xref: /openbmc/linux/fs/cachefiles/daemon.c (revision 8b235f2f) 
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 unsigned int 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 	char buffer[256];
166 	int n;
167 
168 	//_enter(",,%zu,", buflen);
169 
170 	if (!test_bit(CACHEFILES_READY, &cache->flags))
171 		return 0;
172 
173 	/* check how much space the cache has */
174 	cachefiles_has_space(cache, 0, 0);
175 
176 	/* summarise */
177 	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
178 
179 	n = snprintf(buffer, sizeof(buffer),
180 		     "cull=%c"
181 		     " frun=%llx"
182 		     " fcull=%llx"
183 		     " fstop=%llx"
184 		     " brun=%llx"
185 		     " bcull=%llx"
186 		     " bstop=%llx",
187 		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
188 		     (unsigned long long) cache->frun,
189 		     (unsigned long long) cache->fcull,
190 		     (unsigned long long) cache->fstop,
191 		     (unsigned long long) cache->brun,
192 		     (unsigned long long) cache->bcull,
193 		     (unsigned long long) cache->bstop
194 		     );
195 
196 	if (n > buflen)
197 		return -EMSGSIZE;
198 
199 	if (copy_to_user(_buffer, buffer, n) != 0)
200 		return -EFAULT;
201 
202 	return n;
203 }
204 
205 /*
206  * command the cache
207  */
208 static ssize_t cachefiles_daemon_write(struct file *file,
209 				       const char __user *_data,
210 				       size_t datalen,
211 				       loff_t *pos)
212 {
213 	const struct cachefiles_daemon_cmd *cmd;
214 	struct cachefiles_cache *cache = file->private_data;
215 	ssize_t ret;
216 	char *data, *args, *cp;
217 
218 	//_enter(",,%zu,", datalen);
219 
220 	ASSERT(cache);
221 
222 	if (test_bit(CACHEFILES_DEAD, &cache->flags))
223 		return -EIO;
224 
225 	if (datalen < 0 || datalen > PAGE_SIZE - 1)
226 		return -EOPNOTSUPP;
227 
228 	/* drag the command string into the kernel so we can parse it */
229 	data = kmalloc(datalen + 1, GFP_KERNEL);
230 	if (!data)
231 		return -ENOMEM;
232 
233 	ret = -EFAULT;
234 	if (copy_from_user(data, _data, datalen) != 0)
235 		goto error;
236 
237 	data[datalen] = '\0';
238 
239 	ret = -EINVAL;
240 	if (memchr(data, '\0', datalen))
241 		goto error;
242 
243 	/* strip any newline */
244 	cp = memchr(data, '\n', datalen);
245 	if (cp) {
246 		if (cp == data)
247 			goto error;
248 
249 		*cp = '\0';
250 	}
251 
252 	/* parse the command */
253 	ret = -EOPNOTSUPP;
254 
255 	for (args = data; *args; args++)
256 		if (isspace(*args))
257 			break;
258 	if (*args) {
259 		if (args == data)
260 			goto error;
261 		*args = '\0';
262 		args = skip_spaces(++args);
263 	}
264 
265 	/* run the appropriate command handler */
266 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
267 		if (strcmp(cmd->name, data) == 0)
268 			goto found_command;
269 
270 error:
271 	kfree(data);
272 	//_leave(" = %zd", ret);
273 	return ret;
274 
275 found_command:
276 	mutex_lock(&cache->daemon_mutex);
277 
278 	ret = -EIO;
279 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
280 		ret = cmd->handler(cache, args);
281 
282 	mutex_unlock(&cache->daemon_mutex);
283 
284 	if (ret == 0)
285 		ret = datalen;
286 	goto error;
287 }
288 
289 /*
290  * poll for culling state
291  * - use POLLOUT to indicate culling state
292  */
293 static unsigned int cachefiles_daemon_poll(struct file *file,
294 					   struct poll_table_struct *poll)
295 {
296 	struct cachefiles_cache *cache = file->private_data;
297 	unsigned int mask;
298 
299 	poll_wait(file, &cache->daemon_pollwq, poll);
300 	mask = 0;
301 
302 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
303 		mask |= POLLIN;
304 
305 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
306 		mask |= POLLOUT;
307 
308 	return mask;
309 }
310 
311 /*
312  * give a range error for cache space constraints
313  * - can be tail-called
314  */
315 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
316 					 char *args)
317 {
318 	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
319 
320 	return -EINVAL;
321 }
322 
323 /*
324  * set the percentage of files at which to stop culling
325  * - command: "frun <N>%"
326  */
327 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
328 {
329 	unsigned long frun;
330 
331 	_enter(",%s", args);
332 
333 	if (!*args)
334 		return -EINVAL;
335 
336 	frun = simple_strtoul(args, &args, 10);
337 	if (args[0] != '%' || args[1] != '\0')
338 		return -EINVAL;
339 
340 	if (frun <= cache->fcull_percent || frun >= 100)
341 		return cachefiles_daemon_range_error(cache, args);
342 
343 	cache->frun_percent = frun;
344 	return 0;
345 }
346 
347 /*
348  * set the percentage of files at which to start culling
349  * - command: "fcull <N>%"
350  */
351 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
352 {
353 	unsigned long fcull;
354 
355 	_enter(",%s", args);
356 
357 	if (!*args)
358 		return -EINVAL;
359 
360 	fcull = simple_strtoul(args, &args, 10);
361 	if (args[0] != '%' || args[1] != '\0')
362 		return -EINVAL;
363 
364 	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
365 		return cachefiles_daemon_range_error(cache, args);
366 
367 	cache->fcull_percent = fcull;
368 	return 0;
369 }
370 
371 /*
372  * set the percentage of files at which to stop allocating
373  * - command: "fstop <N>%"
374  */
375 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
376 {
377 	unsigned long fstop;
378 
379 	_enter(",%s", args);
380 
381 	if (!*args)
382 		return -EINVAL;
383 
384 	fstop = simple_strtoul(args, &args, 10);
385 	if (args[0] != '%' || args[1] != '\0')
386 		return -EINVAL;
387 
388 	if (fstop < 0 || fstop >= cache->fcull_percent)
389 		return cachefiles_daemon_range_error(cache, args);
390 
391 	cache->fstop_percent = fstop;
392 	return 0;
393 }
394 
395 /*
396  * set the percentage of blocks at which to stop culling
397  * - command: "brun <N>%"
398  */
399 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
400 {
401 	unsigned long brun;
402 
403 	_enter(",%s", args);
404 
405 	if (!*args)
406 		return -EINVAL;
407 
408 	brun = simple_strtoul(args, &args, 10);
409 	if (args[0] != '%' || args[1] != '\0')
410 		return -EINVAL;
411 
412 	if (brun <= cache->bcull_percent || brun >= 100)
413 		return cachefiles_daemon_range_error(cache, args);
414 
415 	cache->brun_percent = brun;
416 	return 0;
417 }
418 
419 /*
420  * set the percentage of blocks at which to start culling
421  * - command: "bcull <N>%"
422  */
423 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
424 {
425 	unsigned long bcull;
426 
427 	_enter(",%s", args);
428 
429 	if (!*args)
430 		return -EINVAL;
431 
432 	bcull = simple_strtoul(args, &args, 10);
433 	if (args[0] != '%' || args[1] != '\0')
434 		return -EINVAL;
435 
436 	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
437 		return cachefiles_daemon_range_error(cache, args);
438 
439 	cache->bcull_percent = bcull;
440 	return 0;
441 }
442 
443 /*
444  * set the percentage of blocks at which to stop allocating
445  * - command: "bstop <N>%"
446  */
447 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
448 {
449 	unsigned long bstop;
450 
451 	_enter(",%s", args);
452 
453 	if (!*args)
454 		return -EINVAL;
455 
456 	bstop = simple_strtoul(args, &args, 10);
457 	if (args[0] != '%' || args[1] != '\0')
458 		return -EINVAL;
459 
460 	if (bstop < 0 || bstop >= cache->bcull_percent)
461 		return cachefiles_daemon_range_error(cache, args);
462 
463 	cache->bstop_percent = bstop;
464 	return 0;
465 }
466 
467 /*
468  * set the cache directory
469  * - command: "dir <name>"
470  */
471 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
472 {
473 	char *dir;
474 
475 	_enter(",%s", args);
476 
477 	if (!*args) {
478 		pr_err("Empty directory specified\n");
479 		return -EINVAL;
480 	}
481 
482 	if (cache->rootdirname) {
483 		pr_err("Second cache directory specified\n");
484 		return -EEXIST;
485 	}
486 
487 	dir = kstrdup(args, GFP_KERNEL);
488 	if (!dir)
489 		return -ENOMEM;
490 
491 	cache->rootdirname = dir;
492 	return 0;
493 }
494 
495 /*
496  * set the cache security context
497  * - command: "secctx <ctx>"
498  */
499 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
500 {
501 	char *secctx;
502 
503 	_enter(",%s", args);
504 
505 	if (!*args) {
506 		pr_err("Empty security context specified\n");
507 		return -EINVAL;
508 	}
509 
510 	if (cache->secctx) {
511 		pr_err("Second security context specified\n");
512 		return -EINVAL;
513 	}
514 
515 	secctx = kstrdup(args, GFP_KERNEL);
516 	if (!secctx)
517 		return -ENOMEM;
518 
519 	cache->secctx = secctx;
520 	return 0;
521 }
522 
523 /*
524  * set the cache tag
525  * - command: "tag <name>"
526  */
527 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
528 {
529 	char *tag;
530 
531 	_enter(",%s", args);
532 
533 	if (!*args) {
534 		pr_err("Empty tag specified\n");
535 		return -EINVAL;
536 	}
537 
538 	if (cache->tag)
539 		return -EEXIST;
540 
541 	tag = kstrdup(args, GFP_KERNEL);
542 	if (!tag)
543 		return -ENOMEM;
544 
545 	cache->tag = tag;
546 	return 0;
547 }
548 
549 /*
550  * request a node in the cache be culled from the current working directory
551  * - command: "cull <name>"
552  */
553 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
554 {
555 	struct path path;
556 	const struct cred *saved_cred;
557 	int ret;
558 
559 	_enter(",%s", args);
560 
561 	if (strchr(args, '/'))
562 		goto inval;
563 
564 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
565 		pr_err("cull applied to unready cache\n");
566 		return -EIO;
567 	}
568 
569 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
570 		pr_err("cull applied to dead cache\n");
571 		return -EIO;
572 	}
573 
574 	/* extract the directory dentry from the cwd */
575 	get_fs_pwd(current->fs, &path);
576 
577 	if (!d_can_lookup(path.dentry))
578 		goto notdir;
579 
580 	cachefiles_begin_secure(cache, &saved_cred);
581 	ret = cachefiles_cull(cache, path.dentry, args);
582 	cachefiles_end_secure(cache, saved_cred);
583 
584 	path_put(&path);
585 	_leave(" = %d", ret);
586 	return ret;
587 
588 notdir:
589 	path_put(&path);
590 	pr_err("cull command requires dirfd to be a directory\n");
591 	return -ENOTDIR;
592 
593 inval:
594 	pr_err("cull command requires dirfd and filename\n");
595 	return -EINVAL;
596 }
597 
598 /*
599  * set debugging mode
600  * - command: "debug <mask>"
601  */
602 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
603 {
604 	unsigned long mask;
605 
606 	_enter(",%s", args);
607 
608 	mask = simple_strtoul(args, &args, 0);
609 	if (args[0] != '\0')
610 		goto inval;
611 
612 	cachefiles_debug = mask;
613 	_leave(" = 0");
614 	return 0;
615 
616 inval:
617 	pr_err("debug command requires mask\n");
618 	return -EINVAL;
619 }
620 
621 /*
622  * find out whether an object in the current working directory is in use or not
623  * - command: "inuse <name>"
624  */
625 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
626 {
627 	struct path path;
628 	const struct cred *saved_cred;
629 	int ret;
630 
631 	//_enter(",%s", args);
632 
633 	if (strchr(args, '/'))
634 		goto inval;
635 
636 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
637 		pr_err("inuse applied to unready cache\n");
638 		return -EIO;
639 	}
640 
641 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
642 		pr_err("inuse applied to dead cache\n");
643 		return -EIO;
644 	}
645 
646 	/* extract the directory dentry from the cwd */
647 	get_fs_pwd(current->fs, &path);
648 
649 	if (!d_can_lookup(path.dentry))
650 		goto notdir;
651 
652 	cachefiles_begin_secure(cache, &saved_cred);
653 	ret = cachefiles_check_in_use(cache, path.dentry, args);
654 	cachefiles_end_secure(cache, saved_cred);
655 
656 	path_put(&path);
657 	//_leave(" = %d", ret);
658 	return ret;
659 
660 notdir:
661 	path_put(&path);
662 	pr_err("inuse command requires dirfd to be a directory\n");
663 	return -ENOTDIR;
664 
665 inval:
666 	pr_err("inuse command requires dirfd and filename\n");
667 	return -EINVAL;
668 }
669 
670 /*
671  * see if we have space for a number of pages and/or a number of files in the
672  * cache
673  */
674 int cachefiles_has_space(struct cachefiles_cache *cache,
675 			 unsigned fnr, unsigned bnr)
676 {
677 	struct kstatfs stats;
678 	struct path path = {
679 		.mnt	= cache->mnt,
680 		.dentry	= cache->mnt->mnt_root,
681 	};
682 	int ret;
683 
684 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
685 	//       (unsigned long long) cache->frun,
686 	//       (unsigned long long) cache->fcull,
687 	//       (unsigned long long) cache->fstop,
688 	//       (unsigned long long) cache->brun,
689 	//       (unsigned long long) cache->bcull,
690 	//       (unsigned long long) cache->bstop,
691 	//       fnr, bnr);
692 
693 	/* find out how many pages of blockdev are available */
694 	memset(&stats, 0, sizeof(stats));
695 
696 	ret = vfs_statfs(&path, &stats);
697 	if (ret < 0) {
698 		if (ret == -EIO)
699 			cachefiles_io_error(cache, "statfs failed");
700 		_leave(" = %d", ret);
701 		return ret;
702 	}
703 
704 	stats.f_bavail >>= cache->bshift;
705 
706 	//_debug("avail %llu,%llu",
707 	//       (unsigned long long) stats.f_ffree,
708 	//       (unsigned long long) stats.f_bavail);
709 
710 	/* see if there is sufficient space */
711 	if (stats.f_ffree > fnr)
712 		stats.f_ffree -= fnr;
713 	else
714 		stats.f_ffree = 0;
715 
716 	if (stats.f_bavail > bnr)
717 		stats.f_bavail -= bnr;
718 	else
719 		stats.f_bavail = 0;
720 
721 	ret = -ENOBUFS;
722 	if (stats.f_ffree < cache->fstop ||
723 	    stats.f_bavail < cache->bstop)
724 		goto begin_cull;
725 
726 	ret = 0;
727 	if (stats.f_ffree < cache->fcull ||
728 	    stats.f_bavail < cache->bcull)
729 		goto begin_cull;
730 
731 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
732 	    stats.f_ffree >= cache->frun &&
733 	    stats.f_bavail >= cache->brun &&
734 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
735 	    ) {
736 		_debug("cease culling");
737 		cachefiles_state_changed(cache);
738 	}
739 
740 	//_leave(" = 0");
741 	return 0;
742 
743 begin_cull:
744 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
745 		_debug("### CULL CACHE ###");
746 		cachefiles_state_changed(cache);
747 	}
748 
749 	_leave(" = %d", ret);
750 	return ret;
751 }
752