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TOMOYO Linux Cross Reference
Linux/kernel/cgroup/cgroup-v1.c

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  1 #include "cgroup-internal.h"
  2 
  3 #include <linux/ctype.h>
  4 #include <linux/kmod.h>
  5 #include <linux/sort.h>
  6 #include <linux/delay.h>
  7 #include <linux/mm.h>
  8 #include <linux/sched/signal.h>
  9 #include <linux/sched/task.h>
 10 #include <linux/magic.h>
 11 #include <linux/slab.h>
 12 #include <linux/vmalloc.h>
 13 #include <linux/delayacct.h>
 14 #include <linux/pid_namespace.h>
 15 #include <linux/cgroupstats.h>
 16 
 17 #include <trace/events/cgroup.h>
 18 
 19 /*
 20  * pidlists linger the following amount before being destroyed.  The goal
 21  * is avoiding frequent destruction in the middle of consecutive read calls
 22  * Expiring in the middle is a performance problem not a correctness one.
 23  * 1 sec should be enough.
 24  */
 25 #define CGROUP_PIDLIST_DESTROY_DELAY    HZ
 26 
 27 /* Controllers blocked by the commandline in v1 */
 28 static u16 cgroup_no_v1_mask;
 29 
 30 /*
 31  * pidlist destructions need to be flushed on cgroup destruction.  Use a
 32  * separate workqueue as flush domain.
 33  */
 34 static struct workqueue_struct *cgroup_pidlist_destroy_wq;
 35 
 36 /*
 37  * Protects cgroup_subsys->release_agent_path.  Modifying it also requires
 38  * cgroup_mutex.  Reading requires either cgroup_mutex or this spinlock.
 39  */
 40 static DEFINE_SPINLOCK(release_agent_path_lock);
 41 
 42 bool cgroup1_ssid_disabled(int ssid)
 43 {
 44         return cgroup_no_v1_mask & (1 << ssid);
 45 }
 46 
 47 /**
 48  * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 49  * @from: attach to all cgroups of a given task
 50  * @tsk: the task to be attached
 51  */
 52 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
 53 {
 54         struct cgroup_root *root;
 55         int retval = 0;
 56 
 57         mutex_lock(&cgroup_mutex);
 58         percpu_down_write(&cgroup_threadgroup_rwsem);
 59         for_each_root(root) {
 60                 struct cgroup *from_cgrp;
 61 
 62                 if (root == &cgrp_dfl_root)
 63                         continue;
 64 
 65                 spin_lock_irq(&css_set_lock);
 66                 from_cgrp = task_cgroup_from_root(from, root);
 67                 spin_unlock_irq(&css_set_lock);
 68 
 69                 retval = cgroup_attach_task(from_cgrp, tsk, false);
 70                 if (retval)
 71                         break;
 72         }
 73         percpu_up_write(&cgroup_threadgroup_rwsem);
 74         mutex_unlock(&cgroup_mutex);
 75 
 76         return retval;
 77 }
 78 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
 79 
 80 /**
 81  * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
 82  * @to: cgroup to which the tasks will be moved
 83  * @from: cgroup in which the tasks currently reside
 84  *
 85  * Locking rules between cgroup_post_fork() and the migration path
 86  * guarantee that, if a task is forking while being migrated, the new child
 87  * is guaranteed to be either visible in the source cgroup after the
 88  * parent's migration is complete or put into the target cgroup.  No task
 89  * can slip out of migration through forking.
 90  */
 91 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 92 {
 93         DEFINE_CGROUP_MGCTX(mgctx);
 94         struct cgrp_cset_link *link;
 95         struct css_task_iter it;
 96         struct task_struct *task;
 97         int ret;
 98 
 99         if (cgroup_on_dfl(to))
100                 return -EINVAL;
101 
102         if (!cgroup_may_migrate_to(to))
103                 return -EBUSY;
104 
105         mutex_lock(&cgroup_mutex);
106 
107         percpu_down_write(&cgroup_threadgroup_rwsem);
108 
109         /* all tasks in @from are being moved, all csets are source */
110         spin_lock_irq(&css_set_lock);
111         list_for_each_entry(link, &from->cset_links, cset_link)
112                 cgroup_migrate_add_src(link->cset, to, &mgctx);
113         spin_unlock_irq(&css_set_lock);
114 
115         ret = cgroup_migrate_prepare_dst(&mgctx);
116         if (ret)
117                 goto out_err;
118 
119         /*
120          * Migrate tasks one-by-one until @from is empty.  This fails iff
121          * ->can_attach() fails.
122          */
123         do {
124                 css_task_iter_start(&from->self, &it);
125                 task = css_task_iter_next(&it);
126                 if (task)
127                         get_task_struct(task);
128                 css_task_iter_end(&it);
129 
130                 if (task) {
131                         ret = cgroup_migrate(task, false, &mgctx);
132                         if (!ret)
133                                 trace_cgroup_transfer_tasks(to, task, false);
134                         put_task_struct(task);
135                 }
136         } while (task && !ret);
137 out_err:
138         cgroup_migrate_finish(&mgctx);
139         percpu_up_write(&cgroup_threadgroup_rwsem);
140         mutex_unlock(&cgroup_mutex);
141         return ret;
142 }
143 
144 /*
145  * Stuff for reading the 'tasks'/'procs' files.
146  *
147  * Reading this file can return large amounts of data if a cgroup has
148  * *lots* of attached tasks. So it may need several calls to read(),
149  * but we cannot guarantee that the information we produce is correct
150  * unless we produce it entirely atomically.
151  *
152  */
153 
154 /* which pidlist file are we talking about? */
155 enum cgroup_filetype {
156         CGROUP_FILE_PROCS,
157         CGROUP_FILE_TASKS,
158 };
159 
160 /*
161  * A pidlist is a list of pids that virtually represents the contents of one
162  * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
163  * a pair (one each for procs, tasks) for each pid namespace that's relevant
164  * to the cgroup.
165  */
166 struct cgroup_pidlist {
167         /*
168          * used to find which pidlist is wanted. doesn't change as long as
169          * this particular list stays in the list.
170         */
171         struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
172         /* array of xids */
173         pid_t *list;
174         /* how many elements the above list has */
175         int length;
176         /* each of these stored in a list by its cgroup */
177         struct list_head links;
178         /* pointer to the cgroup we belong to, for list removal purposes */
179         struct cgroup *owner;
180         /* for delayed destruction */
181         struct delayed_work destroy_dwork;
182 };
183 
184 /*
185  * The following two functions "fix" the issue where there are more pids
186  * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
187  * TODO: replace with a kernel-wide solution to this problem
188  */
189 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
190 static void *pidlist_allocate(int count)
191 {
192         if (PIDLIST_TOO_LARGE(count))
193                 return vmalloc(count * sizeof(pid_t));
194         else
195                 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
196 }
197 
198 static void pidlist_free(void *p)
199 {
200         kvfree(p);
201 }
202 
203 /*
204  * Used to destroy all pidlists lingering waiting for destroy timer.  None
205  * should be left afterwards.
206  */
207 void cgroup1_pidlist_destroy_all(struct cgroup *cgrp)
208 {
209         struct cgroup_pidlist *l, *tmp_l;
210 
211         mutex_lock(&cgrp->pidlist_mutex);
212         list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
213                 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
214         mutex_unlock(&cgrp->pidlist_mutex);
215 
216         flush_workqueue(cgroup_pidlist_destroy_wq);
217         BUG_ON(!list_empty(&cgrp->pidlists));
218 }
219 
220 static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
221 {
222         struct delayed_work *dwork = to_delayed_work(work);
223         struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
224                                                 destroy_dwork);
225         struct cgroup_pidlist *tofree = NULL;
226 
227         mutex_lock(&l->owner->pidlist_mutex);
228 
229         /*
230          * Destroy iff we didn't get queued again.  The state won't change
231          * as destroy_dwork can only be queued while locked.
232          */
233         if (!delayed_work_pending(dwork)) {
234                 list_del(&l->links);
235                 pidlist_free(l->list);
236                 put_pid_ns(l->key.ns);
237                 tofree = l;
238         }
239 
240         mutex_unlock(&l->owner->pidlist_mutex);
241         kfree(tofree);
242 }
243 
244 /*
245  * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
246  * Returns the number of unique elements.
247  */
248 static int pidlist_uniq(pid_t *list, int length)
249 {
250         int src, dest = 1;
251 
252         /*
253          * we presume the 0th element is unique, so i starts at 1. trivial
254          * edge cases first; no work needs to be done for either
255          */
256         if (length == 0 || length == 1)
257                 return length;
258         /* src and dest walk down the list; dest counts unique elements */
259         for (src = 1; src < length; src++) {
260                 /* find next unique element */
261                 while (list[src] == list[src-1]) {
262                         src++;
263                         if (src == length)
264                                 goto after;
265                 }
266                 /* dest always points to where the next unique element goes */
267                 list[dest] = list[src];
268                 dest++;
269         }
270 after:
271         return dest;
272 }
273 
274 /*
275  * The two pid files - task and cgroup.procs - guaranteed that the result
276  * is sorted, which forced this whole pidlist fiasco.  As pid order is
277  * different per namespace, each namespace needs differently sorted list,
278  * making it impossible to use, for example, single rbtree of member tasks
279  * sorted by task pointer.  As pidlists can be fairly large, allocating one
280  * per open file is dangerous, so cgroup had to implement shared pool of
281  * pidlists keyed by cgroup and namespace.
282  */
283 static int cmppid(const void *a, const void *b)
284 {
285         return *(pid_t *)a - *(pid_t *)b;
286 }
287 
288 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
289                                                   enum cgroup_filetype type)
290 {
291         struct cgroup_pidlist *l;
292         /* don't need task_nsproxy() if we're looking at ourself */
293         struct pid_namespace *ns = task_active_pid_ns(current);
294 
295         lockdep_assert_held(&cgrp->pidlist_mutex);
296 
297         list_for_each_entry(l, &cgrp->pidlists, links)
298                 if (l->key.type == type && l->key.ns == ns)
299                         return l;
300         return NULL;
301 }
302 
303 /*
304  * find the appropriate pidlist for our purpose (given procs vs tasks)
305  * returns with the lock on that pidlist already held, and takes care
306  * of the use count, or returns NULL with no locks held if we're out of
307  * memory.
308  */
309 static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
310                                                 enum cgroup_filetype type)
311 {
312         struct cgroup_pidlist *l;
313 
314         lockdep_assert_held(&cgrp->pidlist_mutex);
315 
316         l = cgroup_pidlist_find(cgrp, type);
317         if (l)
318                 return l;
319 
320         /* entry not found; create a new one */
321         l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
322         if (!l)
323                 return l;
324 
325         INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
326         l->key.type = type;
327         /* don't need task_nsproxy() if we're looking at ourself */
328         l->key.ns = get_pid_ns(task_active_pid_ns(current));
329         l->owner = cgrp;
330         list_add(&l->links, &cgrp->pidlists);
331         return l;
332 }
333 
334 /**
335  * cgroup_task_count - count the number of tasks in a cgroup.
336  * @cgrp: the cgroup in question
337  */
338 int cgroup_task_count(const struct cgroup *cgrp)
339 {
340         int count = 0;
341         struct cgrp_cset_link *link;
342 
343         spin_lock_irq(&css_set_lock);
344         list_for_each_entry(link, &cgrp->cset_links, cset_link)
345                 count += link->cset->nr_tasks;
346         spin_unlock_irq(&css_set_lock);
347         return count;
348 }
349 
350 /*
351  * Load a cgroup's pidarray with either procs' tgids or tasks' pids
352  */
353 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
354                               struct cgroup_pidlist **lp)
355 {
356         pid_t *array;
357         int length;
358         int pid, n = 0; /* used for populating the array */
359         struct css_task_iter it;
360         struct task_struct *tsk;
361         struct cgroup_pidlist *l;
362 
363         lockdep_assert_held(&cgrp->pidlist_mutex);
364 
365         /*
366          * If cgroup gets more users after we read count, we won't have
367          * enough space - tough.  This race is indistinguishable to the
368          * caller from the case that the additional cgroup users didn't
369          * show up until sometime later on.
370          */
371         length = cgroup_task_count(cgrp);
372         array = pidlist_allocate(length);
373         if (!array)
374                 return -ENOMEM;
375         /* now, populate the array */
376         css_task_iter_start(&cgrp->self, &it);
377         while ((tsk = css_task_iter_next(&it))) {
378                 if (unlikely(n == length))
379                         break;
380                 /* get tgid or pid for procs or tasks file respectively */
381                 if (type == CGROUP_FILE_PROCS)
382                         pid = task_tgid_vnr(tsk);
383                 else
384                         pid = task_pid_vnr(tsk);
385                 if (pid > 0) /* make sure to only use valid results */
386                         array[n++] = pid;
387         }
388         css_task_iter_end(&it);
389         length = n;
390         /* now sort & (if procs) strip out duplicates */
391         sort(array, length, sizeof(pid_t), cmppid, NULL);
392         if (type == CGROUP_FILE_PROCS)
393                 length = pidlist_uniq(array, length);
394 
395         l = cgroup_pidlist_find_create(cgrp, type);
396         if (!l) {
397                 pidlist_free(array);
398                 return -ENOMEM;
399         }
400 
401         /* store array, freeing old if necessary */
402         pidlist_free(l->list);
403         l->list = array;
404         l->length = length;
405         *lp = l;
406         return 0;
407 }
408 
409 /*
410  * seq_file methods for the tasks/procs files. The seq_file position is the
411  * next pid to display; the seq_file iterator is a pointer to the pid
412  * in the cgroup->l->list array.
413  */
414 
415 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
416 {
417         /*
418          * Initially we receive a position value that corresponds to
419          * one more than the last pid shown (or 0 on the first call or
420          * after a seek to the start). Use a binary-search to find the
421          * next pid to display, if any
422          */
423         struct kernfs_open_file *of = s->private;
424         struct cgroup *cgrp = seq_css(s)->cgroup;
425         struct cgroup_pidlist *l;
426         enum cgroup_filetype type = seq_cft(s)->private;
427         int index = 0, pid = *pos;
428         int *iter, ret;
429 
430         mutex_lock(&cgrp->pidlist_mutex);
431 
432         /*
433          * !NULL @of->priv indicates that this isn't the first start()
434          * after open.  If the matching pidlist is around, we can use that.
435          * Look for it.  Note that @of->priv can't be used directly.  It
436          * could already have been destroyed.
437          */
438         if (of->priv)
439                 of->priv = cgroup_pidlist_find(cgrp, type);
440 
441         /*
442          * Either this is the first start() after open or the matching
443          * pidlist has been destroyed inbetween.  Create a new one.
444          */
445         if (!of->priv) {
446                 ret = pidlist_array_load(cgrp, type,
447                                          (struct cgroup_pidlist **)&of->priv);
448                 if (ret)
449                         return ERR_PTR(ret);
450         }
451         l = of->priv;
452 
453         if (pid) {
454                 int end = l->length;
455 
456                 while (index < end) {
457                         int mid = (index + end) / 2;
458                         if (l->list[mid] == pid) {
459                                 index = mid;
460                                 break;
461                         } else if (l->list[mid] <= pid)
462                                 index = mid + 1;
463                         else
464                                 end = mid;
465                 }
466         }
467         /* If we're off the end of the array, we're done */
468         if (index >= l->length)
469                 return NULL;
470         /* Update the abstract position to be the actual pid that we found */
471         iter = l->list + index;
472         *pos = *iter;
473         return iter;
474 }
475 
476 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
477 {
478         struct kernfs_open_file *of = s->private;
479         struct cgroup_pidlist *l = of->priv;
480 
481         if (l)
482                 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
483                                  CGROUP_PIDLIST_DESTROY_DELAY);
484         mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
485 }
486 
487 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
488 {
489         struct kernfs_open_file *of = s->private;
490         struct cgroup_pidlist *l = of->priv;
491         pid_t *p = v;
492         pid_t *end = l->list + l->length;
493         /*
494          * Advance to the next pid in the array. If this goes off the
495          * end, we're done
496          */
497         p++;
498         if (p >= end) {
499                 return NULL;
500         } else {
501                 *pos = *p;
502                 return p;
503         }
504 }
505 
506 static int cgroup_pidlist_show(struct seq_file *s, void *v)
507 {
508         seq_printf(s, "%d\n", *(int *)v);
509 
510         return 0;
511 }
512 
513 static ssize_t cgroup_tasks_write(struct kernfs_open_file *of,
514                                   char *buf, size_t nbytes, loff_t off)
515 {
516         return __cgroup_procs_write(of, buf, nbytes, off, false);
517 }
518 
519 static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
520                                           char *buf, size_t nbytes, loff_t off)
521 {
522         struct cgroup *cgrp;
523 
524         BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
525 
526         cgrp = cgroup_kn_lock_live(of->kn, false);
527         if (!cgrp)
528                 return -ENODEV;
529         spin_lock(&release_agent_path_lock);
530         strlcpy(cgrp->root->release_agent_path, strstrip(buf),
531                 sizeof(cgrp->root->release_agent_path));
532         spin_unlock(&release_agent_path_lock);
533         cgroup_kn_unlock(of->kn);
534         return nbytes;
535 }
536 
537 static int cgroup_release_agent_show(struct seq_file *seq, void *v)
538 {
539         struct cgroup *cgrp = seq_css(seq)->cgroup;
540 
541         spin_lock(&release_agent_path_lock);
542         seq_puts(seq, cgrp->root->release_agent_path);
543         spin_unlock(&release_agent_path_lock);
544         seq_putc(seq, '\n');
545         return 0;
546 }
547 
548 static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
549 {
550         seq_puts(seq, "\n");
551         return 0;
552 }
553 
554 static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
555                                          struct cftype *cft)
556 {
557         return notify_on_release(css->cgroup);
558 }
559 
560 static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
561                                           struct cftype *cft, u64 val)
562 {
563         if (val)
564                 set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
565         else
566                 clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
567         return 0;
568 }
569 
570 static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
571                                       struct cftype *cft)
572 {
573         return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
574 }
575 
576 static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
577                                        struct cftype *cft, u64 val)
578 {
579         if (val)
580                 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
581         else
582                 clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
583         return 0;
584 }
585 
586 /* cgroup core interface files for the legacy hierarchies */
587 struct cftype cgroup1_base_files[] = {
588         {
589                 .name = "cgroup.procs",
590                 .seq_start = cgroup_pidlist_start,
591                 .seq_next = cgroup_pidlist_next,
592                 .seq_stop = cgroup_pidlist_stop,
593                 .seq_show = cgroup_pidlist_show,
594                 .private = CGROUP_FILE_PROCS,
595                 .write = cgroup_procs_write,
596         },
597         {
598                 .name = "cgroup.clone_children",
599                 .read_u64 = cgroup_clone_children_read,
600                 .write_u64 = cgroup_clone_children_write,
601         },
602         {
603                 .name = "cgroup.sane_behavior",
604                 .flags = CFTYPE_ONLY_ON_ROOT,
605                 .seq_show = cgroup_sane_behavior_show,
606         },
607         {
608                 .name = "tasks",
609                 .seq_start = cgroup_pidlist_start,
610                 .seq_next = cgroup_pidlist_next,
611                 .seq_stop = cgroup_pidlist_stop,
612                 .seq_show = cgroup_pidlist_show,
613                 .private = CGROUP_FILE_TASKS,
614                 .write = cgroup_tasks_write,
615         },
616         {
617                 .name = "notify_on_release",
618                 .read_u64 = cgroup_read_notify_on_release,
619                 .write_u64 = cgroup_write_notify_on_release,
620         },
621         {
622                 .name = "release_agent",
623                 .flags = CFTYPE_ONLY_ON_ROOT,
624                 .seq_show = cgroup_release_agent_show,
625                 .write = cgroup_release_agent_write,
626                 .max_write_len = PATH_MAX - 1,
627         },
628         { }     /* terminate */
629 };
630 
631 /* Display information about each subsystem and each hierarchy */
632 static int proc_cgroupstats_show(struct seq_file *m, void *v)
633 {
634         struct cgroup_subsys *ss;
635         int i;
636 
637         seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
638         /*
639          * ideally we don't want subsystems moving around while we do this.
640          * cgroup_mutex is also necessary to guarantee an atomic snapshot of
641          * subsys/hierarchy state.
642          */
643         mutex_lock(&cgroup_mutex);
644 
645         for_each_subsys(ss, i)
646                 seq_printf(m, "%s\t%d\t%d\t%d\n",
647                            ss->legacy_name, ss->root->hierarchy_id,
648                            atomic_read(&ss->root->nr_cgrps),
649                            cgroup_ssid_enabled(i));
650 
651         mutex_unlock(&cgroup_mutex);
652         return 0;
653 }
654 
655 static int cgroupstats_open(struct inode *inode, struct file *file)
656 {
657         return single_open(file, proc_cgroupstats_show, NULL);
658 }
659 
660 const struct file_operations proc_cgroupstats_operations = {
661         .open = cgroupstats_open,
662         .read = seq_read,
663         .llseek = seq_lseek,
664         .release = single_release,
665 };
666 
667 /**
668  * cgroupstats_build - build and fill cgroupstats
669  * @stats: cgroupstats to fill information into
670  * @dentry: A dentry entry belonging to the cgroup for which stats have
671  * been requested.
672  *
673  * Build and fill cgroupstats so that taskstats can export it to user
674  * space.
675  */
676 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
677 {
678         struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
679         struct cgroup *cgrp;
680         struct css_task_iter it;
681         struct task_struct *tsk;
682 
683         /* it should be kernfs_node belonging to cgroupfs and is a directory */
684         if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
685             kernfs_type(kn) != KERNFS_DIR)
686                 return -EINVAL;
687 
688         mutex_lock(&cgroup_mutex);
689 
690         /*
691          * We aren't being called from kernfs and there's no guarantee on
692          * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
693          * @kn->priv is RCU safe.  Let's do the RCU dancing.
694          */
695         rcu_read_lock();
696         cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
697         if (!cgrp || cgroup_is_dead(cgrp)) {
698                 rcu_read_unlock();
699                 mutex_unlock(&cgroup_mutex);
700                 return -ENOENT;
701         }
702         rcu_read_unlock();
703 
704         css_task_iter_start(&cgrp->self, &it);
705         while ((tsk = css_task_iter_next(&it))) {
706                 switch (tsk->state) {
707                 case TASK_RUNNING:
708                         stats->nr_running++;
709                         break;
710                 case TASK_INTERRUPTIBLE:
711                         stats->nr_sleeping++;
712                         break;
713                 case TASK_UNINTERRUPTIBLE:
714                         stats->nr_uninterruptible++;
715                         break;
716                 case TASK_STOPPED:
717                         stats->nr_stopped++;
718                         break;
719                 default:
720                         if (delayacct_is_task_waiting_on_io(tsk))
721                                 stats->nr_io_wait++;
722                         break;
723                 }
724         }
725         css_task_iter_end(&it);
726 
727         mutex_unlock(&cgroup_mutex);
728         return 0;
729 }
730 
731 void cgroup1_check_for_release(struct cgroup *cgrp)
732 {
733         if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
734             !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
735                 schedule_work(&cgrp->release_agent_work);
736 }
737 
738 /*
739  * Notify userspace when a cgroup is released, by running the
740  * configured release agent with the name of the cgroup (path
741  * relative to the root of cgroup file system) as the argument.
742  *
743  * Most likely, this user command will try to rmdir this cgroup.
744  *
745  * This races with the possibility that some other task will be
746  * attached to this cgroup before it is removed, or that some other
747  * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
748  * The presumed 'rmdir' will fail quietly if this cgroup is no longer
749  * unused, and this cgroup will be reprieved from its death sentence,
750  * to continue to serve a useful existence.  Next time it's released,
751  * we will get notified again, if it still has 'notify_on_release' set.
752  *
753  * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
754  * means only wait until the task is successfully execve()'d.  The
755  * separate release agent task is forked by call_usermodehelper(),
756  * then control in this thread returns here, without waiting for the
757  * release agent task.  We don't bother to wait because the caller of
758  * this routine has no use for the exit status of the release agent
759  * task, so no sense holding our caller up for that.
760  */
761 void cgroup1_release_agent(struct work_struct *work)
762 {
763         struct cgroup *cgrp =
764                 container_of(work, struct cgroup, release_agent_work);
765         char *pathbuf = NULL, *agentbuf = NULL;
766         char *argv[3], *envp[3];
767         int ret;
768 
769         mutex_lock(&cgroup_mutex);
770 
771         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
772         agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
773         if (!pathbuf || !agentbuf)
774                 goto out;
775 
776         spin_lock_irq(&css_set_lock);
777         ret = cgroup_path_ns_locked(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
778         spin_unlock_irq(&css_set_lock);
779         if (ret < 0 || ret >= PATH_MAX)
780                 goto out;
781 
782         argv[0] = agentbuf;
783         argv[1] = pathbuf;
784         argv[2] = NULL;
785 
786         /* minimal command environment */
787         envp[0] = "HOME=/";
788         envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
789         envp[2] = NULL;
790 
791         mutex_unlock(&cgroup_mutex);
792         call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
793         goto out_free;
794 out:
795         mutex_unlock(&cgroup_mutex);
796 out_free:
797         kfree(agentbuf);
798         kfree(pathbuf);
799 }
800 
801 /*
802  * cgroup_rename - Only allow simple rename of directories in place.
803  */
804 static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
805                           const char *new_name_str)
806 {
807         struct cgroup *cgrp = kn->priv;
808         int ret;
809 
810         if (kernfs_type(kn) != KERNFS_DIR)
811                 return -ENOTDIR;
812         if (kn->parent != new_parent)
813                 return -EIO;
814 
815         /*
816          * We're gonna grab cgroup_mutex which nests outside kernfs
817          * active_ref.  kernfs_rename() doesn't require active_ref
818          * protection.  Break them before grabbing cgroup_mutex.
819          */
820         kernfs_break_active_protection(new_parent);
821         kernfs_break_active_protection(kn);
822 
823         mutex_lock(&cgroup_mutex);
824 
825         ret = kernfs_rename(kn, new_parent, new_name_str);
826         if (!ret)
827                 trace_cgroup_rename(cgrp);
828 
829         mutex_unlock(&cgroup_mutex);
830 
831         kernfs_unbreak_active_protection(kn);
832         kernfs_unbreak_active_protection(new_parent);
833         return ret;
834 }
835 
836 static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
837 {
838         struct cgroup_root *root = cgroup_root_from_kf(kf_root);
839         struct cgroup_subsys *ss;
840         int ssid;
841 
842         for_each_subsys(ss, ssid)
843                 if (root->subsys_mask & (1 << ssid))
844                         seq_show_option(seq, ss->legacy_name, NULL);
845         if (root->flags & CGRP_ROOT_NOPREFIX)
846                 seq_puts(seq, ",noprefix");
847         if (root->flags & CGRP_ROOT_XATTR)
848                 seq_puts(seq, ",xattr");
849 
850         spin_lock(&release_agent_path_lock);
851         if (strlen(root->release_agent_path))
852                 seq_show_option(seq, "release_agent",
853                                 root->release_agent_path);
854         spin_unlock(&release_agent_path_lock);
855 
856         if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
857                 seq_puts(seq, ",clone_children");
858         if (strlen(root->name))
859                 seq_show_option(seq, "name", root->name);
860         return 0;
861 }
862 
863 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
864 {
865         char *token, *o = data;
866         bool all_ss = false, one_ss = false;
867         u16 mask = U16_MAX;
868         struct cgroup_subsys *ss;
869         int nr_opts = 0;
870         int i;
871 
872 #ifdef CONFIG_CPUSETS
873         mask = ~((u16)1 << cpuset_cgrp_id);
874 #endif
875 
876         memset(opts, 0, sizeof(*opts));
877 
878         while ((token = strsep(&o, ",")) != NULL) {
879                 nr_opts++;
880 
881                 if (!*token)
882                         return -EINVAL;
883                 if (!strcmp(token, "none")) {
884                         /* Explicitly have no subsystems */
885                         opts->none = true;
886                         continue;
887                 }
888                 if (!strcmp(token, "all")) {
889                         /* Mutually exclusive option 'all' + subsystem name */
890                         if (one_ss)
891                                 return -EINVAL;
892                         all_ss = true;
893                         continue;
894                 }
895                 if (!strcmp(token, "noprefix")) {
896                         opts->flags |= CGRP_ROOT_NOPREFIX;
897                         continue;
898                 }
899                 if (!strcmp(token, "clone_children")) {
900                         opts->cpuset_clone_children = true;
901                         continue;
902                 }
903                 if (!strcmp(token, "xattr")) {
904                         opts->flags |= CGRP_ROOT_XATTR;
905                         continue;
906                 }
907                 if (!strncmp(token, "release_agent=", 14)) {
908                         /* Specifying two release agents is forbidden */
909                         if (opts->release_agent)
910                                 return -EINVAL;
911                         opts->release_agent =
912                                 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
913                         if (!opts->release_agent)
914                                 return -ENOMEM;
915                         continue;
916                 }
917                 if (!strncmp(token, "name=", 5)) {
918                         const char *name = token + 5;
919                         /* Can't specify an empty name */
920                         if (!strlen(name))
921                                 return -EINVAL;
922                         /* Must match [\w.-]+ */
923                         for (i = 0; i < strlen(name); i++) {
924                                 char c = name[i];
925                                 if (isalnum(c))
926                                         continue;
927                                 if ((c == '.') || (c == '-') || (c == '_'))
928                                         continue;
929                                 return -EINVAL;
930                         }
931                         /* Specifying two names is forbidden */
932                         if (opts->name)
933                                 return -EINVAL;
934                         opts->name = kstrndup(name,
935                                               MAX_CGROUP_ROOT_NAMELEN - 1,
936                                               GFP_KERNEL);
937                         if (!opts->name)
938                                 return -ENOMEM;
939 
940                         continue;
941                 }
942 
943                 for_each_subsys(ss, i) {
944                         if (strcmp(token, ss->legacy_name))
945                                 continue;
946                         if (!cgroup_ssid_enabled(i))
947                                 continue;
948                         if (cgroup1_ssid_disabled(i))
949                                 continue;
950 
951                         /* Mutually exclusive option 'all' + subsystem name */
952                         if (all_ss)
953                                 return -EINVAL;
954                         opts->subsys_mask |= (1 << i);
955                         one_ss = true;
956 
957                         break;
958                 }
959                 if (i == CGROUP_SUBSYS_COUNT)
960                         return -ENOENT;
961         }
962 
963         /*
964          * If the 'all' option was specified select all the subsystems,
965          * otherwise if 'none', 'name=' and a subsystem name options were
966          * not specified, let's default to 'all'
967          */
968         if (all_ss || (!one_ss && !opts->none && !opts->name))
969                 for_each_subsys(ss, i)
970                         if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
971                                 opts->subsys_mask |= (1 << i);
972 
973         /*
974          * We either have to specify by name or by subsystems. (So all
975          * empty hierarchies must have a name).
976          */
977         if (!opts->subsys_mask && !opts->name)
978                 return -EINVAL;
979 
980         /*
981          * Option noprefix was introduced just for backward compatibility
982          * with the old cpuset, so we allow noprefix only if mounting just
983          * the cpuset subsystem.
984          */
985         if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
986                 return -EINVAL;
987 
988         /* Can't specify "none" and some subsystems */
989         if (opts->subsys_mask && opts->none)
990                 return -EINVAL;
991 
992         return 0;
993 }
994 
995 static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
996 {
997         int ret = 0;
998         struct cgroup_root *root = cgroup_root_from_kf(kf_root);
999         struct cgroup_sb_opts opts;
1000         u16 added_mask, removed_mask;
1001 
1002         cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1003 
1004         /* See what subsystems are wanted */
1005         ret = parse_cgroupfs_options(data, &opts);
1006         if (ret)
1007                 goto out_unlock;
1008 
1009         if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
1010                 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1011                         task_tgid_nr(current), current->comm);
1012 
1013         added_mask = opts.subsys_mask & ~root->subsys_mask;
1014         removed_mask = root->subsys_mask & ~opts.subsys_mask;
1015 
1016         /* Don't allow flags or name to change at remount */
1017         if ((opts.flags ^ root->flags) ||
1018             (opts.name && strcmp(opts.name, root->name))) {
1019                 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1020                        opts.flags, opts.name ?: "", root->flags, root->name);
1021                 ret = -EINVAL;
1022                 goto out_unlock;
1023         }
1024 
1025         /* remounting is not allowed for populated hierarchies */
1026         if (!list_empty(&root->cgrp.self.children)) {
1027                 ret = -EBUSY;
1028                 goto out_unlock;
1029         }
1030 
1031         ret = rebind_subsystems(root, added_mask);
1032         if (ret)
1033                 goto out_unlock;
1034 
1035         WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
1036 
1037         if (opts.release_agent) {
1038                 spin_lock(&release_agent_path_lock);
1039                 strcpy(root->release_agent_path, opts.release_agent);
1040                 spin_unlock(&release_agent_path_lock);
1041         }
1042 
1043         trace_cgroup_remount(root);
1044 
1045  out_unlock:
1046         kfree(opts.release_agent);
1047         kfree(opts.name);
1048         mutex_unlock(&cgroup_mutex);
1049         return ret;
1050 }
1051 
1052 struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
1053         .rename                 = cgroup1_rename,
1054         .show_options           = cgroup1_show_options,
1055         .remount_fs             = cgroup1_remount,
1056         .mkdir                  = cgroup_mkdir,
1057         .rmdir                  = cgroup_rmdir,
1058         .show_path              = cgroup_show_path,
1059 };
1060 
1061 struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
1062                              void *data, unsigned long magic,
1063                              struct cgroup_namespace *ns)
1064 {
1065         struct super_block *pinned_sb = NULL;
1066         struct cgroup_sb_opts opts;
1067         struct cgroup_root *root;
1068         struct cgroup_subsys *ss;
1069         struct dentry *dentry;
1070         int i, ret;
1071         bool new_root = false;
1072 
1073         cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1074 
1075         /* First find the desired set of subsystems */
1076         ret = parse_cgroupfs_options(data, &opts);
1077         if (ret)
1078                 goto out_unlock;
1079 
1080         /*
1081          * Destruction of cgroup root is asynchronous, so subsystems may
1082          * still be dying after the previous unmount.  Let's drain the
1083          * dying subsystems.  We just need to ensure that the ones
1084          * unmounted previously finish dying and don't care about new ones
1085          * starting.  Testing ref liveliness is good enough.
1086          */
1087         for_each_subsys(ss, i) {
1088                 if (!(opts.subsys_mask & (1 << i)) ||
1089                     ss->root == &cgrp_dfl_root)
1090                         continue;
1091 
1092                 if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
1093                         mutex_unlock(&cgroup_mutex);
1094                         msleep(10);
1095                         ret = restart_syscall();
1096                         goto out_free;
1097                 }
1098                 cgroup_put(&ss->root->cgrp);
1099         }
1100 
1101         for_each_root(root) {
1102                 bool name_match = false;
1103 
1104                 if (root == &cgrp_dfl_root)
1105                         continue;
1106 
1107                 /*
1108                  * If we asked for a name then it must match.  Also, if
1109                  * name matches but sybsys_mask doesn't, we should fail.
1110                  * Remember whether name matched.
1111                  */
1112                 if (opts.name) {
1113                         if (strcmp(opts.name, root->name))
1114                                 continue;
1115                         name_match = true;
1116                 }
1117 
1118                 /*
1119                  * If we asked for subsystems (or explicitly for no
1120                  * subsystems) then they must match.
1121                  */
1122                 if ((opts.subsys_mask || opts.none) &&
1123                     (opts.subsys_mask != root->subsys_mask)) {
1124                         if (!name_match)
1125                                 continue;
1126                         ret = -EBUSY;
1127                         goto out_unlock;
1128                 }
1129 
1130                 if (root->flags ^ opts.flags)
1131                         pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1132 
1133                 /*
1134                  * We want to reuse @root whose lifetime is governed by its
1135                  * ->cgrp.  Let's check whether @root is alive and keep it
1136                  * that way.  As cgroup_kill_sb() can happen anytime, we
1137                  * want to block it by pinning the sb so that @root doesn't
1138                  * get killed before mount is complete.
1139                  *
1140                  * With the sb pinned, tryget_live can reliably indicate
1141                  * whether @root can be reused.  If it's being killed,
1142                  * drain it.  We can use wait_queue for the wait but this
1143                  * path is super cold.  Let's just sleep a bit and retry.
1144                  */
1145                 pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
1146                 if (IS_ERR(pinned_sb) ||
1147                     !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
1148                         mutex_unlock(&cgroup_mutex);
1149                         if (!IS_ERR_OR_NULL(pinned_sb))
1150                                 deactivate_super(pinned_sb);
1151                         msleep(10);
1152                         ret = restart_syscall();
1153                         goto out_free;
1154                 }
1155 
1156                 ret = 0;
1157                 goto out_unlock;
1158         }
1159 
1160         /*
1161          * No such thing, create a new one.  name= matching without subsys
1162          * specification is allowed for already existing hierarchies but we
1163          * can't create new one without subsys specification.
1164          */
1165         if (!opts.subsys_mask && !opts.none) {
1166                 ret = -EINVAL;
1167                 goto out_unlock;
1168         }
1169 
1170         /* Hierarchies may only be created in the initial cgroup namespace. */
1171         if (ns != &init_cgroup_ns) {
1172                 ret = -EPERM;
1173                 goto out_unlock;
1174         }
1175 
1176         root = kzalloc(sizeof(*root), GFP_KERNEL);
1177         if (!root) {
1178                 ret = -ENOMEM;
1179                 goto out_unlock;
1180         }
1181         new_root = true;
1182 
1183         init_cgroup_root(root, &opts);
1184 
1185         ret = cgroup_setup_root(root, opts.subsys_mask, PERCPU_REF_INIT_DEAD);
1186         if (ret)
1187                 cgroup_free_root(root);
1188 
1189 out_unlock:
1190         mutex_unlock(&cgroup_mutex);
1191 out_free:
1192         kfree(opts.release_agent);
1193         kfree(opts.name);
1194 
1195         if (ret)
1196                 return ERR_PTR(ret);
1197 
1198         dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
1199                                  CGROUP_SUPER_MAGIC, ns);
1200 
1201         /*
1202          * There's a race window after we release cgroup_mutex and before
1203          * allocating a superblock. Make sure a concurrent process won't
1204          * be able to re-use the root during this window by delaying the
1205          * initialization of root refcnt.
1206          */
1207         if (new_root) {
1208                 mutex_lock(&cgroup_mutex);
1209                 percpu_ref_reinit(&root->cgrp.self.refcnt);
1210                 mutex_unlock(&cgroup_mutex);
1211         }
1212 
1213         /*
1214          * If @pinned_sb, we're reusing an existing root and holding an
1215          * extra ref on its sb.  Mount is complete.  Put the extra ref.
1216          */
1217         if (pinned_sb)
1218                 deactivate_super(pinned_sb);
1219 
1220         return dentry;
1221 }
1222 
1223 static int __init cgroup1_wq_init(void)
1224 {
1225         /*
1226          * Used to destroy pidlists and separate to serve as flush domain.
1227          * Cap @max_active to 1 too.
1228          */
1229         cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
1230                                                     0, 1);
1231         BUG_ON(!cgroup_pidlist_destroy_wq);
1232         return 0;
1233 }
1234 core_initcall(cgroup1_wq_init);
1235 
1236 static int __init cgroup_no_v1(char *str)
1237 {
1238         struct cgroup_subsys *ss;
1239         char *token;
1240         int i;
1241 
1242         while ((token = strsep(&str, ",")) != NULL) {
1243                 if (!*token)
1244                         continue;
1245 
1246                 if (!strcmp(token, "all")) {
1247                         cgroup_no_v1_mask = U16_MAX;
1248                         break;
1249                 }
1250 
1251                 for_each_subsys(ss, i) {
1252                         if (strcmp(token, ss->name) &&
1253                             strcmp(token, ss->legacy_name))
1254                                 continue;
1255 
1256                         cgroup_no_v1_mask |= 1 << i;
1257                 }
1258         }
1259         return 1;
1260 }
1261 __setup("cgroup_no_v1=", cgroup_no_v1);
1262 

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