rwsem: introduce down_write_non_owner and up_write_non_owner

Introduce these two functions that allow the semaphore to be released
by a different process.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 include/linux/rwsem.h |    6 +++++-
 kernel/rwsem.c        |   16 ++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

Index: linux-3.0-fast/include/linux/rwsem.h
===================================================================
--- linux-3.0-fast.orig/include/linux/rwsem.h	2011-08-18 22:42:30.000000000 +0200
+++ linux-3.0-fast/include/linux/rwsem.h	2011-08-18 22:43:42.000000000 +0200
@@ -132,11 +132,15 @@ extern void down_write_nested(struct rw_
  */
 extern void down_read_non_owner(struct rw_semaphore *sem);
 extern void up_read_non_owner(struct rw_semaphore *sem);
+extern void down_write_non_owner(struct rw_semaphore *sem);
+extern void up_write_non_owner(struct rw_semaphore *sem);
 #else
-# define down_read_nested(sem, subclass)		down_read(sem)
+# define down_read_nested(sem, subclass)	down_read(sem)
 # define down_write_nested(sem, subclass)	down_write(sem)
 # define down_read_non_owner(sem)		down_read(sem)
 # define up_read_non_owner(sem)			up_read(sem)
+# define down_write_non_owner(sem)		down_write(sem)
+# define up_write_non_owner(sem)		up_write(sem)
 #endif
 
 #endif /* _LINUX_RWSEM_H */
Index: linux-3.0-fast/kernel/rwsem.c
===================================================================
--- linux-3.0-fast.orig/kernel/rwsem.c	2011-08-18 22:41:04.000000000 +0200
+++ linux-3.0-fast/kernel/rwsem.c	2011-08-18 22:42:26.000000000 +0200
@@ -136,6 +136,15 @@ void down_write_nested(struct rw_semapho
 
 EXPORT_SYMBOL(down_write_nested);
 
+void down_write_non_owner(struct rw_semaphore *sem)
+{
+	might_sleep();
+
+	__down_write(sem);
+}
+
+EXPORT_SYMBOL(down_write_non_owner);
+
 void up_read_non_owner(struct rw_semaphore *sem)
 {
 	__up_read(sem);
@@ -143,6 +152,13 @@ void up_read_non_owner(struct rw_semapho
 
 EXPORT_SYMBOL(up_read_non_owner);
 
+void up_write_non_owner(struct rw_semaphore *sem)
+{
+	__up_write(sem);
+}
+
+EXPORT_SYMBOL(up_write_non_owner);
+
 #endif