[SMB3] Add parsing for new mount option controlling persistent handles

"nopersistenthandles" and "persistenthandles" mount options added.
The former will not request persistent handles on open even when
SMB3 negotiated and Continuous Availability share.  The latter
will request persistent handles (as long as server notes the
capability in protocol negotiation) even if share is not Continuous
Availability share.
Signed-off-by: Steve French <steve.french@primarydata.com>
Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>

fs/cifs/cifsglob.h

@@ -493,7 +493,9 @@ struct smb_vol {
 	bool mfsymlinks:1; /* use Minshall+French Symlinks */
 	bool multiuser:1;
 	bool rwpidforward:1; /* pid forward for read/write operations */
-	bool nosharesock;
+	bool nosharesock:1;
+	bool persistent:1;
+	bool nopersistent:1;
 	unsigned int rsize;
 	unsigned int wsize;
 	bool sockopt_tcp_nodelay:1;

fs/cifs/connect.c

@@ -87,6 +87,7 @@ enum {
 	Opt_sign, Opt_seal, Opt_noac,
 	Opt_fsc, Opt_mfsymlinks,
 	Opt_multiuser, Opt_sloppy, Opt_nosharesock,
+	Opt_persistent, Opt_nopersistent,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid, Opt_backupgid, Opt_uid,
@@ -169,6 +170,8 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_multiuser, "multiuser" },
 	{ Opt_sloppy, "sloppy" },
 	{ Opt_nosharesock, "nosharesock" },
+	{ Opt_persistent, "persistenthandles"},
+	{ Opt_nopersistent, "nopersistenthandles"},
 
 	{ Opt_backupuid, "backupuid=%s" },
 	{ Opt_backupgid, "backupgid=%s" },
@@ -1497,6 +1500,22 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 		case Opt_nosharesock:
 			vol->nosharesock = true;
 			break;
+		case Opt_nopersistent:
+			vol->nopersistent = true;
+			if (vol->persistent) {
+				cifs_dbg(VFS,
+				  "persistenthandles mount options conflict\n");
+				goto cifs_parse_mount_err;
+			}
+			break;
+		case Opt_persistent:
+			vol->persistent = true;
+			if (vol->nopersistent) {
+				cifs_dbg(VFS,
+				  "persistenthandles mount options conflict\n");
+				goto cifs_parse_mount_err;
+			}
+			break;
 
 		/* Numeric Values */
 		case Opt_backupuid: