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>

fs/gfs2/glock.c

@@ -334,7 +334,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	gl->gl_state = LM_ST_UNLOCKED;
 	gl->gl_demote_state = LM_ST_EXCLUSIVE;
 	gl->gl_hash = hash;
-	gl->gl_owner_pid = 0;
+	gl->gl_owner_pid = NULL;
 	gl->gl_ip = 0;
 	gl->gl_ops = glops;
 	gl->gl_req_gh = NULL;
@@ -632,7 +632,7 @@ static void gfs2_glmutex_lock(struct gfs2_glock *gl)
 		wait_on_holder(&gh);
 		gfs2_holder_uninit(&gh);
 	} else {
-		gl->gl_owner_pid = current->pid;
+		gl->gl_owner_pid = get_pid(task_pid(current));
 		gl->gl_ip = (unsigned long)__builtin_return_address(0);
 		spin_unlock(&gl->gl_spin);
 	}
@@ -653,7 +653,7 @@ static int gfs2_glmutex_trylock(struct gfs2_glock *gl)
 	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
 		acquired = 0;
 	} else {
-		gl->gl_owner_pid = current->pid;
+		gl->gl_owner_pid = get_pid(task_pid(current));
 		gl->gl_ip = (unsigned long)__builtin_return_address(0);
 	}
 	spin_unlock(&gl->gl_spin);
@@ -669,12 +669,17 @@ static int gfs2_glmutex_trylock(struct gfs2_glock *gl)
 
 static void gfs2_glmutex_unlock(struct gfs2_glock *gl)
 {
+	struct pid *pid;
+
 	spin_lock(&gl->gl_spin);
 	clear_bit(GLF_LOCK, &gl->gl_flags);
-	gl->gl_owner_pid = 0;
+	pid = gl->gl_owner_pid;
+	gl->gl_owner_pid = NULL;
 	gl->gl_ip = 0;
 	run_queue(gl);
 	spin_unlock(&gl->gl_spin);
+
+	put_pid(pid);
 }
 
 /**
@@ -1881,13 +1886,13 @@ static int dump_glock(struct glock_iter *gi, struct gfs2_glock *gl)
 	print_dbg(gi, "  gl_ref = %d\n", atomic_read(&gl->gl_ref));
 	print_dbg(gi, "  gl_state = %u\n", gl->gl_state);
 	if (gl->gl_owner_pid) {
-		gl_owner = find_task_by_pid(gl->gl_owner_pid);
+		gl_owner = pid_task(gl->gl_owner_pid, PIDTYPE_PID);
 		if (gl_owner)
 			print_dbg(gi, "  gl_owner = pid %d (%s)\n",
-				  gl->gl_owner_pid, gl_owner->comm);
+				  pid_nr(gl->gl_owner_pid), gl_owner->comm);
 		else
 			print_dbg(gi, "  gl_owner = %d (ended)\n",
-				  gl->gl_owner_pid);
+				  pid_nr(gl->gl_owner_pid));
 	} else
 		print_dbg(gi, "  gl_owner = -1\n");
 	print_dbg(gi, "  gl_ip = %lu\n", gl->gl_ip);

fs/gfs2/incore.h

@@ -182,7 +182,7 @@ struct gfs2_glock {
 	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 */

kernel/pid.c

@@ -368,6 +368,7 @@ struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)
 	}
 	return result;
 }
+EXPORT_SYMBOL(pid_task);
 
 /*
  * Must be called under rcu_read_lock() or with tasklist_lock read-held.