aboutsummaryrefslogtreecommitdiff
path: root/fs/hostfs/hostfs_kern.c
blob: e965eb11d76fa4e92034ceb0bcba4e69f1f0271d (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
/*
 * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
 * Licensed under the GPL
 *
 * Ported the filesystem routines to 2.5.
 * 2003-02-10 Petr Baudis <pasky@ucw.cz>
 */

#include <linux/stddef.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include <linux/list.h>
#include <linux/statfs.h>
#include <linux/kdev_t.h>
#include <asm/uaccess.h>
#include "hostfs.h"
#include "kern_util.h"
#include "kern.h"
#include "user_util.h"
#include "init.h"

struct hostfs_inode_info {
	char *host_filename;
	int fd;
	int mode;
	struct inode vfs_inode;
};

static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
{
	return(list_entry(inode, struct hostfs_inode_info, vfs_inode));
}

#define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)

int hostfs_d_delete(struct dentry *dentry)
{
	return(1);
}

struct dentry_operations hostfs_dentry_ops = {
	.d_delete		= hostfs_d_delete,
};

/* Changed in hostfs_args before the kernel starts running */
static char *root_ino = "/";
static int append = 0;

#define HOSTFS_SUPER_MAGIC 0x00c0ffee

static const struct inode_operations hostfs_iops;
static const struct inode_operations hostfs_dir_iops;
static const struct address_space_operations hostfs_link_aops;

#ifndef MODULE
static int __init hostfs_args(char *options, int *add)
{
	char *ptr;

	ptr = strchr(options, ',');
	if(ptr != NULL)
		*ptr++ = '\0';
	if(*options != '\0')
		root_ino = options;

	options = ptr;
	while(options){
		ptr = strchr(options, ',');
		if(ptr != NULL)
			*ptr++ = '\0';
		if(*options != '\0'){
			if(!strcmp(options, "append"))
				append = 1;
			else printf("hostfs_args - unsupported option - %s\n",
				    options);
		}
		options = ptr;
	}
	return(0);
}

__uml_setup("hostfs=", hostfs_args,
"hostfs=<root dir>,<flags>,...\n"
"    This is used to set hostfs parameters.  The root directory argument\n"
"    is used to confine all hostfs mounts to within the specified directory\n"
"    tree on the host.  If this isn't specified, then a user inside UML can\n"
"    mount anything on the host that's accessible to the user that's running\n"
"    it.\n"
"    The only flag currently supported is 'append', which specifies that all\n"
"    files opened by hostfs will be opened in append mode.\n\n"
);
#endif

static char *dentry_name(struct dentry *dentry, int extra)
{
	struct dentry *parent;
	char *root, *name;
	int len;

	len = 0;
	parent = dentry;
	while(parent->d_parent != parent){
		len += parent->d_name.len + 1;
		parent = parent->d_parent;
	}

	root = HOSTFS_I(parent->d_inode)->host_filename;
	len += strlen(root);
	name = kmalloc(len + extra + 1, GFP_KERNEL);
	if(name == NULL) return(NULL);

	name[len] = '\0';
	parent = dentry;
	while(parent->d_parent != parent){
		len -= parent->d_name.len + 1;
		name[len] = '/';
		strncpy(&name[len + 1], parent->d_name.name,
			parent->d_name.len);
		parent = parent->d_parent;
	}
	strncpy(name, root, strlen(root));
	return(name);
}

static char *inode_name(struct inode *ino, int extra)
{
	struct dentry *dentry;

	dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
	return(dentry_name(dentry, extra));
}

static int read_name(struct inode *ino, char *name)
{
	/* The non-int inode fields are copied into ints by stat_file and
	 * then copied into the inode because passing the actual pointers
	 * in and having them treated as int * breaks on big-endian machines
	 */
	int err;
	int i_mode, i_nlink, i_blksize;
	unsigned long long i_size;
	unsigned long long i_ino;
	unsigned long long i_blocks;

	err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
			&ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
			&ino->i_ctime, &i_blksize, &i_blocks);
	if(err)
		return(err);

	ino->i_ino = i_ino;
	ino->i_mode = i_mode;
	ino->i_nlink = i_nlink;
	ino->i_size = i_size;
	ino->i_blocks = i_blocks;
	return(0);
}

static char *follow_link(char *link)
{
	int len, n;
	char *name, *resolved, *end;

	len = 64;
	while(1){
		n = -ENOMEM;
		name = kmalloc(len, GFP_KERNEL);
		if(name == NULL)
			goto out;

		n = do_readlink(link, name, len);
		if(n < len)
			break;
		len *= 2;
		kfree(name);
	}
	if(n < 0)
		goto out_free;

	if(*name == '/')
		return(name);

	end = strrchr(link, '/');
	if(end == NULL)
		return(name);

	*(end + 1) = '\0';
	len = strlen(link) + strlen(name) + 1;

	resolved = kmalloc(len, GFP_KERNEL);
	if(resolved == NULL){
		n = -ENOMEM;
		goto out_free;
	}

	sprintf(resolved, "%s%s", link, name);
	kfree(name);
	kfree(link);
	return(resolved);

 out_free:
	kfree(name);
 out:
	return(ERR_PTR(n));
}

static int read_inode(struct inode *ino)
{
	char *name;
	int err = 0;

	/* Unfortunately, we are called from iget() when we don't have a dentry
	 * allocated yet.
	 */
	if(list_empty(&ino->i_dentry))
		goto out;

	err = -ENOMEM;
	name = inode_name(ino, 0);
	if(name == NULL)
		goto out;

	if(file_type(name, NULL, NULL) == OS_TYPE_SYMLINK){
		name = follow_link(name);
		if(IS_ERR(name)){
			err = PTR_ERR(name);
			goto out;
		}
	}

	err = read_name(ino, name);
	kfree(name);
 out:
	return(err);
}

int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
{
	/* do_statfs uses struct statfs64 internally, but the linux kernel
	 * struct statfs still has 32-bit versions for most of these fields,
	 * so we convert them here
	 */
	int err;
	long long f_blocks;
	long long f_bfree;
	long long f_bavail;
	long long f_files;
	long long f_ffree;

	err = do_statfs(HOSTFS_I(dentry->d_sb->s_root->d_inode)->host_filename,
			&sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
			&f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
			&sf->f_namelen, sf->f_spare);
	if(err) return(err);
	sf->f_blocks = f_blocks;
	sf->f_bfree = f_bfree;
	sf->f_bavail = f_bavail;
	sf->f_files = f_files;
	sf->f_ffree = f_ffree;
	sf->f_type = HOSTFS_SUPER_MAGIC;
	return(0);
}

static struct inode *hostfs_alloc_inode(struct super_block *sb)
{
	struct hostfs_inode_info *hi;

	hi = kmalloc(sizeof(*hi), GFP_KERNEL);
	if(hi == NULL)
		return(NULL);

	*hi = ((struct hostfs_inode_info) { .host_filename	= NULL,
					    .fd			= -1,
					    .mode		= 0 });
	inode_init_once(&hi->vfs_inode);
	return(&hi->vfs_inode);
}

static void hostfs_delete_inode(struct inode *inode)
{
	truncate_inode_pages(&inode->i_data, 0);
	if(HOSTFS_I(inode)->fd != -1) {
		close_file(&HOSTFS_I(inode)->fd);
		HOSTFS_I(inode)->fd = -1;
	}
	clear_inode(inode);
}

static void hostfs_destroy_inode(struct inode *inode)
{
	kfree(HOSTFS_I(inode)->host_filename);

	/*XXX: This should not happen, probably. The check is here for
	 * additional safety.*/
	if(HOSTFS_I(inode)->fd != -1) {
		close_file(&HOSTFS_I(inode)->fd);
		printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
	}

	kfree(HOSTFS_I(inode));
}

static void hostfs_read_inode(struct inode *inode)
{
	read_inode(inode);
}

static const struct super_operations hostfs_sbops = {
	.alloc_inode	= hostfs_alloc_inode,
	.drop_inode	= generic_delete_inode,
	.delete_inode   = hostfs_delete_inode,
	.destroy_inode	= hostfs_destroy_inode,
	.read_inode	= hostfs_read_inode,
	.statfs		= hostfs_statfs,
};

int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
{
	void *dir;
	char *name;
	unsigned long long next, ino;
	int error, len;

	name = dentry_name(file->f_path.dentry, 0);
	if(name == NULL) return(-ENOMEM);
	dir = open_dir(name, &error);
	kfree(name);
	if(dir == NULL) return(-error);
	next = file->f_pos;
	while((name = read_dir(dir, &next, &ino, &len)) != NULL){
		error = (*filldir)(ent, name, len, file->f_pos,
				   ino, DT_UNKNOWN);
		if(error) break;
		file->f_pos = next;
	}
	close_dir(dir);
	return(0);
}

int hostfs_file_open(struct inode *ino, struct file *file)
{
	char *name;
	int mode = 0, r = 0, w = 0, fd;

	mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
	if((mode & HOSTFS_I(ino)->mode) == mode)
		return(0);

	/* The file may already have been opened, but with the wrong access,
	 * so this resets things and reopens the file with the new access.
	 */
	if(HOSTFS_I(ino)->fd != -1){
		close_file(&HOSTFS_I(ino)->fd);
		HOSTFS_I(ino)->fd = -1;
	}

	HOSTFS_I(ino)->mode |= mode;
	if(HOSTFS_I(ino)->mode & FMODE_READ)
		r = 1;
	if(HOSTFS_I(ino)->mode & FMODE_WRITE)
		w = 1;
	if(w)
		r = 1;

	name = dentry_name(file->f_path.dentry, 0);
	if(name == NULL)
		return(-ENOMEM);

	fd = open_file(name, r, w, append);
	kfree(name);
	if(fd < 0) return(fd);
	FILE_HOSTFS_I(file)->fd = fd;

	return(0);
}

int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
	return fsync_file(HOSTFS_I(dentry->d_inode)->fd, datasync);
}

static const struct file_operations hostfs_file_fops = {
	.llseek		= generic_file_llseek,
	.read		= do_sync_read,
	.sendfile	= generic_file_sendfile,
	.aio_read	= generic_file_aio_read,
	.aio_write	= generic_file_aio_write,
	.write		= do_sync_write,
	.mmap		= generic_file_mmap,
	.open		= hostfs_file_open,
	.release	= NULL,
	.fsync		= hostfs_fsync,
};

static const struct file_operations hostfs_dir_fops = {
	.llseek		= generic_file_llseek,
	.readdir	= hostfs_readdir,
	.read		= generic_read_dir,
};

int hostfs_writepage(struct page *page, struct writeback_control *wbc)
{
	struct address_space *mapping = page->mapping;
	struct inode *inode = mapping->host;
	char *buffer;
	unsigned long long base;
	int count = PAGE_CACHE_SIZE;
	int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
	int err;

	if (page->index >= end_index)
		count = inode->i_size & (PAGE_CACHE_SIZE-1);

	buffer = kmap(page);
	base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;

	err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
	if(err != count){
		ClearPageUptodate(page);
		goto out;
	}

	if (base > inode->i_size)
		inode->i_size = base;

	if (PageError(page))
		ClearPageError(page);
	err = 0;

 out:
	kunmap(page);

	unlock_page(page);
	return err;
}

int hostfs_readpage(struct file *file, struct page *page)
{
	char *buffer;
	long long start;
	int err = 0;

	start = (long long) page->index << PAGE_CACHE_SHIFT;
	buffer = kmap(page);
	err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
			PAGE_CACHE_SIZE);
	if(err < 0) goto out;

	memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);

	flush_dcache_page(page);
	SetPageUptodate(page);
	if (PageError(page)) ClearPageError(page);
	err = 0;
 out:
	kunmap(page);
	unlock_page(page);
	return(err);
}

int hostfs_prepare_write(struct file *file, struct page *page,
			 unsigned int from, unsigned int to)
{
	char *buffer;
	long long start, tmp;
	int err;

	start = (long long) page->index << PAGE_CACHE_SHIFT;
	buffer = kmap(page);
	if(from != 0){
		tmp = start;
		err = read_file(FILE_HOSTFS_I(file)->fd, &tmp, buffer,
				from);
		if(err < 0) goto out;
	}
	if(to != PAGE_CACHE_SIZE){
		start += to;
		err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer + to,
				PAGE_CACHE_SIZE - to);
		if(err < 0) goto out;
	}
	err = 0;
 out:
	kunmap(page);
	return(err);
}

int hostfs_commit_write(struct file *file, struct page *page, unsigned from,
		 unsigned to)
{
	struct address_space *mapping = page->mapping;
	struct inode *inode = mapping->host;
	char *buffer;
	long long start;
	int err = 0;

	start = (((long long) page->index) << PAGE_CACHE_SHIFT) + from;
	buffer = kmap(page);
	err = write_file(FILE_HOSTFS_I(file)->fd, &start, buffer + from,
			 to - from);
	if(err > 0) err = 0;

	/* Actually, if !err, write_file has added to-from to start, so, despite
	 * the appearance, we are comparing i_size against the _last_ written
	 * location, as we should. */

	if(!err && (start > inode->i_size))
		inode->i_size = start;

	kunmap(page);
	return(err);
}

static const struct address_space_operations hostfs_aops = {
	.writepage 	= hostfs_writepage,
	.readpage	= hostfs_readpage,
	.set_page_dirty = __set_page_dirty_nobuffers,
	.prepare_write	= hostfs_prepare_write,
	.commit_write	= hostfs_commit_write
};

static int init_inode(struct inode *inode, struct dentry *dentry)
{
	char *name;
	int type, err = -ENOMEM;
	int maj, min;
	dev_t rdev = 0;

	if(dentry){
		name = dentry_name(dentry, 0);
		if(name == NULL)
			goto out;
		type = file_type(name, &maj, &min);
		/*Reencode maj and min with the kernel encoding.*/
		rdev = MKDEV(maj, min);
		kfree(name);
	}
	else type = OS_TYPE_DIR;

	err = 0;
	if(type == OS_TYPE_SYMLINK)
		inode->i_op = &page_symlink_inode_operations;
	else if(type == OS_TYPE_DIR)
		inode->i_op = &hostfs_dir_iops;
	else inode->i_op = &hostfs_iops;

	if(type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
	else inode->i_fop = &hostfs_file_fops;

	if(type == OS_TYPE_SYMLINK)
		inode->i_mapping->a_ops = &hostfs_link_aops;
	else inode->i_mapping->a_ops = &hostfs_aops;

	switch (type) {
	case OS_TYPE_CHARDEV:
		init_special_inode(inode, S_IFCHR, rdev);
		break;
	case OS_TYPE_BLOCKDEV:
		init_special_inode(inode, S_IFBLK, rdev);
		break;
	case OS_TYPE_FIFO:
		init_special_inode(inode, S_IFIFO, 0);
		break;
	case OS_TYPE_SOCK:
		init_special_inode(inode, S_IFSOCK, 0);
		break;
	}
 out:
	return(err);
}

int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
                 struct nameidata *nd)
{
	struct inode *inode;
	char *name;
	int error, fd;

	error = -ENOMEM;
	inode = iget(dir->i_sb, 0);
	if(inode == NULL) goto out;

	error = init_inode(inode, dentry);
	if(error)
		goto out_put;

	error = -ENOMEM;
	name = dentry_name(dentry, 0);
	if(name == NULL)
		goto out_put;

	fd = file_create(name,
			 mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
			 mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
			 mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
	if(fd < 0)
		error = fd;
	else error = read_name(inode, name);

	kfree(name);
	if(error)
		goto out_put;

	HOSTFS_I(inode)->fd = fd;
	HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
	d_instantiate(dentry, inode);
	return(0);

 out_put:
	iput(inode);
 out:
	return(error);
}

struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
                            struct nameidata *nd)
{
	struct inode *inode;
	char *name;
	int err;

	err = -ENOMEM;
	inode = iget(ino->i_sb, 0);
	if(inode == NULL)
		goto out;

	err = init_inode(inode, dentry);
	if(err)
		goto out_put;

	err = -ENOMEM;
	name = dentry_name(dentry, 0);
	if(name == NULL)
		goto out_put;

	err = read_name(inode, name);
	kfree(name);
	if(err == -ENOENT){
		iput(inode);
		inode = NULL;
	}
	else if(err)
		goto out_put;

	d_add(dentry, inode);
	dentry->d_op = &hostfs_dentry_ops;
	return(NULL);

 out_put:
	iput(inode);
 out:
	return(ERR_PTR(err));
}

static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
{
        char *file;
	int len;

	file = inode_name(ino, dentry->d_name.len + 1);
	if(file == NULL) return(NULL);
        strcat(file, "/");
	len = strlen(file);
        strncat(file, dentry->d_name.name, dentry->d_name.len);
	file[len + dentry->d_name.len] = '\0';
        return(file);
}

int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
{
        char *from_name, *to_name;
        int err;

        if((from_name = inode_dentry_name(ino, from)) == NULL)
                return(-ENOMEM);
        to_name = dentry_name(to, 0);
	if(to_name == NULL){
		kfree(from_name);
		return(-ENOMEM);
	}
        err = link_file(to_name, from_name);
        kfree(from_name);
        kfree(to_name);
        return(err);
}

int hostfs_unlink(struct inode *ino, struct dentry *dentry)
{
	char *file;
	int err;

	if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
	if(append)
		return(-EPERM);

	err = unlink_file(file);
	kfree(file);
	return(err);
}

int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
{
	char *file;
	int err;

	if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
	err = make_symlink(file, to);
	kfree(file);
	return(err);
}

int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
{
	char *file;
	int err;

	if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
	err = do_mkdir(file, mode);
	kfree(file);
	return(err);
}

int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
{
	char *file;
	int err;

	if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
	err = do_rmdir(file);
	kfree(file);
	return(err);
}

int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
	struct inode *inode;
	char *name;
	int err = -ENOMEM;

	inode = iget(dir->i_sb, 0);
	if(inode == NULL)
		goto out;

	err = init_inode(inode, dentry);
	if(err)
		goto out_put;

	err = -ENOMEM;
	name = dentry_name(dentry, 0);
	if(name == NULL)
		goto out_put;

	init_special_inode(inode, mode, dev);
	err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
	if(err)
		goto out_free;

	err = read_name(inode, name);
	kfree(name);
	if(err)
		goto out_put;

	d_instantiate(dentry, inode);
	return(0);

 out_free:
	kfree(name);
 out_put:
	iput(inode);
 out:
	return(err);
}

int hostfs_rename(struct inode *from_ino, struct dentry *from,
		  struct inode *to_ino, struct dentry *to)
{
	char *from_name, *to_name;
	int err;

	if((from_name = inode_dentry_name(from_ino, from)) == NULL)
		return(-ENOMEM);
	if((to_name = inode_dentry_name(to_ino, to)) == NULL){
		kfree(from_name);
		return(-ENOMEM);
	}
	err = rename_file(from_name, to_name);
	kfree(from_name);
	kfree(to_name);
	return(err);
}

int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
{
	char *name;
	int r = 0, w = 0, x = 0, err;

	if (desired & MAY_READ) r = 1;
	if (desired & MAY_WRITE) w = 1;
	if (desired & MAY_EXEC) x = 1;
	name = inode_name(ino, 0);
	if (name == NULL) return(-ENOMEM);

	if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
			S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
		err = 0;
	else
		err = access_file(name, r, w, x);
	kfree(name);
	if(!err)
		err = generic_permission(ino, desired, NULL);
	return err;
}

int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
{
	struct hostfs_iattr attrs;
	char *name;
	int err;

	err = inode_change_ok(dentry->d_inode, attr);
	if (err)
		return err;

	if(append)
		attr->ia_valid &= ~ATTR_SIZE;

	attrs.ia_valid = 0;
	if(attr->ia_valid & ATTR_MODE){
		attrs.ia_valid |= HOSTFS_ATTR_MODE;
		attrs.ia_mode = attr->ia_mode;
	}
	if(attr->ia_valid & ATTR_UID){
		attrs.ia_valid |= HOSTFS_ATTR_UID;
		attrs.ia_uid = attr->ia_uid;
	}
	if(attr->ia_valid & ATTR_GID){
		attrs.ia_valid |= HOSTFS_ATTR_GID;
		attrs.ia_gid = attr->ia_gid;
	}
	if(attr->ia_valid & ATTR_SIZE){
		attrs.ia_valid |= HOSTFS_ATTR_SIZE;
		attrs.ia_size = attr->ia_size;
	}
	if(attr->ia_valid & ATTR_ATIME){
		attrs.ia_valid |= HOSTFS_ATTR_ATIME;
		attrs.ia_atime = attr->ia_atime;
	}
	if(attr->ia_valid & ATTR_MTIME){
		attrs.ia_valid |= HOSTFS_ATTR_MTIME;
		attrs.ia_mtime = attr->ia_mtime;
	}
	if(attr->ia_valid & ATTR_CTIME){
		attrs.ia_valid |= HOSTFS_ATTR_CTIME;
		attrs.ia_ctime = attr->ia_ctime;
	}
	if(attr->ia_valid & ATTR_ATIME_SET){
		attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
	}
	if(attr->ia_valid & ATTR_MTIME_SET){
		attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
	}
	name = dentry_name(dentry, 0);
	if(name == NULL) return(-ENOMEM);
	err = set_attr(name, &attrs);
	kfree(name);
	if(err)
		return(err);

	return(inode_setattr(dentry->d_inode, attr));
}

int hostfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
	   struct kstat *stat)
{
	generic_fillattr(dentry->d_inode, stat);
	return(0);
}

static const struct inode_operations hostfs_iops = {
	.create		= hostfs_create,
	.link		= hostfs_link,
	.unlink		= hostfs_unlink,
	.symlink	= hostfs_symlink,
	.mkdir		= hostfs_mkdir,
	.rmdir		= hostfs_rmdir,
	.mknod		= hostfs_mknod,
	.rename		= hostfs_rename,
	.permission	= hostfs_permission,
	.setattr	= hostfs_setattr,
	.getattr	= hostfs_getattr,
};

static const struct inode_operations hostfs_dir_iops = {
	.create		= hostfs_create,
	.lookup		= hostfs_lookup,
	.link		= hostfs_link,
	.unlink		= hostfs_unlink,
	.symlink	= hostfs_symlink,
	.mkdir		= hostfs_mkdir,
	.rmdir		= hostfs_rmdir,
	.mknod		= hostfs_mknod,
	.rename		= hostfs_rename,
	.permission	= hostfs_permission,
	.setattr	= hostfs_setattr,
	.getattr	= hostfs_getattr,
};

int hostfs_link_readpage(struct file *file, struct page *page)
{
	char *buffer, *name;
	int err;

	buffer = kmap(page);
	name = inode_name(page->mapping->host, 0);
	if(name == NULL) return(-ENOMEM);
	err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
	kfree(name);
	if(err == PAGE_CACHE_SIZE)
		err = -E2BIG;
	else if(err > 0){
		flush_dcache_page(page);
		SetPageUptodate(page);
		if (PageError(page)) ClearPageError(page);
		err = 0;
	}
	kunmap(page);
	unlock_page(page);
	return(err);
}

static const struct address_space_operations hostfs_link_aops = {
	.readpage	= hostfs_link_readpage,
};

static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
{
	struct inode *root_inode;
	char *name, *data = d;
	int err;

	sb->s_blocksize = 1024;
	sb->s_blocksize_bits = 10;
	sb->s_magic = HOSTFS_SUPER_MAGIC;
	sb->s_op = &hostfs_sbops;

	if((data == NULL) || (*data == '\0'))
		data = root_ino;

	err = -ENOMEM;
	name = kmalloc(strlen(data) + 1, GFP_KERNEL);
	if(name == NULL)
		goto out;

	strcpy(name, data);

	root_inode = iget(sb, 0);
	if(root_inode == NULL)
		goto out_free;

	err = init_inode(root_inode, NULL);
	if(err)
		goto out_put;

	HOSTFS_I(root_inode)->host_filename = name;

	err = -ENOMEM;
	sb->s_root = d_alloc_root(root_inode);
	if(sb->s_root == NULL)
		goto out_put;

	err = read_inode(root_inode);
	if(err){
                /* No iput in this case because the dput does that for us */
                dput(sb->s_root);
                sb->s_root = NULL;
		goto out_free;
        }

	return(0);

 out_put:
        iput(root_inode);
 out_free:
	kfree(name);
 out:
	return(err);
}

static int hostfs_read_sb(struct file_system_type *type,
			  int flags, const char *dev_name,
			  void *data, struct vfsmount *mnt)
{
	return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
}

static struct file_system_type hostfs_type = {
	.owner 		= THIS_MODULE,
	.name 		= "hostfs",
	.get_sb 	= hostfs_read_sb,
	.kill_sb	= kill_anon_super,
	.fs_flags 	= 0,
};

static int __init init_hostfs(void)
{
	return(register_filesystem(&hostfs_type));
}

static void __exit exit_hostfs(void)
{
	unregister_filesystem(&hostfs_type);
}

module_init(init_hostfs)
module_exit(exit_hostfs)
MODULE_LICENSE("GPL");

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */