// 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/security.h>
#include <linux/sched/task.h>
#include "blk.h"
#include "blk-mq-sched.h"
/*
* For io context allocations
*/
static struct kmem_cache *iocontext_cachep;
#ifdef CONFIG_BLK_ICQ
/**
* get_io_context - increment reference count to io_context
* @ioc: io_context to get
*
* Increment reference count to @ioc.
*/
static 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;
}
static void ioc_exit_icqs(struct io_context *ioc)
{
struct io_cq *icq;
spin_lock_irq(&ioc->lock);
hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
ioc_exit_icq(icq);
spin_unlock_irq(&ioc->lock);
}
/*
* 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);
lockdep_assert_held(&q->queue_lock);
if (icq->flags & ICQ_DESTROYED)
return;
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);
ioc_destroy_icq(icq);
spin_unlock(&q->queue_lock);
rcu_read_unlock();
}
}
spin_unlock_irq(&ioc->lock);
kmem_cache_free(iocontext_cachep, ioc);
}
/*
* Releasing icqs requires reverse order double locking and we may already be
* holding a queue_lock. Do it asynchronously from a workqueue.
*/
static bool ioc_delay_free(struct io_context *ioc)
{
unsigned long flags;
spin_lock_irqsave(&ioc->lock, flags);
if (!hlist_empty(&ioc->icq_list)) {
queue_work(system_power_efficient_wq, &ioc->release_work);
spin_unlock_irqrestore(&ioc->lock, flags);
return true;
}
spin_unlock_irqrestore(&ioc->lock, flags);
return false;
}
/**
* 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)
{
spin_lock_irq(&q->queue_lock);
while (!list_empty(&q->icq_list)) {
struct io_cq *icq =
list_first_entry(&q->icq_list, struct io_cq, q_node);
/*
* Other context won't hold ioc lock to wait for queue_lock, see
* details in ioc_release_fn().
*/
spin_lock(&icq->ioc->lock);
ioc_destroy_icq(icq);
spin_unlock(&icq->ioc->lock);
}
spin_unlock_irq(&q->queue_lock);
}
#else /* CONFIG_BLK_ICQ */
static inline void ioc_exit_icqs(struct io_context *ioc)
{
}
static inline bool ioc_delay_free(struct io_context *ioc)
{
return false;
}
#endif /* CONFIG_BLK_ICQ */
/**
* 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)
{
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL_GPL(put_io_context);
/* 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);
if (atomic_dec_and_test(&ioc->active_ref)) {
ioc_exit_icqs(ioc);
put_io_context(ioc);
}
}
static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ioc;
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
node);
if (unlikely(!ioc))
return NULL;
atomic_long_set(&ioc->refcount, 1);
atomic_set(&ioc->active_ref, 1);
#ifdef CONFIG_BLK_ICQ
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);
#endif
ioc->ioprio = IOPRIO_DEFAULT;
return ioc;
}
int set_task_ioprio(struct task_struct *task, int ioprio)
{
int err;
const struct cred *cred = current_cred(), *tcred;
rcu_read_lock();
tcred = __task_cred(task);
if (!uid_eq(tcred->uid, cred->euid) &&
!uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
rcu_read_unlock();
return -EPERM;
}
rcu_read_unlock();
err = security_task_setioprio(task, ioprio);
if (err)
return err;
task_lock(task);
if (unlikely(!task->io_context)) {
struct io_context *ioc;
task_unlock(task);
ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
if (!ioc)
return -ENOMEM;
task_lock(task);
if (task->flags & PF_EXITING) {
kmem_cache_free(iocontext_cachep, ioc);
goto out;
}
if (task->io_context)
kmem_cache_free(iocontext_cachep, ioc);
else
task->io_context = ioc;
}
task->io_context->ioprio = ioprio;
out:
task_unlock(task);
return 0;
}
EXPORT_SYMBOL_GPL(set_task_ioprio);
int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
{
struct io_context *ioc = current->io_context;
/*
* Share io context with parent, if CLONE_IO is set
*/
if (clone_flags & CLONE_IO) {
atomic_inc(&ioc->active_ref);
tsk->io_context = ioc;
} else if (ioprio_valid(ioc->ioprio)) {
tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
if (!tsk->io_context)
return -ENOMEM;
tsk->io_context->ioprio = ioc->ioprio;
}
return 0;
}
#ifdef CONFIG_BLK_ICQ
/**
* ioc_lookup_icq - lookup io_cq from ioc
* @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 request_queue *q)
{
struct io_context *ioc = current->io_context;
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
* @q: request_queue of interest
*
* 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.
*/
static struct io_cq *ioc_create_icq(struct request_queue *q)
{
struct io_context *ioc = current->io_context;
struct elevator_type *et = q->elevator->type;
struct io_cq *icq;
/* allocate stuff */
icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
q->node);
if (!icq)
return NULL;
if (radix_tree_maybe_preload(GFP_ATOMIC) < 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(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;
}
struct io_cq *ioc_find_get_icq(struct request_queue *q)
{
struct io_context *ioc = current->io_context;
struct io_cq *icq = NULL;
if (unlikely(!ioc)) {
ioc = alloc_io_context(GFP_ATOMIC, q->node);
if (!ioc)
return NULL;
task_lock(current);
if (current->io_context) {
kmem_cache_free(iocontext_cachep, ioc);
ioc = current->io_context;
} else {
current->io_context = ioc;
}
get_io_context(ioc);
task_unlock(current);
} else {
get_io_context(ioc);
spin_lock_irq(&q->queue_lock);
icq = ioc_lookup_icq(q);
spin_unlock_irq(&q->queue_lock);
}
if (!icq) {
icq = ioc_create_icq(q);
if (!icq) {
put_io_context(ioc);
return NULL;
}
}
return icq;
}
EXPORT_SYMBOL_GPL(ioc_find_get_icq);
#endif /* CONFIG_BLK_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);
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