xref: /openbmc/linux/fs/cachefiles/daemon.c (revision cd4d09ec) 
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 = memdup_user_nul(_data, datalen);
230 	if (IS_ERR(data))
231 		return PTR_ERR(data);
232 
233 	ret = -EINVAL;
234 	if (memchr(data, '\0', datalen))
235 		goto error;
236 
237 	/* strip any newline */
238 	cp = memchr(data, '\n', datalen);
239 	if (cp) {
240 		if (cp == data)
241 			goto error;
242 
243 		*cp = '\0';
244 	}
245 
246 	/* parse the command */
247 	ret = -EOPNOTSUPP;
248 
249 	for (args = data; *args; args++)
250 		if (isspace(*args))
251 			break;
252 	if (*args) {
253 		if (args == data)
254 			goto error;
255 		*args = '\0';
256 		args = skip_spaces(++args);
257 	}
258 
259 	/* run the appropriate command handler */
260 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
261 		if (strcmp(cmd->name, data) == 0)
262 			goto found_command;
263 
264 error:
265 	kfree(data);
266 	//_leave(" = %zd", ret);
267 	return ret;
268 
269 found_command:
270 	mutex_lock(&cache->daemon_mutex);
271 
272 	ret = -EIO;
273 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
274 		ret = cmd->handler(cache, args);
275 
276 	mutex_unlock(&cache->daemon_mutex);
277 
278 	if (ret == 0)
279 		ret = datalen;
280 	goto error;
281 }
282 
283 /*
284  * poll for culling state
285  * - use POLLOUT to indicate culling state
286  */
287 static unsigned int cachefiles_daemon_poll(struct file *file,
288 					   struct poll_table_struct *poll)
289 {
290 	struct cachefiles_cache *cache = file->private_data;
291 	unsigned int mask;
292 
293 	poll_wait(file, &cache->daemon_pollwq, poll);
294 	mask = 0;
295 
296 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
297 		mask |= POLLIN;
298 
299 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
300 		mask |= POLLOUT;
301 
302 	return mask;
303 }
304 
305 /*
306  * give a range error for cache space constraints
307  * - can be tail-called
308  */
309 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
310 					 char *args)
311 {
312 	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
313 
314 	return -EINVAL;
315 }
316 
317 /*
318  * set the percentage of files at which to stop culling
319  * - command: "frun <N>%"
320  */
321 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
322 {
323 	unsigned long frun;
324 
325 	_enter(",%s", args);
326 
327 	if (!*args)
328 		return -EINVAL;
329 
330 	frun = simple_strtoul(args, &args, 10);
331 	if (args[0] != '%' || args[1] != '\0')
332 		return -EINVAL;
333 
334 	if (frun <= cache->fcull_percent || frun >= 100)
335 		return cachefiles_daemon_range_error(cache, args);
336 
337 	cache->frun_percent = frun;
338 	return 0;
339 }
340 
341 /*
342  * set the percentage of files at which to start culling
343  * - command: "fcull <N>%"
344  */
345 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
346 {
347 	unsigned long fcull;
348 
349 	_enter(",%s", args);
350 
351 	if (!*args)
352 		return -EINVAL;
353 
354 	fcull = simple_strtoul(args, &args, 10);
355 	if (args[0] != '%' || args[1] != '\0')
356 		return -EINVAL;
357 
358 	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
359 		return cachefiles_daemon_range_error(cache, args);
360 
361 	cache->fcull_percent = fcull;
362 	return 0;
363 }
364 
365 /*
366  * set the percentage of files at which to stop allocating
367  * - command: "fstop <N>%"
368  */
369 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
370 {
371 	unsigned long fstop;
372 
373 	_enter(",%s", args);
374 
375 	if (!*args)
376 		return -EINVAL;
377 
378 	fstop = simple_strtoul(args, &args, 10);
379 	if (args[0] != '%' || args[1] != '\0')
380 		return -EINVAL;
381 
382 	if (fstop < 0 || fstop >= cache->fcull_percent)
383 		return cachefiles_daemon_range_error(cache, args);
384 
385 	cache->fstop_percent = fstop;
386 	return 0;
387 }
388 
389 /*
390  * set the percentage of blocks at which to stop culling
391  * - command: "brun <N>%"
392  */
393 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
394 {
395 	unsigned long brun;
396 
397 	_enter(",%s", args);
398 
399 	if (!*args)
400 		return -EINVAL;
401 
402 	brun = simple_strtoul(args, &args, 10);
403 	if (args[0] != '%' || args[1] != '\0')
404 		return -EINVAL;
405 
406 	if (brun <= cache->bcull_percent || brun >= 100)
407 		return cachefiles_daemon_range_error(cache, args);
408 
409 	cache->brun_percent = brun;
410 	return 0;
411 }
412 
413 /*
414  * set the percentage of blocks at which to start culling
415  * - command: "bcull <N>%"
416  */
417 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
418 {
419 	unsigned long bcull;
420 
421 	_enter(",%s", args);
422 
423 	if (!*args)
424 		return -EINVAL;
425 
426 	bcull = simple_strtoul(args, &args, 10);
427 	if (args[0] != '%' || args[1] != '\0')
428 		return -EINVAL;
429 
430 	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
431 		return cachefiles_daemon_range_error(cache, args);
432 
433 	cache->bcull_percent = bcull;
434 	return 0;
435 }
436 
437 /*
438  * set the percentage of blocks at which to stop allocating
439  * - command: "bstop <N>%"
440  */
441 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
442 {
443 	unsigned long bstop;
444 
445 	_enter(",%s", args);
446 
447 	if (!*args)
448 		return -EINVAL;
449 
450 	bstop = simple_strtoul(args, &args, 10);
451 	if (args[0] != '%' || args[1] != '\0')
452 		return -EINVAL;
453 
454 	if (bstop < 0 || bstop >= cache->bcull_percent)
455 		return cachefiles_daemon_range_error(cache, args);
456 
457 	cache->bstop_percent = bstop;
458 	return 0;
459 }
460 
461 /*
462  * set the cache directory
463  * - command: "dir <name>"
464  */
465 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
466 {
467 	char *dir;
468 
469 	_enter(",%s", args);
470 
471 	if (!*args) {
472 		pr_err("Empty directory specified\n");
473 		return -EINVAL;
474 	}
475 
476 	if (cache->rootdirname) {
477 		pr_err("Second cache directory specified\n");
478 		return -EEXIST;
479 	}
480 
481 	dir = kstrdup(args, GFP_KERNEL);
482 	if (!dir)
483 		return -ENOMEM;
484 
485 	cache->rootdirname = dir;
486 	return 0;
487 }
488 
489 /*
490  * set the cache security context
491  * - command: "secctx <ctx>"
492  */
493 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
494 {
495 	char *secctx;
496 
497 	_enter(",%s", args);
498 
499 	if (!*args) {
500 		pr_err("Empty security context specified\n");
501 		return -EINVAL;
502 	}
503 
504 	if (cache->secctx) {
505 		pr_err("Second security context specified\n");
506 		return -EINVAL;
507 	}
508 
509 	secctx = kstrdup(args, GFP_KERNEL);
510 	if (!secctx)
511 		return -ENOMEM;
512 
513 	cache->secctx = secctx;
514 	return 0;
515 }
516 
517 /*
518  * set the cache tag
519  * - command: "tag <name>"
520  */
521 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
522 {
523 	char *tag;
524 
525 	_enter(",%s", args);
526 
527 	if (!*args) {
528 		pr_err("Empty tag specified\n");
529 		return -EINVAL;
530 	}
531 
532 	if (cache->tag)
533 		return -EEXIST;
534 
535 	tag = kstrdup(args, GFP_KERNEL);
536 	if (!tag)
537 		return -ENOMEM;
538 
539 	cache->tag = tag;
540 	return 0;
541 }
542 
543 /*
544  * request a node in the cache be culled from the current working directory
545  * - command: "cull <name>"
546  */
547 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
548 {
549 	struct path path;
550 	const struct cred *saved_cred;
551 	int ret;
552 
553 	_enter(",%s", args);
554 
555 	if (strchr(args, '/'))
556 		goto inval;
557 
558 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
559 		pr_err("cull applied to unready cache\n");
560 		return -EIO;
561 	}
562 
563 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
564 		pr_err("cull applied to dead cache\n");
565 		return -EIO;
566 	}
567 
568 	/* extract the directory dentry from the cwd */
569 	get_fs_pwd(current->fs, &path);
570 
571 	if (!d_can_lookup(path.dentry))
572 		goto notdir;
573 
574 	cachefiles_begin_secure(cache, &saved_cred);
575 	ret = cachefiles_cull(cache, path.dentry, args);
576 	cachefiles_end_secure(cache, saved_cred);
577 
578 	path_put(&path);
579 	_leave(" = %d", ret);
580 	return ret;
581 
582 notdir:
583 	path_put(&path);
584 	pr_err("cull command requires dirfd to be a directory\n");
585 	return -ENOTDIR;
586 
587 inval:
588 	pr_err("cull command requires dirfd and filename\n");
589 	return -EINVAL;
590 }
591 
592 /*
593  * set debugging mode
594  * - command: "debug <mask>"
595  */
596 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
597 {
598 	unsigned long mask;
599 
600 	_enter(",%s", args);
601 
602 	mask = simple_strtoul(args, &args, 0);
603 	if (args[0] != '\0')
604 		goto inval;
605 
606 	cachefiles_debug = mask;
607 	_leave(" = 0");
608 	return 0;
609 
610 inval:
611 	pr_err("debug command requires mask\n");
612 	return -EINVAL;
613 }
614 
615 /*
616  * find out whether an object in the current working directory is in use or not
617  * - command: "inuse <name>"
618  */
619 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
620 {
621 	struct path path;
622 	const struct cred *saved_cred;
623 	int ret;
624 
625 	//_enter(",%s", args);
626 
627 	if (strchr(args, '/'))
628 		goto inval;
629 
630 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
631 		pr_err("inuse applied to unready cache\n");
632 		return -EIO;
633 	}
634 
635 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
636 		pr_err("inuse applied to dead cache\n");
637 		return -EIO;
638 	}
639 
640 	/* extract the directory dentry from the cwd */
641 	get_fs_pwd(current->fs, &path);
642 
643 	if (!d_can_lookup(path.dentry))
644 		goto notdir;
645 
646 	cachefiles_begin_secure(cache, &saved_cred);
647 	ret = cachefiles_check_in_use(cache, path.dentry, args);
648 	cachefiles_end_secure(cache, saved_cred);
649 
650 	path_put(&path);
651 	//_leave(" = %d", ret);
652 	return ret;
653 
654 notdir:
655 	path_put(&path);
656 	pr_err("inuse command requires dirfd to be a directory\n");
657 	return -ENOTDIR;
658 
659 inval:
660 	pr_err("inuse command requires dirfd and filename\n");
661 	return -EINVAL;
662 }
663 
664 /*
665  * see if we have space for a number of pages and/or a number of files in the
666  * cache
667  */
668 int cachefiles_has_space(struct cachefiles_cache *cache,
669 			 unsigned fnr, unsigned bnr)
670 {
671 	struct kstatfs stats;
672 	struct path path = {
673 		.mnt	= cache->mnt,
674 		.dentry	= cache->mnt->mnt_root,
675 	};
676 	int ret;
677 
678 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
679 	//       (unsigned long long) cache->frun,
680 	//       (unsigned long long) cache->fcull,
681 	//       (unsigned long long) cache->fstop,
682 	//       (unsigned long long) cache->brun,
683 	//       (unsigned long long) cache->bcull,
684 	//       (unsigned long long) cache->bstop,
685 	//       fnr, bnr);
686 
687 	/* find out how many pages of blockdev are available */
688 	memset(&stats, 0, sizeof(stats));
689 
690 	ret = vfs_statfs(&path, &stats);
691 	if (ret < 0) {
692 		if (ret == -EIO)
693 			cachefiles_io_error(cache, "statfs failed");
694 		_leave(" = %d", ret);
695 		return ret;
696 	}
697 
698 	stats.f_bavail >>= cache->bshift;
699 
700 	//_debug("avail %llu,%llu",
701 	//       (unsigned long long) stats.f_ffree,
702 	//       (unsigned long long) stats.f_bavail);
703 
704 	/* see if there is sufficient space */
705 	if (stats.f_ffree > fnr)
706 		stats.f_ffree -= fnr;
707 	else
708 		stats.f_ffree = 0;
709 
710 	if (stats.f_bavail > bnr)
711 		stats.f_bavail -= bnr;
712 	else
713 		stats.f_bavail = 0;
714 
715 	ret = -ENOBUFS;
716 	if (stats.f_ffree < cache->fstop ||
717 	    stats.f_bavail < cache->bstop)
718 		goto begin_cull;
719 
720 	ret = 0;
721 	if (stats.f_ffree < cache->fcull ||
722 	    stats.f_bavail < cache->bcull)
723 		goto begin_cull;
724 
725 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
726 	    stats.f_ffree >= cache->frun &&
727 	    stats.f_bavail >= cache->brun &&
728 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
729 	    ) {
730 		_debug("cease culling");
731 		cachefiles_state_changed(cache);
732 	}
733 
734 	//_leave(" = 0");
735 	return 0;
736 
737 begin_cull:
738 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
739 		_debug("### CULL CACHE ###");
740 		cachefiles_state_changed(cache);
741 	}
742 
743 	_leave(" = %d", ret);
744 	return ret;
745 }
746