mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 01:10:04 +00:00
![Jens Axboe](/assets/img/avatar_default.png)
It's cumbersome to browse a radix tree from start to finish, especially since we modify keys when a process exits. So add a hlist for the single purpose of browsing over all known cfq_io_contexts, used for exit, io prio change, etc. This fixes http://bugzilla.kernel.org/show_bug.cgi?id=9948 Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
180 lines
4 KiB
C
180 lines
4 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 "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 = list_entry(ioc->cic_list.first, struct cfq_io_context,
|
|
cic_list);
|
|
cic->dtor(ioc);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* IO Context helper functions. put_io_context() returns 1 if there are no
|
|
* more users of this io context, 0 otherwise.
|
|
*/
|
|
int put_io_context(struct io_context *ioc)
|
|
{
|
|
if (ioc == NULL)
|
|
return 1;
|
|
|
|
BUG_ON(atomic_read(&ioc->refcount) == 0);
|
|
|
|
if (atomic_dec_and_test(&ioc->refcount)) {
|
|
rcu_read_lock();
|
|
if (ioc->aic && ioc->aic->dtor)
|
|
ioc->aic->dtor(ioc->aic);
|
|
rcu_read_unlock();
|
|
cfq_dtor(ioc);
|
|
|
|
kmem_cache_free(iocontext_cachep, ioc);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
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 = list_entry(ioc->cic_list.first, struct cfq_io_context,
|
|
cic_list);
|
|
cic->exit(ioc);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/* Called by the exitting task */
|
|
void exit_io_context(void)
|
|
{
|
|
struct io_context *ioc;
|
|
|
|
task_lock(current);
|
|
ioc = current->io_context;
|
|
current->io_context = NULL;
|
|
task_unlock(current);
|
|
|
|
if (atomic_dec_and_test(&ioc->nr_tasks)) {
|
|
if (ioc->aic && ioc->aic->exit)
|
|
ioc->aic->exit(ioc->aic);
|
|
cfq_exit(ioc);
|
|
|
|
put_io_context(ioc);
|
|
}
|
|
}
|
|
|
|
struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
|
|
{
|
|
struct io_context *ret;
|
|
|
|
ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
|
|
if (ret) {
|
|
atomic_set(&ret->refcount, 1);
|
|
atomic_set(&ret->nr_tasks, 1);
|
|
spin_lock_init(&ret->lock);
|
|
ret->ioprio_changed = 0;
|
|
ret->ioprio = 0;
|
|
ret->last_waited = jiffies; /* doesn't matter... */
|
|
ret->nr_batch_requests = 0; /* because this is 0 */
|
|
ret->aic = NULL;
|
|
INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
|
|
INIT_HLIST_HEAD(&ret->cic_list);
|
|
ret->ioc_data = NULL;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* If the current task has no IO context then create one and initialise it.
|
|
* Otherwise, return its existing IO context.
|
|
*
|
|
* This returned IO context doesn't have a specifically elevated refcount,
|
|
* but since the current task itself holds a reference, the context can be
|
|
* used in general code, so long as it stays within `current` context.
|
|
*/
|
|
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 *ret = NULL;
|
|
|
|
/*
|
|
* Check for unlikely race with exiting task. ioc ref count is
|
|
* zero when ioc is being detached.
|
|
*/
|
|
do {
|
|
ret = current_io_context(gfp_flags, node);
|
|
if (unlikely(!ret))
|
|
break;
|
|
} while (!atomic_inc_not_zero(&ret->refcount));
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(get_io_context);
|
|
|
|
void copy_io_context(struct io_context **pdst, struct io_context **psrc)
|
|
{
|
|
struct io_context *src = *psrc;
|
|
struct io_context *dst = *pdst;
|
|
|
|
if (src) {
|
|
BUG_ON(atomic_read(&src->refcount) == 0);
|
|
atomic_inc(&src->refcount);
|
|
put_io_context(dst);
|
|
*pdst = src;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(copy_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);
|