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[PATCH] autofs4: fix another race between mount and expire
[mirror_ubuntu-eoan-kernel.git] / fs / autofs4 / root.c
1 /* -*- c -*- --------------------------------------------------------------- *
2 *
3 * linux/fs/autofs/root.c
4 *
5 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
6 * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
7 * Copyright 2001-2006 Ian Kent <raven@themaw.net>
8 *
9 * This file is part of the Linux kernel and is made available under
10 * the terms of the GNU General Public License, version 2, or at your
11 * option, any later version, incorporated herein by reference.
12 *
13 * ------------------------------------------------------------------------- */
14
15 #include <linux/capability.h>
16 #include <linux/errno.h>
17 #include <linux/stat.h>
18 #include <linux/param.h>
19 #include <linux/time.h>
20 #include <linux/smp_lock.h>
21 #include "autofs_i.h"
22
23 static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
24 static int autofs4_dir_unlink(struct inode *,struct dentry *);
25 static int autofs4_dir_rmdir(struct inode *,struct dentry *);
26 static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
27 static int autofs4_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
28 static int autofs4_dir_open(struct inode *inode, struct file *file);
29 static int autofs4_dir_close(struct inode *inode, struct file *file);
30 static int autofs4_dir_readdir(struct file * filp, void * dirent, filldir_t filldir);
31 static int autofs4_root_readdir(struct file * filp, void * dirent, filldir_t filldir);
32 static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
33 static void *autofs4_follow_link(struct dentry *, struct nameidata *);
34
35 const struct file_operations autofs4_root_operations = {
36 .open = dcache_dir_open,
37 .release = dcache_dir_close,
38 .read = generic_read_dir,
39 .readdir = autofs4_root_readdir,
40 .ioctl = autofs4_root_ioctl,
41 };
42
43 const struct file_operations autofs4_dir_operations = {
44 .open = autofs4_dir_open,
45 .release = autofs4_dir_close,
46 .read = generic_read_dir,
47 .readdir = autofs4_dir_readdir,
48 };
49
50 const struct inode_operations autofs4_indirect_root_inode_operations = {
51 .lookup = autofs4_lookup,
52 .unlink = autofs4_dir_unlink,
53 .symlink = autofs4_dir_symlink,
54 .mkdir = autofs4_dir_mkdir,
55 .rmdir = autofs4_dir_rmdir,
56 };
57
58 const struct inode_operations autofs4_direct_root_inode_operations = {
59 .lookup = autofs4_lookup,
60 .unlink = autofs4_dir_unlink,
61 .mkdir = autofs4_dir_mkdir,
62 .rmdir = autofs4_dir_rmdir,
63 .follow_link = autofs4_follow_link,
64 };
65
66 const struct inode_operations autofs4_dir_inode_operations = {
67 .lookup = autofs4_lookup,
68 .unlink = autofs4_dir_unlink,
69 .symlink = autofs4_dir_symlink,
70 .mkdir = autofs4_dir_mkdir,
71 .rmdir = autofs4_dir_rmdir,
72 };
73
74 static int autofs4_root_readdir(struct file *file, void *dirent,
75 filldir_t filldir)
76 {
77 struct autofs_sb_info *sbi = autofs4_sbi(file->f_path.dentry->d_sb);
78 int oz_mode = autofs4_oz_mode(sbi);
79
80 DPRINTK("called, filp->f_pos = %lld", file->f_pos);
81
82 /*
83 * Don't set reghost flag if:
84 * 1) f_pos is larger than zero -- we've already been here.
85 * 2) we haven't even enabled reghosting in the 1st place.
86 * 3) this is the daemon doing a readdir
87 */
88 if (oz_mode && file->f_pos == 0 && sbi->reghost_enabled)
89 sbi->needs_reghost = 1;
90
91 DPRINTK("needs_reghost = %d", sbi->needs_reghost);
92
93 return dcache_readdir(file, dirent, filldir);
94 }
95
96 static int autofs4_dir_open(struct inode *inode, struct file *file)
97 {
98 struct dentry *dentry = file->f_path.dentry;
99 struct vfsmount *mnt = file->f_path.mnt;
100 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
101 struct dentry *cursor;
102 int status;
103
104 status = dcache_dir_open(inode, file);
105 if (status)
106 goto out;
107
108 cursor = file->private_data;
109 cursor->d_fsdata = NULL;
110
111 DPRINTK("file=%p dentry=%p %.*s",
112 file, dentry, dentry->d_name.len, dentry->d_name.name);
113
114 if (autofs4_oz_mode(sbi))
115 goto out;
116
117 if (autofs4_ispending(dentry)) {
118 DPRINTK("dentry busy");
119 dcache_dir_close(inode, file);
120 status = -EBUSY;
121 goto out;
122 }
123
124 status = -ENOENT;
125 if (!d_mountpoint(dentry) && dentry->d_op && dentry->d_op->d_revalidate) {
126 struct nameidata nd;
127 int empty, ret;
128
129 /* In case there are stale directory dentrys from a failed mount */
130 spin_lock(&dcache_lock);
131 empty = list_empty(&dentry->d_subdirs);
132 spin_unlock(&dcache_lock);
133
134 if (!empty)
135 d_invalidate(dentry);
136
137 nd.flags = LOOKUP_DIRECTORY;
138 ret = (dentry->d_op->d_revalidate)(dentry, &nd);
139
140 if (ret <= 0) {
141 if (ret < 0)
142 status = ret;
143 dcache_dir_close(inode, file);
144 goto out;
145 }
146 }
147
148 if (d_mountpoint(dentry)) {
149 struct file *fp = NULL;
150 struct vfsmount *fp_mnt = mntget(mnt);
151 struct dentry *fp_dentry = dget(dentry);
152
153 if (!autofs4_follow_mount(&fp_mnt, &fp_dentry)) {
154 dput(fp_dentry);
155 mntput(fp_mnt);
156 dcache_dir_close(inode, file);
157 goto out;
158 }
159
160 fp = dentry_open(fp_dentry, fp_mnt, file->f_flags);
161 status = PTR_ERR(fp);
162 if (IS_ERR(fp)) {
163 dcache_dir_close(inode, file);
164 goto out;
165 }
166 cursor->d_fsdata = fp;
167 }
168 return 0;
169 out:
170 return status;
171 }
172
173 static int autofs4_dir_close(struct inode *inode, struct file *file)
174 {
175 struct dentry *dentry = file->f_path.dentry;
176 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
177 struct dentry *cursor = file->private_data;
178 int status = 0;
179
180 DPRINTK("file=%p dentry=%p %.*s",
181 file, dentry, dentry->d_name.len, dentry->d_name.name);
182
183 if (autofs4_oz_mode(sbi))
184 goto out;
185
186 if (autofs4_ispending(dentry)) {
187 DPRINTK("dentry busy");
188 status = -EBUSY;
189 goto out;
190 }
191
192 if (d_mountpoint(dentry)) {
193 struct file *fp = cursor->d_fsdata;
194 if (!fp) {
195 status = -ENOENT;
196 goto out;
197 }
198 filp_close(fp, current->files);
199 }
200 out:
201 dcache_dir_close(inode, file);
202 return status;
203 }
204
205 static int autofs4_dir_readdir(struct file *file, void *dirent, filldir_t filldir)
206 {
207 struct dentry *dentry = file->f_path.dentry;
208 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
209 struct dentry *cursor = file->private_data;
210 int status;
211
212 DPRINTK("file=%p dentry=%p %.*s",
213 file, dentry, dentry->d_name.len, dentry->d_name.name);
214
215 if (autofs4_oz_mode(sbi))
216 goto out;
217
218 if (autofs4_ispending(dentry)) {
219 DPRINTK("dentry busy");
220 return -EBUSY;
221 }
222
223 if (d_mountpoint(dentry)) {
224 struct file *fp = cursor->d_fsdata;
225
226 if (!fp)
227 return -ENOENT;
228
229 if (!fp->f_op || !fp->f_op->readdir)
230 goto out;
231
232 status = vfs_readdir(fp, filldir, dirent);
233 file->f_pos = fp->f_pos;
234 if (status)
235 autofs4_copy_atime(file, fp);
236 return status;
237 }
238 out:
239 return dcache_readdir(file, dirent, filldir);
240 }
241
242 static int try_to_fill_dentry(struct dentry *dentry, int flags)
243 {
244 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
245 struct autofs_info *ino = autofs4_dentry_ino(dentry);
246 int status = 0;
247
248 /* Block on any pending expiry here; invalidate the dentry
249 when expiration is done to trigger mount request with a new
250 dentry */
251 if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
252 DPRINTK("waiting for expire %p name=%.*s",
253 dentry, dentry->d_name.len, dentry->d_name.name);
254
255 status = autofs4_wait(sbi, dentry, NFY_NONE);
256
257 DPRINTK("expire done status=%d", status);
258
259 /*
260 * If the directory still exists the mount request must
261 * continue otherwise it can't be followed at the right
262 * time during the walk.
263 */
264 status = d_invalidate(dentry);
265 if (status != -EBUSY)
266 return -EAGAIN;
267 }
268
269 DPRINTK("dentry=%p %.*s ino=%p",
270 dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
271
272 /*
273 * Wait for a pending mount, triggering one if there
274 * isn't one already
275 */
276 if (dentry->d_inode == NULL) {
277 DPRINTK("waiting for mount name=%.*s",
278 dentry->d_name.len, dentry->d_name.name);
279
280 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
281
282 DPRINTK("mount done status=%d", status);
283
284 /* Turn this into a real negative dentry? */
285 if (status == -ENOENT) {
286 spin_lock(&dentry->d_lock);
287 dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
288 spin_unlock(&dentry->d_lock);
289 return status;
290 } else if (status) {
291 /* Return a negative dentry, but leave it "pending" */
292 return status;
293 }
294 /* Trigger mount for path component or follow link */
295 } else if (flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY) ||
296 current->link_count) {
297 DPRINTK("waiting for mount name=%.*s",
298 dentry->d_name.len, dentry->d_name.name);
299
300 spin_lock(&dentry->d_lock);
301 dentry->d_flags |= DCACHE_AUTOFS_PENDING;
302 spin_unlock(&dentry->d_lock);
303 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
304
305 DPRINTK("mount done status=%d", status);
306
307 if (status) {
308 spin_lock(&dentry->d_lock);
309 dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
310 spin_unlock(&dentry->d_lock);
311 return status;
312 }
313 }
314
315 /* Initialize expiry counter after successful mount */
316 if (ino)
317 ino->last_used = jiffies;
318
319 spin_lock(&dentry->d_lock);
320 dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
321 spin_unlock(&dentry->d_lock);
322 return status;
323 }
324
325 /* For autofs direct mounts the follow link triggers the mount */
326 static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
327 {
328 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
329 struct autofs_info *ino = autofs4_dentry_ino(dentry);
330 int oz_mode = autofs4_oz_mode(sbi);
331 unsigned int lookup_type;
332 int status;
333
334 DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
335 dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
336 nd->flags);
337
338 /* If it's our master or we shouldn't trigger a mount we're done */
339 lookup_type = nd->flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY);
340 if (oz_mode || !lookup_type)
341 goto done;
342
343 /* If an expire request is pending wait for it. */
344 if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
345 DPRINTK("waiting for active request %p name=%.*s",
346 dentry, dentry->d_name.len, dentry->d_name.name);
347
348 status = autofs4_wait(sbi, dentry, NFY_NONE);
349
350 DPRINTK("request done status=%d", status);
351 }
352
353 /*
354 * If the dentry contains directories then it is an
355 * autofs multi-mount with no root mount offset. So
356 * don't try to mount it again.
357 */
358 spin_lock(&dcache_lock);
359 if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
360 spin_unlock(&dcache_lock);
361
362 status = try_to_fill_dentry(dentry, 0);
363 if (status)
364 goto out_error;
365
366 /*
367 * The mount succeeded but if there is no root mount
368 * it must be an autofs multi-mount with no root offset
369 * so we don't need to follow the mount.
370 */
371 if (d_mountpoint(dentry)) {
372 if (!autofs4_follow_mount(&nd->mnt, &nd->dentry)) {
373 status = -ENOENT;
374 goto out_error;
375 }
376 }
377
378 goto done;
379 }
380 spin_unlock(&dcache_lock);
381
382 done:
383 return NULL;
384
385 out_error:
386 path_release(nd);
387 return ERR_PTR(status);
388 }
389
390 /*
391 * Revalidate is called on every cache lookup. Some of those
392 * cache lookups may actually happen while the dentry is not
393 * yet completely filled in, and revalidate has to delay such
394 * lookups..
395 */
396 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
397 {
398 struct inode *dir = dentry->d_parent->d_inode;
399 struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
400 int oz_mode = autofs4_oz_mode(sbi);
401 int flags = nd ? nd->flags : 0;
402 int status = 1;
403
404 /* Pending dentry */
405 if (autofs4_ispending(dentry)) {
406 /* The daemon never causes a mount to trigger */
407 if (oz_mode)
408 return 1;
409
410 /*
411 * A zero status is success otherwise we have a
412 * negative error code.
413 */
414 status = try_to_fill_dentry(dentry, flags);
415 if (status == 0)
416 return 1;
417
418 /*
419 * A status of EAGAIN here means that the dentry has gone
420 * away while waiting for an expire to complete. If we are
421 * racing with expire lookup will wait for it so this must
422 * be a revalidate and we need to send it to lookup.
423 */
424 if (status == -EAGAIN)
425 return 0;
426
427 return status;
428 }
429
430 /* Negative dentry.. invalidate if "old" */
431 if (dentry->d_inode == NULL)
432 return 0;
433
434 /* Check for a non-mountpoint directory with no contents */
435 spin_lock(&dcache_lock);
436 if (S_ISDIR(dentry->d_inode->i_mode) &&
437 !d_mountpoint(dentry) &&
438 __simple_empty(dentry)) {
439 DPRINTK("dentry=%p %.*s, emptydir",
440 dentry, dentry->d_name.len, dentry->d_name.name);
441 spin_unlock(&dcache_lock);
442 /* The daemon never causes a mount to trigger */
443 if (oz_mode)
444 return 1;
445
446 /*
447 * A zero status is success otherwise we have a
448 * negative error code.
449 */
450 status = try_to_fill_dentry(dentry, flags);
451 if (status == 0)
452 return 1;
453
454 return status;
455 }
456 spin_unlock(&dcache_lock);
457
458 return 1;
459 }
460
461 void autofs4_dentry_release(struct dentry *de)
462 {
463 struct autofs_info *inf;
464
465 DPRINTK("releasing %p", de);
466
467 inf = autofs4_dentry_ino(de);
468 de->d_fsdata = NULL;
469
470 if (inf) {
471 struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);
472
473 inf->dentry = NULL;
474 inf->inode = NULL;
475
476 if (sbi) {
477 spin_lock(&sbi->rehash_lock);
478 if (!list_empty(&inf->rehash))
479 list_del(&inf->rehash);
480 spin_unlock(&sbi->rehash_lock);
481 }
482
483 autofs4_free_ino(inf);
484 }
485 }
486
487 /* For dentries of directories in the root dir */
488 static struct dentry_operations autofs4_root_dentry_operations = {
489 .d_revalidate = autofs4_revalidate,
490 .d_release = autofs4_dentry_release,
491 };
492
493 /* For other dentries */
494 static struct dentry_operations autofs4_dentry_operations = {
495 .d_revalidate = autofs4_revalidate,
496 .d_release = autofs4_dentry_release,
497 };
498
499 static struct dentry *autofs4_lookup_unhashed(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name)
500 {
501 unsigned int len = name->len;
502 unsigned int hash = name->hash;
503 const unsigned char *str = name->name;
504 struct list_head *p, *head;
505
506 spin_lock(&dcache_lock);
507 spin_lock(&sbi->rehash_lock);
508 head = &sbi->rehash_list;
509 list_for_each(p, head) {
510 struct autofs_info *ino;
511 struct dentry *dentry;
512 struct qstr *qstr;
513
514 ino = list_entry(p, struct autofs_info, rehash);
515 dentry = ino->dentry;
516
517 spin_lock(&dentry->d_lock);
518
519 /* Bad luck, we've already been dentry_iput */
520 if (!dentry->d_inode)
521 goto next;
522
523 qstr = &dentry->d_name;
524
525 if (dentry->d_name.hash != hash)
526 goto next;
527 if (dentry->d_parent != parent)
528 goto next;
529
530 if (qstr->len != len)
531 goto next;
532 if (memcmp(qstr->name, str, len))
533 goto next;
534
535 if (d_unhashed(dentry)) {
536 struct autofs_info *ino = autofs4_dentry_ino(dentry);
537 struct inode *inode = dentry->d_inode;
538
539 list_del_init(&ino->rehash);
540 dget(dentry);
541 /*
542 * Make the rehashed dentry negative so the VFS
543 * behaves as it should.
544 */
545 if (inode) {
546 dentry->d_inode = NULL;
547 list_del_init(&dentry->d_alias);
548 spin_unlock(&dentry->d_lock);
549 spin_unlock(&sbi->rehash_lock);
550 spin_unlock(&dcache_lock);
551 iput(inode);
552 return dentry;
553 }
554 spin_unlock(&dentry->d_lock);
555 spin_unlock(&sbi->rehash_lock);
556 spin_unlock(&dcache_lock);
557 return dentry;
558 }
559 next:
560 spin_unlock(&dentry->d_lock);
561 }
562 spin_unlock(&sbi->rehash_lock);
563 spin_unlock(&dcache_lock);
564
565 return NULL;
566 }
567
568 /* Lookups in the root directory */
569 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
570 {
571 struct autofs_sb_info *sbi;
572 struct dentry *unhashed;
573 int oz_mode;
574
575 DPRINTK("name = %.*s",
576 dentry->d_name.len, dentry->d_name.name);
577
578 /* File name too long to exist */
579 if (dentry->d_name.len > NAME_MAX)
580 return ERR_PTR(-ENAMETOOLONG);
581
582 sbi = autofs4_sbi(dir->i_sb);
583 oz_mode = autofs4_oz_mode(sbi);
584
585 DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
586 current->pid, process_group(current), sbi->catatonic, oz_mode);
587
588 unhashed = autofs4_lookup_unhashed(sbi, dentry->d_parent, &dentry->d_name);
589 if (!unhashed) {
590 /*
591 * Mark the dentry incomplete, but add it. This is needed so
592 * that the VFS layer knows about the dentry, and we can count
593 * on catching any lookups through the revalidate.
594 *
595 * Let all the hard work be done by the revalidate function that
596 * needs to be able to do this anyway..
597 *
598 * We need to do this before we release the directory semaphore.
599 */
600 dentry->d_op = &autofs4_root_dentry_operations;
601
602 dentry->d_fsdata = NULL;
603 d_add(dentry, NULL);
604 } else {
605 struct autofs_info *ino = autofs4_dentry_ino(unhashed);
606 DPRINTK("rehash %p with %p", dentry, unhashed);
607 /*
608 * If we are racing with expire the request might not
609 * be quite complete but the directory has been removed
610 * so it must have been successful, so just wait for it.
611 */
612 if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
613 DPRINTK("wait for incomplete expire %p name=%.*s",
614 unhashed, unhashed->d_name.len,
615 unhashed->d_name.name);
616 autofs4_wait(sbi, unhashed, NFY_NONE);
617 DPRINTK("request completed");
618 }
619 d_rehash(unhashed);
620 dentry = unhashed;
621 }
622
623 if (!oz_mode) {
624 spin_lock(&dentry->d_lock);
625 dentry->d_flags |= DCACHE_AUTOFS_PENDING;
626 spin_unlock(&dentry->d_lock);
627 }
628
629 if (dentry->d_op && dentry->d_op->d_revalidate) {
630 mutex_unlock(&dir->i_mutex);
631 (dentry->d_op->d_revalidate)(dentry, nd);
632 mutex_lock(&dir->i_mutex);
633 }
634
635 /*
636 * If we are still pending, check if we had to handle
637 * a signal. If so we can force a restart..
638 */
639 if (dentry->d_flags & DCACHE_AUTOFS_PENDING) {
640 /* See if we were interrupted */
641 if (signal_pending(current)) {
642 sigset_t *sigset = &current->pending.signal;
643 if (sigismember (sigset, SIGKILL) ||
644 sigismember (sigset, SIGQUIT) ||
645 sigismember (sigset, SIGINT)) {
646 if (unhashed)
647 dput(unhashed);
648 return ERR_PTR(-ERESTARTNOINTR);
649 }
650 }
651 spin_lock(&dentry->d_lock);
652 dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
653 spin_unlock(&dentry->d_lock);
654 }
655
656 /*
657 * If this dentry is unhashed, then we shouldn't honour this
658 * lookup even if the dentry is positive. Returning ENOENT here
659 * doesn't do the right thing for all system calls, but it should
660 * be OK for the operations we permit from an autofs.
661 */
662 if (dentry->d_inode && d_unhashed(dentry)) {
663 if (unhashed)
664 dput(unhashed);
665 return ERR_PTR(-ENOENT);
666 }
667
668 if (unhashed)
669 return dentry;
670
671 return NULL;
672 }
673
674 static int autofs4_dir_symlink(struct inode *dir,
675 struct dentry *dentry,
676 const char *symname)
677 {
678 struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
679 struct autofs_info *ino = autofs4_dentry_ino(dentry);
680 struct autofs_info *p_ino;
681 struct inode *inode;
682 char *cp;
683
684 DPRINTK("%s <- %.*s", symname,
685 dentry->d_name.len, dentry->d_name.name);
686
687 if (!autofs4_oz_mode(sbi))
688 return -EACCES;
689
690 ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
691 if (ino == NULL)
692 return -ENOSPC;
693
694 ino->size = strlen(symname);
695 ino->u.symlink = cp = kmalloc(ino->size + 1, GFP_KERNEL);
696
697 if (cp == NULL) {
698 kfree(ino);
699 return -ENOSPC;
700 }
701
702 strcpy(cp, symname);
703
704 inode = autofs4_get_inode(dir->i_sb, ino);
705 d_instantiate(dentry, inode);
706
707 if (dir == dir->i_sb->s_root->d_inode)
708 dentry->d_op = &autofs4_root_dentry_operations;
709 else
710 dentry->d_op = &autofs4_dentry_operations;
711
712 dentry->d_fsdata = ino;
713 ino->dentry = dget(dentry);
714 atomic_inc(&ino->count);
715 p_ino = autofs4_dentry_ino(dentry->d_parent);
716 if (p_ino && dentry->d_parent != dentry)
717 atomic_inc(&p_ino->count);
718 ino->inode = inode;
719
720 dir->i_mtime = CURRENT_TIME;
721
722 return 0;
723 }
724
725 /*
726 * NOTE!
727 *
728 * Normal filesystems would do a "d_delete()" to tell the VFS dcache
729 * that the file no longer exists. However, doing that means that the
730 * VFS layer can turn the dentry into a negative dentry. We don't want
731 * this, because the unlink is probably the result of an expire.
732 * We simply d_drop it and add it to a rehash candidates list in the
733 * super block, which allows the dentry lookup to reuse it retaining
734 * the flags, such as expire in progress, in case we're racing with expire.
735 *
736 * If a process is blocked on the dentry waiting for the expire to finish,
737 * it will invalidate the dentry and try to mount with a new one.
738 *
739 * Also see autofs4_dir_rmdir()..
740 */
741 static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
742 {
743 struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
744 struct autofs_info *ino = autofs4_dentry_ino(dentry);
745 struct autofs_info *p_ino;
746
747 /* This allows root to remove symlinks */
748 if ( !autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN) )
749 return -EACCES;
750
751 if (atomic_dec_and_test(&ino->count)) {
752 p_ino = autofs4_dentry_ino(dentry->d_parent);
753 if (p_ino && dentry->d_parent != dentry)
754 atomic_dec(&p_ino->count);
755 }
756 dput(ino->dentry);
757
758 dentry->d_inode->i_size = 0;
759 clear_nlink(dentry->d_inode);
760
761 dir->i_mtime = CURRENT_TIME;
762
763 spin_lock(&dcache_lock);
764 spin_lock(&sbi->rehash_lock);
765 list_add(&ino->rehash, &sbi->rehash_list);
766 spin_unlock(&sbi->rehash_lock);
767 spin_lock(&dentry->d_lock);
768 __d_drop(dentry);
769 spin_unlock(&dentry->d_lock);
770 spin_unlock(&dcache_lock);
771
772 return 0;
773 }
774
775 static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
776 {
777 struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
778 struct autofs_info *ino = autofs4_dentry_ino(dentry);
779 struct autofs_info *p_ino;
780
781 DPRINTK("dentry %p, removing %.*s",
782 dentry, dentry->d_name.len, dentry->d_name.name);
783
784 if (!autofs4_oz_mode(sbi))
785 return -EACCES;
786
787 spin_lock(&dcache_lock);
788 if (!list_empty(&dentry->d_subdirs)) {
789 spin_unlock(&dcache_lock);
790 return -ENOTEMPTY;
791 }
792 spin_lock(&sbi->rehash_lock);
793 list_add(&ino->rehash, &sbi->rehash_list);
794 spin_unlock(&sbi->rehash_lock);
795 spin_lock(&dentry->d_lock);
796 __d_drop(dentry);
797 spin_unlock(&dentry->d_lock);
798 spin_unlock(&dcache_lock);
799
800 if (atomic_dec_and_test(&ino->count)) {
801 p_ino = autofs4_dentry_ino(dentry->d_parent);
802 if (p_ino && dentry->d_parent != dentry)
803 atomic_dec(&p_ino->count);
804 }
805 dput(ino->dentry);
806 dentry->d_inode->i_size = 0;
807 clear_nlink(dentry->d_inode);
808
809 if (dir->i_nlink)
810 drop_nlink(dir);
811
812 return 0;
813 }
814
815 static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
816 {
817 struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
818 struct autofs_info *ino = autofs4_dentry_ino(dentry);
819 struct autofs_info *p_ino;
820 struct inode *inode;
821
822 if ( !autofs4_oz_mode(sbi) )
823 return -EACCES;
824
825 DPRINTK("dentry %p, creating %.*s",
826 dentry, dentry->d_name.len, dentry->d_name.name);
827
828 ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
829 if (ino == NULL)
830 return -ENOSPC;
831
832 inode = autofs4_get_inode(dir->i_sb, ino);
833 d_instantiate(dentry, inode);
834
835 if (dir == dir->i_sb->s_root->d_inode)
836 dentry->d_op = &autofs4_root_dentry_operations;
837 else
838 dentry->d_op = &autofs4_dentry_operations;
839
840 dentry->d_fsdata = ino;
841 ino->dentry = dget(dentry);
842 atomic_inc(&ino->count);
843 p_ino = autofs4_dentry_ino(dentry->d_parent);
844 if (p_ino && dentry->d_parent != dentry)
845 atomic_inc(&p_ino->count);
846 ino->inode = inode;
847 inc_nlink(dir);
848 dir->i_mtime = CURRENT_TIME;
849
850 return 0;
851 }
852
853 /* Get/set timeout ioctl() operation */
854 static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
855 unsigned long __user *p)
856 {
857 int rv;
858 unsigned long ntimeout;
859
860 if ( (rv = get_user(ntimeout, p)) ||
861 (rv = put_user(sbi->exp_timeout/HZ, p)) )
862 return rv;
863
864 if ( ntimeout > ULONG_MAX/HZ )
865 sbi->exp_timeout = 0;
866 else
867 sbi->exp_timeout = ntimeout * HZ;
868
869 return 0;
870 }
871
872 /* Return protocol version */
873 static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
874 {
875 return put_user(sbi->version, p);
876 }
877
878 /* Return protocol sub version */
879 static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
880 {
881 return put_user(sbi->sub_version, p);
882 }
883
884 /*
885 * Tells the daemon whether we need to reghost or not. Also, clears
886 * the reghost_needed flag.
887 */
888 static inline int autofs4_ask_reghost(struct autofs_sb_info *sbi, int __user *p)
889 {
890 int status;
891
892 DPRINTK("returning %d", sbi->needs_reghost);
893
894 status = put_user(sbi->needs_reghost, p);
895 if ( status )
896 return status;
897
898 sbi->needs_reghost = 0;
899 return 0;
900 }
901
902 /*
903 * Enable / Disable reghosting ioctl() operation
904 */
905 static inline int autofs4_toggle_reghost(struct autofs_sb_info *sbi, int __user *p)
906 {
907 int status;
908 int val;
909
910 status = get_user(val, p);
911
912 DPRINTK("reghost = %d", val);
913
914 if (status)
915 return status;
916
917 /* turn on/off reghosting, with the val */
918 sbi->reghost_enabled = val;
919 return 0;
920 }
921
922 /*
923 * Tells the daemon whether it can umount the autofs mount.
924 */
925 static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
926 {
927 int status = 0;
928
929 if (may_umount(mnt))
930 status = 1;
931
932 DPRINTK("returning %d", status);
933
934 status = put_user(status, p);
935
936 return status;
937 }
938
939 /* Identify autofs4_dentries - this is so we can tell if there's
940 an extra dentry refcount or not. We only hold a refcount on the
941 dentry if its non-negative (ie, d_inode != NULL)
942 */
943 int is_autofs4_dentry(struct dentry *dentry)
944 {
945 return dentry && dentry->d_inode &&
946 (dentry->d_op == &autofs4_root_dentry_operations ||
947 dentry->d_op == &autofs4_dentry_operations) &&
948 dentry->d_fsdata != NULL;
949 }
950
951 /*
952 * ioctl()'s on the root directory is the chief method for the daemon to
953 * generate kernel reactions
954 */
955 static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
956 unsigned int cmd, unsigned long arg)
957 {
958 struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
959 void __user *p = (void __user *)arg;
960
961 DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
962 cmd,arg,sbi,process_group(current));
963
964 if ( _IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
965 _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT )
966 return -ENOTTY;
967
968 if ( !autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN) )
969 return -EPERM;
970
971 switch(cmd) {
972 case AUTOFS_IOC_READY: /* Wait queue: go ahead and retry */
973 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
974 case AUTOFS_IOC_FAIL: /* Wait queue: fail with ENOENT */
975 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
976 case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
977 autofs4_catatonic_mode(sbi);
978 return 0;
979 case AUTOFS_IOC_PROTOVER: /* Get protocol version */
980 return autofs4_get_protover(sbi, p);
981 case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
982 return autofs4_get_protosubver(sbi, p);
983 case AUTOFS_IOC_SETTIMEOUT:
984 return autofs4_get_set_timeout(sbi, p);
985
986 case AUTOFS_IOC_TOGGLEREGHOST:
987 return autofs4_toggle_reghost(sbi, p);
988 case AUTOFS_IOC_ASKREGHOST:
989 return autofs4_ask_reghost(sbi, p);
990
991 case AUTOFS_IOC_ASKUMOUNT:
992 return autofs4_ask_umount(filp->f_path.mnt, p);
993
994 /* return a single thing to expire */
995 case AUTOFS_IOC_EXPIRE:
996 return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
997 /* same as above, but can send multiple expires through pipe */
998 case AUTOFS_IOC_EXPIRE_MULTI:
999 return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);
1000
1001 default:
1002 return -ENOSYS;
1003 }
1004 }
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