Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/block/blk-cgroup.c

  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  * For policy-specific per-blkcg data:
 14  * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
 15  *                    Arianna Avanzini <avanzini.arianna@gmail.com>
 16  */
 17 #include <linux/ioprio.h>
 18 #include <linux/kdev_t.h>
 19 #include <linux/module.h>
 20 #include <linux/err.h>
 21 #include <linux/blkdev.h>
 22 #include <linux/backing-dev.h>
 23 #include <linux/slab.h>
 24 #include <linux/genhd.h>
 25 #include <linux/delay.h>
 26 #include <linux/atomic.h>
 27 #include <linux/ctype.h>
 28 #include <linux/blk-cgroup.h>
 29 #include "blk.h"
 30 
 31 #define MAX_KEY_LEN 100
 32 
 33 /*
 34  * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
 35  * blkcg_pol_register_mutex nests outside of it and synchronizes entire
 36  * policy [un]register operations including cgroup file additions /
 37  * removals.  Putting cgroup file registration outside blkcg_pol_mutex
 38  * allows grabbing it from cgroup callbacks.
 39  */
 40 static DEFINE_MUTEX(blkcg_pol_register_mutex);
 41 static DEFINE_MUTEX(blkcg_pol_mutex);
 42 
 43 struct blkcg blkcg_root;
 44 EXPORT_SYMBOL_GPL(blkcg_root);
 45 
 46 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
 47 
 48 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
 49 
 50 static LIST_HEAD(all_blkcgs);           /* protected by blkcg_pol_mutex */
 51 
 52 static bool blkcg_policy_enabled(struct request_queue *q,
 53                                  const struct blkcg_policy *pol)
 54 {
 55         return pol && test_bit(pol->plid, q->blkcg_pols);
 56 }
 57 
 58 /**
 59  * blkg_free - free a blkg
 60  * @blkg: blkg to free
 61  *
 62  * Free @blkg which may be partially allocated.
 63  */
 64 static void blkg_free(struct blkcg_gq *blkg)
 65 {
 66         int i;
 67 
 68         if (!blkg)
 69                 return;
 70 
 71         for (i = 0; i < BLKCG_MAX_POLS; i++)
 72                 if (blkg->pd[i])
 73                         blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
 74 
 75         if (blkg->blkcg != &blkcg_root)
 76                 blk_exit_rl(&blkg->rl);
 77 
 78         blkg_rwstat_exit(&blkg->stat_ios);
 79         blkg_rwstat_exit(&blkg->stat_bytes);
 80         kfree(blkg);
 81 }
 82 
 83 /**
 84  * blkg_alloc - allocate a blkg
 85  * @blkcg: block cgroup the new blkg is associated with
 86  * @q: request_queue the new blkg is associated with
 87  * @gfp_mask: allocation mask to use
 88  *
 89  * Allocate a new blkg assocating @blkcg and @q.
 90  */
 91 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 92                                    gfp_t gfp_mask)
 93 {
 94         struct blkcg_gq *blkg;
 95         int i;
 96 
 97         /* alloc and init base part */
 98         blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
 99         if (!blkg)
100                 return NULL;
101 
102         if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) ||
103             blkg_rwstat_init(&blkg->stat_ios, gfp_mask))
104                 goto err_free;
105 
106         blkg->q = q;
107         INIT_LIST_HEAD(&blkg->q_node);
108         blkg->blkcg = blkcg;
109         atomic_set(&blkg->refcnt, 1);
110 
111         /* root blkg uses @q->root_rl, init rl only for !root blkgs */
112         if (blkcg != &blkcg_root) {
113                 if (blk_init_rl(&blkg->rl, q, gfp_mask))
114                         goto err_free;
115                 blkg->rl.blkg = blkg;
116         }
117 
118         for (i = 0; i < BLKCG_MAX_POLS; i++) {
119                 struct blkcg_policy *pol = blkcg_policy[i];
120                 struct blkg_policy_data *pd;
121 
122                 if (!blkcg_policy_enabled(q, pol))
123                         continue;
124 
125                 /* alloc per-policy data and attach it to blkg */
126                 pd = pol->pd_alloc_fn(gfp_mask, q->node);
127                 if (!pd)
128                         goto err_free;
129 
130                 blkg->pd[i] = pd;
131                 pd->blkg = blkg;
132                 pd->plid = i;
133         }
134 
135         return blkg;
136 
137 err_free:
138         blkg_free(blkg);
139         return NULL;
140 }
141 
142 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
143                                       struct request_queue *q, bool update_hint)
144 {
145         struct blkcg_gq *blkg;
146 
147         /*
148          * Hint didn't match.  Look up from the radix tree.  Note that the
149          * hint can only be updated under queue_lock as otherwise @blkg
150          * could have already been removed from blkg_tree.  The caller is
151          * responsible for grabbing queue_lock if @update_hint.
152          */
153         blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
154         if (blkg && blkg->q == q) {
155                 if (update_hint) {
156                         lockdep_assert_held(q->queue_lock);
157                         rcu_assign_pointer(blkcg->blkg_hint, blkg);
158                 }
159                 return blkg;
160         }
161 
162         return NULL;
163 }
164 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
165 
166 /*
167  * If @new_blkg is %NULL, this function tries to allocate a new one as
168  * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.
169  */
170 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
171                                     struct request_queue *q,
172                                     struct blkcg_gq *new_blkg)
173 {
174         struct blkcg_gq *blkg;
175         struct bdi_writeback_congested *wb_congested;
176         int i, ret;
177 
178         WARN_ON_ONCE(!rcu_read_lock_held());
179         lockdep_assert_held(q->queue_lock);
180 
181         /* blkg holds a reference to blkcg */
182         if (!css_tryget_online(&blkcg->css)) {
183                 ret = -ENODEV;
184                 goto err_free_blkg;
185         }
186 
187         wb_congested = wb_congested_get_create(&q->backing_dev_info,
188                                                blkcg->css.id,
189                                                GFP_NOWAIT | __GFP_NOWARN);
190         if (!wb_congested) {
191                 ret = -ENOMEM;
192                 goto err_put_css;
193         }
194 
195         /* allocate */
196         if (!new_blkg) {
197                 new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN);
198                 if (unlikely(!new_blkg)) {
199                         ret = -ENOMEM;
200                         goto err_put_congested;
201                 }
202         }
203         blkg = new_blkg;
204         blkg->wb_congested = wb_congested;
205 
206         /* link parent */
207         if (blkcg_parent(blkcg)) {
208                 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
209                 if (WARN_ON_ONCE(!blkg->parent)) {
210                         ret = -ENODEV;
211                         goto err_put_congested;
212                 }
213                 blkg_get(blkg->parent);
214         }
215 
216         /* invoke per-policy init */
217         for (i = 0; i < BLKCG_MAX_POLS; i++) {
218                 struct blkcg_policy *pol = blkcg_policy[i];
219 
220                 if (blkg->pd[i] && pol->pd_init_fn)
221                         pol->pd_init_fn(blkg->pd[i]);
222         }
223 
224         /* insert */
225         spin_lock(&blkcg->lock);
226         ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
227         if (likely(!ret)) {
228                 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
229                 list_add(&blkg->q_node, &q->blkg_list);
230 
231                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
232                         struct blkcg_policy *pol = blkcg_policy[i];
233 
234                         if (blkg->pd[i] && pol->pd_online_fn)
235                                 pol->pd_online_fn(blkg->pd[i]);
236                 }
237         }
238         blkg->online = true;
239         spin_unlock(&blkcg->lock);
240 
241         if (!ret)
242                 return blkg;
243 
244         /* @blkg failed fully initialized, use the usual release path */
245         blkg_put(blkg);
246         return ERR_PTR(ret);
247 
248 err_put_congested:
249         wb_congested_put(wb_congested);
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) ? -ENODEV : -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 
309 static void blkg_destroy(struct blkcg_gq *blkg)
310 {
311         struct blkcg *blkcg = blkg->blkcg;
312         struct blkcg_gq *parent = blkg->parent;
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->pd[i]);
327         }
328 
329         if (parent) {
330                 blkg_rwstat_add_aux(&parent->stat_bytes, &blkg->stat_bytes);
331                 blkg_rwstat_add_aux(&parent->stat_ios, &blkg->stat_ios);
332         }
333 
334         blkg->online = false;
335 
336         radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
337         list_del_init(&blkg->q_node);
338         hlist_del_init_rcu(&blkg->blkcg_node);
339 
340         /*
341          * Both setting lookup hint to and clearing it from @blkg are done
342          * under queue_lock.  If it's not pointing to @blkg now, it never
343          * will.  Hint assignment itself can race safely.
344          */
345         if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
346                 rcu_assign_pointer(blkcg->blkg_hint, NULL);
347 
348         /*
349          * Put the reference taken at the time of creation so that when all
350          * queues are gone, group can be destroyed.
351          */
352         blkg_put(blkg);
353 }
354 
355 /**
356  * blkg_destroy_all - destroy all blkgs associated with a request_queue
357  * @q: request_queue of interest
358  *
359  * Destroy all blkgs associated with @q.
360  */
361 static void blkg_destroy_all(struct request_queue *q)
362 {
363         struct blkcg_gq *blkg, *n;
364 
365         lockdep_assert_held(q->queue_lock);
366 
367         list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
368                 struct blkcg *blkcg = blkg->blkcg;
369 
370                 spin_lock(&blkcg->lock);
371                 blkg_destroy(blkg);
372                 spin_unlock(&blkcg->lock);
373         }
374 
375         q->root_blkg = NULL;
376         q->root_rl.blkg = NULL;
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 
391         /* release the blkcg and parent blkg refs this blkg has been holding */
392         css_put(&blkg->blkcg->css);
393         if (blkg->parent)
394                 blkg_put(blkg->parent);
395 
396         wb_congested_put(blkg->wb_congested);
397 
398         blkg_free(blkg);
399 }
400 EXPORT_SYMBOL_GPL(__blkg_release_rcu);
401 
402 /*
403  * The next function used by blk_queue_for_each_rl().  It's a bit tricky
404  * because the root blkg uses @q->root_rl instead of its own rl.
405  */
406 struct request_list *__blk_queue_next_rl(struct request_list *rl,
407                                          struct request_queue *q)
408 {
409         struct list_head *ent;
410         struct blkcg_gq *blkg;
411 
412         /*
413          * Determine the current blkg list_head.  The first entry is
414          * root_rl which is off @q->blkg_list and mapped to the head.
415          */
416         if (rl == &q->root_rl) {
417                 ent = &q->blkg_list;
418                 /* There are no more block groups, hence no request lists */
419                 if (list_empty(ent))
420                         return NULL;
421         } else {
422                 blkg = container_of(rl, struct blkcg_gq, rl);
423                 ent = &blkg->q_node;
424         }
425 
426         /* walk to the next list_head, skip root blkcg */
427         ent = ent->next;
428         if (ent == &q->root_blkg->q_node)
429                 ent = ent->next;
430         if (ent == &q->blkg_list)
431                 return NULL;
432 
433         blkg = container_of(ent, struct blkcg_gq, q_node);
434         return &blkg->rl;
435 }
436 
437 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
438                              struct cftype *cftype, u64 val)
439 {
440         struct blkcg *blkcg = css_to_blkcg(css);
441         struct blkcg_gq *blkg;
442         int i;
443 
444         mutex_lock(&blkcg_pol_mutex);
445         spin_lock_irq(&blkcg->lock);
446 
447         /*
448          * Note that stat reset is racy - it doesn't synchronize against
449          * stat updates.  This is a debug feature which shouldn't exist
450          * anyway.  If you get hit by a race, retry.
451          */
452         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
453                 blkg_rwstat_reset(&blkg->stat_bytes);
454                 blkg_rwstat_reset(&blkg->stat_ios);
455 
456                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
457                         struct blkcg_policy *pol = blkcg_policy[i];
458 
459                         if (blkg->pd[i] && pol->pd_reset_stats_fn)
460                                 pol->pd_reset_stats_fn(blkg->pd[i]);
461                 }
462         }
463 
464         spin_unlock_irq(&blkcg->lock);
465         mutex_unlock(&blkcg_pol_mutex);
466         return 0;
467 }
468 
469 const char *blkg_dev_name(struct blkcg_gq *blkg)
470 {
471         /* some drivers (floppy) instantiate a queue w/o disk registered */
472         if (blkg->q->backing_dev_info.dev)
473                 return dev_name(blkg->q->backing_dev_info.dev);
474         return NULL;
475 }
476 EXPORT_SYMBOL_GPL(blkg_dev_name);
477 
478 /**
479  * blkcg_print_blkgs - helper for printing per-blkg data
480  * @sf: seq_file to print to
481  * @blkcg: blkcg of interest
482  * @prfill: fill function to print out a blkg
483  * @pol: policy in question
484  * @data: data to be passed to @prfill
485  * @show_total: to print out sum of prfill return values or not
486  *
487  * This function invokes @prfill on each blkg of @blkcg if pd for the
488  * policy specified by @pol exists.  @prfill is invoked with @sf, the
489  * policy data and @data and the matching queue lock held.  If @show_total
490  * is %true, the sum of the return values from @prfill is printed with
491  * "Total" label at the end.
492  *
493  * This is to be used to construct print functions for
494  * cftype->read_seq_string method.
495  */
496 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
497                        u64 (*prfill)(struct seq_file *,
498                                      struct blkg_policy_data *, int),
499                        const struct blkcg_policy *pol, int data,
500                        bool show_total)
501 {
502         struct blkcg_gq *blkg;
503         u64 total = 0;
504 
505         rcu_read_lock();
506         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
507                 spin_lock_irq(blkg->q->queue_lock);
508                 if (blkcg_policy_enabled(blkg->q, pol))
509                         total += prfill(sf, blkg->pd[pol->plid], data);
510                 spin_unlock_irq(blkg->q->queue_lock);
511         }
512         rcu_read_unlock();
513 
514         if (show_total)
515                 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
516 }
517 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
518 
519 /**
520  * __blkg_prfill_u64 - prfill helper for a single u64 value
521  * @sf: seq_file to print to
522  * @pd: policy private data of interest
523  * @v: value to print
524  *
525  * Print @v to @sf for the device assocaited with @pd.
526  */
527 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
528 {
529         const char *dname = blkg_dev_name(pd->blkg);
530 
531         if (!dname)
532                 return 0;
533 
534         seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
535         return v;
536 }
537 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
538 
539 /**
540  * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
541  * @sf: seq_file to print to
542  * @pd: policy private data of interest
543  * @rwstat: rwstat to print
544  *
545  * Print @rwstat to @sf for the device assocaited with @pd.
546  */
547 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
548                          const struct blkg_rwstat *rwstat)
549 {
550         static const char *rwstr[] = {
551                 [BLKG_RWSTAT_READ]      = "Read",
552                 [BLKG_RWSTAT_WRITE]     = "Write",
553                 [BLKG_RWSTAT_SYNC]      = "Sync",
554                 [BLKG_RWSTAT_ASYNC]     = "Async",
555         };
556         const char *dname = blkg_dev_name(pd->blkg);
557         u64 v;
558         int i;
559 
560         if (!dname)
561                 return 0;
562 
563         for (i = 0; i < BLKG_RWSTAT_NR; i++)
564                 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
565                            (unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
566 
567         v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
568                 atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]);
569         seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
570         return v;
571 }
572 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
573 
574 /**
575  * blkg_prfill_stat - prfill callback for blkg_stat
576  * @sf: seq_file to print to
577  * @pd: policy private data of interest
578  * @off: offset to the blkg_stat in @pd
579  *
580  * prfill callback for printing a blkg_stat.
581  */
582 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
583 {
584         return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
585 }
586 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
587 
588 /**
589  * blkg_prfill_rwstat - prfill callback for blkg_rwstat
590  * @sf: seq_file to print to
591  * @pd: policy private data of interest
592  * @off: offset to the blkg_rwstat in @pd
593  *
594  * prfill callback for printing a blkg_rwstat.
595  */
596 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
597                        int off)
598 {
599         struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
600 
601         return __blkg_prfill_rwstat(sf, pd, &rwstat);
602 }
603 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
604 
605 static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
606                                     struct blkg_policy_data *pd, int off)
607 {
608         struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
609 
610         return __blkg_prfill_rwstat(sf, pd, &rwstat);
611 }
612 
613 /**
614  * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes
615  * @sf: seq_file to print to
616  * @v: unused
617  *
618  * To be used as cftype->seq_show to print blkg->stat_bytes.
619  * cftype->private must be set to the blkcg_policy.
620  */
621 int blkg_print_stat_bytes(struct seq_file *sf, void *v)
622 {
623         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
624                           blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
625                           offsetof(struct blkcg_gq, stat_bytes), true);
626         return 0;
627 }
628 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes);
629 
630 /**
631  * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios
632  * @sf: seq_file to print to
633  * @v: unused
634  *
635  * To be used as cftype->seq_show to print blkg->stat_ios.  cftype->private
636  * must be set to the blkcg_policy.
637  */
638 int blkg_print_stat_ios(struct seq_file *sf, void *v)
639 {
640         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
641                           blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
642                           offsetof(struct blkcg_gq, stat_ios), true);
643         return 0;
644 }
645 EXPORT_SYMBOL_GPL(blkg_print_stat_ios);
646 
647 static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
648                                               struct blkg_policy_data *pd,
649                                               int off)
650 {
651         struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
652                                                               NULL, off);
653         return __blkg_prfill_rwstat(sf, pd, &rwstat);
654 }
655 
656 /**
657  * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes
658  * @sf: seq_file to print to
659  * @v: unused
660  */
661 int blkg_print_stat_bytes_recursive(struct seq_file *sf, void *v)
662 {
663         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
664                           blkg_prfill_rwstat_field_recursive,
665                           (void *)seq_cft(sf)->private,
666                           offsetof(struct blkcg_gq, stat_bytes), true);
667         return 0;
668 }
669 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive);
670 
671 /**
672  * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios
673  * @sf: seq_file to print to
674  * @v: unused
675  */
676 int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v)
677 {
678         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
679                           blkg_prfill_rwstat_field_recursive,
680                           (void *)seq_cft(sf)->private,
681                           offsetof(struct blkcg_gq, stat_ios), true);
682         return 0;
683 }
684 EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive);
685 
686 /**
687  * blkg_stat_recursive_sum - collect hierarchical blkg_stat
688  * @blkg: blkg of interest
689  * @pol: blkcg_policy which contains the blkg_stat
690  * @off: offset to the blkg_stat in blkg_policy_data or @blkg
691  *
692  * Collect the blkg_stat specified by @blkg, @pol and @off and all its
693  * online descendants and their aux counts.  The caller must be holding the
694  * queue lock for online tests.
695  *
696  * If @pol is NULL, blkg_stat is at @off bytes into @blkg; otherwise, it is
697  * at @off bytes into @blkg's blkg_policy_data of the policy.
698  */
699 u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
700                             struct blkcg_policy *pol, int off)
701 {
702         struct blkcg_gq *pos_blkg;
703         struct cgroup_subsys_state *pos_css;
704         u64 sum = 0;
705 
706         lockdep_assert_held(blkg->q->queue_lock);
707 
708         rcu_read_lock();
709         blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
710                 struct blkg_stat *stat;
711 
712                 if (!pos_blkg->online)
713                         continue;
714 
715                 if (pol)
716                         stat = (void *)blkg_to_pd(pos_blkg, pol) + off;
717                 else
718                         stat = (void *)blkg + off;
719 
720                 sum += blkg_stat_read(stat) + atomic64_read(&stat->aux_cnt);
721         }
722         rcu_read_unlock();
723 
724         return sum;
725 }
726 EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
727 
728 /**
729  * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
730  * @blkg: blkg of interest
731  * @pol: blkcg_policy which contains the blkg_rwstat
732  * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
733  *
734  * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
735  * online descendants and their aux counts.  The caller must be holding the
736  * queue lock for online tests.
737  *
738  * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
739  * is at @off bytes into @blkg's blkg_policy_data of the policy.
740  */
741 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
742                                              struct blkcg_policy *pol, int off)
743 {
744         struct blkcg_gq *pos_blkg;
745         struct cgroup_subsys_state *pos_css;
746         struct blkg_rwstat sum = { };
747         int i;
748 
749         lockdep_assert_held(blkg->q->queue_lock);
750 
751         rcu_read_lock();
752         blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
753                 struct blkg_rwstat *rwstat;
754 
755                 if (!pos_blkg->online)
756                         continue;
757 
758                 if (pol)
759                         rwstat = (void *)blkg_to_pd(pos_blkg, pol) + off;
760                 else
761                         rwstat = (void *)pos_blkg + off;
762 
763                 for (i = 0; i < BLKG_RWSTAT_NR; i++)
764                         atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) +
765                                 percpu_counter_sum_positive(&rwstat->cpu_cnt[i]),
766                                 &sum.aux_cnt[i]);
767         }
768         rcu_read_unlock();
769 
770         return sum;
771 }
772 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
773 
774 /**
775  * blkg_conf_prep - parse and prepare for per-blkg config update
776  * @blkcg: target block cgroup
777  * @pol: target policy
778  * @input: input string
779  * @ctx: blkg_conf_ctx to be filled
780  *
781  * Parse per-blkg config update from @input and initialize @ctx with the
782  * result.  @ctx->blkg points to the blkg to be updated and @ctx->body the
783  * part of @input following MAJ:MIN.  This function returns with RCU read
784  * lock and queue lock held and must be paired with blkg_conf_finish().
785  */
786 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
787                    char *input, struct blkg_conf_ctx *ctx)
788         __acquires(rcu) __acquires(disk->queue->queue_lock)
789 {
790         struct gendisk *disk;
791         struct blkcg_gq *blkg;
792         struct module *owner;
793         unsigned int major, minor;
794         int key_len, part, ret;
795         char *body;
796 
797         if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
798                 return -EINVAL;
799 
800         body = input + key_len;
801         if (!isspace(*body))
802                 return -EINVAL;
803         body = skip_spaces(body);
804 
805         disk = get_gendisk(MKDEV(major, minor), &part);
806         if (!disk)
807                 return -ENODEV;
808         if (part) {
809                 owner = disk->fops->owner;
810                 put_disk(disk);
811                 module_put(owner);
812                 return -ENODEV;
813         }
814 
815         rcu_read_lock();
816         spin_lock_irq(disk->queue->queue_lock);
817 
818         if (blkcg_policy_enabled(disk->queue, pol))
819                 blkg = blkg_lookup_create(blkcg, disk->queue);
820         else
821                 blkg = ERR_PTR(-EOPNOTSUPP);
822 
823         if (IS_ERR(blkg)) {
824                 ret = PTR_ERR(blkg);
825                 rcu_read_unlock();
826                 spin_unlock_irq(disk->queue->queue_lock);
827                 owner = disk->fops->owner;
828                 put_disk(disk);
829                 module_put(owner);
830                 /*
831                  * If queue was bypassing, we should retry.  Do so after a
832                  * short msleep().  It isn't strictly necessary but queue
833                  * can be bypassing for some time and it's always nice to
834                  * avoid busy looping.
835                  */
836                 if (ret == -EBUSY) {
837                         msleep(10);
838                         ret = restart_syscall();
839                 }
840                 return ret;
841         }
842 
843         ctx->disk = disk;
844         ctx->blkg = blkg;
845         ctx->body = body;
846         return 0;
847 }
848 EXPORT_SYMBOL_GPL(blkg_conf_prep);
849 
850 /**
851  * blkg_conf_finish - finish up per-blkg config update
852  * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
853  *
854  * Finish up after per-blkg config update.  This function must be paired
855  * with blkg_conf_prep().
856  */
857 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
858         __releases(ctx->disk->queue->queue_lock) __releases(rcu)
859 {
860         struct module *owner;
861 
862         spin_unlock_irq(ctx->disk->queue->queue_lock);
863         rcu_read_unlock();
864         owner = ctx->disk->fops->owner;
865         put_disk(ctx->disk);
866         module_put(owner);
867 }
868 EXPORT_SYMBOL_GPL(blkg_conf_finish);
869 
870 static int blkcg_print_stat(struct seq_file *sf, void *v)
871 {
872         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
873         struct blkcg_gq *blkg;
874 
875         rcu_read_lock();
876 
877         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
878                 const char *dname;
879                 struct blkg_rwstat rwstat;
880                 u64 rbytes, wbytes, rios, wios;
881 
882                 dname = blkg_dev_name(blkg);
883                 if (!dname)
884                         continue;
885 
886                 spin_lock_irq(blkg->q->queue_lock);
887 
888                 rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
889                                         offsetof(struct blkcg_gq, stat_bytes));
890                 rbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
891                 wbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
892 
893                 rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
894                                         offsetof(struct blkcg_gq, stat_ios));
895                 rios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
896                 wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
897 
898                 spin_unlock_irq(blkg->q->queue_lock);
899 
900                 if (rbytes || wbytes || rios || wios)
901                         seq_printf(sf, "%s rbytes=%llu wbytes=%llu rios=%llu wios=%llu\n",
902                                    dname, rbytes, wbytes, rios, wios);
903         }
904 
905         rcu_read_unlock();
906         return 0;
907 }
908 
909 static struct cftype blkcg_files[] = {
910         {
911                 .name = "stat",
912                 .flags = CFTYPE_NOT_ON_ROOT,
913                 .seq_show = blkcg_print_stat,
914         },
915         { }     /* terminate */
916 };
917 
918 static struct cftype blkcg_legacy_files[] = {
919         {
920                 .name = "reset_stats",
921                 .write_u64 = blkcg_reset_stats,
922         },
923         { }     /* terminate */
924 };
925 
926 /**
927  * blkcg_css_offline - cgroup css_offline callback
928  * @css: css of interest
929  *
930  * This function is called when @css is about to go away and responsible
931  * for shooting down all blkgs associated with @css.  blkgs should be
932  * removed while holding both q and blkcg locks.  As blkcg lock is nested
933  * inside q lock, this function performs reverse double lock dancing.
934  *
935  * This is the blkcg counterpart of ioc_release_fn().
936  */
937 static void blkcg_css_offline(struct cgroup_subsys_state *css)
938 {
939         struct blkcg *blkcg = css_to_blkcg(css);
940 
941         spin_lock_irq(&blkcg->lock);
942 
943         while (!hlist_empty(&blkcg->blkg_list)) {
944                 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
945                                                 struct blkcg_gq, blkcg_node);
946                 struct request_queue *q = blkg->q;
947 
948                 if (spin_trylock(q->queue_lock)) {
949                         blkg_destroy(blkg);
950                         spin_unlock(q->queue_lock);
951                 } else {
952                         spin_unlock_irq(&blkcg->lock);
953                         cpu_relax();
954                         spin_lock_irq(&blkcg->lock);
955                 }
956         }
957 
958         spin_unlock_irq(&blkcg->lock);
959 
960         wb_blkcg_offline(blkcg);
961 }
962 
963 static void blkcg_css_free(struct cgroup_subsys_state *css)
964 {
965         struct blkcg *blkcg = css_to_blkcg(css);
966         int i;
967 
968         mutex_lock(&blkcg_pol_mutex);
969 
970         list_del(&blkcg->all_blkcgs_node);
971 
972         for (i = 0; i < BLKCG_MAX_POLS; i++)
973                 if (blkcg->cpd[i])
974                         blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
975 
976         mutex_unlock(&blkcg_pol_mutex);
977 
978         kfree(blkcg);
979 }
980 
981 static struct cgroup_subsys_state *
982 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
983 {
984         struct blkcg *blkcg;
985         struct cgroup_subsys_state *ret;
986         int i;
987 
988         mutex_lock(&blkcg_pol_mutex);
989 
990         if (!parent_css) {
991                 blkcg = &blkcg_root;
992         } else {
993                 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
994                 if (!blkcg) {
995                         ret = ERR_PTR(-ENOMEM);
996                         goto free_blkcg;
997                 }
998         }
999 
1000         for (i = 0; i < BLKCG_MAX_POLS ; i++) {
1001                 struct blkcg_policy *pol = blkcg_policy[i];
1002                 struct blkcg_policy_data *cpd;
1003 
1004                 /*
1005                  * If the policy hasn't been attached yet, wait for it
1006                  * to be attached before doing anything else. Otherwise,
1007                  * check if the policy requires any specific per-cgroup
1008                  * data: if it does, allocate and initialize it.
1009                  */
1010                 if (!pol || !pol->cpd_alloc_fn)
1011                         continue;
1012 
1013                 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1014                 if (!cpd) {
1015                         ret = ERR_PTR(-ENOMEM);
1016                         goto free_pd_blkcg;
1017                 }
1018                 blkcg->cpd[i] = cpd;
1019                 cpd->blkcg = blkcg;
1020                 cpd->plid = i;
1021                 if (pol->cpd_init_fn)
1022                         pol->cpd_init_fn(cpd);
1023         }
1024 
1025         spin_lock_init(&blkcg->lock);
1026         INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
1027         INIT_HLIST_HEAD(&blkcg->blkg_list);
1028 #ifdef CONFIG_CGROUP_WRITEBACK
1029         INIT_LIST_HEAD(&blkcg->cgwb_list);
1030 #endif
1031         list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
1032 
1033         mutex_unlock(&blkcg_pol_mutex);
1034         return &blkcg->css;
1035 
1036 free_pd_blkcg:
1037         for (i--; i >= 0; i--)
1038                 if (blkcg->cpd[i])
1039                         blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1040 free_blkcg:
1041         kfree(blkcg);
1042         mutex_unlock(&blkcg_pol_mutex);
1043         return ret;
1044 }
1045 
1046 /**
1047  * blkcg_init_queue - initialize blkcg part of request queue
1048  * @q: request_queue to initialize
1049  *
1050  * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
1051  * part of new request_queue @q.
1052  *
1053  * RETURNS:
1054  * 0 on success, -errno on failure.
1055  */
1056 int blkcg_init_queue(struct request_queue *q)
1057 {
1058         struct blkcg_gq *new_blkg, *blkg;
1059         bool preloaded;
1060         int ret;
1061 
1062         new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
1063         if (!new_blkg)
1064                 return -ENOMEM;
1065 
1066         preloaded = !radix_tree_preload(GFP_KERNEL);
1067 
1068         /*
1069          * Make sure the root blkg exists and count the existing blkgs.  As
1070          * @q is bypassing at this point, blkg_lookup_create() can't be
1071          * used.  Open code insertion.
1072          */
1073         rcu_read_lock();
1074         spin_lock_irq(q->queue_lock);
1075         blkg = blkg_create(&blkcg_root, q, new_blkg);
1076         spin_unlock_irq(q->queue_lock);
1077         rcu_read_unlock();
1078 
1079         if (preloaded)
1080                 radix_tree_preload_end();
1081 
1082         if (IS_ERR(blkg)) {
1083                 blkg_free(new_blkg);
1084                 return PTR_ERR(blkg);
1085         }
1086 
1087         q->root_blkg = blkg;
1088         q->root_rl.blkg = blkg;
1089 
1090         ret = blk_throtl_init(q);
1091         if (ret) {
1092                 spin_lock_irq(q->queue_lock);
1093                 blkg_destroy_all(q);
1094                 spin_unlock_irq(q->queue_lock);
1095         }
1096         return ret;
1097 }
1098 
1099 /**
1100  * blkcg_drain_queue - drain blkcg part of request_queue
1101  * @q: request_queue to drain
1102  *
1103  * Called from blk_drain_queue().  Responsible for draining blkcg part.
1104  */
1105 void blkcg_drain_queue(struct request_queue *q)
1106 {
1107         lockdep_assert_held(q->queue_lock);
1108 
1109         /*
1110          * @q could be exiting and already have destroyed all blkgs as
1111          * indicated by NULL root_blkg.  If so, don't confuse policies.
1112          */
1113         if (!q->root_blkg)
1114                 return;
1115 
1116         blk_throtl_drain(q);
1117 }
1118 
1119 /**
1120  * blkcg_exit_queue - exit and release blkcg part of request_queue
1121  * @q: request_queue being released
1122  *
1123  * Called from blk_release_queue().  Responsible for exiting blkcg part.
1124  */
1125 void blkcg_exit_queue(struct request_queue *q)
1126 {
1127         spin_lock_irq(q->queue_lock);
1128         blkg_destroy_all(q);
1129         spin_unlock_irq(q->queue_lock);
1130 
1131         blk_throtl_exit(q);
1132 }
1133 
1134 /*
1135  * We cannot support shared io contexts, as we have no mean to support
1136  * two tasks with the same ioc in two different groups without major rework
1137  * of the main cic data structures.  For now we allow a task to change
1138  * its cgroup only if it's the only owner of its ioc.
1139  */
1140 static int blkcg_can_attach(struct cgroup_taskset *tset)
1141 {
1142         struct task_struct *task;
1143         struct cgroup_subsys_state *dst_css;
1144         struct io_context *ioc;
1145         int ret = 0;
1146 
1147         /* task_lock() is needed to avoid races with exit_io_context() */
1148         cgroup_taskset_for_each(task, dst_css, tset) {
1149                 task_lock(task);
1150                 ioc = task->io_context;
1151                 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
1152                         ret = -EINVAL;
1153                 task_unlock(task);
1154                 if (ret)
1155                         break;
1156         }
1157         return ret;
1158 }
1159 
1160 static void blkcg_bind(struct cgroup_subsys_state *root_css)
1161 {
1162         int i;
1163 
1164         mutex_lock(&blkcg_pol_mutex);
1165 
1166         for (i = 0; i < BLKCG_MAX_POLS; i++) {
1167                 struct blkcg_policy *pol = blkcg_policy[i];
1168                 struct blkcg *blkcg;
1169 
1170                 if (!pol || !pol->cpd_bind_fn)
1171                         continue;
1172 
1173                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
1174                         if (blkcg->cpd[pol->plid])
1175                                 pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
1176         }
1177         mutex_unlock(&blkcg_pol_mutex);
1178 }
1179 
1180 struct cgroup_subsys io_cgrp_subsys = {
1181         .css_alloc = blkcg_css_alloc,
1182         .css_offline = blkcg_css_offline,
1183         .css_free = blkcg_css_free,
1184         .can_attach = blkcg_can_attach,
1185         .bind = blkcg_bind,
1186         .dfl_cftypes = blkcg_files,
1187         .legacy_cftypes = blkcg_legacy_files,
1188         .legacy_name = "blkio",
1189 #ifdef CONFIG_MEMCG
1190         /*
1191          * This ensures that, if available, memcg is automatically enabled
1192          * together on the default hierarchy so that the owner cgroup can
1193          * be retrieved from writeback pages.
1194          */
1195         .depends_on = 1 << memory_cgrp_id,
1196 #endif
1197 };
1198 EXPORT_SYMBOL_GPL(io_cgrp_subsys);
1199 
1200 /**
1201  * blkcg_activate_policy - activate a blkcg policy on a request_queue
1202  * @q: request_queue of interest
1203  * @pol: blkcg policy to activate
1204  *
1205  * Activate @pol on @q.  Requires %GFP_KERNEL context.  @q goes through
1206  * bypass mode to populate its blkgs with policy_data for @pol.
1207  *
1208  * Activation happens with @q bypassed, so nobody would be accessing blkgs
1209  * from IO path.  Update of each blkg is protected by both queue and blkcg
1210  * locks so that holding either lock and testing blkcg_policy_enabled() is
1211  * always enough for dereferencing policy data.
1212  *
1213  * The caller is responsible for synchronizing [de]activations and policy
1214  * [un]registerations.  Returns 0 on success, -errno on failure.
1215  */
1216 int blkcg_activate_policy(struct request_queue *q,
1217                           const struct blkcg_policy *pol)
1218 {
1219         struct blkg_policy_data *pd_prealloc = NULL;
1220         struct blkcg_gq *blkg;
1221         int ret;
1222 
1223         if (blkcg_policy_enabled(q, pol))
1224                 return 0;
1225 
1226         blk_queue_bypass_start(q);
1227 pd_prealloc:
1228         if (!pd_prealloc) {
1229                 pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node);
1230                 if (!pd_prealloc) {
1231                         ret = -ENOMEM;
1232                         goto out_bypass_end;
1233                 }
1234         }
1235 
1236         spin_lock_irq(q->queue_lock);
1237 
1238         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1239                 struct blkg_policy_data *pd;
1240 
1241                 if (blkg->pd[pol->plid])
1242                         continue;
1243 
1244                 pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q->node);
1245                 if (!pd)
1246                         swap(pd, pd_prealloc);
1247                 if (!pd) {
1248                         spin_unlock_irq(q->queue_lock);
1249                         goto pd_prealloc;
1250                 }
1251 
1252                 blkg->pd[pol->plid] = pd;
1253                 pd->blkg = blkg;
1254                 pd->plid = pol->plid;
1255                 if (pol->pd_init_fn)
1256                         pol->pd_init_fn(pd);
1257         }
1258 
1259         __set_bit(pol->plid, q->blkcg_pols);
1260         ret = 0;
1261 
1262         spin_unlock_irq(q->queue_lock);
1263 out_bypass_end:
1264         blk_queue_bypass_end(q);
1265         if (pd_prealloc)
1266                 pol->pd_free_fn(pd_prealloc);
1267         return ret;
1268 }
1269 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1270 
1271 /**
1272  * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1273  * @q: request_queue of interest
1274  * @pol: blkcg policy to deactivate
1275  *
1276  * Deactivate @pol on @q.  Follows the same synchronization rules as
1277  * blkcg_activate_policy().
1278  */
1279 void blkcg_deactivate_policy(struct request_queue *q,
1280                              const struct blkcg_policy *pol)
1281 {
1282         struct blkcg_gq *blkg;
1283 
1284         if (!blkcg_policy_enabled(q, pol))
1285                 return;
1286 
1287         blk_queue_bypass_start(q);
1288         spin_lock_irq(q->queue_lock);
1289 
1290         __clear_bit(pol->plid, q->blkcg_pols);
1291 
1292         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1293                 /* grab blkcg lock too while removing @pd from @blkg */
1294                 spin_lock(&blkg->blkcg->lock);
1295 
1296                 if (blkg->pd[pol->plid]) {
1297                         if (pol->pd_offline_fn)
1298                                 pol->pd_offline_fn(blkg->pd[pol->plid]);
1299                         pol->pd_free_fn(blkg->pd[pol->plid]);
1300                         blkg->pd[pol->plid] = NULL;
1301                 }
1302 
1303                 spin_unlock(&blkg->blkcg->lock);
1304         }
1305 
1306         spin_unlock_irq(q->queue_lock);
1307         blk_queue_bypass_end(q);
1308 }
1309 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1310 
1311 /**
1312  * blkcg_policy_register - register a blkcg policy
1313  * @pol: blkcg policy to register
1314  *
1315  * Register @pol with blkcg core.  Might sleep and @pol may be modified on
1316  * successful registration.  Returns 0 on success and -errno on failure.
1317  */
1318 int blkcg_policy_register(struct blkcg_policy *pol)
1319 {
1320         struct blkcg *blkcg;
1321         int i, ret;
1322 
1323         mutex_lock(&blkcg_pol_register_mutex);
1324         mutex_lock(&blkcg_pol_mutex);
1325 
1326         /* find an empty slot */
1327         ret = -ENOSPC;
1328         for (i = 0; i < BLKCG_MAX_POLS; i++)
1329                 if (!blkcg_policy[i])
1330                         break;
1331         if (i >= BLKCG_MAX_POLS)
1332                 goto err_unlock;
1333 
1334         /* register @pol */
1335         pol->plid = i;
1336         blkcg_policy[pol->plid] = pol;
1337 
1338         /* allocate and install cpd's */
1339         if (pol->cpd_alloc_fn) {
1340                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1341                         struct blkcg_policy_data *cpd;
1342 
1343                         cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1344                         if (!cpd)
1345                                 goto err_free_cpds;
1346 
1347                         blkcg->cpd[pol->plid] = cpd;
1348                         cpd->blkcg = blkcg;
1349                         cpd->plid = pol->plid;
1350                         pol->cpd_init_fn(cpd);
1351                 }
1352         }
1353 
1354         mutex_unlock(&blkcg_pol_mutex);
1355 
1356         /* everything is in place, add intf files for the new policy */
1357         if (pol->dfl_cftypes)
1358                 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
1359                                                pol->dfl_cftypes));
1360         if (pol->legacy_cftypes)
1361                 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
1362                                                   pol->legacy_cftypes));
1363         mutex_unlock(&blkcg_pol_register_mutex);
1364         return 0;
1365 
1366 err_free_cpds:
1367         if (pol->cpd_alloc_fn) {
1368                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1369                         if (blkcg->cpd[pol->plid]) {
1370                                 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1371                                 blkcg->cpd[pol->plid] = NULL;
1372                         }
1373                 }
1374         }
1375         blkcg_policy[pol->plid] = NULL;
1376 err_unlock:
1377         mutex_unlock(&blkcg_pol_mutex);
1378         mutex_unlock(&blkcg_pol_register_mutex);
1379         return ret;
1380 }
1381 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1382 
1383 /**
1384  * blkcg_policy_unregister - unregister a blkcg policy
1385  * @pol: blkcg policy to unregister
1386  *
1387  * Undo blkcg_policy_register(@pol).  Might sleep.
1388  */
1389 void blkcg_policy_unregister(struct blkcg_policy *pol)
1390 {
1391         struct blkcg *blkcg;
1392 
1393         mutex_lock(&blkcg_pol_register_mutex);
1394 
1395         if (WARN_ON(blkcg_policy[pol->plid] != pol))
1396                 goto out_unlock;
1397 
1398         /* kill the intf files first */
1399         if (pol->dfl_cftypes)
1400                 cgroup_rm_cftypes(pol->dfl_cftypes);
1401         if (pol->legacy_cftypes)
1402                 cgroup_rm_cftypes(pol->legacy_cftypes);
1403 
1404         /* remove cpds and unregister */
1405         mutex_lock(&blkcg_pol_mutex);
1406 
1407         if (pol->cpd_alloc_fn) {
1408                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1409                         if (blkcg->cpd[pol->plid]) {
1410                                 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1411                                 blkcg->cpd[pol->plid] = NULL;
1412                         }
1413                 }
1414         }
1415         blkcg_policy[pol->plid] = NULL;
1416 
1417         mutex_unlock(&blkcg_pol_mutex);
1418 out_unlock:
1419         mutex_unlock(&blkcg_pol_register_mutex);
1420 }
1421 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
1422 

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