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From: Kevin Lo <kevlo@FreeBSD.org>
Date: Mon, 25 Oct 2010 06:16:27 +0000 (UTC)
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Subject: svn commit: r214316 - stable/8/sys/fs/msdosfs
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Author: kevlo
Date: Mon Oct 25 06:16:27 2010
New Revision: 214316
URL: http://svn.freebsd.org/changeset/base/214316

Log:
  MFC r214001:
  Fix a possible, but very unlikely race where the directory dirent is
  moved to the location that was used by ".." entry.

Modified:
  stable/8/sys/fs/msdosfs/msdosfs_lookup.c

Modified: stable/8/sys/fs/msdosfs/msdosfs_lookup.c
==============================================================================
--- stable/8/sys/fs/msdosfs/msdosfs_lookup.c	Mon Oct 25 05:37:12 2010	(r214315)
+++ stable/8/sys/fs/msdosfs/msdosfs_lookup.c	Mon Oct 25 06:16:27 2010	(r214316)
@@ -594,10 +594,15 @@ msdosfs_deget_dotdot(struct vnode *vp, u
 	vfs_unbusy(mp);
 	if (error == 0)
 		*rvp = DETOV(rdp);
-	vn_lock(vp, ltype | LK_RETRY);
+	if (*rvp != vp)
+		vn_lock(vp, ltype | LK_RETRY);
 	if (vp->v_iflag & VI_DOOMED) {
-		if (error == 0)
-			vput(*rvp);
+		if (error == 0) {
+			if (*rvp == vp)
+				vunref(*rvp);
+			else
+				vput(*rvp);
+		}
 		error = ENOENT;
 	}
 	return (error);