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ddbcc7e8 PM |
1 | /* |
2 | * kernel/cgroup.c | |
3 | * | |
4 | * Generic process-grouping system. | |
5 | * | |
6 | * Based originally on the cpuset system, extracted by Paul Menage | |
7 | * Copyright (C) 2006 Google, Inc | |
8 | * | |
9 | * Copyright notices from the original cpuset code: | |
10 | * -------------------------------------------------- | |
11 | * Copyright (C) 2003 BULL SA. | |
12 | * Copyright (C) 2004-2006 Silicon Graphics, Inc. | |
13 | * | |
14 | * Portions derived from Patrick Mochel's sysfs code. | |
15 | * sysfs is Copyright (c) 2001-3 Patrick Mochel | |
16 | * | |
17 | * 2003-10-10 Written by Simon Derr. | |
18 | * 2003-10-22 Updates by Stephen Hemminger. | |
19 | * 2004 May-July Rework by Paul Jackson. | |
20 | * --------------------------------------------------- | |
21 | * | |
22 | * This file is subject to the terms and conditions of the GNU General Public | |
23 | * License. See the file COPYING in the main directory of the Linux | |
24 | * distribution for more details. | |
25 | */ | |
26 | ||
27 | #include <linux/cgroup.h> | |
28 | #include <linux/errno.h> | |
29 | #include <linux/fs.h> | |
30 | #include <linux/kernel.h> | |
31 | #include <linux/list.h> | |
32 | #include <linux/mm.h> | |
33 | #include <linux/mutex.h> | |
34 | #include <linux/mount.h> | |
35 | #include <linux/pagemap.h> | |
36 | #include <linux/rcupdate.h> | |
37 | #include <linux/sched.h> | |
38 | #include <linux/seq_file.h> | |
39 | #include <linux/slab.h> | |
40 | #include <linux/magic.h> | |
41 | #include <linux/spinlock.h> | |
42 | #include <linux/string.h> | |
bbcb81d0 | 43 | #include <linux/sort.h> |
ddbcc7e8 PM |
44 | #include <asm/atomic.h> |
45 | ||
46 | /* Generate an array of cgroup subsystem pointers */ | |
47 | #define SUBSYS(_x) &_x ## _subsys, | |
48 | ||
49 | static struct cgroup_subsys *subsys[] = { | |
50 | #include <linux/cgroup_subsys.h> | |
51 | }; | |
52 | ||
53 | /* | |
54 | * A cgroupfs_root represents the root of a cgroup hierarchy, | |
55 | * and may be associated with a superblock to form an active | |
56 | * hierarchy | |
57 | */ | |
58 | struct cgroupfs_root { | |
59 | struct super_block *sb; | |
60 | ||
61 | /* | |
62 | * The bitmask of subsystems intended to be attached to this | |
63 | * hierarchy | |
64 | */ | |
65 | unsigned long subsys_bits; | |
66 | ||
67 | /* The bitmask of subsystems currently attached to this hierarchy */ | |
68 | unsigned long actual_subsys_bits; | |
69 | ||
70 | /* A list running through the attached subsystems */ | |
71 | struct list_head subsys_list; | |
72 | ||
73 | /* The root cgroup for this hierarchy */ | |
74 | struct cgroup top_cgroup; | |
75 | ||
76 | /* Tracks how many cgroups are currently defined in hierarchy.*/ | |
77 | int number_of_cgroups; | |
78 | ||
79 | /* A list running through the mounted hierarchies */ | |
80 | struct list_head root_list; | |
81 | ||
82 | /* Hierarchy-specific flags */ | |
83 | unsigned long flags; | |
84 | }; | |
85 | ||
86 | ||
87 | /* | |
88 | * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the | |
89 | * subsystems that are otherwise unattached - it never has more than a | |
90 | * single cgroup, and all tasks are part of that cgroup. | |
91 | */ | |
92 | static struct cgroupfs_root rootnode; | |
93 | ||
94 | /* The list of hierarchy roots */ | |
95 | ||
96 | static LIST_HEAD(roots); | |
97 | ||
98 | /* dummytop is a shorthand for the dummy hierarchy's top cgroup */ | |
99 | #define dummytop (&rootnode.top_cgroup) | |
100 | ||
101 | /* This flag indicates whether tasks in the fork and exit paths should | |
102 | * take callback_mutex and check for fork/exit handlers to call. This | |
103 | * avoids us having to do extra work in the fork/exit path if none of the | |
104 | * subsystems need to be called. | |
105 | */ | |
106 | static int need_forkexit_callback; | |
107 | ||
108 | /* bits in struct cgroup flags field */ | |
109 | enum { | |
110 | CONT_REMOVED, | |
111 | }; | |
112 | ||
113 | /* convenient tests for these bits */ | |
114 | inline int cgroup_is_removed(const struct cgroup *cont) | |
115 | { | |
116 | return test_bit(CONT_REMOVED, &cont->flags); | |
117 | } | |
118 | ||
119 | /* bits in struct cgroupfs_root flags field */ | |
120 | enum { | |
121 | ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ | |
122 | }; | |
123 | ||
124 | /* | |
125 | * for_each_subsys() allows you to iterate on each subsystem attached to | |
126 | * an active hierarchy | |
127 | */ | |
128 | #define for_each_subsys(_root, _ss) \ | |
129 | list_for_each_entry(_ss, &_root->subsys_list, sibling) | |
130 | ||
131 | /* for_each_root() allows you to iterate across the active hierarchies */ | |
132 | #define for_each_root(_root) \ | |
133 | list_for_each_entry(_root, &roots, root_list) | |
134 | ||
135 | /* | |
136 | * There is one global cgroup mutex. We also require taking | |
137 | * task_lock() when dereferencing a task's cgroup subsys pointers. | |
138 | * See "The task_lock() exception", at the end of this comment. | |
139 | * | |
140 | * A task must hold cgroup_mutex to modify cgroups. | |
141 | * | |
142 | * Any task can increment and decrement the count field without lock. | |
143 | * So in general, code holding cgroup_mutex can't rely on the count | |
144 | * field not changing. However, if the count goes to zero, then only | |
145 | * attach_task() can increment it again. Because a count of zero | |
146 | * means that no tasks are currently attached, therefore there is no | |
147 | * way a task attached to that cgroup can fork (the other way to | |
148 | * increment the count). So code holding cgroup_mutex can safely | |
149 | * assume that if the count is zero, it will stay zero. Similarly, if | |
150 | * a task holds cgroup_mutex on a cgroup with zero count, it | |
151 | * knows that the cgroup won't be removed, as cgroup_rmdir() | |
152 | * needs that mutex. | |
153 | * | |
154 | * The cgroup_common_file_write handler for operations that modify | |
155 | * the cgroup hierarchy holds cgroup_mutex across the entire operation, | |
156 | * single threading all such cgroup modifications across the system. | |
157 | * | |
158 | * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't | |
159 | * (usually) take cgroup_mutex. These are the two most performance | |
160 | * critical pieces of code here. The exception occurs on cgroup_exit(), | |
161 | * when a task in a notify_on_release cgroup exits. Then cgroup_mutex | |
162 | * is taken, and if the cgroup count is zero, a usermode call made | |
163 | * to /sbin/cgroup_release_agent with the name of the cgroup (path | |
164 | * relative to the root of cgroup file system) as the argument. | |
165 | * | |
166 | * A cgroup can only be deleted if both its 'count' of using tasks | |
167 | * is zero, and its list of 'children' cgroups is empty. Since all | |
168 | * tasks in the system use _some_ cgroup, and since there is always at | |
169 | * least one task in the system (init, pid == 1), therefore, top_cgroup | |
170 | * always has either children cgroups and/or using tasks. So we don't | |
171 | * need a special hack to ensure that top_cgroup cannot be deleted. | |
172 | * | |
173 | * The task_lock() exception | |
174 | * | |
175 | * The need for this exception arises from the action of | |
176 | * attach_task(), which overwrites one tasks cgroup pointer with | |
177 | * another. It does so using cgroup_mutexe, however there are | |
178 | * several performance critical places that need to reference | |
179 | * task->cgroup without the expense of grabbing a system global | |
180 | * mutex. Therefore except as noted below, when dereferencing or, as | |
181 | * in attach_task(), modifying a task'ss cgroup pointer we use | |
182 | * task_lock(), which acts on a spinlock (task->alloc_lock) already in | |
183 | * the task_struct routinely used for such matters. | |
184 | * | |
185 | * P.S. One more locking exception. RCU is used to guard the | |
186 | * update of a tasks cgroup pointer by attach_task() | |
187 | */ | |
188 | ||
189 | static DEFINE_MUTEX(cgroup_mutex); | |
190 | ||
191 | /** | |
192 | * cgroup_lock - lock out any changes to cgroup structures | |
193 | * | |
194 | */ | |
195 | ||
196 | void cgroup_lock(void) | |
197 | { | |
198 | mutex_lock(&cgroup_mutex); | |
199 | } | |
200 | ||
201 | /** | |
202 | * cgroup_unlock - release lock on cgroup changes | |
203 | * | |
204 | * Undo the lock taken in a previous cgroup_lock() call. | |
205 | */ | |
206 | ||
207 | void cgroup_unlock(void) | |
208 | { | |
209 | mutex_unlock(&cgroup_mutex); | |
210 | } | |
211 | ||
212 | /* | |
213 | * A couple of forward declarations required, due to cyclic reference loop: | |
214 | * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir -> | |
215 | * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations | |
216 | * -> cgroup_mkdir. | |
217 | */ | |
218 | ||
219 | static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode); | |
220 | static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry); | |
221 | static int cgroup_populate_dir(struct cgroup *cont); | |
222 | static struct inode_operations cgroup_dir_inode_operations; | |
223 | ||
224 | static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb) | |
225 | { | |
226 | struct inode *inode = new_inode(sb); | |
227 | static struct backing_dev_info cgroup_backing_dev_info = { | |
228 | .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, | |
229 | }; | |
230 | ||
231 | if (inode) { | |
232 | inode->i_mode = mode; | |
233 | inode->i_uid = current->fsuid; | |
234 | inode->i_gid = current->fsgid; | |
235 | inode->i_blocks = 0; | |
236 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; | |
237 | inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info; | |
238 | } | |
239 | return inode; | |
240 | } | |
241 | ||
242 | static void cgroup_diput(struct dentry *dentry, struct inode *inode) | |
243 | { | |
244 | /* is dentry a directory ? if so, kfree() associated cgroup */ | |
245 | if (S_ISDIR(inode->i_mode)) { | |
246 | struct cgroup *cont = dentry->d_fsdata; | |
247 | BUG_ON(!(cgroup_is_removed(cont))); | |
248 | kfree(cont); | |
249 | } | |
250 | iput(inode); | |
251 | } | |
252 | ||
253 | static void remove_dir(struct dentry *d) | |
254 | { | |
255 | struct dentry *parent = dget(d->d_parent); | |
256 | ||
257 | d_delete(d); | |
258 | simple_rmdir(parent->d_inode, d); | |
259 | dput(parent); | |
260 | } | |
261 | ||
262 | static void cgroup_clear_directory(struct dentry *dentry) | |
263 | { | |
264 | struct list_head *node; | |
265 | ||
266 | BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); | |
267 | spin_lock(&dcache_lock); | |
268 | node = dentry->d_subdirs.next; | |
269 | while (node != &dentry->d_subdirs) { | |
270 | struct dentry *d = list_entry(node, struct dentry, d_u.d_child); | |
271 | list_del_init(node); | |
272 | if (d->d_inode) { | |
273 | /* This should never be called on a cgroup | |
274 | * directory with child cgroups */ | |
275 | BUG_ON(d->d_inode->i_mode & S_IFDIR); | |
276 | d = dget_locked(d); | |
277 | spin_unlock(&dcache_lock); | |
278 | d_delete(d); | |
279 | simple_unlink(dentry->d_inode, d); | |
280 | dput(d); | |
281 | spin_lock(&dcache_lock); | |
282 | } | |
283 | node = dentry->d_subdirs.next; | |
284 | } | |
285 | spin_unlock(&dcache_lock); | |
286 | } | |
287 | ||
288 | /* | |
289 | * NOTE : the dentry must have been dget()'ed | |
290 | */ | |
291 | static void cgroup_d_remove_dir(struct dentry *dentry) | |
292 | { | |
293 | cgroup_clear_directory(dentry); | |
294 | ||
295 | spin_lock(&dcache_lock); | |
296 | list_del_init(&dentry->d_u.d_child); | |
297 | spin_unlock(&dcache_lock); | |
298 | remove_dir(dentry); | |
299 | } | |
300 | ||
301 | static int rebind_subsystems(struct cgroupfs_root *root, | |
302 | unsigned long final_bits) | |
303 | { | |
304 | unsigned long added_bits, removed_bits; | |
305 | struct cgroup *cont = &root->top_cgroup; | |
306 | int i; | |
307 | ||
308 | removed_bits = root->actual_subsys_bits & ~final_bits; | |
309 | added_bits = final_bits & ~root->actual_subsys_bits; | |
310 | /* Check that any added subsystems are currently free */ | |
311 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
312 | unsigned long long bit = 1ull << i; | |
313 | struct cgroup_subsys *ss = subsys[i]; | |
314 | if (!(bit & added_bits)) | |
315 | continue; | |
316 | if (ss->root != &rootnode) { | |
317 | /* Subsystem isn't free */ | |
318 | return -EBUSY; | |
319 | } | |
320 | } | |
321 | ||
322 | /* Currently we don't handle adding/removing subsystems when | |
323 | * any child cgroups exist. This is theoretically supportable | |
324 | * but involves complex error handling, so it's being left until | |
325 | * later */ | |
326 | if (!list_empty(&cont->children)) | |
327 | return -EBUSY; | |
328 | ||
329 | /* Process each subsystem */ | |
330 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
331 | struct cgroup_subsys *ss = subsys[i]; | |
332 | unsigned long bit = 1UL << i; | |
333 | if (bit & added_bits) { | |
334 | /* We're binding this subsystem to this hierarchy */ | |
335 | BUG_ON(cont->subsys[i]); | |
336 | BUG_ON(!dummytop->subsys[i]); | |
337 | BUG_ON(dummytop->subsys[i]->cgroup != dummytop); | |
338 | cont->subsys[i] = dummytop->subsys[i]; | |
339 | cont->subsys[i]->cgroup = cont; | |
340 | list_add(&ss->sibling, &root->subsys_list); | |
341 | rcu_assign_pointer(ss->root, root); | |
342 | if (ss->bind) | |
343 | ss->bind(ss, cont); | |
344 | ||
345 | } else if (bit & removed_bits) { | |
346 | /* We're removing this subsystem */ | |
347 | BUG_ON(cont->subsys[i] != dummytop->subsys[i]); | |
348 | BUG_ON(cont->subsys[i]->cgroup != cont); | |
349 | if (ss->bind) | |
350 | ss->bind(ss, dummytop); | |
351 | dummytop->subsys[i]->cgroup = dummytop; | |
352 | cont->subsys[i] = NULL; | |
353 | rcu_assign_pointer(subsys[i]->root, &rootnode); | |
354 | list_del(&ss->sibling); | |
355 | } else if (bit & final_bits) { | |
356 | /* Subsystem state should already exist */ | |
357 | BUG_ON(!cont->subsys[i]); | |
358 | } else { | |
359 | /* Subsystem state shouldn't exist */ | |
360 | BUG_ON(cont->subsys[i]); | |
361 | } | |
362 | } | |
363 | root->subsys_bits = root->actual_subsys_bits = final_bits; | |
364 | synchronize_rcu(); | |
365 | ||
366 | return 0; | |
367 | } | |
368 | ||
369 | static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs) | |
370 | { | |
371 | struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info; | |
372 | struct cgroup_subsys *ss; | |
373 | ||
374 | mutex_lock(&cgroup_mutex); | |
375 | for_each_subsys(root, ss) | |
376 | seq_printf(seq, ",%s", ss->name); | |
377 | if (test_bit(ROOT_NOPREFIX, &root->flags)) | |
378 | seq_puts(seq, ",noprefix"); | |
379 | mutex_unlock(&cgroup_mutex); | |
380 | return 0; | |
381 | } | |
382 | ||
383 | struct cgroup_sb_opts { | |
384 | unsigned long subsys_bits; | |
385 | unsigned long flags; | |
386 | }; | |
387 | ||
388 | /* Convert a hierarchy specifier into a bitmask of subsystems and | |
389 | * flags. */ | |
390 | static int parse_cgroupfs_options(char *data, | |
391 | struct cgroup_sb_opts *opts) | |
392 | { | |
393 | char *token, *o = data ?: "all"; | |
394 | ||
395 | opts->subsys_bits = 0; | |
396 | opts->flags = 0; | |
397 | ||
398 | while ((token = strsep(&o, ",")) != NULL) { | |
399 | if (!*token) | |
400 | return -EINVAL; | |
401 | if (!strcmp(token, "all")) { | |
402 | opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1; | |
403 | } else if (!strcmp(token, "noprefix")) { | |
404 | set_bit(ROOT_NOPREFIX, &opts->flags); | |
405 | } else { | |
406 | struct cgroup_subsys *ss; | |
407 | int i; | |
408 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
409 | ss = subsys[i]; | |
410 | if (!strcmp(token, ss->name)) { | |
411 | set_bit(i, &opts->subsys_bits); | |
412 | break; | |
413 | } | |
414 | } | |
415 | if (i == CGROUP_SUBSYS_COUNT) | |
416 | return -ENOENT; | |
417 | } | |
418 | } | |
419 | ||
420 | /* We can't have an empty hierarchy */ | |
421 | if (!opts->subsys_bits) | |
422 | return -EINVAL; | |
423 | ||
424 | return 0; | |
425 | } | |
426 | ||
427 | static int cgroup_remount(struct super_block *sb, int *flags, char *data) | |
428 | { | |
429 | int ret = 0; | |
430 | struct cgroupfs_root *root = sb->s_fs_info; | |
431 | struct cgroup *cont = &root->top_cgroup; | |
432 | struct cgroup_sb_opts opts; | |
433 | ||
434 | mutex_lock(&cont->dentry->d_inode->i_mutex); | |
435 | mutex_lock(&cgroup_mutex); | |
436 | ||
437 | /* See what subsystems are wanted */ | |
438 | ret = parse_cgroupfs_options(data, &opts); | |
439 | if (ret) | |
440 | goto out_unlock; | |
441 | ||
442 | /* Don't allow flags to change at remount */ | |
443 | if (opts.flags != root->flags) { | |
444 | ret = -EINVAL; | |
445 | goto out_unlock; | |
446 | } | |
447 | ||
448 | ret = rebind_subsystems(root, opts.subsys_bits); | |
449 | ||
450 | /* (re)populate subsystem files */ | |
451 | if (!ret) | |
452 | cgroup_populate_dir(cont); | |
453 | ||
454 | out_unlock: | |
455 | mutex_unlock(&cgroup_mutex); | |
456 | mutex_unlock(&cont->dentry->d_inode->i_mutex); | |
457 | return ret; | |
458 | } | |
459 | ||
460 | static struct super_operations cgroup_ops = { | |
461 | .statfs = simple_statfs, | |
462 | .drop_inode = generic_delete_inode, | |
463 | .show_options = cgroup_show_options, | |
464 | .remount_fs = cgroup_remount, | |
465 | }; | |
466 | ||
467 | static void init_cgroup_root(struct cgroupfs_root *root) | |
468 | { | |
469 | struct cgroup *cont = &root->top_cgroup; | |
470 | INIT_LIST_HEAD(&root->subsys_list); | |
471 | INIT_LIST_HEAD(&root->root_list); | |
472 | root->number_of_cgroups = 1; | |
473 | cont->root = root; | |
474 | cont->top_cgroup = cont; | |
475 | INIT_LIST_HEAD(&cont->sibling); | |
476 | INIT_LIST_HEAD(&cont->children); | |
477 | } | |
478 | ||
479 | static int cgroup_test_super(struct super_block *sb, void *data) | |
480 | { | |
481 | struct cgroupfs_root *new = data; | |
482 | struct cgroupfs_root *root = sb->s_fs_info; | |
483 | ||
484 | /* First check subsystems */ | |
485 | if (new->subsys_bits != root->subsys_bits) | |
486 | return 0; | |
487 | ||
488 | /* Next check flags */ | |
489 | if (new->flags != root->flags) | |
490 | return 0; | |
491 | ||
492 | return 1; | |
493 | } | |
494 | ||
495 | static int cgroup_set_super(struct super_block *sb, void *data) | |
496 | { | |
497 | int ret; | |
498 | struct cgroupfs_root *root = data; | |
499 | ||
500 | ret = set_anon_super(sb, NULL); | |
501 | if (ret) | |
502 | return ret; | |
503 | ||
504 | sb->s_fs_info = root; | |
505 | root->sb = sb; | |
506 | ||
507 | sb->s_blocksize = PAGE_CACHE_SIZE; | |
508 | sb->s_blocksize_bits = PAGE_CACHE_SHIFT; | |
509 | sb->s_magic = CGROUP_SUPER_MAGIC; | |
510 | sb->s_op = &cgroup_ops; | |
511 | ||
512 | return 0; | |
513 | } | |
514 | ||
515 | static int cgroup_get_rootdir(struct super_block *sb) | |
516 | { | |
517 | struct inode *inode = | |
518 | cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb); | |
519 | struct dentry *dentry; | |
520 | ||
521 | if (!inode) | |
522 | return -ENOMEM; | |
523 | ||
524 | inode->i_op = &simple_dir_inode_operations; | |
525 | inode->i_fop = &simple_dir_operations; | |
526 | inode->i_op = &cgroup_dir_inode_operations; | |
527 | /* directories start off with i_nlink == 2 (for "." entry) */ | |
528 | inc_nlink(inode); | |
529 | dentry = d_alloc_root(inode); | |
530 | if (!dentry) { | |
531 | iput(inode); | |
532 | return -ENOMEM; | |
533 | } | |
534 | sb->s_root = dentry; | |
535 | return 0; | |
536 | } | |
537 | ||
538 | static int cgroup_get_sb(struct file_system_type *fs_type, | |
539 | int flags, const char *unused_dev_name, | |
540 | void *data, struct vfsmount *mnt) | |
541 | { | |
542 | struct cgroup_sb_opts opts; | |
543 | int ret = 0; | |
544 | struct super_block *sb; | |
545 | struct cgroupfs_root *root; | |
546 | ||
547 | /* First find the desired set of subsystems */ | |
548 | ret = parse_cgroupfs_options(data, &opts); | |
549 | if (ret) | |
550 | return ret; | |
551 | ||
552 | root = kzalloc(sizeof(*root), GFP_KERNEL); | |
553 | if (!root) | |
554 | return -ENOMEM; | |
555 | ||
556 | init_cgroup_root(root); | |
557 | root->subsys_bits = opts.subsys_bits; | |
558 | root->flags = opts.flags; | |
559 | ||
560 | sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root); | |
561 | ||
562 | if (IS_ERR(sb)) { | |
563 | kfree(root); | |
564 | return PTR_ERR(sb); | |
565 | } | |
566 | ||
567 | if (sb->s_fs_info != root) { | |
568 | /* Reusing an existing superblock */ | |
569 | BUG_ON(sb->s_root == NULL); | |
570 | kfree(root); | |
571 | root = NULL; | |
572 | } else { | |
573 | /* New superblock */ | |
574 | struct cgroup *cont = &root->top_cgroup; | |
575 | ||
576 | BUG_ON(sb->s_root != NULL); | |
577 | ||
578 | ret = cgroup_get_rootdir(sb); | |
579 | if (ret) | |
580 | goto drop_new_super; | |
581 | ||
582 | mutex_lock(&cgroup_mutex); | |
583 | ||
584 | ret = rebind_subsystems(root, root->subsys_bits); | |
585 | if (ret == -EBUSY) { | |
586 | mutex_unlock(&cgroup_mutex); | |
587 | goto drop_new_super; | |
588 | } | |
589 | ||
590 | /* EBUSY should be the only error here */ | |
591 | BUG_ON(ret); | |
592 | ||
593 | list_add(&root->root_list, &roots); | |
594 | ||
595 | sb->s_root->d_fsdata = &root->top_cgroup; | |
596 | root->top_cgroup.dentry = sb->s_root; | |
597 | ||
598 | BUG_ON(!list_empty(&cont->sibling)); | |
599 | BUG_ON(!list_empty(&cont->children)); | |
600 | BUG_ON(root->number_of_cgroups != 1); | |
601 | ||
602 | /* | |
603 | * I believe that it's safe to nest i_mutex inside | |
604 | * cgroup_mutex in this case, since no-one else can | |
605 | * be accessing this directory yet. But we still need | |
606 | * to teach lockdep that this is the case - currently | |
607 | * a cgroupfs remount triggers a lockdep warning | |
608 | */ | |
609 | mutex_lock(&cont->dentry->d_inode->i_mutex); | |
610 | cgroup_populate_dir(cont); | |
611 | mutex_unlock(&cont->dentry->d_inode->i_mutex); | |
612 | mutex_unlock(&cgroup_mutex); | |
613 | } | |
614 | ||
615 | return simple_set_mnt(mnt, sb); | |
616 | ||
617 | drop_new_super: | |
618 | up_write(&sb->s_umount); | |
619 | deactivate_super(sb); | |
620 | return ret; | |
621 | } | |
622 | ||
623 | static void cgroup_kill_sb(struct super_block *sb) { | |
624 | struct cgroupfs_root *root = sb->s_fs_info; | |
625 | struct cgroup *cont = &root->top_cgroup; | |
626 | int ret; | |
627 | ||
628 | BUG_ON(!root); | |
629 | ||
630 | BUG_ON(root->number_of_cgroups != 1); | |
631 | BUG_ON(!list_empty(&cont->children)); | |
632 | BUG_ON(!list_empty(&cont->sibling)); | |
633 | ||
634 | mutex_lock(&cgroup_mutex); | |
635 | ||
636 | /* Rebind all subsystems back to the default hierarchy */ | |
637 | ret = rebind_subsystems(root, 0); | |
638 | /* Shouldn't be able to fail ... */ | |
639 | BUG_ON(ret); | |
640 | ||
641 | if (!list_empty(&root->root_list)) | |
642 | list_del(&root->root_list); | |
643 | mutex_unlock(&cgroup_mutex); | |
644 | ||
645 | kfree(root); | |
646 | kill_litter_super(sb); | |
647 | } | |
648 | ||
649 | static struct file_system_type cgroup_fs_type = { | |
650 | .name = "cgroup", | |
651 | .get_sb = cgroup_get_sb, | |
652 | .kill_sb = cgroup_kill_sb, | |
653 | }; | |
654 | ||
655 | static inline struct cgroup *__d_cont(struct dentry *dentry) | |
656 | { | |
657 | return dentry->d_fsdata; | |
658 | } | |
659 | ||
660 | static inline struct cftype *__d_cft(struct dentry *dentry) | |
661 | { | |
662 | return dentry->d_fsdata; | |
663 | } | |
664 | ||
665 | /* | |
666 | * Called with cgroup_mutex held. Writes path of cgroup into buf. | |
667 | * Returns 0 on success, -errno on error. | |
668 | */ | |
669 | int cgroup_path(const struct cgroup *cont, char *buf, int buflen) | |
670 | { | |
671 | char *start; | |
672 | ||
673 | if (cont == dummytop) { | |
674 | /* | |
675 | * Inactive subsystems have no dentry for their root | |
676 | * cgroup | |
677 | */ | |
678 | strcpy(buf, "/"); | |
679 | return 0; | |
680 | } | |
681 | ||
682 | start = buf + buflen; | |
683 | ||
684 | *--start = '\0'; | |
685 | for (;;) { | |
686 | int len = cont->dentry->d_name.len; | |
687 | if ((start -= len) < buf) | |
688 | return -ENAMETOOLONG; | |
689 | memcpy(start, cont->dentry->d_name.name, len); | |
690 | cont = cont->parent; | |
691 | if (!cont) | |
692 | break; | |
693 | if (!cont->parent) | |
694 | continue; | |
695 | if (--start < buf) | |
696 | return -ENAMETOOLONG; | |
697 | *start = '/'; | |
698 | } | |
699 | memmove(buf, start, buf + buflen - start); | |
700 | return 0; | |
701 | } | |
702 | ||
bbcb81d0 PM |
703 | /* |
704 | * Return the first subsystem attached to a cgroup's hierarchy, and | |
705 | * its subsystem id. | |
706 | */ | |
707 | ||
708 | static void get_first_subsys(const struct cgroup *cont, | |
709 | struct cgroup_subsys_state **css, int *subsys_id) | |
710 | { | |
711 | const struct cgroupfs_root *root = cont->root; | |
712 | const struct cgroup_subsys *test_ss; | |
713 | BUG_ON(list_empty(&root->subsys_list)); | |
714 | test_ss = list_entry(root->subsys_list.next, | |
715 | struct cgroup_subsys, sibling); | |
716 | if (css) { | |
717 | *css = cont->subsys[test_ss->subsys_id]; | |
718 | BUG_ON(!*css); | |
719 | } | |
720 | if (subsys_id) | |
721 | *subsys_id = test_ss->subsys_id; | |
722 | } | |
723 | ||
724 | /* | |
725 | * Attach task 'tsk' to cgroup 'cont' | |
726 | * | |
727 | * Call holding cgroup_mutex. May take task_lock of | |
728 | * the task 'pid' during call. | |
729 | */ | |
730 | static int attach_task(struct cgroup *cont, struct task_struct *tsk) | |
731 | { | |
732 | int retval = 0; | |
733 | struct cgroup_subsys *ss; | |
734 | struct cgroup *oldcont; | |
735 | struct css_set *cg = &tsk->cgroups; | |
736 | struct cgroupfs_root *root = cont->root; | |
737 | int i; | |
738 | int subsys_id; | |
739 | ||
740 | get_first_subsys(cont, NULL, &subsys_id); | |
741 | ||
742 | /* Nothing to do if the task is already in that cgroup */ | |
743 | oldcont = task_cgroup(tsk, subsys_id); | |
744 | if (cont == oldcont) | |
745 | return 0; | |
746 | ||
747 | for_each_subsys(root, ss) { | |
748 | if (ss->can_attach) { | |
749 | retval = ss->can_attach(ss, cont, tsk); | |
750 | if (retval) { | |
751 | return retval; | |
752 | } | |
753 | } | |
754 | } | |
755 | ||
756 | task_lock(tsk); | |
757 | if (tsk->flags & PF_EXITING) { | |
758 | task_unlock(tsk); | |
759 | return -ESRCH; | |
760 | } | |
761 | /* Update the css_set pointers for the subsystems in this | |
762 | * hierarchy */ | |
763 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
764 | if (root->subsys_bits & (1ull << i)) { | |
765 | /* Subsystem is in this hierarchy. So we want | |
766 | * the subsystem state from the new | |
767 | * cgroup. Transfer the refcount from the | |
768 | * old to the new */ | |
769 | atomic_inc(&cont->count); | |
770 | atomic_dec(&cg->subsys[i]->cgroup->count); | |
771 | rcu_assign_pointer(cg->subsys[i], cont->subsys[i]); | |
772 | } | |
773 | } | |
774 | task_unlock(tsk); | |
775 | ||
776 | for_each_subsys(root, ss) { | |
777 | if (ss->attach) { | |
778 | ss->attach(ss, cont, oldcont, tsk); | |
779 | } | |
780 | } | |
781 | ||
782 | synchronize_rcu(); | |
783 | return 0; | |
784 | } | |
785 | ||
786 | /* | |
787 | * Attach task with pid 'pid' to cgroup 'cont'. Call with | |
788 | * cgroup_mutex, may take task_lock of task | |
789 | */ | |
790 | static int attach_task_by_pid(struct cgroup *cont, char *pidbuf) | |
791 | { | |
792 | pid_t pid; | |
793 | struct task_struct *tsk; | |
794 | int ret; | |
795 | ||
796 | if (sscanf(pidbuf, "%d", &pid) != 1) | |
797 | return -EIO; | |
798 | ||
799 | if (pid) { | |
800 | rcu_read_lock(); | |
801 | tsk = find_task_by_pid(pid); | |
802 | if (!tsk || tsk->flags & PF_EXITING) { | |
803 | rcu_read_unlock(); | |
804 | return -ESRCH; | |
805 | } | |
806 | get_task_struct(tsk); | |
807 | rcu_read_unlock(); | |
808 | ||
809 | if ((current->euid) && (current->euid != tsk->uid) | |
810 | && (current->euid != tsk->suid)) { | |
811 | put_task_struct(tsk); | |
812 | return -EACCES; | |
813 | } | |
814 | } else { | |
815 | tsk = current; | |
816 | get_task_struct(tsk); | |
817 | } | |
818 | ||
819 | ret = attach_task(cont, tsk); | |
820 | put_task_struct(tsk); | |
821 | return ret; | |
822 | } | |
823 | ||
ddbcc7e8 PM |
824 | /* The various types of files and directories in a cgroup file system */ |
825 | ||
826 | enum cgroup_filetype { | |
827 | FILE_ROOT, | |
828 | FILE_DIR, | |
829 | FILE_TASKLIST, | |
830 | }; | |
831 | ||
bbcb81d0 PM |
832 | static ssize_t cgroup_common_file_write(struct cgroup *cont, |
833 | struct cftype *cft, | |
834 | struct file *file, | |
835 | const char __user *userbuf, | |
836 | size_t nbytes, loff_t *unused_ppos) | |
837 | { | |
838 | enum cgroup_filetype type = cft->private; | |
839 | char *buffer; | |
840 | int retval = 0; | |
841 | ||
842 | if (nbytes >= PATH_MAX) | |
843 | return -E2BIG; | |
844 | ||
845 | /* +1 for nul-terminator */ | |
846 | buffer = kmalloc(nbytes + 1, GFP_KERNEL); | |
847 | if (buffer == NULL) | |
848 | return -ENOMEM; | |
849 | ||
850 | if (copy_from_user(buffer, userbuf, nbytes)) { | |
851 | retval = -EFAULT; | |
852 | goto out1; | |
853 | } | |
854 | buffer[nbytes] = 0; /* nul-terminate */ | |
855 | ||
856 | mutex_lock(&cgroup_mutex); | |
857 | ||
858 | if (cgroup_is_removed(cont)) { | |
859 | retval = -ENODEV; | |
860 | goto out2; | |
861 | } | |
862 | ||
863 | switch (type) { | |
864 | case FILE_TASKLIST: | |
865 | retval = attach_task_by_pid(cont, buffer); | |
866 | break; | |
867 | default: | |
868 | retval = -EINVAL; | |
869 | goto out2; | |
870 | } | |
871 | ||
872 | if (retval == 0) | |
873 | retval = nbytes; | |
874 | out2: | |
875 | mutex_unlock(&cgroup_mutex); | |
876 | out1: | |
877 | kfree(buffer); | |
878 | return retval; | |
879 | } | |
880 | ||
ddbcc7e8 PM |
881 | static ssize_t cgroup_file_write(struct file *file, const char __user *buf, |
882 | size_t nbytes, loff_t *ppos) | |
883 | { | |
884 | struct cftype *cft = __d_cft(file->f_dentry); | |
885 | struct cgroup *cont = __d_cont(file->f_dentry->d_parent); | |
886 | ||
887 | if (!cft) | |
888 | return -ENODEV; | |
889 | if (!cft->write) | |
890 | return -EINVAL; | |
891 | ||
892 | return cft->write(cont, cft, file, buf, nbytes, ppos); | |
893 | } | |
894 | ||
895 | static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft, | |
896 | struct file *file, | |
897 | char __user *buf, size_t nbytes, | |
898 | loff_t *ppos) | |
899 | { | |
900 | char tmp[64]; | |
901 | u64 val = cft->read_uint(cont, cft); | |
902 | int len = sprintf(tmp, "%llu\n", (unsigned long long) val); | |
903 | ||
904 | return simple_read_from_buffer(buf, nbytes, ppos, tmp, len); | |
905 | } | |
906 | ||
907 | static ssize_t cgroup_file_read(struct file *file, char __user *buf, | |
908 | size_t nbytes, loff_t *ppos) | |
909 | { | |
910 | struct cftype *cft = __d_cft(file->f_dentry); | |
911 | struct cgroup *cont = __d_cont(file->f_dentry->d_parent); | |
912 | ||
913 | if (!cft) | |
914 | return -ENODEV; | |
915 | ||
916 | if (cft->read) | |
917 | return cft->read(cont, cft, file, buf, nbytes, ppos); | |
918 | if (cft->read_uint) | |
919 | return cgroup_read_uint(cont, cft, file, buf, nbytes, ppos); | |
920 | return -EINVAL; | |
921 | } | |
922 | ||
923 | static int cgroup_file_open(struct inode *inode, struct file *file) | |
924 | { | |
925 | int err; | |
926 | struct cftype *cft; | |
927 | ||
928 | err = generic_file_open(inode, file); | |
929 | if (err) | |
930 | return err; | |
931 | ||
932 | cft = __d_cft(file->f_dentry); | |
933 | if (!cft) | |
934 | return -ENODEV; | |
935 | if (cft->open) | |
936 | err = cft->open(inode, file); | |
937 | else | |
938 | err = 0; | |
939 | ||
940 | return err; | |
941 | } | |
942 | ||
943 | static int cgroup_file_release(struct inode *inode, struct file *file) | |
944 | { | |
945 | struct cftype *cft = __d_cft(file->f_dentry); | |
946 | if (cft->release) | |
947 | return cft->release(inode, file); | |
948 | return 0; | |
949 | } | |
950 | ||
951 | /* | |
952 | * cgroup_rename - Only allow simple rename of directories in place. | |
953 | */ | |
954 | static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry, | |
955 | struct inode *new_dir, struct dentry *new_dentry) | |
956 | { | |
957 | if (!S_ISDIR(old_dentry->d_inode->i_mode)) | |
958 | return -ENOTDIR; | |
959 | if (new_dentry->d_inode) | |
960 | return -EEXIST; | |
961 | if (old_dir != new_dir) | |
962 | return -EIO; | |
963 | return simple_rename(old_dir, old_dentry, new_dir, new_dentry); | |
964 | } | |
965 | ||
966 | static struct file_operations cgroup_file_operations = { | |
967 | .read = cgroup_file_read, | |
968 | .write = cgroup_file_write, | |
969 | .llseek = generic_file_llseek, | |
970 | .open = cgroup_file_open, | |
971 | .release = cgroup_file_release, | |
972 | }; | |
973 | ||
974 | static struct inode_operations cgroup_dir_inode_operations = { | |
975 | .lookup = simple_lookup, | |
976 | .mkdir = cgroup_mkdir, | |
977 | .rmdir = cgroup_rmdir, | |
978 | .rename = cgroup_rename, | |
979 | }; | |
980 | ||
981 | static int cgroup_create_file(struct dentry *dentry, int mode, | |
982 | struct super_block *sb) | |
983 | { | |
984 | static struct dentry_operations cgroup_dops = { | |
985 | .d_iput = cgroup_diput, | |
986 | }; | |
987 | ||
988 | struct inode *inode; | |
989 | ||
990 | if (!dentry) | |
991 | return -ENOENT; | |
992 | if (dentry->d_inode) | |
993 | return -EEXIST; | |
994 | ||
995 | inode = cgroup_new_inode(mode, sb); | |
996 | if (!inode) | |
997 | return -ENOMEM; | |
998 | ||
999 | if (S_ISDIR(mode)) { | |
1000 | inode->i_op = &cgroup_dir_inode_operations; | |
1001 | inode->i_fop = &simple_dir_operations; | |
1002 | ||
1003 | /* start off with i_nlink == 2 (for "." entry) */ | |
1004 | inc_nlink(inode); | |
1005 | ||
1006 | /* start with the directory inode held, so that we can | |
1007 | * populate it without racing with another mkdir */ | |
1008 | mutex_lock(&inode->i_mutex); | |
1009 | } else if (S_ISREG(mode)) { | |
1010 | inode->i_size = 0; | |
1011 | inode->i_fop = &cgroup_file_operations; | |
1012 | } | |
1013 | dentry->d_op = &cgroup_dops; | |
1014 | d_instantiate(dentry, inode); | |
1015 | dget(dentry); /* Extra count - pin the dentry in core */ | |
1016 | return 0; | |
1017 | } | |
1018 | ||
1019 | /* | |
1020 | * cgroup_create_dir - create a directory for an object. | |
1021 | * cont: the cgroup we create the directory for. | |
1022 | * It must have a valid ->parent field | |
1023 | * And we are going to fill its ->dentry field. | |
1024 | * dentry: dentry of the new container | |
1025 | * mode: mode to set on new directory. | |
1026 | */ | |
1027 | static int cgroup_create_dir(struct cgroup *cont, struct dentry *dentry, | |
1028 | int mode) | |
1029 | { | |
1030 | struct dentry *parent; | |
1031 | int error = 0; | |
1032 | ||
1033 | parent = cont->parent->dentry; | |
1034 | error = cgroup_create_file(dentry, S_IFDIR | mode, cont->root->sb); | |
1035 | if (!error) { | |
1036 | dentry->d_fsdata = cont; | |
1037 | inc_nlink(parent->d_inode); | |
1038 | cont->dentry = dentry; | |
1039 | dget(dentry); | |
1040 | } | |
1041 | dput(dentry); | |
1042 | ||
1043 | return error; | |
1044 | } | |
1045 | ||
1046 | int cgroup_add_file(struct cgroup *cont, | |
1047 | struct cgroup_subsys *subsys, | |
1048 | const struct cftype *cft) | |
1049 | { | |
1050 | struct dentry *dir = cont->dentry; | |
1051 | struct dentry *dentry; | |
1052 | int error; | |
1053 | ||
1054 | char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 }; | |
1055 | if (subsys && !test_bit(ROOT_NOPREFIX, &cont->root->flags)) { | |
1056 | strcpy(name, subsys->name); | |
1057 | strcat(name, "."); | |
1058 | } | |
1059 | strcat(name, cft->name); | |
1060 | BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex)); | |
1061 | dentry = lookup_one_len(name, dir, strlen(name)); | |
1062 | if (!IS_ERR(dentry)) { | |
1063 | error = cgroup_create_file(dentry, 0644 | S_IFREG, | |
1064 | cont->root->sb); | |
1065 | if (!error) | |
1066 | dentry->d_fsdata = (void *)cft; | |
1067 | dput(dentry); | |
1068 | } else | |
1069 | error = PTR_ERR(dentry); | |
1070 | return error; | |
1071 | } | |
1072 | ||
1073 | int cgroup_add_files(struct cgroup *cont, | |
1074 | struct cgroup_subsys *subsys, | |
1075 | const struct cftype cft[], | |
1076 | int count) | |
1077 | { | |
1078 | int i, err; | |
1079 | for (i = 0; i < count; i++) { | |
1080 | err = cgroup_add_file(cont, subsys, &cft[i]); | |
1081 | if (err) | |
1082 | return err; | |
1083 | } | |
1084 | return 0; | |
1085 | } | |
1086 | ||
bbcb81d0 PM |
1087 | /* Count the number of tasks in a cgroup. Could be made more |
1088 | * time-efficient but less space-efficient with more linked lists | |
1089 | * running through each cgroup and the css_set structures that | |
1090 | * referenced it. Must be called with tasklist_lock held for read or | |
1091 | * write or in an rcu critical section. | |
1092 | */ | |
1093 | int __cgroup_task_count(const struct cgroup *cont) | |
1094 | { | |
1095 | int count = 0; | |
1096 | struct task_struct *g, *p; | |
1097 | struct cgroup_subsys_state *css; | |
1098 | int subsys_id; | |
1099 | ||
1100 | get_first_subsys(cont, &css, &subsys_id); | |
1101 | do_each_thread(g, p) { | |
1102 | if (task_subsys_state(p, subsys_id) == css) | |
1103 | count ++; | |
1104 | } while_each_thread(g, p); | |
1105 | return count; | |
1106 | } | |
1107 | ||
1108 | /* | |
1109 | * Stuff for reading the 'tasks' file. | |
1110 | * | |
1111 | * Reading this file can return large amounts of data if a cgroup has | |
1112 | * *lots* of attached tasks. So it may need several calls to read(), | |
1113 | * but we cannot guarantee that the information we produce is correct | |
1114 | * unless we produce it entirely atomically. | |
1115 | * | |
1116 | * Upon tasks file open(), a struct ctr_struct is allocated, that | |
1117 | * will have a pointer to an array (also allocated here). The struct | |
1118 | * ctr_struct * is stored in file->private_data. Its resources will | |
1119 | * be freed by release() when the file is closed. The array is used | |
1120 | * to sprintf the PIDs and then used by read(). | |
1121 | */ | |
1122 | struct ctr_struct { | |
1123 | char *buf; | |
1124 | int bufsz; | |
1125 | }; | |
1126 | ||
1127 | /* | |
1128 | * Load into 'pidarray' up to 'npids' of the tasks using cgroup | |
1129 | * 'cont'. Return actual number of pids loaded. No need to | |
1130 | * task_lock(p) when reading out p->cgroup, since we're in an RCU | |
1131 | * read section, so the css_set can't go away, and is | |
1132 | * immutable after creation. | |
1133 | */ | |
1134 | static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cont) | |
1135 | { | |
1136 | int n = 0; | |
1137 | struct task_struct *g, *p; | |
1138 | struct cgroup_subsys_state *css; | |
1139 | int subsys_id; | |
1140 | ||
1141 | get_first_subsys(cont, &css, &subsys_id); | |
1142 | rcu_read_lock(); | |
1143 | do_each_thread(g, p) { | |
1144 | if (task_subsys_state(p, subsys_id) == css) { | |
1145 | pidarray[n++] = pid_nr(task_pid(p)); | |
1146 | if (unlikely(n == npids)) | |
1147 | goto array_full; | |
1148 | } | |
1149 | } while_each_thread(g, p); | |
1150 | ||
1151 | array_full: | |
1152 | rcu_read_unlock(); | |
1153 | return n; | |
1154 | } | |
1155 | ||
1156 | static int cmppid(const void *a, const void *b) | |
1157 | { | |
1158 | return *(pid_t *)a - *(pid_t *)b; | |
1159 | } | |
1160 | ||
1161 | /* | |
1162 | * Convert array 'a' of 'npids' pid_t's to a string of newline separated | |
1163 | * decimal pids in 'buf'. Don't write more than 'sz' chars, but return | |
1164 | * count 'cnt' of how many chars would be written if buf were large enough. | |
1165 | */ | |
1166 | static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids) | |
1167 | { | |
1168 | int cnt = 0; | |
1169 | int i; | |
1170 | ||
1171 | for (i = 0; i < npids; i++) | |
1172 | cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]); | |
1173 | return cnt; | |
1174 | } | |
1175 | ||
1176 | /* | |
1177 | * Handle an open on 'tasks' file. Prepare a buffer listing the | |
1178 | * process id's of tasks currently attached to the cgroup being opened. | |
1179 | * | |
1180 | * Does not require any specific cgroup mutexes, and does not take any. | |
1181 | */ | |
1182 | static int cgroup_tasks_open(struct inode *unused, struct file *file) | |
1183 | { | |
1184 | struct cgroup *cont = __d_cont(file->f_dentry->d_parent); | |
1185 | struct ctr_struct *ctr; | |
1186 | pid_t *pidarray; | |
1187 | int npids; | |
1188 | char c; | |
1189 | ||
1190 | if (!(file->f_mode & FMODE_READ)) | |
1191 | return 0; | |
1192 | ||
1193 | ctr = kmalloc(sizeof(*ctr), GFP_KERNEL); | |
1194 | if (!ctr) | |
1195 | goto err0; | |
1196 | ||
1197 | /* | |
1198 | * If cgroup gets more users after we read count, we won't have | |
1199 | * enough space - tough. This race is indistinguishable to the | |
1200 | * caller from the case that the additional cgroup users didn't | |
1201 | * show up until sometime later on. | |
1202 | */ | |
1203 | npids = cgroup_task_count(cont); | |
1204 | if (npids) { | |
1205 | pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL); | |
1206 | if (!pidarray) | |
1207 | goto err1; | |
1208 | ||
1209 | npids = pid_array_load(pidarray, npids, cont); | |
1210 | sort(pidarray, npids, sizeof(pid_t), cmppid, NULL); | |
1211 | ||
1212 | /* Call pid_array_to_buf() twice, first just to get bufsz */ | |
1213 | ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1; | |
1214 | ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL); | |
1215 | if (!ctr->buf) | |
1216 | goto err2; | |
1217 | ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids); | |
1218 | ||
1219 | kfree(pidarray); | |
1220 | } else { | |
1221 | ctr->buf = 0; | |
1222 | ctr->bufsz = 0; | |
1223 | } | |
1224 | file->private_data = ctr; | |
1225 | return 0; | |
1226 | ||
1227 | err2: | |
1228 | kfree(pidarray); | |
1229 | err1: | |
1230 | kfree(ctr); | |
1231 | err0: | |
1232 | return -ENOMEM; | |
1233 | } | |
1234 | ||
1235 | static ssize_t cgroup_tasks_read(struct cgroup *cont, | |
1236 | struct cftype *cft, | |
1237 | struct file *file, char __user *buf, | |
1238 | size_t nbytes, loff_t *ppos) | |
1239 | { | |
1240 | struct ctr_struct *ctr = file->private_data; | |
1241 | ||
1242 | return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz); | |
1243 | } | |
1244 | ||
1245 | static int cgroup_tasks_release(struct inode *unused_inode, | |
1246 | struct file *file) | |
1247 | { | |
1248 | struct ctr_struct *ctr; | |
1249 | ||
1250 | if (file->f_mode & FMODE_READ) { | |
1251 | ctr = file->private_data; | |
1252 | kfree(ctr->buf); | |
1253 | kfree(ctr); | |
1254 | } | |
1255 | return 0; | |
1256 | } | |
1257 | ||
1258 | /* | |
1259 | * for the common functions, 'private' gives the type of file | |
1260 | */ | |
1261 | static struct cftype cft_tasks = { | |
1262 | .name = "tasks", | |
1263 | .open = cgroup_tasks_open, | |
1264 | .read = cgroup_tasks_read, | |
1265 | .write = cgroup_common_file_write, | |
1266 | .release = cgroup_tasks_release, | |
1267 | .private = FILE_TASKLIST, | |
1268 | }; | |
1269 | ||
ddbcc7e8 PM |
1270 | static int cgroup_populate_dir(struct cgroup *cont) |
1271 | { | |
1272 | int err; | |
1273 | struct cgroup_subsys *ss; | |
1274 | ||
1275 | /* First clear out any existing files */ | |
1276 | cgroup_clear_directory(cont->dentry); | |
1277 | ||
bbcb81d0 PM |
1278 | err = cgroup_add_file(cont, NULL, &cft_tasks); |
1279 | if (err < 0) | |
1280 | return err; | |
1281 | ||
ddbcc7e8 PM |
1282 | for_each_subsys(cont->root, ss) { |
1283 | if (ss->populate && (err = ss->populate(ss, cont)) < 0) | |
1284 | return err; | |
1285 | } | |
1286 | ||
1287 | return 0; | |
1288 | } | |
1289 | ||
1290 | static void init_cgroup_css(struct cgroup_subsys_state *css, | |
1291 | struct cgroup_subsys *ss, | |
1292 | struct cgroup *cont) | |
1293 | { | |
1294 | css->cgroup = cont; | |
1295 | atomic_set(&css->refcnt, 0); | |
1296 | css->flags = 0; | |
1297 | if (cont == dummytop) | |
1298 | set_bit(CSS_ROOT, &css->flags); | |
1299 | BUG_ON(cont->subsys[ss->subsys_id]); | |
1300 | cont->subsys[ss->subsys_id] = css; | |
1301 | } | |
1302 | ||
1303 | /* | |
1304 | * cgroup_create - create a cgroup | |
1305 | * parent: cgroup that will be parent of the new cgroup. | |
1306 | * name: name of the new cgroup. Will be strcpy'ed. | |
1307 | * mode: mode to set on new inode | |
1308 | * | |
1309 | * Must be called with the mutex on the parent inode held | |
1310 | */ | |
1311 | ||
1312 | static long cgroup_create(struct cgroup *parent, struct dentry *dentry, | |
1313 | int mode) | |
1314 | { | |
1315 | struct cgroup *cont; | |
1316 | struct cgroupfs_root *root = parent->root; | |
1317 | int err = 0; | |
1318 | struct cgroup_subsys *ss; | |
1319 | struct super_block *sb = root->sb; | |
1320 | ||
1321 | cont = kzalloc(sizeof(*cont), GFP_KERNEL); | |
1322 | if (!cont) | |
1323 | return -ENOMEM; | |
1324 | ||
1325 | /* Grab a reference on the superblock so the hierarchy doesn't | |
1326 | * get deleted on unmount if there are child cgroups. This | |
1327 | * can be done outside cgroup_mutex, since the sb can't | |
1328 | * disappear while someone has an open control file on the | |
1329 | * fs */ | |
1330 | atomic_inc(&sb->s_active); | |
1331 | ||
1332 | mutex_lock(&cgroup_mutex); | |
1333 | ||
1334 | cont->flags = 0; | |
1335 | INIT_LIST_HEAD(&cont->sibling); | |
1336 | INIT_LIST_HEAD(&cont->children); | |
1337 | ||
1338 | cont->parent = parent; | |
1339 | cont->root = parent->root; | |
1340 | cont->top_cgroup = parent->top_cgroup; | |
1341 | ||
1342 | for_each_subsys(root, ss) { | |
1343 | struct cgroup_subsys_state *css = ss->create(ss, cont); | |
1344 | if (IS_ERR(css)) { | |
1345 | err = PTR_ERR(css); | |
1346 | goto err_destroy; | |
1347 | } | |
1348 | init_cgroup_css(css, ss, cont); | |
1349 | } | |
1350 | ||
1351 | list_add(&cont->sibling, &cont->parent->children); | |
1352 | root->number_of_cgroups++; | |
1353 | ||
1354 | err = cgroup_create_dir(cont, dentry, mode); | |
1355 | if (err < 0) | |
1356 | goto err_remove; | |
1357 | ||
1358 | /* The cgroup directory was pre-locked for us */ | |
1359 | BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex)); | |
1360 | ||
1361 | err = cgroup_populate_dir(cont); | |
1362 | /* If err < 0, we have a half-filled directory - oh well ;) */ | |
1363 | ||
1364 | mutex_unlock(&cgroup_mutex); | |
1365 | mutex_unlock(&cont->dentry->d_inode->i_mutex); | |
1366 | ||
1367 | return 0; | |
1368 | ||
1369 | err_remove: | |
1370 | ||
1371 | list_del(&cont->sibling); | |
1372 | root->number_of_cgroups--; | |
1373 | ||
1374 | err_destroy: | |
1375 | ||
1376 | for_each_subsys(root, ss) { | |
1377 | if (cont->subsys[ss->subsys_id]) | |
1378 | ss->destroy(ss, cont); | |
1379 | } | |
1380 | ||
1381 | mutex_unlock(&cgroup_mutex); | |
1382 | ||
1383 | /* Release the reference count that we took on the superblock */ | |
1384 | deactivate_super(sb); | |
1385 | ||
1386 | kfree(cont); | |
1387 | return err; | |
1388 | } | |
1389 | ||
1390 | static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode) | |
1391 | { | |
1392 | struct cgroup *c_parent = dentry->d_parent->d_fsdata; | |
1393 | ||
1394 | /* the vfs holds inode->i_mutex already */ | |
1395 | return cgroup_create(c_parent, dentry, mode | S_IFDIR); | |
1396 | } | |
1397 | ||
1398 | static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) | |
1399 | { | |
1400 | struct cgroup *cont = dentry->d_fsdata; | |
1401 | struct dentry *d; | |
1402 | struct cgroup *parent; | |
1403 | struct cgroup_subsys *ss; | |
1404 | struct super_block *sb; | |
1405 | struct cgroupfs_root *root; | |
1406 | int css_busy = 0; | |
1407 | ||
1408 | /* the vfs holds both inode->i_mutex already */ | |
1409 | ||
1410 | mutex_lock(&cgroup_mutex); | |
1411 | if (atomic_read(&cont->count) != 0) { | |
1412 | mutex_unlock(&cgroup_mutex); | |
1413 | return -EBUSY; | |
1414 | } | |
1415 | if (!list_empty(&cont->children)) { | |
1416 | mutex_unlock(&cgroup_mutex); | |
1417 | return -EBUSY; | |
1418 | } | |
1419 | ||
1420 | parent = cont->parent; | |
1421 | root = cont->root; | |
1422 | sb = root->sb; | |
1423 | ||
1424 | /* Check the reference count on each subsystem. Since we | |
1425 | * already established that there are no tasks in the | |
1426 | * cgroup, if the css refcount is also 0, then there should | |
1427 | * be no outstanding references, so the subsystem is safe to | |
1428 | * destroy */ | |
1429 | for_each_subsys(root, ss) { | |
1430 | struct cgroup_subsys_state *css; | |
1431 | css = cont->subsys[ss->subsys_id]; | |
1432 | if (atomic_read(&css->refcnt)) { | |
1433 | css_busy = 1; | |
1434 | break; | |
1435 | } | |
1436 | } | |
1437 | if (css_busy) { | |
1438 | mutex_unlock(&cgroup_mutex); | |
1439 | return -EBUSY; | |
1440 | } | |
1441 | ||
1442 | for_each_subsys(root, ss) { | |
1443 | if (cont->subsys[ss->subsys_id]) | |
1444 | ss->destroy(ss, cont); | |
1445 | } | |
1446 | ||
1447 | set_bit(CONT_REMOVED, &cont->flags); | |
1448 | /* delete my sibling from parent->children */ | |
1449 | list_del(&cont->sibling); | |
1450 | spin_lock(&cont->dentry->d_lock); | |
1451 | d = dget(cont->dentry); | |
1452 | cont->dentry = NULL; | |
1453 | spin_unlock(&d->d_lock); | |
1454 | ||
1455 | cgroup_d_remove_dir(d); | |
1456 | dput(d); | |
1457 | root->number_of_cgroups--; | |
1458 | ||
1459 | mutex_unlock(&cgroup_mutex); | |
1460 | /* Drop the active superblock reference that we took when we | |
1461 | * created the cgroup */ | |
1462 | deactivate_super(sb); | |
1463 | return 0; | |
1464 | } | |
1465 | ||
1466 | static void cgroup_init_subsys(struct cgroup_subsys *ss) | |
1467 | { | |
1468 | struct task_struct *g, *p; | |
1469 | struct cgroup_subsys_state *css; | |
1470 | printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name); | |
1471 | ||
1472 | /* Create the top cgroup state for this subsystem */ | |
1473 | ss->root = &rootnode; | |
1474 | css = ss->create(ss, dummytop); | |
1475 | /* We don't handle early failures gracefully */ | |
1476 | BUG_ON(IS_ERR(css)); | |
1477 | init_cgroup_css(css, ss, dummytop); | |
1478 | ||
1479 | /* Update all tasks to contain a subsys pointer to this state | |
1480 | * - since the subsystem is newly registered, all tasks are in | |
1481 | * the subsystem's top cgroup. */ | |
1482 | ||
1483 | /* If this subsystem requested that it be notified with fork | |
1484 | * events, we should send it one now for every process in the | |
1485 | * system */ | |
1486 | ||
1487 | read_lock(&tasklist_lock); | |
1488 | init_task.cgroups.subsys[ss->subsys_id] = css; | |
1489 | if (ss->fork) | |
1490 | ss->fork(ss, &init_task); | |
1491 | ||
1492 | do_each_thread(g, p) { | |
1493 | printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid); | |
1494 | p->cgroups.subsys[ss->subsys_id] = css; | |
1495 | if (ss->fork) | |
1496 | ss->fork(ss, p); | |
1497 | } while_each_thread(g, p); | |
1498 | read_unlock(&tasklist_lock); | |
1499 | ||
1500 | need_forkexit_callback |= ss->fork || ss->exit; | |
1501 | ||
1502 | ss->active = 1; | |
1503 | } | |
1504 | ||
1505 | /** | |
1506 | * cgroup_init_early - initialize cgroups at system boot, and | |
1507 | * initialize any subsystems that request early init. | |
1508 | */ | |
1509 | int __init cgroup_init_early(void) | |
1510 | { | |
1511 | int i; | |
1512 | init_cgroup_root(&rootnode); | |
1513 | list_add(&rootnode.root_list, &roots); | |
1514 | ||
1515 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
1516 | struct cgroup_subsys *ss = subsys[i]; | |
1517 | ||
1518 | BUG_ON(!ss->name); | |
1519 | BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN); | |
1520 | BUG_ON(!ss->create); | |
1521 | BUG_ON(!ss->destroy); | |
1522 | if (ss->subsys_id != i) { | |
1523 | printk(KERN_ERR "Subsys %s id == %d\n", | |
1524 | ss->name, ss->subsys_id); | |
1525 | BUG(); | |
1526 | } | |
1527 | ||
1528 | if (ss->early_init) | |
1529 | cgroup_init_subsys(ss); | |
1530 | } | |
1531 | return 0; | |
1532 | } | |
1533 | ||
1534 | /** | |
1535 | * cgroup_init - register cgroup filesystem and /proc file, and | |
1536 | * initialize any subsystems that didn't request early init. | |
1537 | */ | |
1538 | int __init cgroup_init(void) | |
1539 | { | |
1540 | int err; | |
1541 | int i; | |
1542 | ||
1543 | for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { | |
1544 | struct cgroup_subsys *ss = subsys[i]; | |
1545 | if (!ss->early_init) | |
1546 | cgroup_init_subsys(ss); | |
1547 | } | |
1548 | ||
1549 | err = register_filesystem(&cgroup_fs_type); | |
1550 | if (err < 0) | |
1551 | goto out; | |
1552 | ||
1553 | out: | |
1554 | return err; | |
1555 | } |