iomap: build the block based code conditionally

Only build the block based iomap code if CONFIG_BLOCK is set.  Currently
that is always the case, but it will change soon.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-29-hch@lst.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

fs/Kconfig

@@ -15,11 +15,11 @@ config VALIDATE_FS_PARSER
 	  Enable this to perform validation of the parameter description for a
 	  filesystem when it is registered.
 
-if BLOCK
-
 config FS_IOMAP
 	bool
 
+if BLOCK
+
 source "fs/ext2/Kconfig"
 source "fs/ext4/Kconfig"
 source "fs/jbd2/Kconfig"

fs/iomap/Makefile

@@ -9,9 +9,9 @@ ccflags-y += -I $(srctree)/$(src)		# needed for trace events
 obj-$(CONFIG_FS_IOMAP)		+= iomap.o
 
 iomap-y				+= trace.o \
-				   buffered-io.o \
+				   iter.o
+iomap-$(CONFIG_BLOCK)		+= buffered-io.o \
 				   direct-io.o \
 				   fiemap.o \
-				   iter.o \
 				   seek.o
 iomap-$(CONFIG_SWAP)		+= swapfile.o