Add SMB2.02 dialect support

This patch enables optional for original SMB2 (SMB2.02) dialect
by specifying vers=2.0 on mount.
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -178,6 +178,7 @@ struct smb_rqst {
 
 enum smb_version {
 	Smb_1 = 1,
+	Smb_20,
 	Smb_21,
 	Smb_30,
 };

fs/cifs/connect.c

@@ -274,6 +274,7 @@ static const match_table_t cifs_cacheflavor_tokens = {
 
 static const match_table_t cifs_smb_version_tokens = {
 	{ Smb_1, SMB1_VERSION_STRING },
+	{ Smb_20, SMB20_VERSION_STRING},
 	{ Smb_21, SMB21_VERSION_STRING },
 	{ Smb_30, SMB30_VERSION_STRING },
 };
@@ -1074,6 +1075,10 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol)
 		vol->vals = &smb1_values;
 		break;
 #ifdef CONFIG_CIFS_SMB2
+	case Smb_20:
+		vol->ops = &smb21_operations; /* currently identical with 2.1 */
+		vol->vals = &smb20_values;
+		break;
 	case Smb_21:
 		vol->ops = &smb21_operations;
 		vol->vals = &smb21_values;

fs/cifs/smb2ops.c

@@ -625,6 +625,23 @@ struct smb_version_operations smb21_operations = {
 	.new_lease_key = smb2_new_lease_key,
 };
 
+struct smb_version_values smb20_values = {
+	.version_string = SMB20_VERSION_STRING,
+	.protocol_id = SMB20_PROT_ID,
+	.req_capabilities = 0, /* MBZ */
+	.large_lock_type = 0,
+	.exclusive_lock_type = SMB2_LOCKFLAG_EXCLUSIVE_LOCK,
+	.shared_lock_type = SMB2_LOCKFLAG_SHARED_LOCK,
+	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
+	.header_size = sizeof(struct smb2_hdr),
+	.max_header_size = MAX_SMB2_HDR_SIZE,
+	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.lock_cmd = SMB2_LOCK,
+	.cap_unix = 0,
+	.cap_nt_find = SMB2_NT_FIND,
+	.cap_large_files = SMB2_LARGE_FILES,
+};
+
 struct smb_version_values smb21_values = {
 	.version_string = SMB21_VERSION_STRING,
 	.protocol_id = SMB21_PROT_ID,