gfs2: report "already frozen/thawed" errors

Before this patch, gfs2's freeze function failed to report an error
when the target file system was already frozen as it should (and as
generic vfs function freeze_super does. Similarly, gfs2's thaw function
failed to report an error when trying to thaw a file system that is not
frozen, as vfs function thaw_super does. The errors were checked, but
it always returned a 0 return code.

This patch adds the missing error return codes to gfs2 freeze and thaw.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/super.c

@@ -752,11 +752,13 @@ void gfs2_freeze_func(struct work_struct *work)
 static int gfs2_freeze(struct super_block *sb)
 {
 	struct gfs2_sbd *sdp = sb->s_fs_info;
-	int error = 0;
+	int error;
 
 	mutex_lock(&sdp->sd_freeze_mutex);
-	if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN)
+	if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN) {
+		error = -EBUSY;
 		goto out;
+	}
 
 	for (;;) {
 		if (gfs2_withdrawn(sdp)) {
@@ -797,10 +799,10 @@ static int gfs2_unfreeze(struct super_block *sb)
 	struct gfs2_sbd *sdp = sb->s_fs_info;
 
 	mutex_lock(&sdp->sd_freeze_mutex);
-        if (atomic_read(&sdp->sd_freeze_state) != SFS_FROZEN ||
+	if (atomic_read(&sdp->sd_freeze_state) != SFS_FROZEN ||
 	    !gfs2_holder_initialized(&sdp->sd_freeze_gh)) {
 		mutex_unlock(&sdp->sd_freeze_mutex);
-                return 0;
+		return -EINVAL;
 	}
 
 	gfs2_freeze_unlock(&sdp->sd_freeze_gh);