--- 2153f9bdbebdcb3cb094a76c73b9948815b30e2d
+++ 6ad6282e3076f4d16b6ff134253ac8a59b456063
@@ -2002,7 +2002,9 @@ nfs4_file_downgrade(struct file *filp, u
 {
 	if (share_access & NFS4_SHARE_ACCESS_WRITE) {
 		drop_file_write_access(filp);
+		spin_lock(&filp->f_lock);
 		filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
+		spin_unlock(&filp->f_lock);
 	}
 }