165 lines
3.6 KiB
C
165 lines
3.6 KiB
C
/*
|
|
* 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;
|
|
|
|
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;
|
|
|
|
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);
|
|
}
|
|
|
|
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;
|
|
|
|
/* 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);
|
|
|
|
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)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
struct io_context *ret;
|
|
|
|
ret = tsk->io_context;
|
|
if (likely(ret))
|
|
return ret;
|
|
|
|
ret = alloc_io_context(gfp_flags, node);
|
|
if (ret) {
|
|
/* make sure set_task_ioprio() sees the settings above */
|
|
smp_wmb();
|
|
tsk->io_context = ret;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* If the current task has no IO context then create one and initialise it.
|
|
* If it does have a context, take a ref on it.
|
|
*
|
|
* This is always called in the context of the task which submitted the I/O.
|
|
*/
|
|
struct io_context *get_io_context(gfp_t gfp_flags, int node)
|
|
{
|
|
struct io_context *ioc = NULL;
|
|
|
|
/*
|
|
* Check for unlikely race with exiting task. ioc ref count is
|
|
* zero when ioc is being detached.
|
|
*/
|
|
do {
|
|
ioc = current_io_context(gfp_flags, node);
|
|
if (unlikely(!ioc))
|
|
break;
|
|
} while (!atomic_long_inc_not_zero(&ioc->refcount));
|
|
|
|
return ioc;
|
|
}
|
|
EXPORT_SYMBOL(get_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);
|