_entry_safe(bp, n, &tmp, b_list) {
		ASSERT(target == bp->b_target);
		if (wait)
			bp->b_flags &= ~XBF_ASYNC;
		else
			list_del_init(&bp->b_list);

		xfs_buf_iostrategy(bp);
	}

	if (wait)
		blk_run_address_space(target->bt_mapping);

	/*
	 * Remaining list items must be flushed before returning
	 */
	while (!list_empty(&tmp)) {
		bp = list_entry(tmp.next, xfs_buf_t, b_list);

		list_del_init(&bp->b_list);
		xfs_iowait(bp);
		xfs_buf_relse(bp);
	}

	return pincount;
}

int __init
xfs_buf_init(void)
{
#ifdef XFS_BUF_TRACE
	xfs_buf_trace_buf = ktrace_alloc(XFS_BUF_TRACE_SIZE, KM_SLEEP);
#endif

	xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
						KM_ZONE_HWALIGN, NULL);
	if (!xfs_buf_zone)
		goto out_free_trace_buf;

	xfslogd_workqueue = create_freezeable_workqueue("xfslogd");
	if (!xfslogd_workqueue)
		goto out_free_buf_zone;

	xfsdatad_workqueue = create_freezeable_workqueue("xfsdatad");
	if (!xfsdatad_workqueue)
		goto out_destroy_xfslogd_workqueue;

	xfs_buf_shake = kmem_shake_register(xfsbufd_wakeup);
	if (!xfs_buf_shake)
		goto out_destroy_xfsdatad_workqueue;

	return 0;

 out_destroy_xfsdatad_workqueue:
	destroy_workqueue(xfsdatad_workqueue);
 out_destroy_xfslogd_workqueue:
	destroy_workqueue(xfslogd_workqueue);
 out_free_buf_zone:
	kmem_zone_destroy(xfs_buf_zone);
 out_free_trace_buf:
#ifdef XFS_BUF_TRACE
	ktrace_free(xfs_buf_trace_buf);
#endif
	return -ENOMEM;
}

void
xfs_buf_terminate(void)
{
	kmem_shake_deregister(xfs_buf_shake);
	destroy_workqueue(xfsdatad_workqueue);
	destroy_workqueue(xfslogd_workqueue);
	kmem_zone_destroy(xfs_buf_zone);
#ifdef XFS_BUF_TRACE
	ktrace_free(xfs_buf_trace_buf);
#endif
}
OpenPOWER on IntegriCloud