Miklos,

I tried your overlayfs.v9 git repo w/ racer, using two separate ext3 filesystems (one for lowerdir and another for upperdir).  I got the WARN_ON in ovl_permission to trigger within about 10 minutes of testing.  Looking at the code, I see a problem in returning w/o cleaning up an dput-ing the alias dentry.  Simple patch enclosed below.

Cheers,
Erez.


diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3c15d54..6c70f57 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -80,7 +82,8 @@ int ovl_permission(struct inode *inode, int mask, unsigned int flags)
 	realinode = ACCESS_ONCE(realdentry->d_inode);
 	if (!realinode) {
 		WARN_ON(!(flags & IPERM_FLAG_RCU));
-		return -ENOENT;
+		err = -ENOENT;
+		goto out_dput;
 	}
 
 	if (mask & MAY_WRITE) {