xref: /openbmc/linux/fs/cachefiles/daemon.c (revision 5b394b2d) 
1 /* Daemon interface
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public Licence
8  * as published by the Free Software Foundation; either version
9  * 2 of the Licence, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/completion.h>
16 #include <linux/slab.h>
17 #include <linux/fs.h>
18 #include <linux/file.h>
19 #include <linux/namei.h>
20 #include <linux/poll.h>
21 #include <linux/mount.h>
22 #include <linux/statfs.h>
23 #include <linux/ctype.h>
24 #include <linux/string.h>
25 #include <linux/fs_struct.h>
26 #include "internal.h"
27 
28 static int cachefiles_daemon_open(struct inode *, struct file *);
29 static int cachefiles_daemon_release(struct inode *, struct file *);
30 static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
31 				      loff_t *);
32 static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
33 				       size_t, loff_t *);
34 static __poll_t cachefiles_daemon_poll(struct file *,
35 					   struct poll_table_struct *);
36 static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
37 static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
38 static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
39 static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
40 static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
41 static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
42 static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
43 static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
44 static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
45 static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
46 static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
47 static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
48 
49 static unsigned long cachefiles_open;
50 
51 const struct file_operations cachefiles_daemon_fops = {
52 	.owner		= THIS_MODULE,
53 	.open		= cachefiles_daemon_open,
54 	.release	= cachefiles_daemon_release,
55 	.read		= cachefiles_daemon_read,
56 	.write		= cachefiles_daemon_write,
57 	.poll		= cachefiles_daemon_poll,
58 	.llseek		= noop_llseek,
59 };
60 
61 struct cachefiles_daemon_cmd {
62 	char name[8];
63 	int (*handler)(struct cachefiles_cache *cache, char *args);
64 };
65 
66 static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
67 	{ "bind",	cachefiles_daemon_bind		},
68 	{ "brun",	cachefiles_daemon_brun		},
69 	{ "bcull",	cachefiles_daemon_bcull		},
70 	{ "bstop",	cachefiles_daemon_bstop		},
71 	{ "cull",	cachefiles_daemon_cull		},
72 	{ "debug",	cachefiles_daemon_debug		},
73 	{ "dir",	cachefiles_daemon_dir		},
74 	{ "frun",	cachefiles_daemon_frun		},
75 	{ "fcull",	cachefiles_daemon_fcull		},
76 	{ "fstop",	cachefiles_daemon_fstop		},
77 	{ "inuse",	cachefiles_daemon_inuse		},
78 	{ "secctx",	cachefiles_daemon_secctx	},
79 	{ "tag",	cachefiles_daemon_tag		},
80 	{ "",		NULL				}
81 };
82 
83 
84 /*
85  * do various checks
86  */
87 static int cachefiles_daemon_open(struct inode *inode, struct file *file)
88 {
89 	struct cachefiles_cache *cache;
90 
91 	_enter("");
92 
93 	/* only the superuser may do this */
94 	if (!capable(CAP_SYS_ADMIN))
95 		return -EPERM;
96 
97 	/* the cachefiles device may only be open once at a time */
98 	if (xchg(&cachefiles_open, 1) == 1)
99 		return -EBUSY;
100 
101 	/* allocate a cache record */
102 	cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
103 	if (!cache) {
104 		cachefiles_open = 0;
105 		return -ENOMEM;
106 	}
107 
108 	mutex_init(&cache->daemon_mutex);
109 	cache->active_nodes = RB_ROOT;
110 	rwlock_init(&cache->active_lock);
111 	init_waitqueue_head(&cache->daemon_pollwq);
112 
113 	/* set default caching limits
114 	 * - limit at 1% free space and/or free files
115 	 * - cull below 5% free space and/or free files
116 	 * - cease culling above 7% free space and/or free files
117 	 */
118 	cache->frun_percent = 7;
119 	cache->fcull_percent = 5;
120 	cache->fstop_percent = 1;
121 	cache->brun_percent = 7;
122 	cache->bcull_percent = 5;
123 	cache->bstop_percent = 1;
124 
125 	file->private_data = cache;
126 	cache->cachefilesd = file;
127 	return 0;
128 }
129 
130 /*
131  * release a cache
132  */
133 static int cachefiles_daemon_release(struct inode *inode, struct file *file)
134 {
135 	struct cachefiles_cache *cache = file->private_data;
136 
137 	_enter("");
138 
139 	ASSERT(cache);
140 
141 	set_bit(CACHEFILES_DEAD, &cache->flags);
142 
143 	cachefiles_daemon_unbind(cache);
144 
145 	ASSERT(!cache->active_nodes.rb_node);
146 
147 	/* clean up the control file interface */
148 	cache->cachefilesd = NULL;
149 	file->private_data = NULL;
150 	cachefiles_open = 0;
151 
152 	kfree(cache);
153 
154 	_leave("");
155 	return 0;
156 }
157 
158 /*
159  * read the cache state
160  */
161 static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
162 				      size_t buflen, loff_t *pos)
163 {
164 	struct cachefiles_cache *cache = file->private_data;
165 	unsigned long long b_released;
166 	unsigned f_released;
167 	char buffer[256];
168 	int n;
169 
170 	//_enter(",,%zu,", buflen);
171 
172 	if (!test_bit(CACHEFILES_READY, &cache->flags))
173 		return 0;
174 
175 	/* check how much space the cache has */
176 	cachefiles_has_space(cache, 0, 0);
177 
178 	/* summarise */
179 	f_released = atomic_xchg(&cache->f_released, 0);
180 	b_released = atomic_long_xchg(&cache->b_released, 0);
181 	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
182 
183 	n = snprintf(buffer, sizeof(buffer),
184 		     "cull=%c"
185 		     " frun=%llx"
186 		     " fcull=%llx"
187 		     " fstop=%llx"
188 		     " brun=%llx"
189 		     " bcull=%llx"
190 		     " bstop=%llx"
191 		     " freleased=%x"
192 		     " breleased=%llx",
193 		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
194 		     (unsigned long long) cache->frun,
195 		     (unsigned long long) cache->fcull,
196 		     (unsigned long long) cache->fstop,
197 		     (unsigned long long) cache->brun,
198 		     (unsigned long long) cache->bcull,
199 		     (unsigned long long) cache->bstop,
200 		     f_released,
201 		     b_released);
202 
203 	if (n > buflen)
204 		return -EMSGSIZE;
205 
206 	if (copy_to_user(_buffer, buffer, n) != 0)
207 		return -EFAULT;
208 
209 	return n;
210 }
211 
212 /*
213  * command the cache
214  */
215 static ssize_t cachefiles_daemon_write(struct file *file,
216 				       const char __user *_data,
217 				       size_t datalen,
218 				       loff_t *pos)
219 {
220 	const struct cachefiles_daemon_cmd *cmd;
221 	struct cachefiles_cache *cache = file->private_data;
222 	ssize_t ret;
223 	char *data, *args, *cp;
224 
225 	//_enter(",,%zu,", datalen);
226 
227 	ASSERT(cache);
228 
229 	if (test_bit(CACHEFILES_DEAD, &cache->flags))
230 		return -EIO;
231 
232 	if (datalen < 0 || datalen > PAGE_SIZE - 1)
233 		return -EOPNOTSUPP;
234 
235 	/* drag the command string into the kernel so we can parse it */
236 	data = memdup_user_nul(_data, datalen);
237 	if (IS_ERR(data))
238 		return PTR_ERR(data);
239 
240 	ret = -EINVAL;
241 	if (memchr(data, '\0', datalen))
242 		goto error;
243 
244 	/* strip any newline */
245 	cp = memchr(data, '\n', datalen);
246 	if (cp) {
247 		if (cp == data)
248 			goto error;
249 
250 		*cp = '\0';
251 	}
252 
253 	/* parse the command */
254 	ret = -EOPNOTSUPP;
255 
256 	for (args = data; *args; args++)
257 		if (isspace(*args))
258 			break;
259 	if (*args) {
260 		if (args == data)
261 			goto error;
262 		*args = '\0';
263 		args = skip_spaces(++args);
264 	}
265 
266 	/* run the appropriate command handler */
267 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
268 		if (strcmp(cmd->name, data) == 0)
269 			goto found_command;
270 
271 error:
272 	kfree(data);
273 	//_leave(" = %zd", ret);
274 	return ret;
275 
276 found_command:
277 	mutex_lock(&cache->daemon_mutex);
278 
279 	ret = -EIO;
280 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
281 		ret = cmd->handler(cache, args);
282 
283 	mutex_unlock(&cache->daemon_mutex);
284 
285 	if (ret == 0)
286 		ret = datalen;
287 	goto error;
288 }
289 
290 /*
291  * poll for culling state
292  * - use EPOLLOUT to indicate culling state
293  */
294 static __poll_t cachefiles_daemon_poll(struct file *file,
295 					   struct poll_table_struct *poll)
296 {
297 	struct cachefiles_cache *cache = file->private_data;
298 	__poll_t mask;
299 
300 	poll_wait(file, &cache->daemon_pollwq, poll);
301 	mask = 0;
302 
303 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
304 		mask |= EPOLLIN;
305 
306 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
307 		mask |= EPOLLOUT;
308 
309 	return mask;
310 }
311 
312 /*
313  * give a range error for cache space constraints
314  * - can be tail-called
315  */
316 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
317 					 char *args)
318 {
319 	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
320 
321 	return -EINVAL;
322 }
323 
324 /*
325  * set the percentage of files at which to stop culling
326  * - command: "frun <N>%"
327  */
328 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
329 {
330 	unsigned long frun;
331 
332 	_enter(",%s", args);
333 
334 	if (!*args)
335 		return -EINVAL;
336 
337 	frun = simple_strtoul(args, &args, 10);
338 	if (args[0] != '%' || args[1] != '\0')
339 		return -EINVAL;
340 
341 	if (frun <= cache->fcull_percent || frun >= 100)
342 		return cachefiles_daemon_range_error(cache, args);
343 
344 	cache->frun_percent = frun;
345 	return 0;
346 }
347 
348 /*
349  * set the percentage of files at which to start culling
350  * - command: "fcull <N>%"
351  */
352 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
353 {
354 	unsigned long fcull;
355 
356 	_enter(",%s", args);
357 
358 	if (!*args)
359 		return -EINVAL;
360 
361 	fcull = simple_strtoul(args, &args, 10);
362 	if (args[0] != '%' || args[1] != '\0')
363 		return -EINVAL;
364 
365 	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
366 		return cachefiles_daemon_range_error(cache, args);
367 
368 	cache->fcull_percent = fcull;
369 	return 0;
370 }
371 
372 /*
373  * set the percentage of files at which to stop allocating
374  * - command: "fstop <N>%"
375  */
376 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
377 {
378 	unsigned long fstop;
379 
380 	_enter(",%s", args);
381 
382 	if (!*args)
383 		return -EINVAL;
384 
385 	fstop = simple_strtoul(args, &args, 10);
386 	if (args[0] != '%' || args[1] != '\0')
387 		return -EINVAL;
388 
389 	if (fstop < 0 || fstop >= cache->fcull_percent)
390 		return cachefiles_daemon_range_error(cache, args);
391 
392 	cache->fstop_percent = fstop;
393 	return 0;
394 }
395 
396 /*
397  * set the percentage of blocks at which to stop culling
398  * - command: "brun <N>%"
399  */
400 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
401 {
402 	unsigned long brun;
403 
404 	_enter(",%s", args);
405 
406 	if (!*args)
407 		return -EINVAL;
408 
409 	brun = simple_strtoul(args, &args, 10);
410 	if (args[0] != '%' || args[1] != '\0')
411 		return -EINVAL;
412 
413 	if (brun <= cache->bcull_percent || brun >= 100)
414 		return cachefiles_daemon_range_error(cache, args);
415 
416 	cache->brun_percent = brun;
417 	return 0;
418 }
419 
420 /*
421  * set the percentage of blocks at which to start culling
422  * - command: "bcull <N>%"
423  */
424 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
425 {
426 	unsigned long bcull;
427 
428 	_enter(",%s", args);
429 
430 	if (!*args)
431 		return -EINVAL;
432 
433 	bcull = simple_strtoul(args, &args, 10);
434 	if (args[0] != '%' || args[1] != '\0')
435 		return -EINVAL;
436 
437 	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
438 		return cachefiles_daemon_range_error(cache, args);
439 
440 	cache->bcull_percent = bcull;
441 	return 0;
442 }
443 
444 /*
445  * set the percentage of blocks at which to stop allocating
446  * - command: "bstop <N>%"
447  */
448 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
449 {
450 	unsigned long bstop;
451 
452 	_enter(",%s", args);
453 
454 	if (!*args)
455 		return -EINVAL;
456 
457 	bstop = simple_strtoul(args, &args, 10);
458 	if (args[0] != '%' || args[1] != '\0')
459 		return -EINVAL;
460 
461 	if (bstop < 0 || bstop >= cache->bcull_percent)
462 		return cachefiles_daemon_range_error(cache, args);
463 
464 	cache->bstop_percent = bstop;
465 	return 0;
466 }
467 
468 /*
469  * set the cache directory
470  * - command: "dir <name>"
471  */
472 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
473 {
474 	char *dir;
475 
476 	_enter(",%s", args);
477 
478 	if (!*args) {
479 		pr_err("Empty directory specified\n");
480 		return -EINVAL;
481 	}
482 
483 	if (cache->rootdirname) {
484 		pr_err("Second cache directory specified\n");
485 		return -EEXIST;
486 	}
487 
488 	dir = kstrdup(args, GFP_KERNEL);
489 	if (!dir)
490 		return -ENOMEM;
491 
492 	cache->rootdirname = dir;
493 	return 0;
494 }
495 
496 /*
497  * set the cache security context
498  * - command: "secctx <ctx>"
499  */
500 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
501 {
502 	char *secctx;
503 
504 	_enter(",%s", args);
505 
506 	if (!*args) {
507 		pr_err("Empty security context specified\n");
508 		return -EINVAL;
509 	}
510 
511 	if (cache->secctx) {
512 		pr_err("Second security context specified\n");
513 		return -EINVAL;
514 	}
515 
516 	secctx = kstrdup(args, GFP_KERNEL);
517 	if (!secctx)
518 		return -ENOMEM;
519 
520 	cache->secctx = secctx;
521 	return 0;
522 }
523 
524 /*
525  * set the cache tag
526  * - command: "tag <name>"
527  */
528 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
529 {
530 	char *tag;
531 
532 	_enter(",%s", args);
533 
534 	if (!*args) {
535 		pr_err("Empty tag specified\n");
536 		return -EINVAL;
537 	}
538 
539 	if (cache->tag)
540 		return -EEXIST;
541 
542 	tag = kstrdup(args, GFP_KERNEL);
543 	if (!tag)
544 		return -ENOMEM;
545 
546 	cache->tag = tag;
547 	return 0;
548 }
549 
550 /*
551  * request a node in the cache be culled from the current working directory
552  * - command: "cull <name>"
553  */
554 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
555 {
556 	struct path path;
557 	const struct cred *saved_cred;
558 	int ret;
559 
560 	_enter(",%s", args);
561 
562 	if (strchr(args, '/'))
563 		goto inval;
564 
565 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
566 		pr_err("cull applied to unready cache\n");
567 		return -EIO;
568 	}
569 
570 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
571 		pr_err("cull applied to dead cache\n");
572 		return -EIO;
573 	}
574 
575 	/* extract the directory dentry from the cwd */
576 	get_fs_pwd(current->fs, &path);
577 
578 	if (!d_can_lookup(path.dentry))
579 		goto notdir;
580 
581 	cachefiles_begin_secure(cache, &saved_cred);
582 	ret = cachefiles_cull(cache, path.dentry, args);
583 	cachefiles_end_secure(cache, saved_cred);
584 
585 	path_put(&path);
586 	_leave(" = %d", ret);
587 	return ret;
588 
589 notdir:
590 	path_put(&path);
591 	pr_err("cull command requires dirfd to be a directory\n");
592 	return -ENOTDIR;
593 
594 inval:
595 	pr_err("cull command requires dirfd and filename\n");
596 	return -EINVAL;
597 }
598 
599 /*
600  * set debugging mode
601  * - command: "debug <mask>"
602  */
603 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
604 {
605 	unsigned long mask;
606 
607 	_enter(",%s", args);
608 
609 	mask = simple_strtoul(args, &args, 0);
610 	if (args[0] != '\0')
611 		goto inval;
612 
613 	cachefiles_debug = mask;
614 	_leave(" = 0");
615 	return 0;
616 
617 inval:
618 	pr_err("debug command requires mask\n");
619 	return -EINVAL;
620 }
621 
622 /*
623  * find out whether an object in the current working directory is in use or not
624  * - command: "inuse <name>"
625  */
626 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
627 {
628 	struct path path;
629 	const struct cred *saved_cred;
630 	int ret;
631 
632 	//_enter(",%s", args);
633 
634 	if (strchr(args, '/'))
635 		goto inval;
636 
637 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
638 		pr_err("inuse applied to unready cache\n");
639 		return -EIO;
640 	}
641 
642 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
643 		pr_err("inuse applied to dead cache\n");
644 		return -EIO;
645 	}
646 
647 	/* extract the directory dentry from the cwd */
648 	get_fs_pwd(current->fs, &path);
649 
650 	if (!d_can_lookup(path.dentry))
651 		goto notdir;
652 
653 	cachefiles_begin_secure(cache, &saved_cred);
654 	ret = cachefiles_check_in_use(cache, path.dentry, args);
655 	cachefiles_end_secure(cache, saved_cred);
656 
657 	path_put(&path);
658 	//_leave(" = %d", ret);
659 	return ret;
660 
661 notdir:
662 	path_put(&path);
663 	pr_err("inuse command requires dirfd to be a directory\n");
664 	return -ENOTDIR;
665 
666 inval:
667 	pr_err("inuse command requires dirfd and filename\n");
668 	return -EINVAL;
669 }
670 
671 /*
672  * see if we have space for a number of pages and/or a number of files in the
673  * cache
674  */
675 int cachefiles_has_space(struct cachefiles_cache *cache,
676 			 unsigned fnr, unsigned bnr)
677 {
678 	struct kstatfs stats;
679 	struct path path = {
680 		.mnt	= cache->mnt,
681 		.dentry	= cache->mnt->mnt_root,
682 	};
683 	int ret;
684 
685 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
686 	//       (unsigned long long) cache->frun,
687 	//       (unsigned long long) cache->fcull,
688 	//       (unsigned long long) cache->fstop,
689 	//       (unsigned long long) cache->brun,
690 	//       (unsigned long long) cache->bcull,
691 	//       (unsigned long long) cache->bstop,
692 	//       fnr, bnr);
693 
694 	/* find out how many pages of blockdev are available */
695 	memset(&stats, 0, sizeof(stats));
696 
697 	ret = vfs_statfs(&path, &stats);
698 	if (ret < 0) {
699 		if (ret == -EIO)
700 			cachefiles_io_error(cache, "statfs failed");
701 		_leave(" = %d", ret);
702 		return ret;
703 	}
704 
705 	stats.f_bavail >>= cache->bshift;
706 
707 	//_debug("avail %llu,%llu",
708 	//       (unsigned long long) stats.f_ffree,
709 	//       (unsigned long long) stats.f_bavail);
710 
711 	/* see if there is sufficient space */
712 	if (stats.f_ffree > fnr)
713 		stats.f_ffree -= fnr;
714 	else
715 		stats.f_ffree = 0;
716 
717 	if (stats.f_bavail > bnr)
718 		stats.f_bavail -= bnr;
719 	else
720 		stats.f_bavail = 0;
721 
722 	ret = -ENOBUFS;
723 	if (stats.f_ffree < cache->fstop ||
724 	    stats.f_bavail < cache->bstop)
725 		goto begin_cull;
726 
727 	ret = 0;
728 	if (stats.f_ffree < cache->fcull ||
729 	    stats.f_bavail < cache->bcull)
730 		goto begin_cull;
731 
732 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
733 	    stats.f_ffree >= cache->frun &&
734 	    stats.f_bavail >= cache->brun &&
735 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
736 	    ) {
737 		_debug("cease culling");
738 		cachefiles_state_changed(cache);
739 	}
740 
741 	//_leave(" = 0");
742 	return 0;
743 
744 begin_cull:
745 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
746 		_debug("### CULL CACHE ###");
747 		cachefiles_state_changed(cache);
748 	}
749 
750 	_leave(" = %d", ret);
751 	return ret;
752 }
753