summaryrefslogtreecommitdiff
path: root/fs/hugetlbfs/inode.c
blob: afb7c7f05de5ba9d87436b3f58bd1af8e7fd279a (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
/*
 * hugetlbpage-backed filesystem.  Based on ramfs.
 *
 * Nadia Yvette Chambers, 2002
 *
 * Copyright (C) 2002 Linus Torvalds.
 * License: GPL
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/thread_info.h>
#include <asm/current.h>
#include <linux/sched.h>		/* remove ASAP */
#include <linux/falloc.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/kernel.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/capability.h>
#include <linux/ctype.h>
#include <linux/backing-dev.h>
#include <linux/hugetlb.h>
#include <linux/pagevec.h>
#include <linux/parser.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/dnotify.h>
#include <linux/statfs.h>
#include <linux/security.h>
#include <linux/magic.h>
#include <linux/migrate.h>
#include <linux/uio.h>

#include <asm/uaccess.h>

static const struct super_operations hugetlbfs_ops;
static const struct address_space_operations hugetlbfs_aops;
const struct file_operations hugetlbfs_file_operations;
static const struct inode_operations hugetlbfs_dir_inode_operations;
static const struct inode_operations hugetlbfs_inode_operations;

struct hugetlbfs_config {
	kuid_t   uid;
	kgid_t   gid;
	umode_t mode;
	long	max_hpages;
	long	nr_inodes;
	struct hstate *hstate;
	long    min_hpages;
};

struct hugetlbfs_inode_info {
	struct shared_policy policy;
	struct inode vfs_inode;
};

static inline struct hugetlbfs_inode_info *HUGETLBFS_I(struct inode *inode)
{
	return container_of(inode, struct hugetlbfs_inode_info, vfs_inode);
}

int sysctl_hugetlb_shm_group;

enum {
	Opt_size, Opt_nr_inodes,
	Opt_mode, Opt_uid, Opt_gid,
	Opt_pagesize, Opt_min_size,
	Opt_err,
};

static const match_table_t tokens = {
	{Opt_size,	"size=%s"},
	{Opt_nr_inodes,	"nr_inodes=%s"},
	{Opt_mode,	"mode=%o"},
	{Opt_uid,	"uid=%u"},
	{Opt_gid,	"gid=%u"},
	{Opt_pagesize,	"pagesize=%s"},
	{Opt_min_size,	"min_size=%s"},
	{Opt_err,	NULL},
};

#ifdef CONFIG_NUMA
static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
					struct inode *inode, pgoff_t index)
{
	vma->vm_policy = mpol_shared_policy_lookup(&HUGETLBFS_I(inode)->policy,
							index);
}

static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
{
	mpol_cond_put(vma->vm_policy);
}
#else
static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
					struct inode *inode, pgoff_t index)
{
}

static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
{
}
#endif

static void huge_pagevec_release(struct pagevec *pvec)
{
	int i;

	for (i = 0; i < pagevec_count(pvec); ++i)
		put_page(pvec->pages[i]);

	pagevec_reinit(pvec);
}

static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct inode *inode = file_inode(file);
	loff_t len, vma_len;
	int ret;
	struct hstate *h = hstate_file(file);

	/*
	 * vma address alignment (but not the pgoff alignment) has
	 * already been checked by prepare_hugepage_range.  If you add
	 * any error returns here, do so after setting VM_HUGETLB, so
	 * is_vm_hugetlb_page tests below unmap_region go the right
	 * way when do_mmap_pgoff unwinds (may be important on powerpc
	 * and ia64).
	 */
	vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
	vma->vm_ops = &hugetlb_vm_ops;

	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
		return -EINVAL;

	vma_len = (loff_t)(vma->vm_end - vma->vm_start);

	inode_lock(inode);
	file_accessed(file);

	ret = -ENOMEM;
	len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

	if (hugetlb_reserve_pages(inode,
				vma->vm_pgoff >> huge_page_order(h),
				len >> huge_page_shift(h), vma,
				vma->vm_flags))
		goto out;

	ret = 0;
	if (vma->vm_flags & VM_WRITE && inode->i_size < len)
		inode->i_size = len;
out:
	inode_unlock(inode);

	return ret;
}

/*
 * Called under down_write(mmap_sem).
 */

#ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
static unsigned long
hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
		unsigned long len, unsigned long pgoff, unsigned long flags)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	struct hstate *h = hstate_file(file);
	struct vm_unmapped_area_info info;

	if (len & ~huge_page_mask(h))
		return -EINVAL;
	if (len > TASK_SIZE)
		return -ENOMEM;

	if (flags & MAP_FIXED) {
		if (prepare_hugepage_range(file, addr, len))
			return -EINVAL;
		return addr;
	}

	if (addr) {
		addr = ALIGN(addr, huge_page_size(h));
		vma = find_vma(mm, addr);
		if (TASK_SIZE - len >= addr &&
		    (!vma || addr + len <= vma->vm_start))
			return addr;
	}

	info.flags = 0;
	info.length = len;
	info.low_limit = TASK_UNMAPPED_BASE;
	info.high_limit = TASK_SIZE;
	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
	info.align_offset = 0;
	return vm_unmapped_area(&info);
}
#endif

static size_t
hugetlbfs_read_actor(struct page *page, unsigned long offset,
			struct iov_iter *to, unsigned long size)
{
	size_t copied = 0;
	int i, chunksize;

	/* Find which 4k chunk and offset with in that chunk */
	i = offset >> PAGE_SHIFT;
	offset = offset & ~PAGE_MASK;

	while (size) {
		size_t n;
		chunksize = PAGE_SIZE;
		if (offset)
			chunksize -= offset;
		if (chunksize > size)
			chunksize = size;
		n = copy_page_to_iter(&page[i], offset, chunksize, to);
		copied += n;
		if (n != chunksize)
			return copied;
		offset = 0;
		size -= chunksize;
		i++;
	}
	return copied;
}

/*
 * Support for read() - Find the page attached to f_mapping and copy out the
 * data. Its *very* similar to do_generic_mapping_read(), we can't use that
 * since it has PAGE_CACHE_SIZE assumptions.
 */
static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
	struct file *file = iocb->ki_filp;
	struct hstate *h = hstate_file(file);
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	unsigned long index = iocb->ki_pos >> huge_page_shift(h);
	unsigned long offset = iocb->ki_pos & ~huge_page_mask(h);
	unsigned long end_index;
	loff_t isize;
	ssize_t retval = 0;

	while (iov_iter_count(to)) {
		struct page *page;
		size_t nr, copied;

		/* nr is the maximum number of bytes to copy from this page */
		nr = huge_page_size(h);
		isize = i_size_read(inode);
		if (!isize)
			break;
		end_index = (isize - 1) >> huge_page_shift(h);
		if (index > end_index)
			break;
		if (index == end_index) {
			nr = ((isize - 1) & ~huge_page_mask(h)) + 1;
			if (nr <= offset)
				break;
		}
		nr = nr - offset;

		/* Find the page */
		page = find_lock_page(mapping, index);
		if (unlikely(page == NULL)) {
			/*
			 * We have a HOLE, zero out the user-buffer for the
			 * length of the hole or request.
			 */
			copied = iov_iter_zero(nr, to);
		} else {
			unlock_page(page);

			/*
			 * We have the page, copy it to user space buffer.
			 */
			copied = hugetlbfs_read_actor(page, offset, to, nr);
			put_page(page);
		}
		offset += copied;
		retval += copied;
		if (copied != nr && iov_iter_count(to)) {
			if (!retval)
				retval = -EFAULT;
			break;
		}
		index += offset >> huge_page_shift(h);
		offset &= ~huge_page_mask(h);
	}
	iocb->ki_pos = ((loff_t)index << huge_page_shift(h)) + offset;
	return retval;
}

static int hugetlbfs_write_begin(struct file *file,
			struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata)
{
	return -EINVAL;
}

static int hugetlbfs_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	BUG();
	return -EINVAL;
}

static void remove_huge_page(struct page *page)
{
	ClearPageDirty(page);
	ClearPageUptodate(page);
	delete_from_page_cache(page);
}

static void
hugetlb_vmdelete_list(struct rb_root *root, pgoff_t start, pgoff_t end)
{
	struct vm_area_struct *vma;

	/*
	 * end == 0 indicates that the entire range after
	 * start should be unmapped.
	 */
	vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
		unsigned long v_offset;
		unsigned long v_end;

		/*
		 * Can the expression below overflow on 32-bit arches?
		 * No, because the interval tree returns us only those vmas
		 * which overlap the truncated area starting at pgoff,
		 * and no vma on a 32-bit arch can span beyond the 4GB.
		 */
		if (vma->vm_pgoff < start)
			v_offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
		else
			v_offset = 0;

		if (!end)
			v_end = vma->vm_end;
		else {
			v_end = ((end - vma->vm_pgoff) << PAGE_SHIFT)
							+ vma->vm_start;
			if (v_end > vma->vm_end)
				v_end = vma->vm_end;
		}

		unmap_hugepage_range(vma, vma->vm_start + v_offset, v_end,
									NULL);
	}
}

/*
 * remove_inode_hugepages handles two distinct cases: truncation and hole
 * punch.  There are subtle differences in operation for each case.
 *
 * truncation is indicated by end of range being LLONG_MAX
 *	In this case, we first scan the range and release found pages.
 *	After releasing pages, hugetlb_unreserve_pages cleans up region/reserv
 *	maps and global counts.  Page faults can not race with truncation
 *	in this routine.  hugetlb_no_page() prevents page faults in the
 *	truncated range.  It checks i_size before allocation, and again after
 *	with the page table lock for the page held.  The same lock must be
 *	acquired to unmap a page.
 * hole punch is indicated if end is not LLONG_MAX
 *	In the hole punch case we scan the range and release found pages.
 *	Only when releasing a page is the associated region/reserv map
 *	deleted.  The region/reserv map for ranges without associated
 *	pages are not modified.  Page faults can race with hole punch.
 *	This is indicated if we find a mapped page.
 * Note: If the passed end of range value is beyond the end of file, but
 * not LLONG_MAX this routine still performs a hole punch operation.
 */
static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
				   loff_t lend)
{
	struct hstate *h = hstate_inode(inode);
	struct address_space *mapping = &inode->i_data;
	const pgoff_t start = lstart >> huge_page_shift(h);
	const pgoff_t end = lend >> huge_page_shift(h);
	struct vm_area_struct pseudo_vma;
	struct pagevec pvec;
	pgoff_t next;
	int i, freed = 0;
	long lookup_nr = PAGEVEC_SIZE;
	bool truncate_op = (lend == LLONG_MAX);

	memset(&pseudo_vma, 0, sizeof(struct vm_area_struct));
	pseudo_vma.vm_flags = (VM_HUGETLB | VM_MAYSHARE | VM_SHARED);
	pagevec_init(&pvec, 0);
	next = start;
	while (next < end) {
		/*
		 * Don't grab more pages than the number left in the range.
		 */
		if (end - next < lookup_nr)
			lookup_nr = end - next;

		/*
		 * When no more pages are found, we are done.
		 */
		if (!pagevec_lookup(&pvec, mapping, next, lookup_nr))
			break;

		for (i = 0; i < pagevec_count(&pvec); ++i) {
			struct page *page = pvec.pages[i];
			bool rsv_on_error;
			u32 hash;

			/*
			 * The page (index) could be beyond end.  This is
			 * only possible in the punch hole case as end is
			 * max page offset in the truncate case.
			 */
			next = page->index;
			if (next >= end)
				break;

			hash = hugetlb_fault_mutex_hash(h, current->mm,
							&pseudo_vma,
							mapping, next, 0);
			mutex_lock(&hugetlb_fault_mutex_table[hash]);

			/*
			 * If page is mapped, it was faulted in after being
			 * unmapped in caller.  Unmap (again) now after taking
			 * the fault mutex.  The mutex will prevent faults
			 * until we finish removing the page.
			 *
			 * This race can only happen in the hole punch case.
			 * Getting here in a truncate operation is a bug.
			 */
			if (unlikely(page_mapped(page))) {
				BUG_ON(truncate_op);

				i_mmap_lock_write(mapping);
				hugetlb_vmdelete_list(&mapping->i_mmap,
					next * pages_per_huge_page(h),
					(next + 1) * pages_per_huge_page(h));
				i_mmap_unlock_write(mapping);
			}

			lock_page(page);
			/*
			 * We must free the huge page and remove from page
			 * cache (remove_huge_page) BEFORE removing the
			 * region/reserve map (hugetlb_unreserve_pages).  In
			 * rare out of memory conditions, removal of the
			 * region/reserve map could fail.  Before free'ing
			 * the page, note PagePrivate which is used in case
			 * of error.
			 */
			rsv_on_error = !PagePrivate(page);
			remove_huge_page(page);
			freed++;
			if (!truncate_op) {
				if (unlikely(hugetlb_unreserve_pages(inode,
							next, next + 1, 1)))
					hugetlb_fix_reserve_counts(inode,
								rsv_on_error);
			}

			unlock_page(page);
			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
		}
		++next;
		huge_pagevec_release(&pvec);
		cond_resched();
	}

	if (truncate_op)
		(void)hugetlb_unreserve_pages(inode, start, LONG_MAX, freed);
}

static void hugetlbfs_evict_inode(struct inode *inode)
{
	struct resv_map *resv_map;

	remove_inode_hugepages(inode, 0, LLONG_MAX);
	resv_map = (struct resv_map *)inode->i_mapping->private_data;
	/* root inode doesn't have the resv_map, so we should check it */
	if (resv_map)
		resv_map_release(&resv_map->refs);
	clear_inode(inode);
}

static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
	pgoff_t pgoff;
	struct address_space *mapping = inode->i_mapping;
	struct hstate *h = hstate_inode(inode);

	BUG_ON(offset & ~huge_page_mask(h));
	pgoff = offset >> PAGE_SHIFT;

	i_size_write(inode, offset);
	i_mmap_lock_write(mapping);
	if (!RB_EMPTY_ROOT(&mapping->i_mmap))
		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
	i_mmap_unlock_write(mapping);
	remove_inode_hugepages(inode, offset, LLONG_MAX);
	return 0;
}

static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
{
	struct hstate *h = hstate_inode(inode);
	loff_t hpage_size = huge_page_size(h);
	loff_t hole_start, hole_end;

	/*
	 * For hole punch round up the beginning offset of the hole and
	 * round down the end.
	 */
	hole_start = round_up(offset, hpage_size);
	hole_end = round_down(offset + len, hpage_size);

	if (hole_end > hole_start) {
		struct address_space *mapping = inode->i_mapping;

		inode_lock(inode);
		i_mmap_lock_write(mapping);
		if (!RB_EMPTY_ROOT(&mapping->i_mmap))
			hugetlb_vmdelete_list(&mapping->i_mmap,
						hole_start >> PAGE_SHIFT,
						hole_end  >> PAGE_SHIFT);
		i_mmap_unlock_write(mapping);
		remove_inode_hugepages(inode, hole_start, hole_end);
		inode_unlock(inode);
	}

	return 0;
}

static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
				loff_t len)
{
	struct inode *inode = file_inode(file);
	struct address_space *mapping = inode->i_mapping;
	struct hstate *h = hstate_inode(inode);
	struct vm_area_struct pseudo_vma;
	struct mm_struct *mm = current->mm;
	loff_t hpage_size = huge_page_size(h);
	unsigned long hpage_shift = huge_page_shift(h);
	pgoff_t start, index, end;
	int error;
	u32 hash;

	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
		return -EOPNOTSUPP;

	if (mode & FALLOC_FL_PUNCH_HOLE)
		return hugetlbfs_punch_hole(inode, offset, len);

	/*
	 * Default preallocate case.
	 * For this range, start is rounded down and end is rounded up
	 * as well as being converted to page offsets.
	 */
	start = offset >> hpage_shift;
	end = (offset + len + hpage_size - 1) >> hpage_shift;

	inode_lock(inode);

	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
	error = inode_newsize_ok(inode, offset + len);
	if (error)
		goto out;

	/*
	 * Initialize a pseudo vma as this is required by the huge page
	 * allocation routines.  If NUMA is configured, use page index
	 * as input to create an allocation policy.
	 */
	memset(&pseudo_vma, 0, sizeof(struct vm_area_struct));
	pseudo_vma.vm_flags = (VM_HUGETLB | VM_MAYSHARE | VM_SHARED);
	pseudo_vma.vm_file = file;

	for (index = start; index < end; index++) {
		/*
		 * This is supposed to be the vaddr where the page is being
		 * faulted in, but we have no vaddr here.
		 */
		struct page *page;
		unsigned long addr;
		int avoid_reserve = 0;

		cond_resched();

		/*
		 * fallocate(2) manpage permits EINTR; we may have been
		 * interrupted because we are using up too much memory.
		 */
		if (signal_pending(current)) {
			error = -EINTR;
			break;
		}

		/* Set numa allocation policy based on index */
		hugetlb_set_vma_policy(&pseudo_vma, inode, index);

		/* addr is the offset within the file (zero based) */
		addr = index * hpage_size;

		/* mutex taken here, fault path and hole punch */
		hash = hugetlb_fault_mutex_hash(h, mm, &pseudo_vma, mapping,
						index, addr);
		mutex_lock(&hugetlb_fault_mutex_table[hash]);

		/* See if already present in mapping to avoid alloc/free */
		page = find_get_page(mapping, index);
		if (page) {
			put_page(page);
			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
			hugetlb_drop_vma_policy(&pseudo_vma);
			continue;
		}

		/* Allocate page and add to page cache */
		page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
		hugetlb_drop_vma_policy(&pseudo_vma);
		if (IS_ERR(page)) {
			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
			error = PTR_ERR(page);
			goto out;
		}
		clear_huge_page(page, addr, pages_per_huge_page(h));
		__SetPageUptodate(page);
		error = huge_add_to_page_cache(page, mapping, index);
		if (unlikely(error)) {
			put_page(page);
			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
			goto out;
		}

		mutex_unlock(&hugetlb_fault_mutex_table[hash]);

		/*
		 * page_put due to reference from alloc_huge_page()
		 * unlock_page because locked by add_to_page_cache()
		 */
		put_page(page);
		unlock_page(page);
	}

	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
		i_size_write(inode, offset + len);
	inode->i_ctime = CURRENT_TIME;
out:
	inode_unlock(inode);
	return error;
}

static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
{
	struct inode *inode = d_inode(dentry);
	struct hstate *h = hstate_inode(inode);
	int error;
	unsigned int ia_valid = attr->ia_valid;

	BUG_ON(!inode);

	error = inode_change_ok(inode, attr);
	if (error)
		return error;

	if (ia_valid & ATTR_SIZE) {
		error = -EINVAL;
		if (attr->ia_size & ~huge_page_mask(h))
			return -EINVAL;
		error = hugetlb_vmtruncate(inode, attr->ia_size);
		if (error)
			return error;
	}

	setattr_copy(inode, attr);
	mark_inode_dirty(inode);
	return 0;
}

static struct inode *hugetlbfs_get_root(struct super_block *sb,
					struct hugetlbfs_config *config)
{
	struct inode *inode;

	inode = new_inode(sb);
	if (inode) {
		struct hugetlbfs_inode_info *info;
		inode->i_ino = get_next_ino();
		inode->i_mode = S_IFDIR | config->mode;
		inode->i_uid = config->uid;
		inode->i_gid = config->gid;
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		info = HUGETLBFS_I(inode);
		mpol_shared_policy_init(&info->policy, NULL);
		inode->i_op = &hugetlbfs_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;
		/* directory inodes start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);
		lockdep_annotate_inode_mutex_key(inode);
	}
	return inode;
}

/*
 * Hugetlbfs is not reclaimable; therefore its i_mmap_rwsem will never
 * be taken from reclaim -- unlike regular filesystems. This needs an
 * annotation because huge_pmd_share() does an allocation under hugetlb's
 * i_mmap_rwsem.
 */
static struct lock_class_key hugetlbfs_i_mmap_rwsem_key;

static struct inode *hugetlbfs_get_inode(struct super_block *sb,
					struct inode *dir,
					umode_t mode, dev_t dev)
{
	struct inode *inode;
	struct resv_map *resv_map;

	resv_map = resv_map_alloc();
	if (!resv_map)
		return NULL;

	inode = new_inode(sb);
	if (inode) {
		struct hugetlbfs_inode_info *info;
		inode->i_ino = get_next_ino();
		inode_init_owner(inode, dir, mode);
		lockdep_set_class(&inode->i_mapping->i_mmap_rwsem,
				&hugetlbfs_i_mmap_rwsem_key);
		inode->i_mapping->a_ops = &hugetlbfs_aops;
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->private_data = resv_map;
		info = HUGETLBFS_I(inode);
		/*
		 * The policy is initialized here even if we are creating a
		 * private inode because initialization simply creates an
		 * an empty rb tree and calls rwlock_init(), later when we
		 * call mpol_free_shared_policy() it will just return because
		 * the rb tree will still be empty.
		 */
		mpol_shared_policy_init(&info->policy, NULL);
		switch (mode & S_IFMT) {
		default:
			init_special_inode(inode, mode, dev);
			break;
		case S_IFREG:
			inode->i_op = &hugetlbfs_inode_operations;
			inode->i_fop = &hugetlbfs_file_operations;
			break;
		case S_IFDIR:
			inode->i_op = &hugetlbfs_dir_inode_operations;
			inode->i_fop = &simple_dir_operations;

			/* directory inodes start off with i_nlink == 2 (for "." entry) */
			inc_nlink(inode);
			break;
		case S_IFLNK:
			inode->i_op = &page_symlink_inode_operations;
			inode_nohighmem(inode);
			break;
		}
		lockdep_annotate_inode_mutex_key(inode);
	} else
		kref_put(&resv_map->refs, resv_map_release);

	return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
static int hugetlbfs_mknod(struct inode *dir,
			struct dentry *dentry, umode_t mode, dev_t dev)
{
	struct inode *inode;
	int error = -ENOSPC;

	inode = hugetlbfs_get_inode(dir->i_sb, dir, mode, dev);
	if (inode) {
		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
		d_instantiate(dentry, inode);
		dget(dentry);	/* Extra count - pin the dentry in core */
		error = 0;
	}
	return error;
}

static int hugetlbfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
	if (!retval)
		inc_nlink(dir);
	return retval;
}

static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
{
	return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);
}

static int hugetlbfs_symlink(struct inode *dir,
			struct dentry *dentry, const char *symname)
{
	struct inode *inode;
	int error = -ENOSPC;

	inode = hugetlbfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
	if (inode) {
		int l = strlen(symname)+1;
		error = page_symlink(inode, symname, l);
		if (!error) {
			d_instantiate(dentry, inode);
			dget(dentry);
		} else
			iput(inode);
	}
	dir->i_ctime = dir->i_mtime = CURRENT_TIME;

	return error;
}

/*
 * mark the head page dirty
 */
static int hugetlbfs_set_page_dirty(struct page *page)
{
	struct page *head = compound_head(page);

	SetPageDirty(head);
	return 0;
}

static int hugetlbfs_migrate_page(struct address_space *mapping,
				struct page *newpage, struct page *page,
				enum migrate_mode mode)
{
	int rc;

	rc = migrate_huge_page_move_mapping(mapping, newpage, page);
	if (rc != MIGRATEPAGE_SUCCESS)
		return rc;
	migrate_page_copy(newpage, page);

	return MIGRATEPAGE_SUCCESS;
}

static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);
	struct hstate *h = hstate_inode(d_inode(dentry));

	buf->f_type = HUGETLBFS_MAGIC;
	buf->f_bsize = huge_page_size(h);
	if (sbinfo) {
		spin_lock(&sbinfo->stat_lock);
		/* If no limits set, just report 0 for max/free/used
		 * blocks, like simple_statfs() */
		if (sbinfo->spool) {
			long free_pages;

			spin_lock(&sbinfo->spool->lock);
			buf->f_blocks = sbinfo->spool->max_hpages;
			free_pages = sbinfo->spool->max_hpages
				- sbinfo->spool->used_hpages;
			buf->f_bavail = buf->f_bfree = free_pages;
			spin_unlock(&sbinfo->spool->lock);
			buf->f_files = sbinfo->max_inodes;
			buf->f_ffree = sbinfo->free_inodes;
		}
		spin_unlock(&sbinfo->stat_lock);
	}
	buf->f_namelen = NAME_MAX;
	return 0;
}

static void hugetlbfs_put_super(struct super_block *sb)
{
	struct hugetlbfs_sb_info *sbi = HUGETLBFS_SB(sb);

	if (sbi) {
		sb->s_fs_info = NULL;

		if (sbi->spool)
			hugepage_put_subpool(sbi->spool);

		kfree(sbi);
	}
}

static inline int hugetlbfs_dec_free_inodes(struct hugetlbfs_sb_info *sbinfo)
{
	if (sbinfo->free_inodes >= 0) {
		spin_lock(&sbinfo->stat_lock);
		if (unlikely(!sbinfo->free_inodes)) {
			spin_unlock(&sbinfo->stat_lock);
			return 0;
		}
		sbinfo->free_inodes--;
		spin_unlock(&sbinfo->stat_lock);
	}

	return 1;
}

static void hugetlbfs_inc_free_inodes(struct hugetlbfs_sb_info *sbinfo)
{
	if (sbinfo->free_inodes >= 0) {
		spin_lock(&sbinfo->stat_lock);
		sbinfo->free_inodes++;
		spin_unlock(&sbinfo->stat_lock);
	}
}


static struct kmem_cache *hugetlbfs_inode_cachep;

static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
{
	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(sb);
	struct hugetlbfs_inode_info *p;

	if (unlikely(!hugetlbfs_dec_free_inodes(sbinfo)))
		return NULL;
	p = kmem_cache_alloc(hugetlbfs_inode_cachep, GFP_KERNEL);
	if (unlikely(!p)) {
		hugetlbfs_inc_free_inodes(sbinfo);
		return NULL;
	}
	return &p->vfs_inode;
}

static void hugetlbfs_i_callback(struct rcu_head *head)
{
	struct inode *inode = container_of(head, struct inode, i_rcu);
	kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
}

static void hugetlbfs_destroy_inode(struct inode *inode)
{
	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
}

static const struct address_space_operations hugetlbfs_aops = {
	.write_begin	= hugetlbfs_write_begin,
	.write_end	= hugetlbfs_write_end,
	.set_page_dirty	= hugetlbfs_set_page_dirty,
	.migratepage    = hugetlbfs_migrate_page,
};


static void init_once(void *foo)
{
	struct hugetlbfs_inode_info *ei = (struct hugetlbfs_inode_info *)foo;

	inode_init_once(&ei->vfs_inode);
}

const struct file_operations hugetlbfs_file_operations = {
	.read_iter		= hugetlbfs_read_iter,
	.mmap			= hugetlbfs_file_mmap,
	.fsync			= noop_fsync,
	.get_unmapped_area	= hugetlb_get_unmapped_area,
	.llseek			= default_llseek,
	.fallocate		= hugetlbfs_fallocate,
};

static const struct inode_operations hugetlbfs_dir_inode_operations = {
	.create		= hugetlbfs_create,
	.lookup		= simple_lookup,
	.link		= simple_link,
	.unlink		= simple_unlink,
	.symlink	= hugetlbfs_symlink,
	.mkdir		= hugetlbfs_mkdir,
	.rmdir		= simple_rmdir,
	.mknod		= hugetlbfs_mknod,
	.rename		= simple_rename,
	.setattr	= hugetlbfs_setattr,
};

static const struct inode_operations hugetlbfs_inode_operations = {
	.setattr	= hugetlbfs_setattr,
};

static const struct super_operations hugetlbfs_ops = {
	.alloc_inode    = hugetlbfs_alloc_inode,
	.destroy_inode  = hugetlbfs_destroy_inode,
	.evict_inode	= hugetlbfs_evict_inode,
	.statfs		= hugetlbfs_statfs,
	.put_super	= hugetlbfs_put_super,
	.show_options	= generic_show_options,
};

enum { NO_SIZE, SIZE_STD, SIZE_PERCENT };

/*
 * Convert size option passed from command line to number of huge pages
 * in the pool specified by hstate.  Size option could be in bytes
 * (val_type == SIZE_STD) or percentage of the pool (val_type == SIZE_PERCENT).
 */
static long long
hugetlbfs_size_to_hpages(struct hstate *h, unsigned long long size_opt,
								int val_type)
{
	if (val_type == NO_SIZE)
		return -1;

	if (val_type == SIZE_PERCENT) {
		size_opt <<= huge_page_shift(h);
		size_opt *= h->max_huge_pages;
		do_div(size_opt, 100);
	}

	size_opt >>= huge_page_shift(h);
	return size_opt;
}

static int
hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
{
	char *p, *rest;
	substring_t args[MAX_OPT_ARGS];
	int option;
	unsigned long long max_size_opt = 0, min_size_opt = 0;
	int max_val_type = NO_SIZE, min_val_type = NO_SIZE;

	if (!options)
		return 0;

	while ((p = strsep(&options, ",")) != NULL) {
		int token;
		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_uid:
			if (match_int(&args[0], &option))
 				goto bad_val;
			pconfig->uid = make_kuid(current_user_ns(), option);
			if (!uid_valid(pconfig->uid))
				goto bad_val;
			break;

		case Opt_gid:
			if (match_int(&args[0], &option))
 				goto bad_val;
			pconfig->gid = make_kgid(current_user_ns(), option);
			if (!gid_valid(pconfig->gid))
				goto bad_val;
			break;

		case Opt_mode:
			if (match_octal(&args[0], &option))
 				goto bad_val;
			pconfig->mode = option & 01777U;
			break;

		case Opt_size: {
			/* memparse() will accept a K/M/G without a digit */
			if (!isdigit(*args[0].from))
				goto bad_val;
			max_size_opt = memparse(args[0].from, &rest);
			max_val_type = SIZE_STD;
			if (*rest == '%')
				max_val_type = SIZE_PERCENT;
			break;
		}

		case Opt_nr_inodes:
			/* memparse() will accept a K/M/G without a digit */
			if (!isdigit(*args[0].from))
				goto bad_val;
			pconfig->nr_inodes = memparse(args[0].from, &rest);
			break;

		case Opt_pagesize: {
			unsigned long ps;
			ps = memparse(args[0].from, &rest);
			pconfig->hstate = size_to_hstate(ps);
			if (!pconfig->hstate) {
				pr_err("Unsupported page size %lu MB\n",
					ps >> 20);
				return -EINVAL;
			}
			break;
		}

		case Opt_min_size: {
			/* memparse() will accept a K/M/G without a digit */
			if (!isdigit(*args[0].from))
				goto bad_val;
			min_size_opt = memparse(args[0].from, &rest);
			min_val_type = SIZE_STD;
			if (*rest == '%')
				min_val_type = SIZE_PERCENT;
			break;
		}

		default:
			pr_err("Bad mount option: \"%s\"\n", p);
			return -EINVAL;
			break;
		}
	}

	/*
	 * Use huge page pool size (in hstate) to convert the size
	 * options to number of huge pages.  If NO_SIZE, -1 is returned.
	 */
	pconfig->max_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
						max_size_opt, max_val_type);
	pconfig->min_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
						min_size_opt, min_val_type);

	/*
	 * If max_size was specified, then min_size must be smaller
	 */
	if (max_val_type > NO_SIZE &&
	    pconfig->min_hpages > pconfig->max_hpages) {
		pr_err("minimum size can not be greater than maximum size\n");
		return -EINVAL;
	}

	return 0;

bad_val:
	pr_err("Bad value '%s' for mount option '%s'\n", args[0].from, p);
 	return -EINVAL;
}

static int
hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
{
	int ret;
	struct hugetlbfs_config config;
	struct hugetlbfs_sb_info *sbinfo;

	save_mount_options(sb, data);

	config.max_hpages = -1; /* No limit on size by default */
	config.nr_inodes = -1; /* No limit on number of inodes by default */
	config.uid = current_fsuid();
	config.gid = current_fsgid();
	config.mode = 0755;
	config.hstate = &default_hstate;
	config.min_hpages = -1; /* No default minimum size */
	ret = hugetlbfs_parse_options(data, &config);
	if (ret)
		return ret;

	sbinfo = kmalloc(sizeof(struct hugetlbfs_sb_info), GFP_KERNEL);
	if (!sbinfo)
		return -ENOMEM;
	sb->s_fs_info = sbinfo;
	sbinfo->hstate = config.hstate;
	spin_lock_init(&sbinfo->stat_lock);
	sbinfo->max_inodes = config.nr_inodes;
	sbinfo->free_inodes = config.nr_inodes;
	sbinfo->spool = NULL;
	/*
	 * Allocate and initialize subpool if maximum or minimum size is
	 * specified.  Any needed reservations (for minimim size) are taken
	 * taken when the subpool is created.
	 */
	if (config.max_hpages != -1 || config.min_hpages != -1) {
		sbinfo->spool = hugepage_new_subpool(config.hstate,
							config.max_hpages,
							config.min_hpages);
		if (!sbinfo->spool)
			goto out_free;
	}
	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_blocksize = huge_page_size(config.hstate);
	sb->s_blocksize_bits = huge_page_shift(config.hstate);
	sb->s_magic = HUGETLBFS_MAGIC;
	sb->s_op = &hugetlbfs_ops;
	sb->s_time_gran = 1;
	sb->s_root = d_make_root(hugetlbfs_get_root(sb, &config));
	if (!sb->s_root)
		goto out_free;
	return 0;
out_free:
	kfree(sbinfo->spool);
	kfree(sbinfo);
	return -ENOMEM;
}

static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data)
{
	return mount_nodev(fs_type, flags, data, hugetlbfs_fill_super);
}

static struct file_system_type hugetlbfs_fs_type = {
	.name		= "hugetlbfs",
	.mount		= hugetlbfs_mount,
	.kill_sb	= kill_litter_super,
};

static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];

static int can_do_hugetlb_shm(void)
{
	kgid_t shm_group;
	shm_group = make_kgid(&init_user_ns, sysctl_hugetlb_shm_group);
	return capable(CAP_IPC_LOCK) || in_group_p(shm_group);
}

static int get_hstate_idx(int page_size_log)
{
	struct hstate *h = hstate_sizelog(page_size_log);

	if (!h)
		return -1;
	return h - hstates;
}

static const struct dentry_operations anon_ops = {
	.d_dname = simple_dname
};

/*
 * Note that size should be aligned to proper hugepage size in caller side,
 * otherwise hugetlb_reserve_pages reserves one less hugepages than intended.
 */
struct file *hugetlb_file_setup(const char *name, size_t size,
				vm_flags_t acctflag, struct user_struct **user,
				int creat_flags, int page_size_log)
{
	struct file *file = ERR_PTR(-ENOMEM);
	struct inode *inode;
	struct path path;
	struct super_block *sb;
	struct qstr quick_string;
	int hstate_idx;

	hstate_idx = get_hstate_idx(page_size_log);
	if (hstate_idx < 0)
		return ERR_PTR(-ENODEV);

	*user = NULL;
	if (!hugetlbfs_vfsmount[hstate_idx])
		return ERR_PTR(-ENOENT);

	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
		*user = current_user();
		if (user_shm_lock(size, *user)) {
			task_lock(current);
			pr_warn_once("%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
				current->comm, current->pid);
			task_unlock(current);
		} else {
			*user = NULL;
			return ERR_PTR(-EPERM);
		}
	}

	sb = hugetlbfs_vfsmount[hstate_idx]->mnt_sb;
	quick_string.name = name;
	quick_string.len = strlen(quick_string.name);
	quick_string.hash = 0;
	path.dentry = d_alloc_pseudo(sb, &quick_string);
	if (!path.dentry)
		goto out_shm_unlock;

	d_set_d_op(path.dentry, &anon_ops);
	path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);
	file = ERR_PTR(-ENOSPC);
	inode = hugetlbfs_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0);
	if (!inode)
		goto out_dentry;
	if (creat_flags == HUGETLB_SHMFS_INODE)
		inode->i_flags |= S_PRIVATE;

	file = ERR_PTR(-ENOMEM);
	if (hugetlb_reserve_pages(inode, 0,
			size >> huge_page_shift(hstate_inode(inode)), NULL,
			acctflag))
		goto out_inode;

	d_instantiate(path.dentry, inode);
	inode->i_size = size;
	clear_nlink(inode);

	file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
			&hugetlbfs_file_operations);
	if (IS_ERR(file))
		goto out_dentry; /* inode is already attached */

	return file;

out_inode:
	iput(inode);
out_dentry:
	path_put(&path);
out_shm_unlock:
	if (*user) {
		user_shm_unlock(size, *user);
		*user = NULL;
	}
	return file;
}

static int __init init_hugetlbfs_fs(void)
{
	struct hstate *h;
	int error;
	int i;

	if (!hugepages_supported()) {
		pr_info("disabling because there are no supported hugepage sizes\n");
		return -ENOTSUPP;
	}

	error = -ENOMEM;
	hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",
					sizeof(struct hugetlbfs_inode_info),
					0, SLAB_ACCOUNT, init_once);
	if (hugetlbfs_inode_cachep == NULL)
		goto out2;

	error = register_filesystem(&hugetlbfs_fs_type);
	if (error)
		goto out;

	i = 0;
	for_each_hstate(h) {
		char buf[50];
		unsigned ps_kb = 1U << (h->order + PAGE_SHIFT - 10);

		snprintf(buf, sizeof(buf), "pagesize=%uK", ps_kb);
		hugetlbfs_vfsmount[i] = kern_mount_data(&hugetlbfs_fs_type,
							buf);

		if (IS_ERR(hugetlbfs_vfsmount[i])) {
			pr_err("Cannot mount internal hugetlbfs for "
				"page size %uK", ps_kb);
			error = PTR_ERR(hugetlbfs_vfsmount[i]);
			hugetlbfs_vfsmount[i] = NULL;
		}
		i++;
	}
	/* Non default hstates are optional */
	if (!IS_ERR_OR_NULL(hugetlbfs_vfsmount[default_hstate_idx]))
		return 0;

 out:
	kmem_cache_destroy(hugetlbfs_inode_cachep);
 out2:
	return error;
}
fs_initcall(init_hugetlbfs_fs)