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1// SPDX-License-Identifier: GPL-2.02/*3 * Functions related to io context handling4 */5#include <linux/kernel.h>6#include <linux/module.h>7#include <linux/init.h>8#include <linux/bio.h>9#include <linux/blkdev.h>10#include <linux/slab.h>11#include <linux/security.h>12#include <linux/sched/task.h>13 14#include "blk.h"15#include "blk-mq-sched.h"16 17/*18 * For io context allocations19 */20static struct kmem_cache *iocontext_cachep;21 22#ifdef CONFIG_BLK_ICQ23/**24 * get_io_context - increment reference count to io_context25 * @ioc: io_context to get26 *27 * Increment reference count to @ioc.28 */29static void get_io_context(struct io_context *ioc)30{31 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);32 atomic_long_inc(&ioc->refcount);33}34 35static void icq_free_icq_rcu(struct rcu_head *head)36{37 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);38 39 kmem_cache_free(icq->__rcu_icq_cache, icq);40}41 42/*43 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc44 * and queue locked for legacy.45 */46static void ioc_exit_icq(struct io_cq *icq)47{48 struct elevator_type *et = icq->q->elevator->type;49 50 if (icq->flags & ICQ_EXITED)51 return;52 53 if (et->ops.exit_icq)54 et->ops.exit_icq(icq);55 56 icq->flags |= ICQ_EXITED;57}58 59static void ioc_exit_icqs(struct io_context *ioc)60{61 struct io_cq *icq;62 63 spin_lock_irq(&ioc->lock);64 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)65 ioc_exit_icq(icq);66 spin_unlock_irq(&ioc->lock);67}68 69/*70 * Release an icq. Called with ioc locked for blk-mq, and with both ioc71 * and queue locked for legacy.72 */73static void ioc_destroy_icq(struct io_cq *icq)74{75 struct io_context *ioc = icq->ioc;76 struct request_queue *q = icq->q;77 struct elevator_type *et = q->elevator->type;78 79 lockdep_assert_held(&ioc->lock);80 lockdep_assert_held(&q->queue_lock);81 82 if (icq->flags & ICQ_DESTROYED)83 return;84 85 radix_tree_delete(&ioc->icq_tree, icq->q->id);86 hlist_del_init(&icq->ioc_node);87 list_del_init(&icq->q_node);88 89 /*90 * Both setting lookup hint to and clearing it from @icq are done91 * under queue_lock. If it's not pointing to @icq now, it never92 * will. Hint assignment itself can race safely.93 */94 if (rcu_access_pointer(ioc->icq_hint) == icq)95 rcu_assign_pointer(ioc->icq_hint, NULL);96 97 ioc_exit_icq(icq);98 99 /*100 * @icq->q might have gone away by the time RCU callback runs101 * making it impossible to determine icq_cache. Record it in @icq.102 */103 icq->__rcu_icq_cache = et->icq_cache;104 icq->flags |= ICQ_DESTROYED;105 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);106}107 108/*109 * Slow path for ioc release in put_io_context(). Performs double-lock110 * dancing to unlink all icq's and then frees ioc.111 */112static void ioc_release_fn(struct work_struct *work)113{114 struct io_context *ioc = container_of(work, struct io_context,115 release_work);116 spin_lock_irq(&ioc->lock);117 118 while (!hlist_empty(&ioc->icq_list)) {119 struct io_cq *icq = hlist_entry(ioc->icq_list.first,120 struct io_cq, ioc_node);121 struct request_queue *q = icq->q;122 123 if (spin_trylock(&q->queue_lock)) {124 ioc_destroy_icq(icq);125 spin_unlock(&q->queue_lock);126 } else {127 /* Make sure q and icq cannot be freed. */128 rcu_read_lock();129 130 /* Re-acquire the locks in the correct order. */131 spin_unlock(&ioc->lock);132 spin_lock(&q->queue_lock);133 spin_lock(&ioc->lock);134 135 ioc_destroy_icq(icq);136 137 spin_unlock(&q->queue_lock);138 rcu_read_unlock();139 }140 }141 142 spin_unlock_irq(&ioc->lock);143 144 kmem_cache_free(iocontext_cachep, ioc);145}146 147/*148 * Releasing icqs requires reverse order double locking and we may already be149 * holding a queue_lock. Do it asynchronously from a workqueue.150 */151static bool ioc_delay_free(struct io_context *ioc)152{153 unsigned long flags;154 155 spin_lock_irqsave(&ioc->lock, flags);156 if (!hlist_empty(&ioc->icq_list)) {157 queue_work(system_power_efficient_wq, &ioc->release_work);158 spin_unlock_irqrestore(&ioc->lock, flags);159 return true;160 }161 spin_unlock_irqrestore(&ioc->lock, flags);162 return false;163}164 165/**166 * ioc_clear_queue - break any ioc association with the specified queue167 * @q: request_queue being cleared168 *169 * Walk @q->icq_list and exit all io_cq's.170 */171void ioc_clear_queue(struct request_queue *q)172{173 spin_lock_irq(&q->queue_lock);174 while (!list_empty(&q->icq_list)) {175 struct io_cq *icq =176 list_first_entry(&q->icq_list, struct io_cq, q_node);177 178 /*179 * Other context won't hold ioc lock to wait for queue_lock, see180 * details in ioc_release_fn().181 */182 spin_lock(&icq->ioc->lock);183 ioc_destroy_icq(icq);184 spin_unlock(&icq->ioc->lock);185 }186 spin_unlock_irq(&q->queue_lock);187}188#else /* CONFIG_BLK_ICQ */189static inline void ioc_exit_icqs(struct io_context *ioc)190{191}192static inline bool ioc_delay_free(struct io_context *ioc)193{194 return false;195}196#endif /* CONFIG_BLK_ICQ */197 198/**199 * put_io_context - put a reference of io_context200 * @ioc: io_context to put201 *202 * Decrement reference count of @ioc and release it if the count reaches203 * zero.204 */205void put_io_context(struct io_context *ioc)206{207 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);208 if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))209 kmem_cache_free(iocontext_cachep, ioc);210}211EXPORT_SYMBOL_GPL(put_io_context);212 213/* Called by the exiting task */214void exit_io_context(struct task_struct *task)215{216 struct io_context *ioc;217 218 task_lock(task);219 ioc = task->io_context;220 task->io_context = NULL;221 task_unlock(task);222 223 if (atomic_dec_and_test(&ioc->active_ref)) {224 ioc_exit_icqs(ioc);225 put_io_context(ioc);226 }227}228 229static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)230{231 struct io_context *ioc;232 233 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,234 node);235 if (unlikely(!ioc))236 return NULL;237 238 atomic_long_set(&ioc->refcount, 1);239 atomic_set(&ioc->active_ref, 1);240#ifdef CONFIG_BLK_ICQ241 spin_lock_init(&ioc->lock);242 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);243 INIT_HLIST_HEAD(&ioc->icq_list);244 INIT_WORK(&ioc->release_work, ioc_release_fn);245#endif246 ioc->ioprio = IOPRIO_DEFAULT;247 248 return ioc;249}250 251int set_task_ioprio(struct task_struct *task, int ioprio)252{253 int err;254 const struct cred *cred = current_cred(), *tcred;255 256 rcu_read_lock();257 tcred = __task_cred(task);258 if (!uid_eq(tcred->uid, cred->euid) &&259 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {260 rcu_read_unlock();261 return -EPERM;262 }263 rcu_read_unlock();264 265 err = security_task_setioprio(task, ioprio);266 if (err)267 return err;268 269 task_lock(task);270 if (unlikely(!task->io_context)) {271 struct io_context *ioc;272 273 task_unlock(task);274 275 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);276 if (!ioc)277 return -ENOMEM;278 279 task_lock(task);280 if (task->flags & PF_EXITING) {281 kmem_cache_free(iocontext_cachep, ioc);282 goto out;283 }284 if (task->io_context)285 kmem_cache_free(iocontext_cachep, ioc);286 else287 task->io_context = ioc;288 }289 task->io_context->ioprio = ioprio;290out:291 task_unlock(task);292 return 0;293}294EXPORT_SYMBOL_GPL(set_task_ioprio);295 296int __copy_io(unsigned long clone_flags, struct task_struct *tsk)297{298 struct io_context *ioc = current->io_context;299 300 /*301 * Share io context with parent, if CLONE_IO is set302 */303 if (clone_flags & CLONE_IO) {304 atomic_inc(&ioc->active_ref);305 tsk->io_context = ioc;306 } else if (ioprio_valid(ioc->ioprio)) {307 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);308 if (!tsk->io_context)309 return -ENOMEM;310 tsk->io_context->ioprio = ioc->ioprio;311 }312 313 return 0;314}315 316#ifdef CONFIG_BLK_ICQ317/**318 * ioc_lookup_icq - lookup io_cq from ioc319 * @q: the associated request_queue320 *321 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called322 * with @q->queue_lock held.323 */324struct io_cq *ioc_lookup_icq(struct request_queue *q)325{326 struct io_context *ioc = current->io_context;327 struct io_cq *icq;328 329 lockdep_assert_held(&q->queue_lock);330 331 /*332 * icq's are indexed from @ioc using radix tree and hint pointer,333 * both of which are protected with RCU. All removals are done334 * holding both q and ioc locks, and we're holding q lock - if we335 * find a icq which points to us, it's guaranteed to be valid.336 */337 rcu_read_lock();338 icq = rcu_dereference(ioc->icq_hint);339 if (icq && icq->q == q)340 goto out;341 342 icq = radix_tree_lookup(&ioc->icq_tree, q->id);343 if (icq && icq->q == q)344 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */345 else346 icq = NULL;347out:348 rcu_read_unlock();349 return icq;350}351EXPORT_SYMBOL(ioc_lookup_icq);352 353/**354 * ioc_create_icq - create and link io_cq355 * @q: request_queue of interest356 *357 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they358 * will be created using @gfp_mask.359 *360 * The caller is responsible for ensuring @ioc won't go away and @q is361 * alive and will stay alive until this function returns.362 */363static struct io_cq *ioc_create_icq(struct request_queue *q)364{365 struct io_context *ioc = current->io_context;366 struct elevator_type *et = q->elevator->type;367 struct io_cq *icq;368 369 /* allocate stuff */370 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,371 q->node);372 if (!icq)373 return NULL;374 375 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {376 kmem_cache_free(et->icq_cache, icq);377 return NULL;378 }379 380 icq->ioc = ioc;381 icq->q = q;382 INIT_LIST_HEAD(&icq->q_node);383 INIT_HLIST_NODE(&icq->ioc_node);384 385 /* lock both q and ioc and try to link @icq */386 spin_lock_irq(&q->queue_lock);387 spin_lock(&ioc->lock);388 389 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {390 hlist_add_head(&icq->ioc_node, &ioc->icq_list);391 list_add(&icq->q_node, &q->icq_list);392 if (et->ops.init_icq)393 et->ops.init_icq(icq);394 } else {395 kmem_cache_free(et->icq_cache, icq);396 icq = ioc_lookup_icq(q);397 if (!icq)398 printk(KERN_ERR "cfq: icq link failed!\n");399 }400 401 spin_unlock(&ioc->lock);402 spin_unlock_irq(&q->queue_lock);403 radix_tree_preload_end();404 return icq;405}406 407struct io_cq *ioc_find_get_icq(struct request_queue *q)408{409 struct io_context *ioc = current->io_context;410 struct io_cq *icq = NULL;411 412 if (unlikely(!ioc)) {413 ioc = alloc_io_context(GFP_ATOMIC, q->node);414 if (!ioc)415 return NULL;416 417 task_lock(current);418 if (current->io_context) {419 kmem_cache_free(iocontext_cachep, ioc);420 ioc = current->io_context;421 } else {422 current->io_context = ioc;423 }424 425 get_io_context(ioc);426 task_unlock(current);427 } else {428 get_io_context(ioc);429 430 spin_lock_irq(&q->queue_lock);431 icq = ioc_lookup_icq(q);432 spin_unlock_irq(&q->queue_lock);433 }434 435 if (!icq) {436 icq = ioc_create_icq(q);437 if (!icq) {438 put_io_context(ioc);439 return NULL;440 }441 }442 return icq;443}444EXPORT_SYMBOL_GPL(ioc_find_get_icq);445#endif /* CONFIG_BLK_ICQ */446 447static int __init blk_ioc_init(void)448{449 iocontext_cachep = kmem_cache_create("blkdev_ioc",450 sizeof(struct io_context), 0, SLAB_PANIC, NULL);451 return 0;452}453subsys_initcall(blk_ioc_init);454