fs/romfs: correct error-handling code

romfs_fill_super() assumes that romfs_iget() returns NULL when
it fails.  romfs_iget() actually returns ERR_PTR(-ve) in that
case...

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/romfs/super.c

diff --git a/fs/romfs/super.c b/fs/romfs/super.c
index 47f132d..c117fa8 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -528,7 +528,7 @@
 	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 
 	root = romfs_iget(sb, pos);
-	if (!root)
+	if (IS_ERR(root))
 		goto error;
 
 	sb->s_root = d_alloc_root(root);