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/*
* 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/bootmem.h> /* for max_pfn/max_low_pfn */
#include <linux/slab.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);
}
EXPORT_SYMBOL(get_io_context);
static void cfq_dtor(struct io_context *ioc)
{
if (!hlist_empty(&ioc->cic_list)) {
struct cfq_io_context *cic;
cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
cic_list);
cic->dtor(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)
{
if (ioc == NULL)
return;
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
if (!atomic_long_dec_and_test(&ioc->refcount))
return;
rcu_read_lock();
cfq_dtor(ioc);
rcu_read_unlock();
kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL(put_io_context);
static void cfq_exit(struct io_context *ioc)
{
rcu_read_lock();
if (!hlist_empty(&ioc->cic_list)) {
struct cfq_io_context *cic;
cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
cic_list);
cic->exit(ioc);
}
rcu_read_unlock();
}
/* Called by the exiting task */
void exit_io_context(struct task_struct *task)
{
struct io_context *ioc;
/* PF_EXITING prevents new io_context from being attached to @task */
WARN_ON_ONCE(!(current->flags & PF_EXITING));
task_lock(task);
ioc = task->io_context;
task->io_context = NULL;
task_unlock(task);
if (atomic_dec_and_test(&ioc->nr_tasks))
cfq_exit(ioc);
put_io_context(ioc);
}
static struct io_context *create_task_io_context(struct task_struct *task,
gfp_t gfp_flags, int node,
bool take_ref)
{
struct io_context *ioc;
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
node);
if (unlikely(!ioc))
return NULL;
/* initialize */
atomic_long_set(&ioc->refcount, 1);
atomic_set(&ioc->nr_tasks, 1);
spin_lock_init(&ioc->lock);
INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
INIT_HLIST_HEAD(&ioc->cic_list);
/* try to install, somebody might already have beaten us to it */
task_lock(task);
if (!task->io_context && !(task->flags & PF_EXITING)) {
task->io_context = ioc;
} else {
kmem_cache_free(iocontext_cachep, ioc);
ioc = task->io_context;
}
if (ioc && take_ref)
get_io_context(ioc);
task_unlock(task);
return ioc;
}
/**
* current_io_context - get io_context of %current
* @gfp_flags: allocation flags, used if allocation is necessary
* @node: allocation node, used if allocation is necessary
*
* Return io_context of %current. If it doesn't exist, it is created with
* @gfp_flags and @node. The returned io_context does NOT have its
* reference count incremented. Because io_context is exited only on task
* exit, %current can be sure that the returned io_context is valid and
* alive as long as it is executing.
*/
struct io_context *current_io_context(gfp_t gfp_flags, int node)
{
might_sleep_if(gfp_flags & __GFP_WAIT);
if (current->io_context)
return current->io_context;
return create_task_io_context(current, gfp_flags, node, false);
}
EXPORT_SYMBOL(current_io_context);
/**
* 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(gfp_flags & __GFP_WAIT);
task_lock(task);
ioc = task->io_context;
if (likely(ioc)) {
get_io_context(ioc);
task_unlock(task);
return ioc;
}
task_unlock(task);
return create_task_io_context(task, gfp_flags, node, true);
}
EXPORT_SYMBOL(get_task_io_context);
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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