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block: add io_context->active_ref

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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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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);