From d38ecf935fcb10264a6bc190855d9595165e6eeb Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 24 Jan 2008 08:53:35 +0100 Subject: io context sharing: preliminary support Detach task state from ioc, instead keep track of how many processes are accessing the ioc. Signed-off-by: Jens Axboe --- include/linux/iocontext.h | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'include/linux/iocontext.h') diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h index 186807ea62e2..cd44d458124a 100644 --- a/include/linux/iocontext.h +++ b/include/linux/iocontext.h @@ -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 -- cgit