nfscl: fix delegation recall when the file is not open

Without this patch, if a NFSv4 server recalled a
delegation when the file is not open, the renew
thread would block in the NFS VOP_INACTIVE()
trying to acquire the client state lock that it
already holds.

This patch fixes the problem by delaying the
vrele() call until after the client state
lock is released.

This bug has been in the NFSv4 client for
a long time, but since it only affects
delegation when recalled due to another
client opening the file, it got missed
during previous testing.

Until you have this patch in your client,
you should avoid the use of delegations.

MFC after:	2 weeks

sys/fs/nfsclient/nfs_clstate.c

@@ -156,7 +156,8 @@ static void nfscl_freedeleg(struct nfscldeleghead *, struct nfscldeleg *);
 static int nfscl_errmap(struct nfsrv_descript *, u_int32_t);
 static void nfscl_cleanup_common(struct nfsclclient *, u_int8_t *);
 static int nfscl_recalldeleg(struct nfsclclient *, struct nfsmount *,
-    struct nfscldeleg *, vnode_t, struct ucred *, NFSPROC_T *, int);
+    struct nfscldeleg *, vnode_t, struct ucred *, NFSPROC_T *, int,
+    vnode_t *);
 static void nfscl_freeopenowner(struct nfsclowner *, int);
 static void nfscl_cleandeleg(struct nfscldeleg *);
 static int nfscl_trydelegreturn(struct nfscldeleg *, struct ucred *,
@@ -2562,6 +2563,7 @@ nfscl_renewthread(struct nfsclclient *clp, NFSPROC_T *p)
 	struct nfsclds *dsp;
 	bool retok;
 	struct mount *mp;
+	vnode_t vp;
 
 	cred = newnfs_getcred();
 	NFSLOCKCLSTATE();
@@ -2683,7 +2685,7 @@ nfscl_renewthread(struct nfsclclient *clp, NFSPROC_T *p)
 				NFSUNLOCKCLSTATE();
 				newnfs_copycred(&dp->nfsdl_cred, cred);
 				ret = nfscl_recalldeleg(clp, clp->nfsc_nmp, dp,
-				    NULL, cred, p, 1);
+				    NULL, cred, p, 1, &vp);
 				if (!ret) {
 				    nfscl_cleandeleg(dp);
 				    TAILQ_REMOVE(&clp->nfsc_deleg, dp,
@@ -2694,6 +2696,22 @@ nfscl_renewthread(struct nfsclclient *clp, NFSPROC_T *p)
 				    nfsstatsv1.cldelegates--;
 				}
 				NFSLOCKCLSTATE();
+				/*
+				 * The nfsc_lock must be released before doing
+				 * vrele(), since it might call nfs_inactive().
+				 * For the unlikely case where the vnode failed
+				 * to be acquired by nfscl_recalldeleg(), a
+				 * VOP_RECLAIM() should be in progress and it
+				 * will return the delegation.
+				 */
+				nfsv4_unlock(&clp->nfsc_lock, 0);
+				igotlock = 0;
+				if (vp != NULL) {
+					NFSUNLOCKCLSTATE();
+					vrele(vp);
+					NFSLOCKCLSTATE();
+				}
+				goto tryagain;
 			}
 			dp = ndp;
 		}
@@ -3943,16 +3961,18 @@ nfscl_lockt(vnode_t vp, struct nfsclclient *clp, u_int64_t off,
 static int
 nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
     struct nfscldeleg *dp, vnode_t vp, struct ucred *cred, NFSPROC_T *p,
-    int called_from_renewthread)
+    int called_from_renewthread, vnode_t *vpp)
 {
 	struct nfsclowner *owp, *lowp, *nowp;
 	struct nfsclopen *op, *lop;
 	struct nfscllockowner *lp;
 	struct nfscllock *lckp;
 	struct nfsnode *np;
-	int error = 0, ret, gotvp = 0;
+	int error = 0, ret;
 
 	if (vp == NULL) {
+		KASSERT(vpp != NULL, ("nfscl_recalldeleg: vpp NULL"));
+		*vpp = NULL;
 		/*
 		 * First, get a vnode for the file. This is needed to do RPCs.
 		 */
@@ -3966,7 +3986,7 @@ nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
 			return (0);
 		}
 		vp = NFSTOV(np);
-		gotvp = 1;
+		*vpp = vp;
 	} else {
 		np = VTONFS(vp);
 	}
@@ -3993,8 +4013,6 @@ nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
 		 * return now, so that the dirty buffer will be flushed
 		 * later.
 		 */
-		if (gotvp != 0)
-			vrele(vp);
 		return (ret);
 	}
 
@@ -4018,11 +4036,8 @@ nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
 					    owp, dp, cred, p);
 					if (ret == NFSERR_STALECLIENTID ||
 					    ret == NFSERR_STALEDONTRECOVER ||
-					    ret == NFSERR_BADSESSION) {
+					    ret == NFSERR_BADSESSION)
-						if (gotvp)
-							vrele(vp);
 						return (ret);
-					}
 					if (ret) {
 						nfscl_freeopen(lop, 1);
 						if (!error)
@@ -4050,11 +4065,8 @@ nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
 					nfscl_freeopenowner(owp, 0);
 					if (ret == NFSERR_STALECLIENTID ||
 					    ret == NFSERR_STALEDONTRECOVER ||
-					    ret == NFSERR_BADSESSION) {
+					    ret == NFSERR_BADSESSION)
-						if (gotvp)
-							vrele(vp);
 						return (ret);
-					}
 					if (ret) {
 						nfscl_freeopen(lop, 1);
 						if (!error)
@@ -4075,17 +4087,12 @@ nfscl_recalldeleg(struct nfsclclient *clp, struct nfsmount *nmp,
 			if (ret == NFSERR_STALESTATEID ||
 			    ret == NFSERR_STALEDONTRECOVER ||
 			    ret == NFSERR_STALECLIENTID ||
-			    ret == NFSERR_BADSESSION) {
+			    ret == NFSERR_BADSESSION)
-				if (gotvp)
-					vrele(vp);
 				return (ret);
-			}
 			if (ret && !error)
 				error = ret;
 		}
 	}
-	if (gotvp)
-		vrele(vp);
 	return (error);
 }
 
@@ -4497,7 +4504,7 @@ nfscl_removedeleg(vnode_t vp, NFSPROC_T *p, nfsv4stateid_t *stp)
 			NFSUNLOCKCLSTATE();
 			cred = newnfs_getcred();
 			newnfs_copycred(&dp->nfsdl_cred, cred);
-			(void) nfscl_recalldeleg(clp, nmp, dp, vp, cred, p, 0);
+			nfscl_recalldeleg(clp, nmp, dp, vp, cred, p, 0, NULL);
 			NFSFREECRED(cred);
 			triedrecall = 1;
 			NFSLOCKCLSTATE();
@@ -4596,7 +4603,7 @@ nfscl_renamedeleg(vnode_t fvp, nfsv4stateid_t *fstp, int *gotfdp, vnode_t tvp,
 			NFSUNLOCKCLSTATE();
 			cred = newnfs_getcred();
 			newnfs_copycred(&dp->nfsdl_cred, cred);
-			(void) nfscl_recalldeleg(clp, nmp, dp, fvp, cred, p, 0);
+			nfscl_recalldeleg(clp, nmp, dp, fvp, cred, p, 0, NULL);
 			NFSFREECRED(cred);
 			triedrecall = 1;
 			NFSLOCKCLSTATE();