| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Functions related to io context handling |
| */ |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/init.h> |
| #include <linux/bio.h> |
| #include <linux/blkdev.h> |
| #include <linux/slab.h> |
| #include <linux/sched/task.h> |
| |
| #include "blk.h" |
| |
| /* |
| * For io context allocations |
| */ |
| static struct kmem_cache *iocontext_cachep; |
| |
| /** |
| * get_io_context - increment reference count to io_context |
| * @ioc: io_context to get |
| * |
| * Increment reference count to @ioc. |
| */ |
| void get_io_context(struct io_context *ioc) |
| { |
| BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
| atomic_long_inc(&ioc->refcount); |
| } |
| |
| static void icq_free_icq_rcu(struct rcu_head *head) |
| { |
| struct io_cq *icq = container_of(head, struct io_cq, __rcu_head); |
| |
| kmem_cache_free(icq->__rcu_icq_cache, icq); |
| } |
| |
| /* |
| * Exit an icq. Called with ioc locked for blk-mq, and with both ioc |
| * and queue locked for legacy. |
| */ |
| static void ioc_exit_icq(struct io_cq *icq) |
| { |
| struct elevator_type *et = icq->q->elevator->type; |
| |
| if (icq->flags & ICQ_EXITED) |
| return; |
| |
| if (et->ops.exit_icq) |
| et->ops.exit_icq(icq); |
| |
| icq->flags |= ICQ_EXITED; |
| } |
| |
| /* |
| * Release an icq. Called with ioc locked for blk-mq, and with both ioc |
| * and queue locked for legacy. |
| */ |
| static void ioc_destroy_icq(struct io_cq *icq) |
| { |
| struct io_context *ioc = icq->ioc; |
| struct request_queue *q = icq->q; |
| struct elevator_type *et = q->elevator->type; |
| |
| lockdep_assert_held(&ioc->lock); |
| |
| radix_tree_delete(&ioc->icq_tree, icq->q->id); |
| hlist_del_init(&icq->ioc_node); |
| list_del_init(&icq->q_node); |
| |
| /* |
| * Both setting lookup hint to and clearing it from @icq are done |
| * under queue_lock. If it's not pointing to @icq now, it never |
| * will. Hint assignment itself can race safely. |
| */ |
| if (rcu_access_pointer(ioc->icq_hint) == icq) |
| rcu_assign_pointer(ioc->icq_hint, NULL); |
| |
| ioc_exit_icq(icq); |
| |
| /* |
| * @icq->q might have gone away by the time RCU callback runs |
| * making it impossible to determine icq_cache. Record it in @icq. |
| */ |
| icq->__rcu_icq_cache = et->icq_cache; |
| icq->flags |= ICQ_DESTROYED; |
| call_rcu(&icq->__rcu_head, icq_free_icq_rcu); |
| } |
| |
| /* |
| * Slow path for ioc release in put_io_context(). Performs double-lock |
| * dancing to unlink all icq's and then frees ioc. |
| */ |
| static void ioc_release_fn(struct work_struct *work) |
| { |
| struct io_context *ioc = container_of(work, struct io_context, |
| release_work); |
| spin_lock_irq(&ioc->lock); |
| |
| while (!hlist_empty(&ioc->icq_list)) { |
| struct io_cq *icq = hlist_entry(ioc->icq_list.first, |
| struct io_cq, ioc_node); |
| struct request_queue *q = icq->q; |
| |
| if (spin_trylock(&q->queue_lock)) { |
| ioc_destroy_icq(icq); |
| spin_unlock(&q->queue_lock); |
| } else { |
| /* Make sure q and icq cannot be freed. */ |
| rcu_read_lock(); |
| |
| /* Re-acquire the locks in the correct order. */ |
| spin_unlock(&ioc->lock); |
| spin_lock(&q->queue_lock); |
| spin_lock(&ioc->lock); |
| |
| /* |
| * The icq may have been destroyed when the ioc lock |
| * was released. |
| */ |
| if (!(icq->flags & ICQ_DESTROYED)) |
| ioc_destroy_icq(icq); |
| |
| spin_unlock(&q->queue_lock); |
| rcu_read_unlock(); |
| } |
| } |
| |
| spin_unlock_irq(&ioc->lock); |
| |
| kmem_cache_free(iocontext_cachep, ioc); |
| } |
| |
| /** |
| * put_io_context - put a reference of io_context |
| * @ioc: io_context to put |
| * |
| * Decrement reference count of @ioc and release it if the count reaches |
| * zero. |
| */ |
| void put_io_context(struct io_context *ioc) |
| { |
| unsigned long flags; |
| bool free_ioc = false; |
| |
| if (ioc == NULL) |
| return; |
| |
| BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
| |
| /* |
| * Releasing ioc requires reverse order double locking and we may |
| * already be holding a queue_lock. Do it asynchronously from wq. |
| */ |
| if (atomic_long_dec_and_test(&ioc->refcount)) { |
| spin_lock_irqsave(&ioc->lock, flags); |
| if (!hlist_empty(&ioc->icq_list)) |
| queue_work(system_power_efficient_wq, |
| &ioc->release_work); |
| else |
| free_ioc = true; |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| } |
| |
| if (free_ioc) |
| kmem_cache_free(iocontext_cachep, ioc); |
| } |
| |
| /** |
| * put_io_context_active - put active reference on ioc |
| * @ioc: ioc of interest |
| * |
| * Undo get_io_context_active(). If active reference reaches zero after |
| * put, @ioc can never issue further IOs and ioscheds are notified. |
| */ |
| void put_io_context_active(struct io_context *ioc) |
| { |
| struct io_cq *icq; |
| |
| if (!atomic_dec_and_test(&ioc->active_ref)) { |
| put_io_context(ioc); |
| return; |
| } |
| |
| spin_lock_irq(&ioc->lock); |
| hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { |
| if (icq->flags & ICQ_EXITED) |
| continue; |
| |
| ioc_exit_icq(icq); |
| } |
| spin_unlock_irq(&ioc->lock); |
| |
| put_io_context(ioc); |
| } |
| |
| /* Called by the exiting task */ |
| void exit_io_context(struct task_struct *task) |
| { |
| struct io_context *ioc; |
| |
| task_lock(task); |
| ioc = task->io_context; |
| task->io_context = NULL; |
| task_unlock(task); |
| |
| atomic_dec(&ioc->nr_tasks); |
| put_io_context_active(ioc); |
| } |
| |
| static void __ioc_clear_queue(struct list_head *icq_list) |
| { |
| unsigned long flags; |
| |
| rcu_read_lock(); |
| while (!list_empty(icq_list)) { |
| struct io_cq *icq = list_entry(icq_list->next, |
| struct io_cq, q_node); |
| struct io_context *ioc = icq->ioc; |
| |
| spin_lock_irqsave(&ioc->lock, flags); |
| if (icq->flags & ICQ_DESTROYED) { |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| continue; |
| } |
| ioc_destroy_icq(icq); |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| } |
| rcu_read_unlock(); |
| } |
| |
| /** |
| * ioc_clear_queue - break any ioc association with the specified queue |
| * @q: request_queue being cleared |
| * |
| * Walk @q->icq_list and exit all io_cq's. |
| */ |
| void ioc_clear_queue(struct request_queue *q) |
| { |
| LIST_HEAD(icq_list); |
| |
| spin_lock_irq(&q->queue_lock); |
| list_splice_init(&q->icq_list, &icq_list); |
| spin_unlock_irq(&q->queue_lock); |
| |
| __ioc_clear_queue(&icq_list); |
| } |
| |
| int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) |
| { |
| struct io_context *ioc; |
| int ret; |
| |
| ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
| node); |
| if (unlikely(!ioc)) |
| return -ENOMEM; |
| |
| /* initialize */ |
| atomic_long_set(&ioc->refcount, 1); |
| atomic_set(&ioc->nr_tasks, 1); |
| atomic_set(&ioc->active_ref, 1); |
| spin_lock_init(&ioc->lock); |
| INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC); |
| INIT_HLIST_HEAD(&ioc->icq_list); |
| INIT_WORK(&ioc->release_work, ioc_release_fn); |
| ioc->ioprio = IOPRIO_DEFAULT; |
| |
| /* |
| * Try to install. ioc shouldn't be installed if someone else |
| * already did or @task, which isn't %current, is exiting. Note |
| * that we need to allow ioc creation on exiting %current as exit |
| * path may issue IOs from e.g. exit_files(). The exit path is |
| * responsible for not issuing IO after exit_io_context(). |
| */ |
| task_lock(task); |
| if (!task->io_context && |
| (task == current || !(task->flags & PF_EXITING))) |
| task->io_context = ioc; |
| else |
| kmem_cache_free(iocontext_cachep, ioc); |
| |
| ret = task->io_context ? 0 : -EBUSY; |
| |
| task_unlock(task); |
| |
| return ret; |
| } |
| |
| /** |
| * get_task_io_context - get io_context of a task |
| * @task: task of interest |
| * @gfp_flags: allocation flags, used if allocation is necessary |
| * @node: allocation node, used if allocation is necessary |
| * |
| * Return io_context of @task. If it doesn't exist, it is created with |
| * @gfp_flags and @node. The returned io_context has its reference count |
| * incremented. |
| * |
| * This function always goes through task_lock() and it's better to use |
| * %current->io_context + get_io_context() for %current. |
| */ |
| struct io_context *get_task_io_context(struct task_struct *task, |
| gfp_t gfp_flags, int node) |
| { |
| struct io_context *ioc; |
| |
| might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
| |
| do { |
| task_lock(task); |
| ioc = task->io_context; |
| if (likely(ioc)) { |
| get_io_context(ioc); |
| task_unlock(task); |
| return ioc; |
| } |
| task_unlock(task); |
| } while (!create_task_io_context(task, gfp_flags, node)); |
| |
| return NULL; |
| } |
| |
| /** |
| * ioc_lookup_icq - lookup io_cq from ioc |
| * @ioc: the associated io_context |
| * @q: the associated request_queue |
| * |
| * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called |
| * with @q->queue_lock held. |
| */ |
| struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) |
| { |
| struct io_cq *icq; |
| |
| lockdep_assert_held(&q->queue_lock); |
| |
| /* |
| * icq's are indexed from @ioc using radix tree and hint pointer, |
| * both of which are protected with RCU. All removals are done |
| * holding both q and ioc locks, and we're holding q lock - if we |
| * find a icq which points to us, it's guaranteed to be valid. |
| */ |
| rcu_read_lock(); |
| icq = rcu_dereference(ioc->icq_hint); |
| if (icq && icq->q == q) |
| goto out; |
| |
| icq = radix_tree_lookup(&ioc->icq_tree, q->id); |
| if (icq && icq->q == q) |
| rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ |
| else |
| icq = NULL; |
| out: |
| rcu_read_unlock(); |
| return icq; |
| } |
| EXPORT_SYMBOL(ioc_lookup_icq); |
| |
| /** |
| * ioc_create_icq - create and link io_cq |
| * @ioc: io_context of interest |
| * @q: request_queue of interest |
| * @gfp_mask: allocation mask |
| * |
| * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they |
| * will be created using @gfp_mask. |
| * |
| * The caller is responsible for ensuring @ioc won't go away and @q is |
| * alive and will stay alive until this function returns. |
| */ |
| struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q, |
| gfp_t gfp_mask) |
| { |
| struct elevator_type *et = q->elevator->type; |
| struct io_cq *icq; |
| |
| /* allocate stuff */ |
| icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, |
| q->node); |
| if (!icq) |
| return NULL; |
| |
| if (radix_tree_maybe_preload(gfp_mask) < 0) { |
| kmem_cache_free(et->icq_cache, icq); |
| return NULL; |
| } |
| |
| icq->ioc = ioc; |
| icq->q = q; |
| INIT_LIST_HEAD(&icq->q_node); |
| INIT_HLIST_NODE(&icq->ioc_node); |
| |
| /* lock both q and ioc and try to link @icq */ |
| spin_lock_irq(&q->queue_lock); |
| spin_lock(&ioc->lock); |
| |
| if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { |
| hlist_add_head(&icq->ioc_node, &ioc->icq_list); |
| list_add(&icq->q_node, &q->icq_list); |
| if (et->ops.init_icq) |
| et->ops.init_icq(icq); |
| } else { |
| kmem_cache_free(et->icq_cache, icq); |
| icq = ioc_lookup_icq(ioc, q); |
| if (!icq) |
| printk(KERN_ERR "cfq: icq link failed!\n"); |
| } |
| |
| spin_unlock(&ioc->lock); |
| spin_unlock_irq(&q->queue_lock); |
| radix_tree_preload_end(); |
| return icq; |
| } |
| |
| static int __init blk_ioc_init(void) |
| { |
| iocontext_cachep = kmem_cache_create("blkdev_ioc", |
| sizeof(struct io_context), 0, SLAB_PANIC, NULL); |
| return 0; |
| } |
| subsys_initcall(blk_ioc_init); |