Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * Functions related to io context handling
       4             :  */
       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 allocations
      19             :  */
      20             : static struct kmem_cache *iocontext_cachep;
      21             : 
      22             : #ifdef CONFIG_BLK_ICQ
      23             : /**
      24             :  * get_io_context - increment reference count to io_context
      25             :  * @ioc: io_context to get
      26             :  *
      27             :  * Increment reference count to @ioc.
      28             :  */
      29             : static 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             : 
      35             : static 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 ioc
      44             :  * and queue locked for legacy.
      45             :  */
      46             : static 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             : 
      59             : static 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 ioc
      71             :  * and queue locked for legacy.
      72             :  */
      73             : static 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 done
      91             :          * under queue_lock.  If it's not pointing to @icq now, it never
      92             :          * 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 runs
     101             :          * 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-lock
     110             :  * dancing to unlink all icq's and then frees ioc.
     111             :  */
     112             : static 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 be
     149             :  * holding a queue_lock.  Do it asynchronously from a workqueue.
     150             :  */
     151             : static 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 queue
     167             :  * @q: request_queue being cleared
     168             :  *
     169             :  * Walk @q->icq_list and exit all io_cq's.
     170             :  */
     171             : void 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, see
     180             :                  * 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 */
     189             : static inline void ioc_exit_icqs(struct io_context *ioc)
     190             : {
     191             : }
     192             : static 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_context
     200             :  * @ioc: io_context to put
     201             :  *
     202             :  * Decrement reference count of @ioc and release it if the count reaches
     203             :  * zero.
     204             :  */
     205           0 : void put_io_context(struct io_context *ioc)
     206             : {
     207           0 :         BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
     208           0 :         if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
     209           0 :                 kmem_cache_free(iocontext_cachep, ioc);
     210           0 : }
     211             : EXPORT_SYMBOL_GPL(put_io_context);
     212             : 
     213             : /* Called by the exiting task */
     214           0 : void exit_io_context(struct task_struct *task)
     215             : {
     216             :         struct io_context *ioc;
     217             : 
     218           0 :         task_lock(task);
     219           0 :         ioc = task->io_context;
     220           0 :         task->io_context = NULL;
     221           0 :         task_unlock(task);
     222             : 
     223           0 :         if (atomic_dec_and_test(&ioc->active_ref)) {
     224           0 :                 ioc_exit_icqs(ioc);
     225           0 :                 put_io_context(ioc);
     226             :         }
     227           0 : }
     228             : 
     229             : static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
     230             : {
     231             :         struct io_context *ioc;
     232             : 
     233           0 :         ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
     234             :                                     node);
     235           0 :         if (unlikely(!ioc))
     236             :                 return NULL;
     237             : 
     238           0 :         atomic_long_set(&ioc->refcount, 1);
     239           0 :         atomic_set(&ioc->active_ref, 1);
     240             : #ifdef CONFIG_BLK_ICQ
     241             :         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             : #endif
     246           0 :         ioc->ioprio = IOPRIO_DEFAULT;
     247             : 
     248             :         return ioc;
     249             : }
     250             : 
     251           0 : int set_task_ioprio(struct task_struct *task, int ioprio)
     252             : {
     253             :         int err;
     254           0 :         const struct cred *cred = current_cred(), *tcred;
     255             : 
     256             :         rcu_read_lock();
     257           0 :         tcred = __task_cred(task);
     258           0 :         if (!uid_eq(tcred->uid, cred->euid) &&
     259           0 :             !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
     260             :                 rcu_read_unlock();
     261           0 :                 return -EPERM;
     262             :         }
     263           0 :         rcu_read_unlock();
     264             : 
     265           0 :         err = security_task_setioprio(task, ioprio);
     266           0 :         if (err)
     267             :                 return err;
     268             : 
     269           0 :         task_lock(task);
     270           0 :         if (unlikely(!task->io_context)) {
     271             :                 struct io_context *ioc;
     272             : 
     273           0 :                 task_unlock(task);
     274             : 
     275           0 :                 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
     276           0 :                 if (!ioc)
     277             :                         return -ENOMEM;
     278             : 
     279           0 :                 task_lock(task);
     280           0 :                 if (task->flags & PF_EXITING) {
     281           0 :                         kmem_cache_free(iocontext_cachep, ioc);
     282           0 :                         goto out;
     283             :                 }
     284           0 :                 if (task->io_context)
     285           0 :                         kmem_cache_free(iocontext_cachep, ioc);
     286             :                 else
     287           0 :                         task->io_context = ioc;
     288             :         }
     289           0 :         task->io_context->ioprio = ioprio;
     290             : out:
     291           0 :         task_unlock(task);
     292           0 :         return 0;
     293             : }
     294             : EXPORT_SYMBOL_GPL(set_task_ioprio);
     295             : 
     296           0 : int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
     297             : {
     298           0 :         struct io_context *ioc = current->io_context;
     299             : 
     300             :         /*
     301             :          * Share io context with parent, if CLONE_IO is set
     302             :          */
     303           0 :         if (clone_flags & CLONE_IO) {
     304           0 :                 atomic_inc(&ioc->active_ref);
     305           0 :                 tsk->io_context = ioc;
     306           0 :         } else if (ioprio_valid(ioc->ioprio)) {
     307           0 :                 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
     308           0 :                 if (!tsk->io_context)
     309             :                         return -ENOMEM;
     310           0 :                 tsk->io_context->ioprio = ioc->ioprio;
     311             :         }
     312             : 
     313             :         return 0;
     314             : }
     315             : 
     316             : #ifdef CONFIG_BLK_ICQ
     317             : /**
     318             :  * ioc_lookup_icq - lookup io_cq from ioc
     319             :  * @q: the associated request_queue
     320             :  *
     321             :  * Look up io_cq associated with @ioc - @q pair from @ioc.  Must be called
     322             :  * with @q->queue_lock held.
     323             :  */
     324             : struct 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 done
     334             :          * holding both q and ioc locks, and we're holding q lock - if we
     335             :          * 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             :         else
     346             :                 icq = NULL;
     347             : out:
     348             :         rcu_read_unlock();
     349             :         return icq;
     350             : }
     351             : EXPORT_SYMBOL(ioc_lookup_icq);
     352             : 
     353             : /**
     354             :  * ioc_create_icq - create and link io_cq
     355             :  * @q: request_queue of interest
     356             :  *
     357             :  * Make sure io_cq linking @ioc and @q exists.  If icq doesn't exist, they
     358             :  * will be created using @gfp_mask.
     359             :  *
     360             :  * The caller is responsible for ensuring @ioc won't go away and @q is
     361             :  * alive and will stay alive until this function returns.
     362             :  */
     363             : static 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             : 
     407             : struct 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             : }
     444             : EXPORT_SYMBOL_GPL(ioc_find_get_icq);
     445             : #endif /* CONFIG_BLK_ICQ */
     446             : 
     447           1 : static int __init blk_ioc_init(void)
     448             : {
     449           1 :         iocontext_cachep = kmem_cache_create("blkdev_ioc",
     450             :                         sizeof(struct io_context), 0, SLAB_PANIC, NULL);
     451           1 :         return 0;
     452             : }
     453             : subsys_initcall(blk_ioc_init);