block: move CONFIG_BLOCK guard to top Makefile

Every object under block/ depends on CONFIG_BLOCK.

Move the guard to the top Makefile since there is no point to
descend into block/ if CONFIG_BLOCK=n.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210927140000.866249-5-masahiroy@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Makefile

@@ -1115,7 +1115,8 @@ export MODORDER := $(extmod_prefix)modules.order
 export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
 
 ifeq ($(KBUILD_EXTMOD),)
-core-y		+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
+core-y			+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/
+core-$(CONFIG_BLOCK)	+= block/
 
 vmlinux-dirs	:= $(patsubst %/,%,$(filter %/, \
 		     $(core-y) $(core-m) $(drivers-y) $(drivers-m) \

block/Makefile

@@ -3,7 +3,7 @@
 # Makefile for the kernel block layer
 #
 
-obj-$(CONFIG_BLOCK) := bdev.o fops.o bio.o elevator.o blk-core.o blk-sysfs.o \
+obj-y		:= bdev.o fops.o bio.o elevator.o blk-core.o blk-sysfs.o \
 			blk-flush.o blk-settings.o blk-ioc.o blk-map.o \
 			blk-exec.o blk-merge.o blk-timeout.o \
 			blk-lib.o blk-mq.o blk-mq-tag.o blk-stat.o \