From 1ab8f0512b19c420fa538e3d691e86cee0b98f4d Mon Sep 17 00:00:00 2001
From: rmacklem <rmacklem@FreeBSD.org>
Date: Sat, 9 Nov 2013 21:24:56 +0000
Subject: [PATCH] Fix an NFSv4.1 client specific case where a forced dismount
 would hang. The hang occurred in nfsv4_setsequence() when it couldn't find an
 available session slot and is fixed by checking for a forced dismount in
 progress and just returning for this case.

MFC after:	1 month
---
 sys/fs/nfs/nfs_commonsubs.c      | 20 ++++++++++++++++----
 sys/fs/nfs/nfs_var.h             |  3 ++-
 sys/fs/nfsclient/nfs_clcomsubs.c |  5 +++--
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/sys/fs/nfs/nfs_commonsubs.c b/sys/fs/nfs/nfs_commonsubs.c
index b60b0ebf986e..0ee06bd1b280 100644
--- a/sys/fs/nfs/nfs_commonsubs.c
+++ b/sys/fs/nfs/nfs_commonsubs.c
@@ -3693,8 +3693,8 @@ nfsv4_seqsess_cacherep(uint32_t slotid, struct nfsslot *slots, struct mbuf *rep)
  * Generate the xdr for an NFSv4.1 Sequence Operation.
  */
 APPLESTATIC void
-nfsv4_setsequence(struct nfsrv_descript *nd, struct nfsclsession *sep,
-    int dont_replycache)
+nfsv4_setsequence(struct nfsmount *nmp, struct nfsrv_descript *nd,
+    struct nfsclsession *sep, int dont_replycache)
 {
 	uint32_t *tl, slotseq = 0;
 	int i, maxslot, slotpos;
@@ -3717,9 +3717,21 @@ nfsv4_setsequence(struct nfsrv_descript *nd, struct nfsclsession *sep,
 			}
 			bitval <<= 1;
 		}
-		if (slotpos == -1)
+		if (slotpos == -1) {
+			/*
+			 * If a forced dismount is in progress, just return.
+			 * This RPC attempt will fail when it calls
+			 * newnfs_request().
+			 */
+			if ((nmp->nm_mountp->mnt_kern_flag & MNTK_UNMOUNTF)
+			    != 0) {
+				mtx_unlock(&sep->nfsess_mtx);
+				return;
+			}
+			/* Wake up once/sec, to check for a forced dismount. */
 			(void)mtx_sleep(&sep->nfsess_slots, &sep->nfsess_mtx,
-			    PZERO, "nfsclseq", 0);
+			    PZERO, "nfsclseq", hz);
+		}
 	} while (slotpos == -1);
 	/* Now, find the highest slot in use. (nfsc_slots is 64bits) */
 	bitval = 1;
diff --git a/sys/fs/nfs/nfs_var.h b/sys/fs/nfs/nfs_var.h
index 1edb8a3f1297..f6a974ec6983 100644
--- a/sys/fs/nfs/nfs_var.h
+++ b/sys/fs/nfs/nfs_var.h
@@ -265,7 +265,8 @@ int nfsv4_getipaddr(struct nfsrv_descript *, struct sockaddr_storage *,
 int nfsv4_seqsession(uint32_t, uint32_t, uint32_t, struct nfsslot *,
     struct mbuf **, uint16_t);
 void nfsv4_seqsess_cacherep(uint32_t, struct nfsslot *, struct mbuf *);
-void nfsv4_setsequence(struct nfsrv_descript *, struct nfsclsession *, int);
+void nfsv4_setsequence(struct nfsmount *, struct nfsrv_descript *,
+    struct nfsclsession *, int);
 void nfsv4_freeslot(struct nfsclsession *, int);
 
 /* nfs_clcomsubs.c */
diff --git a/sys/fs/nfsclient/nfs_clcomsubs.c b/sys/fs/nfsclient/nfs_clcomsubs.c
index 073c6cceea16..52dcaad18262 100644
--- a/sys/fs/nfsclient/nfs_clcomsubs.c
+++ b/sys/fs/nfsclient/nfs_clcomsubs.c
@@ -203,10 +203,11 @@ nfscl_reqstart(struct nfsrv_descript *nd, int procnum, struct nfsmount *nmp,
 			NFSM_BUILD(tl, u_int32_t *, NFSX_UNSIGNED);
 			*tl = txdr_unsigned(NFSV4OP_SEQUENCE);
 			if (sep == NULL)
-				nfsv4_setsequence(nd, NFSMNT_MDSSESSION(nmp),
+				nfsv4_setsequence(nmp, nd,
+				    NFSMNT_MDSSESSION(nmp),
 				    nfs_bigreply[procnum]);
 			else
-				nfsv4_setsequence(nd, sep,
+				nfsv4_setsequence(nmp, nd, sep,
 				    nfs_bigreply[procnum]);
 		}
 		if (nfsv4_opflag[nfsv4_opmap[procnum].op].needscfh > 0) {