nfscl: Fix another deadlock related to the NFSv4 clientID lock

Without this patch, it is possible to hang the NFSv4 client,
when a rename/remove is being done on a file where the client
holds a delegation, if pNFS is being used.  For a delegation
to be returned, dirty data blocks must be flushed to the NFSv4
server.  When pNFS is in use, a shared lock on the clientID
must be acquired while doing a write to the DS(s).
However, if rename/remove is doing the delegation return
an exclusive lock will be acquired on the clientID, preventing
the write to the DS(s) from acquiring a shared lock on the clientID.

This patch stops rename/remove from doing a delegation return
if pNFS is enabled.  Since doing delegation return in the same
compound as rename/remove is only an optimization, not doing
so should not cause problems.

This problem was detected during a recent NFSv4 interoperability
testing event held by the IETF working group.

MFC after:	1 week

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c
index 6be06b556de8..9a7a879fffd3 100644
--- a/sys/fs/nfsclient/nfs_clstate.c
+++ b/sys/fs/nfsclient/nfs_clstate.c
@@ -4607,6 +4607,8 @@ nfscl_removedeleg(vnode_t vp, NFSPROC_T *p, nfsv4stateid_t *stp)
 	int igotlock = 0, triedrecall = 0, needsrecall, retcnt = 0, islept;
 
 	nmp = VFSTONFS(vp->v_mount);
+	if (NFSHASPNFS(nmp))
+		return (retcnt);
 	NFSLOCKMNT(nmp);
 	if ((nmp->nm_privflag & NFSMNTP_DELEGISSUED) == 0) {
 		NFSUNLOCKMNT(nmp);
@@ -4712,6 +4714,8 @@ nfscl_renamedeleg(vnode_t fvp, nfsv4stateid_t *fstp, int *gotfdp, vnode_t tvp,
 	nmp = VFSTONFS(fvp->v_mount);
 	*gotfdp = 0;
 	*gottdp = 0;
+	if (NFSHASPNFS(nmp))
+		return (retcnt);
 	NFSLOCKCLSTATE();
 	/*
 	 * Loop around waiting for: