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From: Pawel Jakub Dawidek <pjd@FreeBSD.org>
Date: Sat, 12 Sep 2009 19:27:54 +0000 (UTC)
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Cc: 
Subject: svn commit: r197131 -
	head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
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Author: pjd
Date: Sat Sep 12 19:27:54 2009
New Revision: 197131
URL: http://svn.freebsd.org/changeset/base/197131

Log:
  Tighten up the check for race in zfs_zget() - ZTOV(zp) can not only contain
  NULL, but also can point to dead vnode, take that into account.
  
  PR:		kern/132068
  Reported by:	Edward Fisk" <7ogcg7g02@sneakemail.com>, kris
  Fix based on patch from:	Jaakko Heinonen <jh@saunalahti.fi>
  MFC after:	1 week

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c	Sat Sep 12 19:07:03 2009	(r197130)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c	Sat Sep 12 19:27:54 2009	(r197131)
@@ -890,8 +890,16 @@ again:
 		if (zp->z_unlinked) {
 			err = ENOENT;
 		} else {
-			if (ZTOV(zp) != NULL)
-				VN_HOLD(ZTOV(zp));
+			if ((vp = ZTOV(zp)) != NULL) {
+				VI_LOCK(vp);
+				if ((vp->v_iflag & VI_DOOMED) != 0) {
+					VI_UNLOCK(vp);
+					vp = NULL;
+				} else
+					VI_UNLOCK(vp);
+			}
+			if (vp != NULL)
+				VN_HOLD(vp);
 			else {
 				if (first) {
 					ZFS_LOG(1, "dying znode detected (zp=%p)", zp);