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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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22
include/linux/iocontext.h
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@ -54,13 +54,15 @@ struct cfq_io_context {
};
/*
* This is the per-process I/O subsystem state. It is refcounted and
* kmalloc'ed. Currently all fields are modified in process io context
* (apart from the atomic refcount), so require no locking.
* I/O subsystem state of the associated processes. It is refcounted
* and kmalloc'ed. These could be shared between processes.
*/
struct io_context {
atomic_t refcount;
struct task_struct *task;
atomic_t nr_tasks;
/* all the fields below are protected by this lock */
spinlock_t lock;
unsigned short ioprio;
unsigned short ioprio_changed;
@ -76,4 +78,16 @@ struct io_context {
void *ioc_data;
};
static inline struct io_context *ioc_task_link(struct io_context *ioc)
{
/*
* if ref count is zero, don't allow sharing (ioc is going away, it's
* a race).
*/
if (ioc && atomic_inc_not_zero(&ioc->refcount))
return ioc;
return NULL;
}
#endif