forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
422 lines
10 KiB
422 lines
10 KiB
// 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); |
|
|
|
/* |
|
* 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);
|
|
|