ipc: rename ids->rw_mutex

Since in some situations the lock can be shared for readers, we shouldn't
be calling it a mutex, rename it to rwsem.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 4be6581..d43d938 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -81,7 +81,7 @@
 	int next_id;
 	int total, in_use;
 
-	down_write(&ids->rw_mutex);
+	down_write(&ids->rwsem);
 
 	in_use = ids->in_use;
 
@@ -93,7 +93,7 @@
 		free(ns, perm);
 		total++;
 	}
-	up_write(&ids->rw_mutex);
+	up_write(&ids->rwsem);
 }
 
 static void free_ipc_ns(struct ipc_namespace *ns)