GFS2: revert "GFS2: d_splice_alias() can't return error"

0d0d1107 asserts that "d_splice_alias()
can't return error unless it was given an IS_ERR(inode)".

That was true of the implementation of d_splice_alias, but this is
really a problem with d_splice_alias: at a minimum it should be able to
return -ELOOP in the case where inserting the given dentry would cause a
directory loop.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/inode.c

@@ -604,6 +604,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	error = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
 		d = d_splice_alias(inode, dentry);
+		error = PTR_ERR(d);
+		if (IS_ERR(d))
+			goto fail_gunlock;
 		error = 0;
 		if (file) {
 			if (S_ISREG(inode->i_mode)) {
@@ -799,6 +802,11 @@ static struct dentry *__gfs2_lookup(struct inode *dir, struct dentry *dentry,
 	}
 
 	d = d_splice_alias(inode, dentry);
+	if (IS_ERR(d)) {
+		iput(inode);
+		gfs2_glock_dq_uninit(&gh);
+		return d;
+	}
 	if (file && S_ISREG(inode->i_mode))
 		error = finish_open(file, dentry, gfs2_open_common, opened);