aufs module: modularize

Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/Kconfig

 # SPDX-License-Identifier: GPL-2.0
 config AUFS_FS
-	bool "Aufs (Advanced multi layered unification filesystem) support"
+	tristate "Aufs (Advanced multi layered unification filesystem) support"
 	help
 	Aufs is a stackable unification filesystem such as Unionfs,
 	which unifies several directories and provides a merged single
@@ -72,7 +72,7 @@ endchoice
 
 config AUFS_EXPORT
 	bool "NFS-exportable aufs"
-	depends on EXPORTFS = y
+	depends on EXPORTFS
 	help
 	If you want to export your mounted aufs via NFS, then enable this
 	option. There are several requirements for this configuration.

fs/aufs/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
 include ${srctree}/${src}/magic.mk
+ifeq (${CONFIG_AUFS_FS},m)
+include ${srctree}/${src}/conf.mk
+endif
 -include ${srctree}/${src}/priv_def.mk
 
 # cf. include/linux/kernel.h
 # enable pr_debug
 ccflags-y += -DDEBUG
 # sparse requires the full pathname
+ifdef M
+ccflags-y += -include ${M}/../../include/uapi/linux/aufs_type.h
+else
 ccflags-y += -include ${srctree}/include/uapi/linux/aufs_type.h
+endif
 
 obj-$(CONFIG_AUFS_FS) += aufs.o
 aufs-y := module.o sbinfo.o super.o branch.o xino.o sysaufs.o opts.o \

fs/aufs/conf.mk

+# SPDX-License-Identifier: GPL-2.0
+
+AuConfStr = CONFIG_AUFS_FS=${CONFIG_AUFS_FS}
+
+define AuConf
+ifdef ${1}
+AuConfStr += ${1}=${${1}}
+endif
+endef
+
+AuConfAll = BRANCH_MAX_127 BRANCH_MAX_511 BRANCH_MAX_1023 BRANCH_MAX_32767 \
+	SBILIST \
+	HNOTIFY HFSNOTIFY \
+	EXPORT INO_T_64 \
+	XATTR \
+	FHSM \
+	RDU \
+	DIRREN \
+	SHWH \
+	BR_RAMFS \
+	BR_FUSE POLL \
+	BR_HFSPLUS \
+	BDEV_LOOP \
+	DEBUG MAGIC_SYSRQ
+$(foreach i, ${AuConfAll}, \
+	$(eval $(call AuConf,CONFIG_AUFS_${i})))
+
+AuConfName = ${obj}/conf.str
+${AuConfName}.tmp: FORCE
+	@echo ${AuConfStr} | tr ' ' '\n' | sed -e 's/^/"/' -e 's/$$/\\n"/' > $@
+${AuConfName}: ${AuConfName}.tmp
+	@diff -q $< $@ > /dev/null 2>&1 || { \
+	echo '  GEN    ' $@; \
+	cp -p $< $@; \
+	}
+FORCE:
+clean-files += ${AuConfName} ${AuConfName}.tmp
+${obj}/sysfs.o: ${AuConfName}
+
+-include ${srctree}/${src}/conf_priv.mk

fs/aufs/module.c

@@ -132,6 +132,7 @@ MODULE_AUTHOR("Junjiro R. Okajima <aufs-users@lists.sourceforge.net>");
 MODULE_DESCRIPTION(AUFS_NAME
 	" -- Advanced multi layered unification filesystem");
 MODULE_VERSION(AUFS_VERSION);
+MODULE_ALIAS_FS(AUFS_NAME);
 
 /* this module parameter has no meaning when SYSFS is disabled */
 int sysaufs_brs = 1;

fs/aufs/sysfs.c

@@ -11,7 +11,30 @@
 #include <linux/seq_file.h>
 #include "aufs.h"
 
+#ifdef CONFIG_AUFS_FS_MODULE
+/* this entry violates the "one line per file" policy of sysfs */
+static ssize_t config_show(struct kobject *kobj, struct kobj_attribute *attr,
+			   char *buf)
+{
+	ssize_t err;
+	static char *conf =
+/* this file is generated at compiling */
+#include "conf.str"
+		;
+
+	err = snprintf(buf, PAGE_SIZE, conf);
+	if (unlikely(err >= PAGE_SIZE))
+		err = -EFBIG;
+	return err;
+}
+
+static struct kobj_attribute au_config_attr = __ATTR_RO(config);
+#endif
+
 static struct attribute *au_attr[] = {
+#ifdef CONFIG_AUFS_FS_MODULE
+	&au_config_attr.attr,
+#endif
 	NULL,	/* need to NULL terminate the list of attributes */
 };