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From: Rick Macklem <rmacklem@FreeBSD.org>
Date: Wed, 1 May 2013 22:50:45 +0000 (UTC)
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Subject: svn commit: r250162 - head/usr.sbin/nfsd
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Author: rmacklem
Date: Wed May  1 22:50:45 2013
New Revision: 250162
URL: http://svnweb.freebsd.org/changeset/base/250162

Log:
  Document the fact that an NFSv4 mount against a volume on the same host
  can result in a hung NFS server and is not recommended.
  This is a content change.
  
  MFC after:	2 weeks

Modified:
  head/usr.sbin/nfsd/nfsv4.4

Modified: head/usr.sbin/nfsd/nfsv4.4
==============================================================================
--- head/usr.sbin/nfsd/nfsv4.4	Wed May  1 22:47:47 2013	(r250161)
+++ head/usr.sbin/nfsd/nfsv4.4	Wed May  1 22:50:45 2013	(r250162)
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 23, 2012
+.Dd May 1, 2013
 .Dt NFSV4 4
 .Os
 .Sh NAME
@@ -287,6 +287,13 @@ and
 daemons at boot time via the ``nfsuserd_flags'' and ``nfscbd_flags''
 .Xr rc.conf 5
 variables.
+.Pp
+NFSv4 mount(s) against exported volume(s) on the same host are not recommended,
+since this can result in a hung NFS server.
+It occurs when an nfsd thread tries to do an NFSv4 VOP_RECLAIM()/Close RPC
+as part of acquiring a new vnode.
+If all other nfsd threads are blocked waiting for lock(s) held by this nfsd
+thread, then there isn't an nfsd thread to service the Close RPC.
 .Sh FILES
 .Bl -tag -width /var/db/nfs-stablerestart.bak -compact
 .It Pa /var/db/nfs-stablerestart