xref: /openbmc/linux/fs/cachefiles/daemon.c (revision a09d2831) 
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 };
59 
60 struct cachefiles_daemon_cmd {
61 	char name[8];
62 	int (*handler)(struct cachefiles_cache *cache, char *args);
63 };
64 
65 static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
66 	{ "bind",	cachefiles_daemon_bind		},
67 	{ "brun",	cachefiles_daemon_brun		},
68 	{ "bcull",	cachefiles_daemon_bcull		},
69 	{ "bstop",	cachefiles_daemon_bstop		},
70 	{ "cull",	cachefiles_daemon_cull		},
71 	{ "debug",	cachefiles_daemon_debug		},
72 	{ "dir",	cachefiles_daemon_dir		},
73 	{ "frun",	cachefiles_daemon_frun		},
74 	{ "fcull",	cachefiles_daemon_fcull		},
75 	{ "fstop",	cachefiles_daemon_fstop		},
76 	{ "inuse",	cachefiles_daemon_inuse		},
77 	{ "secctx",	cachefiles_daemon_secctx	},
78 	{ "tag",	cachefiles_daemon_tag		},
79 	{ "",		NULL				}
80 };
81 
82 
83 /*
84  * do various checks
85  */
86 static int cachefiles_daemon_open(struct inode *inode, struct file *file)
87 {
88 	struct cachefiles_cache *cache;
89 
90 	_enter("");
91 
92 	/* only the superuser may do this */
93 	if (!capable(CAP_SYS_ADMIN))
94 		return -EPERM;
95 
96 	/* the cachefiles device may only be open once at a time */
97 	if (xchg(&cachefiles_open, 1) == 1)
98 		return -EBUSY;
99 
100 	/* allocate a cache record */
101 	cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
102 	if (!cache) {
103 		cachefiles_open = 0;
104 		return -ENOMEM;
105 	}
106 
107 	mutex_init(&cache->daemon_mutex);
108 	cache->active_nodes = RB_ROOT;
109 	rwlock_init(&cache->active_lock);
110 	init_waitqueue_head(&cache->daemon_pollwq);
111 
112 	/* set default caching limits
113 	 * - limit at 1% free space and/or free files
114 	 * - cull below 5% free space and/or free files
115 	 * - cease culling above 7% free space and/or free files
116 	 */
117 	cache->frun_percent = 7;
118 	cache->fcull_percent = 5;
119 	cache->fstop_percent = 1;
120 	cache->brun_percent = 7;
121 	cache->bcull_percent = 5;
122 	cache->bstop_percent = 1;
123 
124 	file->private_data = cache;
125 	cache->cachefilesd = file;
126 	return 0;
127 }
128 
129 /*
130  * release a cache
131  */
132 static int cachefiles_daemon_release(struct inode *inode, struct file *file)
133 {
134 	struct cachefiles_cache *cache = file->private_data;
135 
136 	_enter("");
137 
138 	ASSERT(cache);
139 
140 	set_bit(CACHEFILES_DEAD, &cache->flags);
141 
142 	cachefiles_daemon_unbind(cache);
143 
144 	ASSERT(!cache->active_nodes.rb_node);
145 
146 	/* clean up the control file interface */
147 	cache->cachefilesd = NULL;
148 	file->private_data = NULL;
149 	cachefiles_open = 0;
150 
151 	kfree(cache);
152 
153 	_leave("");
154 	return 0;
155 }
156 
157 /*
158  * read the cache state
159  */
160 static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
161 				      size_t buflen, loff_t *pos)
162 {
163 	struct cachefiles_cache *cache = file->private_data;
164 	char buffer[256];
165 	int n;
166 
167 	//_enter(",,%zu,", buflen);
168 
169 	if (!test_bit(CACHEFILES_READY, &cache->flags))
170 		return 0;
171 
172 	/* check how much space the cache has */
173 	cachefiles_has_space(cache, 0, 0);
174 
175 	/* summarise */
176 	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
177 
178 	n = snprintf(buffer, sizeof(buffer),
179 		     "cull=%c"
180 		     " frun=%llx"
181 		     " fcull=%llx"
182 		     " fstop=%llx"
183 		     " brun=%llx"
184 		     " bcull=%llx"
185 		     " bstop=%llx",
186 		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
187 		     (unsigned long long) cache->frun,
188 		     (unsigned long long) cache->fcull,
189 		     (unsigned long long) cache->fstop,
190 		     (unsigned long long) cache->brun,
191 		     (unsigned long long) cache->bcull,
192 		     (unsigned long long) cache->bstop
193 		     );
194 
195 	if (n > buflen)
196 		return -EMSGSIZE;
197 
198 	if (copy_to_user(_buffer, buffer, n) != 0)
199 		return -EFAULT;
200 
201 	return n;
202 }
203 
204 /*
205  * command the cache
206  */
207 static ssize_t cachefiles_daemon_write(struct file *file,
208 				       const char __user *_data,
209 				       size_t datalen,
210 				       loff_t *pos)
211 {
212 	const struct cachefiles_daemon_cmd *cmd;
213 	struct cachefiles_cache *cache = file->private_data;
214 	ssize_t ret;
215 	char *data, *args, *cp;
216 
217 	//_enter(",,%zu,", datalen);
218 
219 	ASSERT(cache);
220 
221 	if (test_bit(CACHEFILES_DEAD, &cache->flags))
222 		return -EIO;
223 
224 	if (datalen < 0 || datalen > PAGE_SIZE - 1)
225 		return -EOPNOTSUPP;
226 
227 	/* drag the command string into the kernel so we can parse it */
228 	data = kmalloc(datalen + 1, GFP_KERNEL);
229 	if (!data)
230 		return -ENOMEM;
231 
232 	ret = -EFAULT;
233 	if (copy_from_user(data, _data, datalen) != 0)
234 		goto error;
235 
236 	data[datalen] = '\0';
237 
238 	ret = -EINVAL;
239 	if (memchr(data, '\0', datalen))
240 		goto error;
241 
242 	/* strip any newline */
243 	cp = memchr(data, '\n', datalen);
244 	if (cp) {
245 		if (cp == data)
246 			goto error;
247 
248 		*cp = '\0';
249 	}
250 
251 	/* parse the command */
252 	ret = -EOPNOTSUPP;
253 
254 	for (args = data; *args; args++)
255 		if (isspace(*args))
256 			break;
257 	if (*args) {
258 		if (args == data)
259 			goto error;
260 		*args = '\0';
261 		args = skip_spaces(++args);
262 	}
263 
264 	/* run the appropriate command handler */
265 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
266 		if (strcmp(cmd->name, data) == 0)
267 			goto found_command;
268 
269 error:
270 	kfree(data);
271 	//_leave(" = %zd", ret);
272 	return ret;
273 
274 found_command:
275 	mutex_lock(&cache->daemon_mutex);
276 
277 	ret = -EIO;
278 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
279 		ret = cmd->handler(cache, args);
280 
281 	mutex_unlock(&cache->daemon_mutex);
282 
283 	if (ret == 0)
284 		ret = datalen;
285 	goto error;
286 }
287 
288 /*
289  * poll for culling state
290  * - use POLLOUT to indicate culling state
291  */
292 static unsigned int cachefiles_daemon_poll(struct file *file,
293 					   struct poll_table_struct *poll)
294 {
295 	struct cachefiles_cache *cache = file->private_data;
296 	unsigned int mask;
297 
298 	poll_wait(file, &cache->daemon_pollwq, poll);
299 	mask = 0;
300 
301 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
302 		mask |= POLLIN;
303 
304 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
305 		mask |= POLLOUT;
306 
307 	return mask;
308 }
309 
310 /*
311  * give a range error for cache space constraints
312  * - can be tail-called
313  */
314 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
315 					 char *args)
316 {
317 	kerror("Free space limits must be in range"
318 	       " 0%%<=stop<cull<run<100%%");
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 		kerror("Empty directory specified");
479 		return -EINVAL;
480 	}
481 
482 	if (cache->rootdirname) {
483 		kerror("Second cache directory specified");
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 		kerror("Empty security context specified");
507 		return -EINVAL;
508 	}
509 
510 	if (cache->secctx) {
511 		kerror("Second security context specified");
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 		kerror("Empty tag specified");
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 fs_struct *fs;
556 	struct dentry *dir;
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 		kerror("cull applied to unready cache");
567 		return -EIO;
568 	}
569 
570 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
571 		kerror("cull applied to dead cache");
572 		return -EIO;
573 	}
574 
575 	/* extract the directory dentry from the cwd */
576 	fs = current->fs;
577 	read_lock(&fs->lock);
578 	dir = dget(fs->pwd.dentry);
579 	read_unlock(&fs->lock);
580 
581 	if (!S_ISDIR(dir->d_inode->i_mode))
582 		goto notdir;
583 
584 	cachefiles_begin_secure(cache, &saved_cred);
585 	ret = cachefiles_cull(cache, dir, args);
586 	cachefiles_end_secure(cache, saved_cred);
587 
588 	dput(dir);
589 	_leave(" = %d", ret);
590 	return ret;
591 
592 notdir:
593 	dput(dir);
594 	kerror("cull command requires dirfd to be a directory");
595 	return -ENOTDIR;
596 
597 inval:
598 	kerror("cull command requires dirfd and filename");
599 	return -EINVAL;
600 }
601 
602 /*
603  * set debugging mode
604  * - command: "debug <mask>"
605  */
606 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
607 {
608 	unsigned long mask;
609 
610 	_enter(",%s", args);
611 
612 	mask = simple_strtoul(args, &args, 0);
613 	if (args[0] != '\0')
614 		goto inval;
615 
616 	cachefiles_debug = mask;
617 	_leave(" = 0");
618 	return 0;
619 
620 inval:
621 	kerror("debug command requires mask");
622 	return -EINVAL;
623 }
624 
625 /*
626  * find out whether an object in the current working directory is in use or not
627  * - command: "inuse <name>"
628  */
629 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
630 {
631 	struct fs_struct *fs;
632 	struct dentry *dir;
633 	const struct cred *saved_cred;
634 	int ret;
635 
636 	//_enter(",%s", args);
637 
638 	if (strchr(args, '/'))
639 		goto inval;
640 
641 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
642 		kerror("inuse applied to unready cache");
643 		return -EIO;
644 	}
645 
646 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
647 		kerror("inuse applied to dead cache");
648 		return -EIO;
649 	}
650 
651 	/* extract the directory dentry from the cwd */
652 	fs = current->fs;
653 	read_lock(&fs->lock);
654 	dir = dget(fs->pwd.dentry);
655 	read_unlock(&fs->lock);
656 
657 	if (!S_ISDIR(dir->d_inode->i_mode))
658 		goto notdir;
659 
660 	cachefiles_begin_secure(cache, &saved_cred);
661 	ret = cachefiles_check_in_use(cache, dir, args);
662 	cachefiles_end_secure(cache, saved_cred);
663 
664 	dput(dir);
665 	//_leave(" = %d", ret);
666 	return ret;
667 
668 notdir:
669 	dput(dir);
670 	kerror("inuse command requires dirfd to be a directory");
671 	return -ENOTDIR;
672 
673 inval:
674 	kerror("inuse command requires dirfd and filename");
675 	return -EINVAL;
676 }
677 
678 /*
679  * see if we have space for a number of pages and/or a number of files in the
680  * cache
681  */
682 int cachefiles_has_space(struct cachefiles_cache *cache,
683 			 unsigned fnr, unsigned bnr)
684 {
685 	struct kstatfs stats;
686 	int ret;
687 
688 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
689 	//       (unsigned long long) cache->frun,
690 	//       (unsigned long long) cache->fcull,
691 	//       (unsigned long long) cache->fstop,
692 	//       (unsigned long long) cache->brun,
693 	//       (unsigned long long) cache->bcull,
694 	//       (unsigned long long) cache->bstop,
695 	//       fnr, bnr);
696 
697 	/* find out how many pages of blockdev are available */
698 	memset(&stats, 0, sizeof(stats));
699 
700 	ret = vfs_statfs(cache->mnt->mnt_root, &stats);
701 	if (ret < 0) {
702 		if (ret == -EIO)
703 			cachefiles_io_error(cache, "statfs failed");
704 		_leave(" = %d", ret);
705 		return ret;
706 	}
707 
708 	stats.f_bavail >>= cache->bshift;
709 
710 	//_debug("avail %llu,%llu",
711 	//       (unsigned long long) stats.f_ffree,
712 	//       (unsigned long long) stats.f_bavail);
713 
714 	/* see if there is sufficient space */
715 	if (stats.f_ffree > fnr)
716 		stats.f_ffree -= fnr;
717 	else
718 		stats.f_ffree = 0;
719 
720 	if (stats.f_bavail > bnr)
721 		stats.f_bavail -= bnr;
722 	else
723 		stats.f_bavail = 0;
724 
725 	ret = -ENOBUFS;
726 	if (stats.f_ffree < cache->fstop ||
727 	    stats.f_bavail < cache->bstop)
728 		goto begin_cull;
729 
730 	ret = 0;
731 	if (stats.f_ffree < cache->fcull ||
732 	    stats.f_bavail < cache->bcull)
733 		goto begin_cull;
734 
735 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
736 	    stats.f_ffree >= cache->frun &&
737 	    stats.f_bavail >= cache->brun &&
738 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
739 	    ) {
740 		_debug("cease culling");
741 		cachefiles_state_changed(cache);
742 	}
743 
744 	//_leave(" = 0");
745 	return 0;
746 
747 begin_cull:
748 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
749 		_debug("### CULL CACHE ###");
750 		cachefiles_state_changed(cache);
751 	}
752 
753 	_leave(" = %d", ret);
754 	return ret;
755 }
756