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TOMOYO Linux Cross Reference
Linux/block/blk-cgroup.c

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  1 /*
  2  * Common Block IO controller cgroup interface
  3  *
  4  * Based on ideas and code from CFQ, CFS and BFQ:
  5  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
  6  *
  7  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
  8  *                    Paolo Valente <paolo.valente@unimore.it>
  9  *
 10  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
 11  *                    Nauman Rafique <nauman@google.com>
 12  */
 13 #include <linux/ioprio.h>
 14 #include <linux/kdev_t.h>
 15 #include <linux/module.h>
 16 #include <linux/err.h>
 17 #include <linux/blkdev.h>
 18 #include <linux/slab.h>
 19 #include <linux/genhd.h>
 20 #include <linux/delay.h>
 21 #include <linux/atomic.h>
 22 #include "blk-cgroup.h"
 23 #include "blk.h"
 24 
 25 #define MAX_KEY_LEN 100
 26 
 27 static DEFINE_MUTEX(blkcg_pol_mutex);
 28 
 29 struct blkcg blkcg_root = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT,
 30                             .cfq_leaf_weight = 2 * CFQ_WEIGHT_DEFAULT, };
 31 EXPORT_SYMBOL_GPL(blkcg_root);
 32 
 33 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
 34 
 35 static bool blkcg_policy_enabled(struct request_queue *q,
 36                                  const struct blkcg_policy *pol)
 37 {
 38         return pol && test_bit(pol->plid, q->blkcg_pols);
 39 }
 40 
 41 /**
 42  * blkg_free - free a blkg
 43  * @blkg: blkg to free
 44  *
 45  * Free @blkg which may be partially allocated.
 46  */
 47 static void blkg_free(struct blkcg_gq *blkg)
 48 {
 49         int i;
 50 
 51         if (!blkg)
 52                 return;
 53 
 54         for (i = 0; i < BLKCG_MAX_POLS; i++)
 55                 kfree(blkg->pd[i]);
 56 
 57         blk_exit_rl(&blkg->rl);
 58         kfree(blkg);
 59 }
 60 
 61 /**
 62  * blkg_alloc - allocate a blkg
 63  * @blkcg: block cgroup the new blkg is associated with
 64  * @q: request_queue the new blkg is associated with
 65  * @gfp_mask: allocation mask to use
 66  *
 67  * Allocate a new blkg assocating @blkcg and @q.
 68  */
 69 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 70                                    gfp_t gfp_mask)
 71 {
 72         struct blkcg_gq *blkg;
 73         int i;
 74 
 75         /* alloc and init base part */
 76         blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
 77         if (!blkg)
 78                 return NULL;
 79 
 80         blkg->q = q;
 81         INIT_LIST_HEAD(&blkg->q_node);
 82         blkg->blkcg = blkcg;
 83         atomic_set(&blkg->refcnt, 1);
 84 
 85         /* root blkg uses @q->root_rl, init rl only for !root blkgs */
 86         if (blkcg != &blkcg_root) {
 87                 if (blk_init_rl(&blkg->rl, q, gfp_mask))
 88                         goto err_free;
 89                 blkg->rl.blkg = blkg;
 90         }
 91 
 92         for (i = 0; i < BLKCG_MAX_POLS; i++) {
 93                 struct blkcg_policy *pol = blkcg_policy[i];
 94                 struct blkg_policy_data *pd;
 95 
 96                 if (!blkcg_policy_enabled(q, pol))
 97                         continue;
 98 
 99                 /* alloc per-policy data and attach it to blkg */
100                 pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
101                 if (!pd)
102                         goto err_free;
103 
104                 blkg->pd[i] = pd;
105                 pd->blkg = blkg;
106                 pd->plid = i;
107         }
108 
109         return blkg;
110 
111 err_free:
112         blkg_free(blkg);
113         return NULL;
114 }
115 
116 /**
117  * __blkg_lookup - internal version of blkg_lookup()
118  * @blkcg: blkcg of interest
119  * @q: request_queue of interest
120  * @update_hint: whether to update lookup hint with the result or not
121  *
122  * This is internal version and shouldn't be used by policy
123  * implementations.  Looks up blkgs for the @blkcg - @q pair regardless of
124  * @q's bypass state.  If @update_hint is %true, the caller should be
125  * holding @q->queue_lock and lookup hint is updated on success.
126  */
127 struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
128                                bool update_hint)
129 {
130         struct blkcg_gq *blkg;
131 
132         blkg = rcu_dereference(blkcg->blkg_hint);
133         if (blkg && blkg->q == q)
134                 return blkg;
135 
136         /*
137          * Hint didn't match.  Look up from the radix tree.  Note that the
138          * hint can only be updated under queue_lock as otherwise @blkg
139          * could have already been removed from blkg_tree.  The caller is
140          * responsible for grabbing queue_lock if @update_hint.
141          */
142         blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
143         if (blkg && blkg->q == q) {
144                 if (update_hint) {
145                         lockdep_assert_held(q->queue_lock);
146                         rcu_assign_pointer(blkcg->blkg_hint, blkg);
147                 }
148                 return blkg;
149         }
150 
151         return NULL;
152 }
153 
154 /**
155  * blkg_lookup - lookup blkg for the specified blkcg - q pair
156  * @blkcg: blkcg of interest
157  * @q: request_queue of interest
158  *
159  * Lookup blkg for the @blkcg - @q pair.  This function should be called
160  * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
161  * - see blk_queue_bypass_start() for details.
162  */
163 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
164 {
165         WARN_ON_ONCE(!rcu_read_lock_held());
166 
167         if (unlikely(blk_queue_bypass(q)))
168                 return NULL;
169         return __blkg_lookup(blkcg, q, false);
170 }
171 EXPORT_SYMBOL_GPL(blkg_lookup);
172 
173 /*
174  * If @new_blkg is %NULL, this function tries to allocate a new one as
175  * necessary using %GFP_ATOMIC.  @new_blkg is always consumed on return.
176  */
177 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
178                                     struct request_queue *q,
179                                     struct blkcg_gq *new_blkg)
180 {
181         struct blkcg_gq *blkg;
182         int i, ret;
183 
184         WARN_ON_ONCE(!rcu_read_lock_held());
185         lockdep_assert_held(q->queue_lock);
186 
187         /* blkg holds a reference to blkcg */
188         if (!css_tryget_online(&blkcg->css)) {
189                 ret = -EINVAL;
190                 goto err_free_blkg;
191         }
192 
193         /* allocate */
194         if (!new_blkg) {
195                 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
196                 if (unlikely(!new_blkg)) {
197                         ret = -ENOMEM;
198                         goto err_put_css;
199                 }
200         }
201         blkg = new_blkg;
202 
203         /* link parent */
204         if (blkcg_parent(blkcg)) {
205                 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
206                 if (WARN_ON_ONCE(!blkg->parent)) {
207                         ret = -EINVAL;
208                         goto err_put_css;
209                 }
210                 blkg_get(blkg->parent);
211         }
212 
213         /* invoke per-policy init */
214         for (i = 0; i < BLKCG_MAX_POLS; i++) {
215                 struct blkcg_policy *pol = blkcg_policy[i];
216 
217                 if (blkg->pd[i] && pol->pd_init_fn)
218                         pol->pd_init_fn(blkg);
219         }
220 
221         /* insert */
222         spin_lock(&blkcg->lock);
223         ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
224         if (likely(!ret)) {
225                 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
226                 list_add(&blkg->q_node, &q->blkg_list);
227 
228                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
229                         struct blkcg_policy *pol = blkcg_policy[i];
230 
231                         if (blkg->pd[i] && pol->pd_online_fn)
232                                 pol->pd_online_fn(blkg);
233                 }
234         }
235         blkg->online = true;
236         spin_unlock(&blkcg->lock);
237 
238         if (!ret) {
239                 if (blkcg == &blkcg_root) {
240                         q->root_blkg = blkg;
241                         q->root_rl.blkg = blkg;
242                 }
243                 return blkg;
244         }
245 
246         /* @blkg failed fully initialized, use the usual release path */
247         blkg_put(blkg);
248         return ERR_PTR(ret);
249 
250 err_put_css:
251         css_put(&blkcg->css);
252 err_free_blkg:
253         blkg_free(new_blkg);
254         return ERR_PTR(ret);
255 }
256 
257 /**
258  * blkg_lookup_create - lookup blkg, try to create one if not there
259  * @blkcg: blkcg of interest
260  * @q: request_queue of interest
261  *
262  * Lookup blkg for the @blkcg - @q pair.  If it doesn't exist, try to
263  * create one.  blkg creation is performed recursively from blkcg_root such
264  * that all non-root blkg's have access to the parent blkg.  This function
265  * should be called under RCU read lock and @q->queue_lock.
266  *
267  * Returns pointer to the looked up or created blkg on success, ERR_PTR()
268  * value on error.  If @q is dead, returns ERR_PTR(-EINVAL).  If @q is not
269  * dead and bypassing, returns ERR_PTR(-EBUSY).
270  */
271 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
272                                     struct request_queue *q)
273 {
274         struct blkcg_gq *blkg;
275 
276         WARN_ON_ONCE(!rcu_read_lock_held());
277         lockdep_assert_held(q->queue_lock);
278 
279         /*
280          * This could be the first entry point of blkcg implementation and
281          * we shouldn't allow anything to go through for a bypassing queue.
282          */
283         if (unlikely(blk_queue_bypass(q)))
284                 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
285 
286         blkg = __blkg_lookup(blkcg, q, true);
287         if (blkg)
288                 return blkg;
289 
290         /*
291          * Create blkgs walking down from blkcg_root to @blkcg, so that all
292          * non-root blkgs have access to their parents.
293          */
294         while (true) {
295                 struct blkcg *pos = blkcg;
296                 struct blkcg *parent = blkcg_parent(blkcg);
297 
298                 while (parent && !__blkg_lookup(parent, q, false)) {
299                         pos = parent;
300                         parent = blkcg_parent(parent);
301                 }
302 
303                 blkg = blkg_create(pos, q, NULL);
304                 if (pos == blkcg || IS_ERR(blkg))
305                         return blkg;
306         }
307 }
308 EXPORT_SYMBOL_GPL(blkg_lookup_create);
309 
310 static void blkg_destroy(struct blkcg_gq *blkg)
311 {
312         struct blkcg *blkcg = blkg->blkcg;
313         int i;
314 
315         lockdep_assert_held(blkg->q->queue_lock);
316         lockdep_assert_held(&blkcg->lock);
317 
318         /* Something wrong if we are trying to remove same group twice */
319         WARN_ON_ONCE(list_empty(&blkg->q_node));
320         WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
321 
322         for (i = 0; i < BLKCG_MAX_POLS; i++) {
323                 struct blkcg_policy *pol = blkcg_policy[i];
324 
325                 if (blkg->pd[i] && pol->pd_offline_fn)
326                         pol->pd_offline_fn(blkg);
327         }
328         blkg->online = false;
329 
330         radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
331         list_del_init(&blkg->q_node);
332         hlist_del_init_rcu(&blkg->blkcg_node);
333 
334         /*
335          * Both setting lookup hint to and clearing it from @blkg are done
336          * under queue_lock.  If it's not pointing to @blkg now, it never
337          * will.  Hint assignment itself can race safely.
338          */
339         if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
340                 rcu_assign_pointer(blkcg->blkg_hint, NULL);
341 
342         /*
343          * If root blkg is destroyed.  Just clear the pointer since root_rl
344          * does not take reference on root blkg.
345          */
346         if (blkcg == &blkcg_root) {
347                 blkg->q->root_blkg = NULL;
348                 blkg->q->root_rl.blkg = NULL;
349         }
350 
351         /*
352          * Put the reference taken at the time of creation so that when all
353          * queues are gone, group can be destroyed.
354          */
355         blkg_put(blkg);
356 }
357 
358 /**
359  * blkg_destroy_all - destroy all blkgs associated with a request_queue
360  * @q: request_queue of interest
361  *
362  * Destroy all blkgs associated with @q.
363  */
364 static void blkg_destroy_all(struct request_queue *q)
365 {
366         struct blkcg_gq *blkg, *n;
367 
368         lockdep_assert_held(q->queue_lock);
369 
370         list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
371                 struct blkcg *blkcg = blkg->blkcg;
372 
373                 spin_lock(&blkcg->lock);
374                 blkg_destroy(blkg);
375                 spin_unlock(&blkcg->lock);
376         }
377 }
378 
379 /*
380  * A group is RCU protected, but having an rcu lock does not mean that one
381  * can access all the fields of blkg and assume these are valid.  For
382  * example, don't try to follow throtl_data and request queue links.
383  *
384  * Having a reference to blkg under an rcu allows accesses to only values
385  * local to groups like group stats and group rate limits.
386  */
387 void __blkg_release_rcu(struct rcu_head *rcu_head)
388 {
389         struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
390         int i;
391 
392         /* tell policies that this one is being freed */
393         for (i = 0; i < BLKCG_MAX_POLS; i++) {
394                 struct blkcg_policy *pol = blkcg_policy[i];
395 
396                 if (blkg->pd[i] && pol->pd_exit_fn)
397                         pol->pd_exit_fn(blkg);
398         }
399 
400         /* release the blkcg and parent blkg refs this blkg has been holding */
401         css_put(&blkg->blkcg->css);
402         if (blkg->parent)
403                 blkg_put(blkg->parent);
404 
405         blkg_free(blkg);
406 }
407 EXPORT_SYMBOL_GPL(__blkg_release_rcu);
408 
409 /*
410  * The next function used by blk_queue_for_each_rl().  It's a bit tricky
411  * because the root blkg uses @q->root_rl instead of its own rl.
412  */
413 struct request_list *__blk_queue_next_rl(struct request_list *rl,
414                                          struct request_queue *q)
415 {
416         struct list_head *ent;
417         struct blkcg_gq *blkg;
418 
419         /*
420          * Determine the current blkg list_head.  The first entry is
421          * root_rl which is off @q->blkg_list and mapped to the head.
422          */
423         if (rl == &q->root_rl) {
424                 ent = &q->blkg_list;
425                 /* There are no more block groups, hence no request lists */
426                 if (list_empty(ent))
427                         return NULL;
428         } else {
429                 blkg = container_of(rl, struct blkcg_gq, rl);
430                 ent = &blkg->q_node;
431         }
432 
433         /* walk to the next list_head, skip root blkcg */
434         ent = ent->next;
435         if (ent == &q->root_blkg->q_node)
436                 ent = ent->next;
437         if (ent == &q->blkg_list)
438                 return NULL;
439 
440         blkg = container_of(ent, struct blkcg_gq, q_node);
441         return &blkg->rl;
442 }
443 
444 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
445                              struct cftype *cftype, u64 val)
446 {
447         struct blkcg *blkcg = css_to_blkcg(css);
448         struct blkcg_gq *blkg;
449         int i;
450 
451         /*
452          * XXX: We invoke cgroup_add/rm_cftypes() under blkcg_pol_mutex
453          * which ends up putting cgroup's internal cgroup_tree_mutex under
454          * it; however, cgroup_tree_mutex is nested above cgroup file
455          * active protection and grabbing blkcg_pol_mutex from a cgroup
456          * file operation creates a possible circular dependency.  cgroup
457          * internal locking is planned to go through further simplification
458          * and this issue should go away soon.  For now, let's trylock
459          * blkcg_pol_mutex and restart the write on failure.
460          *
461          * http://lkml.kernel.org/g/5363C04B.4010400@oracle.com
462          */
463         if (!mutex_trylock(&blkcg_pol_mutex))
464                 return restart_syscall();
465         spin_lock_irq(&blkcg->lock);
466 
467         /*
468          * Note that stat reset is racy - it doesn't synchronize against
469          * stat updates.  This is a debug feature which shouldn't exist
470          * anyway.  If you get hit by a race, retry.
471          */
472         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
473                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
474                         struct blkcg_policy *pol = blkcg_policy[i];
475 
476                         if (blkcg_policy_enabled(blkg->q, pol) &&
477                             pol->pd_reset_stats_fn)
478                                 pol->pd_reset_stats_fn(blkg);
479                 }
480         }
481 
482         spin_unlock_irq(&blkcg->lock);
483         mutex_unlock(&blkcg_pol_mutex);
484         return 0;
485 }
486 
487 static const char *blkg_dev_name(struct blkcg_gq *blkg)
488 {
489         /* some drivers (floppy) instantiate a queue w/o disk registered */
490         if (blkg->q->backing_dev_info.dev)
491                 return dev_name(blkg->q->backing_dev_info.dev);
492         return NULL;
493 }
494 
495 /**
496  * blkcg_print_blkgs - helper for printing per-blkg data
497  * @sf: seq_file to print to
498  * @blkcg: blkcg of interest
499  * @prfill: fill function to print out a blkg
500  * @pol: policy in question
501  * @data: data to be passed to @prfill
502  * @show_total: to print out sum of prfill return values or not
503  *
504  * This function invokes @prfill on each blkg of @blkcg if pd for the
505  * policy specified by @pol exists.  @prfill is invoked with @sf, the
506  * policy data and @data and the matching queue lock held.  If @show_total
507  * is %true, the sum of the return values from @prfill is printed with
508  * "Total" label at the end.
509  *
510  * This is to be used to construct print functions for
511  * cftype->read_seq_string method.
512  */
513 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
514                        u64 (*prfill)(struct seq_file *,
515                                      struct blkg_policy_data *, int),
516                        const struct blkcg_policy *pol, int data,
517                        bool show_total)
518 {
519         struct blkcg_gq *blkg;
520         u64 total = 0;
521 
522         rcu_read_lock();
523         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
524                 spin_lock_irq(blkg->q->queue_lock);
525                 if (blkcg_policy_enabled(blkg->q, pol))
526                         total += prfill(sf, blkg->pd[pol->plid], data);
527                 spin_unlock_irq(blkg->q->queue_lock);
528         }
529         rcu_read_unlock();
530 
531         if (show_total)
532                 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
533 }
534 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
535 
536 /**
537  * __blkg_prfill_u64 - prfill helper for a single u64 value
538  * @sf: seq_file to print to
539  * @pd: policy private data of interest
540  * @v: value to print
541  *
542  * Print @v to @sf for the device assocaited with @pd.
543  */
544 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
545 {
546         const char *dname = blkg_dev_name(pd->blkg);
547 
548         if (!dname)
549                 return 0;
550 
551         seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
552         return v;
553 }
554 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
555 
556 /**
557  * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
558  * @sf: seq_file to print to
559  * @pd: policy private data of interest
560  * @rwstat: rwstat to print
561  *
562  * Print @rwstat to @sf for the device assocaited with @pd.
563  */
564 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
565                          const struct blkg_rwstat *rwstat)
566 {
567         static const char *rwstr[] = {
568                 [BLKG_RWSTAT_READ]      = "Read",
569                 [BLKG_RWSTAT_WRITE]     = "Write",
570                 [BLKG_RWSTAT_SYNC]      = "Sync",
571                 [BLKG_RWSTAT_ASYNC]     = "Async",
572         };
573         const char *dname = blkg_dev_name(pd->blkg);
574         u64 v;
575         int i;
576 
577         if (!dname)
578                 return 0;
579 
580         for (i = 0; i < BLKG_RWSTAT_NR; i++)
581                 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
582                            (unsigned long long)rwstat->cnt[i]);
583 
584         v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
585         seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
586         return v;
587 }
588 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
589 
590 /**
591  * blkg_prfill_stat - prfill callback for blkg_stat
592  * @sf: seq_file to print to
593  * @pd: policy private data of interest
594  * @off: offset to the blkg_stat in @pd
595  *
596  * prfill callback for printing a blkg_stat.
597  */
598 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
599 {
600         return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
601 }
602 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
603 
604 /**
605  * blkg_prfill_rwstat - prfill callback for blkg_rwstat
606  * @sf: seq_file to print to
607  * @pd: policy private data of interest
608  * @off: offset to the blkg_rwstat in @pd
609  *
610  * prfill callback for printing a blkg_rwstat.
611  */
612 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
613                        int off)
614 {
615         struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
616 
617         return __blkg_prfill_rwstat(sf, pd, &rwstat);
618 }
619 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
620 
621 /**
622  * blkg_stat_recursive_sum - collect hierarchical blkg_stat
623  * @pd: policy private data of interest
624  * @off: offset to the blkg_stat in @pd
625  *
626  * Collect the blkg_stat specified by @off from @pd and all its online
627  * descendants and return the sum.  The caller must be holding the queue
628  * lock for online tests.
629  */
630 u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off)
631 {
632         struct blkcg_policy *pol = blkcg_policy[pd->plid];
633         struct blkcg_gq *pos_blkg;
634         struct cgroup_subsys_state *pos_css;
635         u64 sum = 0;
636 
637         lockdep_assert_held(pd->blkg->q->queue_lock);
638 
639         rcu_read_lock();
640         blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) {
641                 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
642                 struct blkg_stat *stat = (void *)pos_pd + off;
643 
644                 if (pos_blkg->online)
645                         sum += blkg_stat_read(stat);
646         }
647         rcu_read_unlock();
648 
649         return sum;
650 }
651 EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
652 
653 /**
654  * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
655  * @pd: policy private data of interest
656  * @off: offset to the blkg_stat in @pd
657  *
658  * Collect the blkg_rwstat specified by @off from @pd and all its online
659  * descendants and return the sum.  The caller must be holding the queue
660  * lock for online tests.
661  */
662 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
663                                              int off)
664 {
665         struct blkcg_policy *pol = blkcg_policy[pd->plid];
666         struct blkcg_gq *pos_blkg;
667         struct cgroup_subsys_state *pos_css;
668         struct blkg_rwstat sum = { };
669         int i;
670 
671         lockdep_assert_held(pd->blkg->q->queue_lock);
672 
673         rcu_read_lock();
674         blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) {
675                 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
676                 struct blkg_rwstat *rwstat = (void *)pos_pd + off;
677                 struct blkg_rwstat tmp;
678 
679                 if (!pos_blkg->online)
680                         continue;
681 
682                 tmp = blkg_rwstat_read(rwstat);
683 
684                 for (i = 0; i < BLKG_RWSTAT_NR; i++)
685                         sum.cnt[i] += tmp.cnt[i];
686         }
687         rcu_read_unlock();
688 
689         return sum;
690 }
691 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
692 
693 /**
694  * blkg_conf_prep - parse and prepare for per-blkg config update
695  * @blkcg: target block cgroup
696  * @pol: target policy
697  * @input: input string
698  * @ctx: blkg_conf_ctx to be filled
699  *
700  * Parse per-blkg config update from @input and initialize @ctx with the
701  * result.  @ctx->blkg points to the blkg to be updated and @ctx->v the new
702  * value.  This function returns with RCU read lock and queue lock held and
703  * must be paired with blkg_conf_finish().
704  */
705 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
706                    const char *input, struct blkg_conf_ctx *ctx)
707         __acquires(rcu) __acquires(disk->queue->queue_lock)
708 {
709         struct gendisk *disk;
710         struct blkcg_gq *blkg;
711         unsigned int major, minor;
712         unsigned long long v;
713         int part, ret;
714 
715         if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
716                 return -EINVAL;
717 
718         disk = get_gendisk(MKDEV(major, minor), &part);
719         if (!disk || part)
720                 return -EINVAL;
721 
722         rcu_read_lock();
723         spin_lock_irq(disk->queue->queue_lock);
724 
725         if (blkcg_policy_enabled(disk->queue, pol))
726                 blkg = blkg_lookup_create(blkcg, disk->queue);
727         else
728                 blkg = ERR_PTR(-EINVAL);
729 
730         if (IS_ERR(blkg)) {
731                 ret = PTR_ERR(blkg);
732                 rcu_read_unlock();
733                 spin_unlock_irq(disk->queue->queue_lock);
734                 put_disk(disk);
735                 /*
736                  * If queue was bypassing, we should retry.  Do so after a
737                  * short msleep().  It isn't strictly necessary but queue
738                  * can be bypassing for some time and it's always nice to
739                  * avoid busy looping.
740                  */
741                 if (ret == -EBUSY) {
742                         msleep(10);
743                         ret = restart_syscall();
744                 }
745                 return ret;
746         }
747 
748         ctx->disk = disk;
749         ctx->blkg = blkg;
750         ctx->v = v;
751         return 0;
752 }
753 EXPORT_SYMBOL_GPL(blkg_conf_prep);
754 
755 /**
756  * blkg_conf_finish - finish up per-blkg config update
757  * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
758  *
759  * Finish up after per-blkg config update.  This function must be paired
760  * with blkg_conf_prep().
761  */
762 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
763         __releases(ctx->disk->queue->queue_lock) __releases(rcu)
764 {
765         spin_unlock_irq(ctx->disk->queue->queue_lock);
766         rcu_read_unlock();
767         put_disk(ctx->disk);
768 }
769 EXPORT_SYMBOL_GPL(blkg_conf_finish);
770 
771 struct cftype blkcg_files[] = {
772         {
773                 .name = "reset_stats",
774                 .write_u64 = blkcg_reset_stats,
775         },
776         { }     /* terminate */
777 };
778 
779 /**
780  * blkcg_css_offline - cgroup css_offline callback
781  * @css: css of interest
782  *
783  * This function is called when @css is about to go away and responsible
784  * for shooting down all blkgs associated with @css.  blkgs should be
785  * removed while holding both q and blkcg locks.  As blkcg lock is nested
786  * inside q lock, this function performs reverse double lock dancing.
787  *
788  * This is the blkcg counterpart of ioc_release_fn().
789  */
790 static void blkcg_css_offline(struct cgroup_subsys_state *css)
791 {
792         struct blkcg *blkcg = css_to_blkcg(css);
793 
794         spin_lock_irq(&blkcg->lock);
795 
796         while (!hlist_empty(&blkcg->blkg_list)) {
797                 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
798                                                 struct blkcg_gq, blkcg_node);
799                 struct request_queue *q = blkg->q;
800 
801                 if (spin_trylock(q->queue_lock)) {
802                         blkg_destroy(blkg);
803                         spin_unlock(q->queue_lock);
804                 } else {
805                         spin_unlock_irq(&blkcg->lock);
806                         cpu_relax();
807                         spin_lock_irq(&blkcg->lock);
808                 }
809         }
810 
811         spin_unlock_irq(&blkcg->lock);
812 }
813 
814 static void blkcg_css_free(struct cgroup_subsys_state *css)
815 {
816         struct blkcg *blkcg = css_to_blkcg(css);
817 
818         if (blkcg != &blkcg_root)
819                 kfree(blkcg);
820 }
821 
822 static struct cgroup_subsys_state *
823 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
824 {
825         static atomic64_t id_seq = ATOMIC64_INIT(0);
826         struct blkcg *blkcg;
827 
828         if (!parent_css) {
829                 blkcg = &blkcg_root;
830                 goto done;
831         }
832 
833         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
834         if (!blkcg)
835                 return ERR_PTR(-ENOMEM);
836 
837         blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
838         blkcg->cfq_leaf_weight = CFQ_WEIGHT_DEFAULT;
839         blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
840 done:
841         spin_lock_init(&blkcg->lock);
842         INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
843         INIT_HLIST_HEAD(&blkcg->blkg_list);
844 
845         return &blkcg->css;
846 }
847 
848 /**
849  * blkcg_init_queue - initialize blkcg part of request queue
850  * @q: request_queue to initialize
851  *
852  * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
853  * part of new request_queue @q.
854  *
855  * RETURNS:
856  * 0 on success, -errno on failure.
857  */
858 int blkcg_init_queue(struct request_queue *q)
859 {
860         might_sleep();
861 
862         return blk_throtl_init(q);
863 }
864 
865 /**
866  * blkcg_drain_queue - drain blkcg part of request_queue
867  * @q: request_queue to drain
868  *
869  * Called from blk_drain_queue().  Responsible for draining blkcg part.
870  */
871 void blkcg_drain_queue(struct request_queue *q)
872 {
873         lockdep_assert_held(q->queue_lock);
874 
875         /*
876          * @q could be exiting and already have destroyed all blkgs as
877          * indicated by NULL root_blkg.  If so, don't confuse policies.
878          */
879         if (!q->root_blkg)
880                 return;
881 
882         blk_throtl_drain(q);
883 }
884 
885 /**
886  * blkcg_exit_queue - exit and release blkcg part of request_queue
887  * @q: request_queue being released
888  *
889  * Called from blk_release_queue().  Responsible for exiting blkcg part.
890  */
891 void blkcg_exit_queue(struct request_queue *q)
892 {
893         spin_lock_irq(q->queue_lock);
894         blkg_destroy_all(q);
895         spin_unlock_irq(q->queue_lock);
896 
897         blk_throtl_exit(q);
898 }
899 
900 /*
901  * We cannot support shared io contexts, as we have no mean to support
902  * two tasks with the same ioc in two different groups without major rework
903  * of the main cic data structures.  For now we allow a task to change
904  * its cgroup only if it's the only owner of its ioc.
905  */
906 static int blkcg_can_attach(struct cgroup_subsys_state *css,
907                             struct cgroup_taskset *tset)
908 {
909         struct task_struct *task;
910         struct io_context *ioc;
911         int ret = 0;
912 
913         /* task_lock() is needed to avoid races with exit_io_context() */
914         cgroup_taskset_for_each(task, tset) {
915                 task_lock(task);
916                 ioc = task->io_context;
917                 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
918                         ret = -EINVAL;
919                 task_unlock(task);
920                 if (ret)
921                         break;
922         }
923         return ret;
924 }
925 
926 struct cgroup_subsys blkio_cgrp_subsys = {
927         .css_alloc = blkcg_css_alloc,
928         .css_offline = blkcg_css_offline,
929         .css_free = blkcg_css_free,
930         .can_attach = blkcg_can_attach,
931         .legacy_cftypes = blkcg_files,
932 #ifdef CONFIG_MEMCG
933         /*
934          * This ensures that, if available, memcg is automatically enabled
935          * together on the default hierarchy so that the owner cgroup can
936          * be retrieved from writeback pages.
937          */
938         .depends_on = 1 << memory_cgrp_id,
939 #endif
940 };
941 EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
942 
943 /**
944  * blkcg_activate_policy - activate a blkcg policy on a request_queue
945  * @q: request_queue of interest
946  * @pol: blkcg policy to activate
947  *
948  * Activate @pol on @q.  Requires %GFP_KERNEL context.  @q goes through
949  * bypass mode to populate its blkgs with policy_data for @pol.
950  *
951  * Activation happens with @q bypassed, so nobody would be accessing blkgs
952  * from IO path.  Update of each blkg is protected by both queue and blkcg
953  * locks so that holding either lock and testing blkcg_policy_enabled() is
954  * always enough for dereferencing policy data.
955  *
956  * The caller is responsible for synchronizing [de]activations and policy
957  * [un]registerations.  Returns 0 on success, -errno on failure.
958  */
959 int blkcg_activate_policy(struct request_queue *q,
960                           const struct blkcg_policy *pol)
961 {
962         LIST_HEAD(pds);
963         struct blkcg_gq *blkg, *new_blkg;
964         struct blkg_policy_data *pd, *n;
965         int cnt = 0, ret;
966         bool preloaded;
967 
968         if (blkcg_policy_enabled(q, pol))
969                 return 0;
970 
971         /* preallocations for root blkg */
972         new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
973         if (!new_blkg)
974                 return -ENOMEM;
975 
976         blk_queue_bypass_start(q);
977 
978         preloaded = !radix_tree_preload(GFP_KERNEL);
979 
980         /*
981          * Make sure the root blkg exists and count the existing blkgs.  As
982          * @q is bypassing at this point, blkg_lookup_create() can't be
983          * used.  Open code it.
984          */
985         spin_lock_irq(q->queue_lock);
986 
987         rcu_read_lock();
988         blkg = __blkg_lookup(&blkcg_root, q, false);
989         if (blkg)
990                 blkg_free(new_blkg);
991         else
992                 blkg = blkg_create(&blkcg_root, q, new_blkg);
993         rcu_read_unlock();
994 
995         if (preloaded)
996                 radix_tree_preload_end();
997 
998         if (IS_ERR(blkg)) {
999                 ret = PTR_ERR(blkg);
1000                 goto out_unlock;
1001         }
1002 
1003         list_for_each_entry(blkg, &q->blkg_list, q_node)
1004                 cnt++;
1005 
1006         spin_unlock_irq(q->queue_lock);
1007 
1008         /* allocate policy_data for all existing blkgs */
1009         while (cnt--) {
1010                 pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
1011                 if (!pd) {
1012                         ret = -ENOMEM;
1013                         goto out_free;
1014                 }
1015                 list_add_tail(&pd->alloc_node, &pds);
1016         }
1017 
1018         /*
1019          * Install the allocated pds.  With @q bypassing, no new blkg
1020          * should have been created while the queue lock was dropped.
1021          */
1022         spin_lock_irq(q->queue_lock);
1023 
1024         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1025                 if (WARN_ON(list_empty(&pds))) {
1026                         /* umm... this shouldn't happen, just abort */
1027                         ret = -ENOMEM;
1028                         goto out_unlock;
1029                 }
1030                 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
1031                 list_del_init(&pd->alloc_node);
1032 
1033                 /* grab blkcg lock too while installing @pd on @blkg */
1034                 spin_lock(&blkg->blkcg->lock);
1035 
1036                 blkg->pd[pol->plid] = pd;
1037                 pd->blkg = blkg;
1038                 pd->plid = pol->plid;
1039                 pol->pd_init_fn(blkg);
1040 
1041                 spin_unlock(&blkg->blkcg->lock);
1042         }
1043 
1044         __set_bit(pol->plid, q->blkcg_pols);
1045         ret = 0;
1046 out_unlock:
1047         spin_unlock_irq(q->queue_lock);
1048 out_free:
1049         blk_queue_bypass_end(q);
1050         list_for_each_entry_safe(pd, n, &pds, alloc_node)
1051                 kfree(pd);
1052         return ret;
1053 }
1054 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1055 
1056 /**
1057  * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1058  * @q: request_queue of interest
1059  * @pol: blkcg policy to deactivate
1060  *
1061  * Deactivate @pol on @q.  Follows the same synchronization rules as
1062  * blkcg_activate_policy().
1063  */
1064 void blkcg_deactivate_policy(struct request_queue *q,
1065                              const struct blkcg_policy *pol)
1066 {
1067         struct blkcg_gq *blkg;
1068 
1069         if (!blkcg_policy_enabled(q, pol))
1070                 return;
1071 
1072         blk_queue_bypass_start(q);
1073         spin_lock_irq(q->queue_lock);
1074 
1075         __clear_bit(pol->plid, q->blkcg_pols);
1076 
1077         /* if no policy is left, no need for blkgs - shoot them down */
1078         if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
1079                 blkg_destroy_all(q);
1080 
1081         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1082                 /* grab blkcg lock too while removing @pd from @blkg */
1083                 spin_lock(&blkg->blkcg->lock);
1084 
1085                 if (pol->pd_offline_fn)
1086                         pol->pd_offline_fn(blkg);
1087                 if (pol->pd_exit_fn)
1088                         pol->pd_exit_fn(blkg);
1089 
1090                 kfree(blkg->pd[pol->plid]);
1091                 blkg->pd[pol->plid] = NULL;
1092 
1093                 spin_unlock(&blkg->blkcg->lock);
1094         }
1095 
1096         spin_unlock_irq(q->queue_lock);
1097         blk_queue_bypass_end(q);
1098 }
1099 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1100 
1101 /**
1102  * blkcg_policy_register - register a blkcg policy
1103  * @pol: blkcg policy to register
1104  *
1105  * Register @pol with blkcg core.  Might sleep and @pol may be modified on
1106  * successful registration.  Returns 0 on success and -errno on failure.
1107  */
1108 int blkcg_policy_register(struct blkcg_policy *pol)
1109 {
1110         int i, ret;
1111 
1112         if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
1113                 return -EINVAL;
1114 
1115         mutex_lock(&blkcg_pol_mutex);
1116 
1117         /* find an empty slot */
1118         ret = -ENOSPC;
1119         for (i = 0; i < BLKCG_MAX_POLS; i++)
1120                 if (!blkcg_policy[i])
1121                         break;
1122         if (i >= BLKCG_MAX_POLS)
1123                 goto out_unlock;
1124 
1125         /* register and update blkgs */
1126         pol->plid = i;
1127         blkcg_policy[i] = pol;
1128 
1129         /* everything is in place, add intf files for the new policy */
1130         if (pol->cftypes)
1131                 WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys,
1132                                                   pol->cftypes));
1133         ret = 0;
1134 out_unlock:
1135         mutex_unlock(&blkcg_pol_mutex);
1136         return ret;
1137 }
1138 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1139 
1140 /**
1141  * blkcg_policy_unregister - unregister a blkcg policy
1142  * @pol: blkcg policy to unregister
1143  *
1144  * Undo blkcg_policy_register(@pol).  Might sleep.
1145  */
1146 void blkcg_policy_unregister(struct blkcg_policy *pol)
1147 {
1148         mutex_lock(&blkcg_pol_mutex);
1149 
1150         if (WARN_ON(blkcg_policy[pol->plid] != pol))
1151                 goto out_unlock;
1152 
1153         /* kill the intf files first */
1154         if (pol->cftypes)
1155                 cgroup_rm_cftypes(pol->cftypes);
1156 
1157         /* unregister and update blkgs */
1158         blkcg_policy[pol->plid] = NULL;
1159 out_unlock:
1160         mutex_unlock(&blkcg_pol_mutex);
1161 }
1162 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
1163 

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