gfs2: make gfs2_glock.gl_owner_pid be a struct pid *

The gl_owner_pid field is used to get the lock owning task by its pid, so make
it in a proper manner, i.e.  by using the struct pid pointer and pid_task()
function.

The pid_task() becomes exported for the gfs2 module.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 4b724e7..525dcae 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -182,7 +182,7 @@
 	unsigned int gl_hash;
 	unsigned int gl_demote_state; /* state requested by remote node */
 	unsigned long gl_demote_time; /* time of first demote request */
-	pid_t gl_owner_pid;
+	struct pid *gl_owner_pid;
 	unsigned long gl_ip;
 	struct list_head gl_holders;
 	struct list_head gl_waiters1;	/* HIF_MUTEX */