From 6890c3a990cb4b09bb17e00225082dcdd33bd248 Mon Sep 17 00:00:00 2001
From: Peter Holm <pho@FreeBSD.org>
Date: Mon, 31 Oct 2011 15:01:47 +0000
Subject: [PATCH] The kern_renameat() looks up the fvp using the DELETE flag,
 which causes the removal of the name cache entry for fvp.

Reported by:	Anton Yuzhaninov <citrin citrin ru>
In collaboration with:	kib
MFC after:	1 week
---
 sys/ufs/ufs/ufs_vnops.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
index 733413d319d..105bdafad4b 100644
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -1519,6 +1519,13 @@ relock:
 		cache_purge(fdvp);
 	}
 	error = ufs_dirremove(fdvp, fip, fcnp->cn_flags, 0);
+	/*
+	 * As the relookup of the fvp is done in two steps:
+	 * ufs_lookup_ino() and then VFS_VGET(), another thread might do a
+	 * normal lookup of the from name just before the VFS_VGET() call,
+	 * causing the cache entry to be re-instantiated.
+	 */
+	cache_purge(fvp);
 
 unlockout:
 	vput(fdvp);