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authorJens Axboe <jens.axboe@oracle.com>2008-01-24 08:53:35 +0100
committerJens Axboe <jens.axboe@oracle.com>2008-01-28 10:50:31 +0100
commitd38ecf935fcb10264a6bc190855d9595165e6eeb (patch)
tree64e3146ef76678ad3ae8f75c32df9f25ea470953 /include
parentfd0928df98b9578be8a786ac0cb78a47a5e17a20 (diff)
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 <jens.axboe@oracle.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/blkdev.h2
-rw-r--r--include/linux/iocontext.h22
2 files changed, 19 insertions, 5 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 510a18ba1ec..2483a05231c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -34,7 +34,7 @@ struct sg_io_hdr;
#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */
-void put_io_context(struct io_context *ioc);
+int put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 186807ea62e..cd44d458124 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