cifs: add witness mount option and data structs

Add 'witness' mount option to register for witness notifications.

Signed-off-by: Samuel Cabrero <[e-mail]>
Reviewed-by: Aurelien Aptel <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/cifsfs.c

···
 		seq_printf(s, ",multichannel,max_channels=%zu",
 			   tcon->ses->chan_max);
 
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	if (tcon->use_witness)
+		seq_puts(s, ",witness");
+#endif
+
 	return 0;
 }
 

fs/cifs/cifsglob.h

···
 	int remap:2;
 	struct list_head ulist; /* cache update list */
 #endif
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	bool use_witness:1; /* use witness protocol */
+#endif
 };
 
 /*

fs/cifs/connect.c

···
 		return;
 	}
 
+	/* TODO witness unregister */
+
 	list_del_init(&tcon->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
···
 		}
 		tcon->use_resilient = true;
 	}
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	tcon->use_witness = false;
+	if (ctx->witness) {
+		if (ses->server->vals->protocol_id >= SMB30_PROT_ID) {
+			if (tcon->capabilities & SMB2_SHARE_CAP_CLUSTER) {
+				/* TODO witness register */
+				tcon->use_witness = true;
+			} else {
+				/* TODO: try to extend for non-cluster uses (eg multichannel) */
+				cifs_dbg(VFS, "witness requested on mount but no CLUSTER capability on share\n");
+				rc = -EOPNOTSUPP;
+				goto out_fail;
+			}
+		} else {
+			cifs_dbg(VFS, "SMB3 or later required for witness option\n");
+			rc = -EOPNOTSUPP;
+			goto out_fail;
+		}
+	}
+#endif
 
 	/* If the user really knows what they are doing they can override */
 	if (tcon->share_flags & SMB2_SHAREFLAG_NO_CACHING) {
···
 	ctx->sectype = master_tcon->ses->sectype;
 	ctx->sign = master_tcon->ses->sign;
 	ctx->seal = master_tcon->seal;
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	ctx->witness = master_tcon->use_witness;
+#endif
 
 	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
 	if (rc) {

fs/cifs/fs_context.c

···
 	fsparam_flag("modesid", Opt_modesid),
 	fsparam_flag("rootfs", Opt_rootfs),
 	fsparam_flag("compress", Opt_compress),
+	fsparam_flag("witness", Opt_witness),
 
 	/* Mount options which take numeric value */
 	fsparam_u32("backupuid", Opt_backupuid),
···
 	case Opt_cache:
 		if (cifs_parse_cache_flavor(param->string, ctx) != 0)
 			goto cifs_parse_mount_err;
+		break;
+	case Opt_witness:
+#ifndef CONFIG_CIFS_SWN_UPCALL
+		cifs_dbg(VFS, "Witness support needs CONFIG_CIFS_SWN_UPCALL config option\n");
+			goto cifs_parse_mount_err;
+#endif
+		ctx->witness = true;
 		break;
 	case Opt_rootfs:
 #ifdef CONFIG_CIFS_ROOT

fs/cifs/fs_context.h

···
 	Opt_rootfs,
 	Opt_multichannel,
 	Opt_compress,
+	Opt_witness,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid,
···
 	unsigned int max_channels;
 	__u16 compression; /* compression algorithm 0xFFFF default 0=disabled */
 	bool rootfs:1; /* if it's a SMB root file system */
+	bool witness:1; /* use witness protocol */
 
 	char *mount_options;
 };