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io context sharing: preliminary support

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Detach task state from ioc, instead keep track of how many processes
are accessing the ioc.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
2008-01-24 08:53:35 +01:00
parent fd0928df98
commit d38ecf935f
5 changed files with 49 additions and 23 deletions
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block/ll_rw_blk.c
+30 -16
View File
@@ -3854,12 +3854,13 @@ int __init blk_dev_init(void)
}
/*
* IO Context helper functions
* IO Context helper functions. put_io_context() returns 1 if there are no
* more users of this io context, 0 otherwise.
*/
void put_io_context(struct io_context *ioc)
int put_io_context(struct io_context *ioc)
{
if (ioc == NULL)
return;
return 1;
BUG_ON(atomic_read(&ioc->refcount) == 0);
@@ -3878,7 +3879,9 @@ void put_io_context(struct io_context *ioc)
rcu_read_unlock();
kmem_cache_free(iocontext_cachep, ioc);
return 1;
}
return 0;
}
EXPORT_SYMBOL(put_io_context);
@@ -3893,15 +3896,17 @@ void exit_io_context(void)
current->io_context = NULL;
task_unlock(current);
ioc->task = NULL;
if (ioc->aic && ioc->aic->exit)
ioc->aic->exit(ioc->aic);
if (ioc->cic_root.rb_node != NULL) {
cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
cic->exit(ioc);
}
if (atomic_dec_and_test(&ioc->nr_tasks)) {
if (ioc->aic && ioc->aic->exit)
ioc->aic->exit(ioc->aic);
if (ioc->cic_root.rb_node != NULL) {
cic = rb_entry(rb_first(&ioc->cic_root),
struct cfq_io_context, rb_node);
cic->exit(ioc);
}
put_io_context(ioc);
put_io_context(ioc);
}
}
struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
@@ -3911,7 +3916,8 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
if (ret) {
atomic_set(&ret->refcount, 1);
ret->task = current;
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... */
@@ -3959,10 +3965,18 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
*/
struct io_context *get_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ret;
ret = current_io_context(gfp_flags, node);
if (likely(ret))
atomic_inc(&ret->refcount);
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);