summaryrefslogtreecommitdiffstats
path: root/fs/autofs4/root.c
blob: 6e250030a690bd0a9697d23f80a52d21fbe31508 (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
/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/root.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
 *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/param.h>
#include <linux/time.h>
#include "autofs_i.h"

static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
static int autofs4_dir_unlink(struct inode *,struct dentry *);
static int autofs4_dir_rmdir(struct inode *,struct dentry *);
static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
static int autofs4_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
static int autofs4_dir_open(struct inode *inode, struct file *file);
static int autofs4_dir_close(struct inode *inode, struct file *file);
static int autofs4_dir_readdir(struct file * filp, void * dirent, filldir_t filldir);
static int autofs4_root_readdir(struct file * filp, void * dirent, filldir_t filldir);
static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
static void *autofs4_follow_link(struct dentry *, struct nameidata *);

const struct file_operations autofs4_root_operations = {
	.open		= dcache_dir_open,
	.release	= dcache_dir_close,
	.read		= generic_read_dir,
	.readdir	= autofs4_root_readdir,
	.ioctl		= autofs4_root_ioctl,
};

const struct file_operations autofs4_dir_operations = {
	.open		= autofs4_dir_open,
	.release	= autofs4_dir_close,
	.read		= generic_read_dir,
	.readdir	= autofs4_dir_readdir,
};

const struct inode_operations autofs4_indirect_root_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.symlink	= autofs4_dir_symlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
};

const struct inode_operations autofs4_direct_root_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
	.follow_link	= autofs4_follow_link,
};

const struct inode_operations autofs4_dir_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.symlink	= autofs4_dir_symlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
};

static int autofs4_root_readdir(struct file *file, void *dirent,
				filldir_t filldir)
{
	struct autofs_sb_info *sbi = autofs4_sbi(file->f_path.dentry->d_sb);
	int oz_mode = autofs4_oz_mode(sbi);

	DPRINTK("called, filp->f_pos = %lld", file->f_pos);

	/*
	 * Don't set reghost flag if:
	 * 1) f_pos is larger than zero -- we've already been here.
	 * 2) we haven't even enabled reghosting in the 1st place.
	 * 3) this is the daemon doing a readdir
	 */
	if (oz_mode && file->f_pos == 0 && sbi->reghost_enabled)
		sbi->needs_reghost = 1;

	DPRINTK("needs_reghost = %d", sbi->needs_reghost);

	return dcache_readdir(file, dirent, filldir);
}

static int autofs4_dir_open(struct inode *inode, struct file *file)
{
	struct dentry *dentry = file->f_path.dentry;
	struct vfsmount *mnt = file->f_path.mnt;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor;
	int status;

	status = dcache_dir_open(inode, file);
	if (status)
		goto out;

	cursor = file->private_data;
	cursor->d_fsdata = NULL;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		dcache_dir_close(inode, file);
		status = -EBUSY;
		goto out;
	}

	status = -ENOENT;
	if (!d_mountpoint(dentry) && dentry->d_op && dentry->d_op->d_revalidate) {
		struct nameidata nd;
		int empty, ret;

		/* In case there are stale directory dentrys from a failed mount */
		spin_lock(&dcache_lock);
		empty = list_empty(&dentry->d_subdirs);
		spin_unlock(&dcache_lock);

		if (!empty)
			d_invalidate(dentry);

		nd.flags = LOOKUP_DIRECTORY;
		ret = (dentry->d_op->d_revalidate)(dentry, &nd);

		if (ret <= 0) {
			if (ret < 0)
				status = ret;
			dcache_dir_close(inode, file);
			goto out;
		}
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = NULL;
		struct vfsmount *fp_mnt = mntget(mnt);
		struct dentry *fp_dentry = dget(dentry);

		if (!autofs4_follow_mount(&fp_mnt, &fp_dentry)) {
			dput(fp_dentry);
			mntput(fp_mnt);
			dcache_dir_close(inode, file);
			goto out;
		}

		fp = dentry_open(fp_dentry, fp_mnt, file->f_flags);
		status = PTR_ERR(fp);
		if (IS_ERR(fp)) {
			dcache_dir_close(inode, file);
			goto out;
		}
		cursor->d_fsdata = fp;
	}
	return 0;
out:
	return status;
}

static int autofs4_dir_close(struct inode *inode, struct file *file)
{
	struct dentry *dentry = file->f_path.dentry;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor = file->private_data;
	int status = 0;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		status = -EBUSY;
		goto out;
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = cursor->d_fsdata;
		if (!fp) {
			status = -ENOENT;
			goto out;
		}
		filp_close(fp, current->files);
	}
out:
	dcache_dir_close(inode, file);
	return status;
}

static int autofs4_dir_readdir(struct file *file, void *dirent, filldir_t filldir)
{
	struct dentry *dentry = file->f_path.dentry;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor = file->private_data;
	int status;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		return -EBUSY;
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = cursor->d_fsdata;

		if (!fp)
			return -ENOENT;

		if (!fp->f_op || !fp->f_op->readdir)
			goto out;

		status = vfs_readdir(fp, filldir, dirent);
		file->f_pos = fp->f_pos;
		if (status)
			autofs4_copy_atime(file, fp);
		return status;
	}
out:
	return dcache_readdir(file, dirent, filldir);
}

static int try_to_fill_dentry(struct dentry *dentry, int flags)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	struct dentry *new;
	int status;

	/* Block on any pending expiry here; invalidate the dentry
           when expiration is done to trigger mount request with a new
           dentry */
	if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
		DPRINTK("waiting for expire %p name=%.*s",
			 dentry, dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_NONE);

		DPRINTK("expire done status=%d", status);

		/*
		 * If the directory still exists the mount request must
		 * continue otherwise it can't be followed at the right
		 * time during the walk.
		 */
		status = d_invalidate(dentry);
		if (status != -EBUSY)
			return -EAGAIN;
	}

	DPRINTK("dentry=%p %.*s ino=%p",
		 dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);

	/*
	 * Wait for a pending mount, triggering one if there
	 * isn't one already
	 */
	if (dentry->d_inode == NULL) {
		DPRINTK("waiting for mount name=%.*s",
			 dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_MOUNT);

		DPRINTK("mount done status=%d", status);

		/* Turn this into a real negative dentry? */
		if (status == -ENOENT) {
			spin_lock(&dentry->d_lock);
			dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
			spin_unlock(&dentry->d_lock);
			return status;
		} else if (status) {
			/* Return a negative dentry, but leave it "pending" */
			return status;
		}
	/* Trigger mount for path component or follow link */
	} else if (flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY) ||
			current->link_count) {
		DPRINTK("waiting for mount name=%.*s",
			dentry->d_name.len, dentry->d_name.name);

		spin_lock(&dentry->d_lock);
		dentry->d_flags |= DCACHE_AUTOFS_PENDING;
		spin_unlock(&dentry->d_lock);
		status = autofs4_wait(sbi, dentry, NFY_MOUNT);

		DPRINTK("mount done status=%d", status);

		if (status) {
			spin_lock(&dentry->d_lock);
			dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
			spin_unlock(&dentry->d_lock);
			return status;
		}
	}

	/* Initialize expiry counter after successful mount */
	if (ino)
		ino->last_used = jiffies;

	spin_lock(&dentry->d_lock);
	dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
	spin_unlock(&dentry->d_lock);

	/*
	 * The dentry that is passed in from lookup may not be the one
	 * we end up using, as mkdir can create a new one.  If this
	 * happens, and another process tries the lookup at the same time,
	 * it will set the PENDING flag on this new dentry, but add itself
	 * to our waitq.  Then, if after the lookup succeeds, the first
	 * process that requested the mount performs another lookup of the
	 * same directory, it will show up as still pending!  So, we need
	 * to redo the lookup here and clear pending on that dentry.
	 */
	if (d_unhashed(dentry)) {
		new = d_lookup(dentry->d_parent, &dentry->d_name);
		if (new) {
			spin_lock(&new->d_lock);
			new->d_flags &= ~DCACHE_AUTOFS_PENDING;
			spin_unlock(&new->d_lock);
			dput(new);
		}
	}

	return 0;
}

/* For autofs direct mounts the follow link triggers the mount */
static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	int oz_mode = autofs4_oz_mode(sbi);
	unsigned int lookup_type;
	int status;

	DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
		dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
		nd->flags);

	/* If it's our master or we shouldn't trigger a mount we're done */
	lookup_type = nd->flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY);
	if (oz_mode || !lookup_type)
		goto done;

	/* If an expire request is pending wait for it. */
	if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
		DPRINTK("waiting for active request %p name=%.*s",
			dentry, dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_NONE);

		DPRINTK("request done status=%d", status);
	}

	/*
	 * If the dentry contains directories then it is an
	 * autofs multi-mount with no root mount offset. So
	 * don't try to mount it again.
	 */
	spin_lock(&dcache_lock);
	if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
		spin_unlock(&dcache_lock);

		status = try_to_fill_dentry(dentry, 0);
		if (status)
			goto out_error;

		/*
		 * The mount succeeded but if there is no root mount
		 * it must be an autofs multi-mount with no root offset
		 * so we don't need to follow the mount.
		 */
		if (d_mountpoint(dentry)) {
			if (!autofs4_follow_mount(&nd->path.mnt,
						  &nd->path.dentry)) {
				status = -ENOENT;
				goto out_error;
			}
		}

		goto done;
	}
	spin_unlock(&dcache_lock);

done:
	return NULL;

out_error:
	path_put(&nd->path);
	return ERR_PTR(status);
}

/*
 * Revalidate is called on every cache lookup.  Some of those
 * cache lookups may actually happen while the dentry is not
 * yet completely filled in, and revalidate has to delay such
 * lookups..
 */
static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	struct inode *dir = dentry->d_parent->d_inode;
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	int oz_mode = autofs4_oz_mode(sbi);
	int flags = nd ? nd->flags : 0;
	int status = 1;

	/* Pending dentry */
	if (autofs4_ispending(dentry)) {
		/* The daemon never causes a mount to trigger */
		if (oz_mode)
			return 1;

		/*
		 * A zero status is success otherwise we have a
		 * negative error code.
		 */
		status = try_to_fill_dentry(dentry, flags);
		if (status == 0)
			return 1;

		/*
		 * A status of EAGAIN here means that the dentry has gone
		 * away while waiting for an expire to complete. If we are
		 * racing with expire lookup will wait for it so this must
		 * be a revalidate and we need to send it to lookup.
		 */
		if (status == -EAGAIN)
			return 0;

		return status;
	}

	/* Negative dentry.. invalidate if "old" */
	if (dentry->d_inode == NULL)
		return 0;

	/* Check for a non-mountpoint directory with no contents */
	spin_lock(&dcache_lock);
	if (S_ISDIR(dentry->d_inode->i_mode) &&
	    !d_mountpoint(dentry) && 
	    __simple_empty(dentry)) {
		DPRINTK("dentry=%p %.*s, emptydir",
			 dentry, dentry->d_name.len, dentry->d_name.name);
		spin_unlock(&dcache_lock);
		/* The daemon never causes a mount to trigger */
		if (oz_mode)
			return 1;

		/*
		 * A zero status is success otherwise we have a
		 * negative error code.
		 */
		status = try_to_fill_dentry(dentry, flags);
		if (status == 0)
			return 1;

		return status;
	}
	spin_unlock(&dcache_lock);

	return 1;
}

void autofs4_dentry_release(struct dentry *de)
{
	struct autofs_info *inf;

	DPRINTK("releasing %p", de);

	inf = autofs4_dentry_ino(de);
	de->d_fsdata = NULL;

	if (inf) {
		struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);

		if (sbi) {
			spin_lock(&sbi->rehash_lock);
			if (!list_empty(&inf->rehash))
				list_del(&inf->rehash);
			spin_unlock(&sbi->rehash_lock);
		}

		inf->dentry = NULL;
		inf->inode = NULL;

		autofs4_free_ino(inf);
	}
}

/* For dentries of directories in the root dir */
static struct dentry_operations autofs4_root_dentry_operations = {
	.d_revalidate	= autofs4_revalidate,
	.d_release	= autofs4_dentry_release,
};

/* For other dentries */
static struct dentry_operations autofs4_dentry_operations = {
	.d_revalidate	= autofs4_revalidate,
	.d_release	= autofs4_dentry_release,
};

static struct dentry *autofs4_lookup_unhashed(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name)
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
	struct list_head *p, *head;

	spin_lock(&dcache_lock);
	spin_lock(&sbi->rehash_lock);
	head = &sbi->rehash_list;
	list_for_each(p, head) {
		struct autofs_info *ino;
		struct dentry *dentry;
		struct qstr *qstr;

		ino = list_entry(p, struct autofs_info, rehash);
		dentry = ino->dentry;

		spin_lock(&dentry->d_lock);

		/* Bad luck, we've already been dentry_iput */
		if (!dentry->d_inode)
			goto next;

		qstr = &dentry->d_name;

		if (dentry->d_name.hash != hash)
			goto next;
		if (dentry->d_parent != parent)
			goto next;

		if (qstr->len != len)
			goto next;
		if (memcmp(qstr->name, str, len))
			goto next;

		if (d_unhashed(dentry)) {
			struct inode *inode = dentry->d_inode;

			ino = autofs4_dentry_ino(dentry);
			list_del_init(&ino->rehash);
			dget(dentry);
			/*
			 * Make the rehashed dentry negative so the VFS
			 * behaves as it should.
			 */
			if (inode) {
				dentry->d_inode = NULL;
				list_del_init(&dentry->d_alias);
				spin_unlock(&dentry->d_lock);
				spin_unlock(&sbi->rehash_lock);
				spin_unlock(&dcache_lock);
				iput(inode);
				return dentry;
			}
			spin_unlock(&dentry->d_lock);
			spin_unlock(&sbi->rehash_lock);
			spin_unlock(&dcache_lock);
			return dentry;
		}
next:
		spin_unlock(&dentry->d_lock);
	}
	spin_unlock(&sbi->rehash_lock);
	spin_unlock(&dcache_lock);

	return NULL;
}

/* Lookups in the root directory */
static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	struct autofs_sb_info *sbi;
	struct dentry *unhashed;
	int oz_mode;

	DPRINTK("name = %.*s",
		dentry->d_name.len, dentry->d_name.name);

	/* File name too long to exist */
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);

	sbi = autofs4_sbi(dir->i_sb);
	oz_mode = autofs4_oz_mode(sbi);

	DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
		 current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);

	unhashed = autofs4_lookup_unhashed(sbi, dentry->d_parent, &dentry->d_name);
	if (!unhashed) {
		/*
		 * Mark the dentry incomplete but don't hash it. We do this
		 * to serialize our inode creation operations (symlink and
		 * mkdir) which prevents deadlock during the callback to
		 * the daemon. Subsequent user space lookups for the same
		 * dentry are placed on the wait queue while the daemon
		 * itself is allowed passage unresticted so the create
		 * operation itself can then hash the dentry. Finally,
		 * we check for the hashed dentry and return the newly
		 * hashed dentry.
		 */
		dentry->d_op = &autofs4_root_dentry_operations;

		dentry->d_fsdata = NULL;
		d_instantiate(dentry, NULL);
	} else {
		struct autofs_info *ino = autofs4_dentry_ino(unhashed);
		DPRINTK("rehash %p with %p", dentry, unhashed);
		/*
		 * If we are racing with expire the request might not
		 * be quite complete but the directory has been removed
		 * so it must have been successful, so just wait for it.
		 * We need to ensure the AUTOFS_INF_EXPIRING flag is clear
		 * before continuing as revalidate may fail when calling
		 * try_to_fill_dentry (returning EAGAIN) if we don't.
		 */
		while (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
			DPRINTK("wait for incomplete expire %p name=%.*s",
				unhashed, unhashed->d_name.len,
				unhashed->d_name.name);
			autofs4_wait(sbi, unhashed, NFY_NONE);
			DPRINTK("request completed");
		}
		dentry = unhashed;
	}

	if (!oz_mode) {
		spin_lock(&dentry->d_lock);
		dentry->d_flags |= DCACHE_AUTOFS_PENDING;
		spin_unlock(&dentry->d_lock);
	}

	if (dentry->d_op && dentry->d_op->d_revalidate) {
		mutex_unlock(&dir->i_mutex);
		(dentry->d_op->d_revalidate)(dentry, nd);
		mutex_lock(&dir->i_mutex);
	}

	/*
	 * If we are still pending, check if we had to handle
	 * a signal. If so we can force a restart..
	 */
	if (dentry->d_flags & DCACHE_AUTOFS_PENDING) {
		/* See if we were interrupted */
		if (signal_pending(current)) {
			sigset_t *sigset = &current->pending.signal;
			if (sigismember (sigset, SIGKILL) ||
			    sigismember (sigset, SIGQUIT) ||
			    sigismember (sigset, SIGINT)) {
			    if (unhashed)
				dput(unhashed);
			    return ERR_PTR(-ERESTARTNOINTR);
			}
		}
		spin_lock(&dentry->d_lock);
		dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
		spin_unlock(&dentry->d_lock);
	}

	/*
	 * If this dentry is unhashed, then we shouldn't honour this
	 * lookup.  Returning ENOENT here doesn't do the right thing
	 * for all system calls, but it should be OK for the operations
	 * we permit from an autofs.
	 */
	if (!oz_mode && d_unhashed(dentry)) {
		/*
		 * A user space application can (and has done in the past)
		 * remove and re-create this directory during the callback.
		 * This can leave us with an unhashed dentry, but a
		 * successful mount!  So we need to perform another
		 * cached lookup in case the dentry now exists.
		 */
		struct dentry *parent = dentry->d_parent;
		struct dentry *new = d_lookup(parent, &dentry->d_name);
		if (new != NULL)
			dentry = new;
		else
			dentry = ERR_PTR(-ENOENT);

		if (unhashed)
			dput(unhashed);

		return dentry;
	}

	if (unhashed)
		return dentry;

	return NULL;
}

static int autofs4_dir_symlink(struct inode *dir, 
			       struct dentry *dentry,
			       const char *symname)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	struct autofs_info *p_ino;
	struct inode *inode;
	char *cp;

	DPRINTK("%s <- %.*s", symname,
		dentry->d_name.len, dentry->d_name.name);

	if (!autofs4_oz_mode(sbi))
		return -EACCES;

	ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
	if (ino == NULL)
		return -ENOSPC;

	ino->size = strlen(symname);
	ino->u.symlink = cp = kmalloc(ino->size + 1, GFP_KERNEL);

	if (cp == NULL) {
		kfree(ino);
		return -ENOSPC;
	}

	strcpy(cp, symname);

	inode = autofs4_get_inode(dir->i_sb, ino);
	d_add(dentry, inode);

	if (dir == dir->i_sb->s_root->d_inode)
		dentry->d_op = &autofs4_root_dentry_operations;
	else
		dentry->d_op = &autofs4_dentry_operations;

	dentry->d_fsdata = ino;
	ino->dentry = dget(dentry);
	atomic_inc(&ino->count);
	p_ino = autofs4_dentry_ino(dentry->d_parent);
	if (p_ino && dentry->d_parent != dentry)
		atomic_inc(&p_ino->count);
	ino->inode = inode;

	dir->i_mtime = CURRENT_TIME;

	return 0;
}

/*
 * NOTE!
 *
 * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 * that the file no longer exists. However, doing that means that the
 * VFS layer can turn the dentry into a negative dentry.  We don't want
 * this, because the unlink is probably the result of an expire.
 * We simply d_drop it and add it to a rehash candidates list in the
 * super block, which allows the dentry lookup to reuse it retaining
 * the flags, such as expire in progress, in case we're racing with expire.
 *
 * If a process is blocked on the dentry waiting for the expire to finish,
 * it will invalidate the dentry and try to mount with a new one.
 *
 * Also see autofs4_dir_rmdir()..
 */
static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	struct autofs_info *p_ino;
	
	/* This allows root to remove symlinks */
	if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
		return -EACCES;

	if (atomic_dec_and_test(&ino->count)) {
		p_ino = autofs4_dentry_ino(dentry->d_parent);
		if (p_ino && dentry->d_parent != dentry)
			atomic_dec(&p_ino->count);
	}
	dput(ino->dentry);

	dentry->d_inode->i_size = 0;
	clear_nlink(dentry->d_inode);

	dir->i_mtime = CURRENT_TIME;

	spin_lock(&dcache_lock);
	spin_lock(&sbi->rehash_lock);
	list_add(&ino->rehash, &sbi->rehash_list);
	spin_unlock(&sbi->rehash_lock);
	spin_lock(&dentry->d_lock);
	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);

	return 0;
}

static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	struct autofs_info *p_ino;
	
	DPRINTK("dentry %p, removing %.*s",
		dentry, dentry->d_name.len, dentry->d_name.name);

	if (!autofs4_oz_mode(sbi))
		return -EACCES;

	spin_lock(&dcache_lock);
	if (!list_empty(&dentry->d_subdirs)) {
		spin_unlock(&dcache_lock);
		return -ENOTEMPTY;
	}
	spin_lock(&sbi->rehash_lock);
	list_add(&ino->rehash, &sbi->rehash_list);
	spin_unlock(&sbi->rehash_lock);
	spin_lock(&dentry->d_lock);
	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);

	if (atomic_dec_and_test(&ino->count)) {
		p_ino = autofs4_dentry_ino(dentry->d_parent);
		if (p_ino && dentry->d_parent != dentry)
			atomic_dec(&p_ino->count);
	}
	dput(ino->dentry);
	dentry->d_inode->i_size = 0;
	clear_nlink(dentry->d_inode);

	if (dir->i_nlink)
		drop_nlink(dir);

	return 0;
}

static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	struct autofs_info *p_ino;
	struct inode *inode;

	if (!autofs4_oz_mode(sbi))
		return -EACCES;

	DPRINTK("dentry %p, creating %.*s",
		dentry, dentry->d_name.len, dentry->d_name.name);

	ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
	if (ino == NULL)
		return -ENOSPC;

	inode = autofs4_get_inode(dir->i_sb, ino);
	d_add(dentry, inode);

	if (dir == dir->i_sb->s_root->d_inode)
		dentry->d_op = &autofs4_root_dentry_operations;
	else
		dentry->d_op = &autofs4_dentry_operations;

	dentry->d_fsdata = ino;
	ino->dentry = dget(dentry);
	atomic_inc(&ino->count);
	p_ino = autofs4_dentry_ino(dentry->d_parent);
	if (p_ino && dentry->d_parent != dentry)
		atomic_inc(&p_ino->count);
	ino->inode = inode;
	inc_nlink(dir);
	dir->i_mtime = CURRENT_TIME;

	return 0;
}

/* Get/set timeout ioctl() operation */
static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
					 unsigned long __user *p)
{
	int rv;
	unsigned long ntimeout;

	if ((rv = get_user(ntimeout, p)) ||
	     (rv = put_user(sbi->exp_timeout/HZ, p)))
		return rv;

	if (ntimeout > ULONG_MAX/HZ)
		sbi->exp_timeout = 0;
	else
		sbi->exp_timeout = ntimeout * HZ;

	return 0;
}

/* Return protocol version */
static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
{
	return put_user(sbi->version, p);
}

/* Return protocol sub version */
static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
{
	return put_user(sbi->sub_version, p);
}

/*
 * Tells the daemon whether we need to reghost or not. Also, clears
 * the reghost_needed flag.
 */
static inline int autofs4_ask_reghost(struct autofs_sb_info *sbi, int __user *p)
{
	int status;

	DPRINTK("returning %d", sbi->needs_reghost);

	status = put_user(sbi->needs_reghost, p);
	if (status)
		return status;

	sbi->needs_reghost = 0;
	return 0;
}

/*
 * Enable / Disable reghosting ioctl() operation
 */
static inline int autofs4_toggle_reghost(struct autofs_sb_info *sbi, int __user *p)
{
	int status;
	int val;

	status = get_user(val, p);

	DPRINTK("reghost = %d", val);

	if (status)
		return status;

	/* turn on/off reghosting, with the val */
	sbi->reghost_enabled = val;
	return 0;
}

/*
* Tells the daemon whether it can umount the autofs mount.
*/
static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
{
	int status = 0;

	if (may_umount(mnt))
		status = 1;

	DPRINTK("returning %d", status);

	status = put_user(status, p);

	return status;
}

/* Identify autofs4_dentries - this is so we can tell if there's
   an extra dentry refcount or not.  We only hold a refcount on the
   dentry if its non-negative (ie, d_inode != NULL)
*/
int is_autofs4_dentry(struct dentry *dentry)
{
	return dentry && dentry->d_inode &&
		(dentry->d_op == &autofs4_root_dentry_operations ||
		 dentry->d_op == &autofs4_dentry_operations) &&
		dentry->d_fsdata != NULL;
}

/*
 * ioctl()'s on the root directory is the chief method for the daemon to
 * generate kernel reactions
 */
static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
			     unsigned int cmd, unsigned long arg)
{
	struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
	void __user *p = (void __user *)arg;

	DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
		cmd,arg,sbi,task_pgrp_nr(current));

	if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
	     _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
		return -ENOTTY;
	
	if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	
	switch(cmd) {
	case AUTOFS_IOC_READY:	/* Wait queue: go ahead and retry */
		return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
	case AUTOFS_IOC_FAIL:	/* Wait queue: fail with ENOENT */
		return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
	case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
		autofs4_catatonic_mode(sbi);
		return 0;
	case AUTOFS_IOC_PROTOVER: /* Get protocol version */
		return autofs4_get_protover(sbi, p);
	case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
		return autofs4_get_protosubver(sbi, p);
	case AUTOFS_IOC_SETTIMEOUT:
		return autofs4_get_set_timeout(sbi, p);

	case AUTOFS_IOC_TOGGLEREGHOST:
		return autofs4_toggle_reghost(sbi, p);
	case AUTOFS_IOC_ASKREGHOST:
		return autofs4_ask_reghost(sbi, p);

	case AUTOFS_IOC_ASKUMOUNT:
		return autofs4_ask_umount(filp->f_path.mnt, p);

	/* return a single thing to expire */
	case AUTOFS_IOC_EXPIRE:
		return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
	/* same as above, but can send multiple expires through pipe */
	case AUTOFS_IOC_EXPIRE_MULTI:
		return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);

	default:
		return -ENOSYS;
	}
}
OpenPOWER on IntegriCloud