NFSD: Track svc_export in nfs4_stid

Add an sc_export field to struct nfs4_stid so that each stateid
records the export under which it was acquired.  The export
reference is taken via exp_get() at stateid creation and released
via exp_put() in nfs4_put_stid().

Open stateids record the export from current_fh->fh_export.
Lock stateids and delegations inherit the export from their
parent open stateid. Layout stateids inherit from their
parent stateid. Directory delegations record the export from
cstate->current_fh.

A subsequent commit uses sc_export to scope state revocation to a
specific export, avoiding the need to walk inode dentry aliases at
revocation time.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4layouts.c

@@ -234,6 +234,8 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
 
 	get_nfs4_file(fp);
 	stp->sc_file = fp;
+	if (parent->sc_export)
+		stp->sc_export = exp_get(parent->sc_export);
 
 	ls = layoutstateid(stp);
 	INIT_LIST_HEAD(&ls->ls_perclnt);

fs/nfsd/nfs4state.c

@@ -1168,6 +1168,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 void
 nfs4_put_stid(struct nfs4_stid *s)
 {
+	struct svc_export *exp = s->sc_export;
 	struct nfs4_file *fp = s->sc_file;
 	struct nfs4_client *clp = s->sc_client;
 
@@ -1183,6 +1184,8 @@ nfs4_put_stid(struct nfs4_stid *s)
 	nfs4_free_cpntf_statelist(clp->net, s);
 	spin_unlock(&clp->cl_lock);
 	s->sc_free(s);
+	if (exp)
+		exp_put(exp);
 	if (fp)
 		put_nfs4_file(fp);
 }
@@ -1763,6 +1766,25 @@ static struct nfs4_stid *find_one_sb_stid(struct nfs4_client *clp,
 	return stid;
 }
 
+/*
+ * Release the export reference an admin-revoked stateid holds,
+ * so the svc_export (and its vfsmount) is not pinned until the
+ * client issues FREE_STATEID.  sc_export is no longer consulted
+ * once SC_STATUS_ADMIN_REVOKED is set.
+ */
+static void drop_stid_export(struct nfs4_client *clp,
+			     struct nfs4_stid *stid)
+{
+	struct svc_export *exp;
+
+	spin_lock(&clp->cl_lock);
+	exp = stid->sc_export;
+	stid->sc_export = NULL;
+	spin_unlock(&clp->cl_lock);
+	if (exp)
+		exp_put(exp);
+}
+
 static void revoke_ol_stid(struct nfs4_client *clp,
 			   struct nfs4_ol_stateid *stp)
 {
@@ -1787,6 +1809,7 @@ static void revoke_ol_stid(struct nfs4_client *clp,
 			}
 		}
 		release_all_access(stp);
+		drop_stid_export(clp, stid);
 	} else
 		spin_unlock(&clp->cl_lock);
 }
@@ -1820,9 +1843,10 @@ static void revoke_one_stid(struct nfsd_net *nn, struct nfs4_client *clp,
 		if (!unhash_delegation_locked(dp, SC_STATUS_ADMIN_REVOKED))
 			dp = NULL;
 		spin_unlock(&nn->deleg_lock);
-		if (dp)
+		if (dp) {
 			revoke_delegation(dp);
-		else
+			drop_stid_export(clp, stid);
+		} else
 			nfs4_put_stid(stid);
 		break;
 	case SC_TYPE_LAYOUT:
@@ -1833,6 +1857,7 @@ static void revoke_one_stid(struct nfsd_net *nn, struct nfs4_client *clp,
 		}
 		spin_unlock(&clp->cl_lock);
 		nfsd4_close_layout(layoutstateid(stid));
+		drop_stid_export(clp, stid);
 		break;
 	}
 }
@@ -6172,6 +6197,8 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	dp = alloc_init_deleg(clp, fp, odstate, dl_type);
 	if (!dp)
 		goto out_delegees;
+	if (stp->st_stid.sc_export)
+		dp->dl_stid.sc_export = exp_get(stp->st_stid.sc_export);
 
 	fl = nfs4_alloc_init_lease(dp);
 	if (!fl)
@@ -6505,8 +6532,11 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
 			goto out;
 		}
 
-		if (!open->op_stp)
+		if (!open->op_stp) {
 			new_stp = true;
+			stp->st_stid.sc_export =
+				exp_get(current_fh->fh_export);
+		}
 	}
 
 	/*
@@ -8202,6 +8232,9 @@ init_lock_stateid(struct nfs4_ol_stateid *stp, struct nfs4_lockowner *lo,
 	stp->st_stateowner = nfs4_get_stateowner(&lo->lo_owner);
 	get_nfs4_file(fp);
 	stp->st_stid.sc_file = fp;
+	if (open_stp->st_stid.sc_export)
+		stp->st_stid.sc_export =
+			exp_get(open_stp->st_stid.sc_export);
 	stp->st_access_bmap = 0;
 	stp->st_deny_bmap = open_stp->st_deny_bmap;
 	stp->st_openstp = open_stp;
@@ -9532,6 +9565,9 @@ nfsd_get_dir_deleg(struct nfsd4_compound_state *cstate,
 	dp = alloc_init_deleg(clp, fp, NULL, NFS4_OPEN_DELEGATE_READ);
 	if (!dp)
 		goto out_delegees;
+	if (cstate->current_fh.fh_export)
+		dp->dl_stid.sc_export =
+			exp_get(cstate->current_fh.fh_export);
 
 	fl = nfs4_alloc_init_lease(dp);
 	if (!fl)

fs/nfsd/state.h

@@ -145,6 +145,7 @@ struct nfs4_stid {
 	spinlock_t		sc_lock;
 	struct nfs4_client	*sc_client;
 	struct nfs4_file	*sc_file;
+	struct svc_export	*sc_export;
 	void			(*sc_free)(struct nfs4_stid *);
 };