NFS: Fix a race in nfs_call_unlink()

We should check that the filehandles match before transferring the
sillyrename data to the newly looked-up dentry in case the name was
reused on the server.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/unlink.c

@@ -139,6 +139,7 @@ static int nfs_call_unlink(struct dentry *dentry, struct inode *inode, struct nf
 		 */
 		spin_lock(&alias->d_lock);
 		if (d_really_is_positive(alias) &&
+		    !nfs_compare_fh(NFS_FH(inode), NFS_FH(d_inode(alias))) &&
 		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
 			devname_garbage = alias->d_fsdata;
 			alias->d_fsdata = data;