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block: add io_context->active_ref 

Currently ioc->nr_tasks is used to decide two things - whether an ioc
is done issuing IOs and whether it's shared by multiple tasks.  This
patch separate out the first into ioc->active_ref, which is acquired
and released using {get|put}_io_context_active() respectively.

This will be used to associate bio's with a given task.  This patch
doesn't introduce any visible behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2012-03-05 13:15:26 -08:00 committed by Jens Axboe
parent 3d48749d93
commit f6e8d01bee
3 changed files with 47 additions and 15 deletions
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36
block/blk-ioc.c
View File

@ -149,20 +149,20 @@ void put_io_context(struct io_context *ioc)
}
EXPORT_SYMBOL(put_io_context);
/* Called by the exiting task */
void exit_io_context(struct task_struct *task)
/**
* put_io_context_active - put active reference on ioc
* @ioc: ioc of interest
*
* Undo get_io_context_active(). If active reference reaches zero after
* put, @ioc can never issue further IOs and ioscheds are notified.
*/
void put_io_context_active(struct io_context *ioc)
{
struct io_context *ioc;
struct io_cq *icq;
struct hlist_node *n;
unsigned long flags;
struct io_cq *icq;
task_lock(task);
ioc = task->io_context;
task->io_context = NULL;
task_unlock(task);
if (!atomic_dec_and_test(&ioc->nr_tasks)) {
if (!atomic_dec_and_test(&ioc->active_ref)) {
put_io_context(ioc);
return;
}
@ -191,6 +191,20 @@ retry:
put_io_context(ioc);
}
/* 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);
atomic_dec(&ioc->nr_tasks);
put_io_context_active(ioc);
}
/**
* ioc_clear_queue - break any ioc association with the specified queue
* @q: request_queue being cleared
@ -223,7 +237,7 @@ int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
/* initialize */
atomic_long_set(&ioc->refcount, 1);
atomic_set(&ioc->nr_tasks, 1);
atomic_set(&ioc->active_ref, 1);
spin_lock_init(&ioc->lock);
INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
INIT_HLIST_HEAD(&ioc->icq_list);

4
block/cfq-iosched.c
View File

@ -1865,7 +1865,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
* task has exited, don't wait
*/
cic = cfqd->active_cic;
if (!cic || !atomic_read(&cic->icq.ioc->nr_tasks))
if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
return;
/*
@ -2841,7 +2841,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
enable_idle = 0;
else if (!atomic_read(&cic->icq.ioc->nr_tasks) ||
else if (!atomic_read(&cic->icq.ioc->active_ref) ||
!cfqd->cfq_slice_idle ||
(!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
enable_idle = 0;

22
include/linux/iocontext.h
View File

@ -100,6 +100,7 @@ struct io_cq {
*/
struct io_context {
atomic_long_t refcount;
atomic_t active_ref;
atomic_t nr_tasks;
/* all the fields below are protected by this lock */
@ -120,17 +121,34 @@ struct io_context {
struct work_struct release_work;
};
static inline void ioc_task_link(struct io_context *ioc)
/**
* get_io_context_active - get active reference on ioc
* @ioc: ioc of interest
*
* Only iocs with active reference can issue new IOs. This function
* acquires an active reference on @ioc. The caller must already have an
* active reference on @ioc.
*/
static inline void get_io_context_active(struct io_context *ioc)
{
WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);
WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0);
atomic_long_inc(&ioc->refcount);
atomic_inc(&ioc->active_ref);
}
static inline void ioc_task_link(struct io_context *ioc)
{
get_io_context_active(ioc);
WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
atomic_inc(&ioc->nr_tasks);
}
struct task_struct;
#ifdef CONFIG_BLOCK
void put_io_context(struct io_context *ioc);
void put_io_context_active(struct io_context *ioc);
void exit_io_context(struct task_struct *task);
struct io_context *get_task_io_context(struct task_struct *task,
gfp_t gfp_flags, int node);