rd: support XIP

Support direct_access XIP method with brd.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 8be67cd..b6d230b 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -357,6 +357,16 @@
 	  The default value is 4096 kilobytes. Only change this if you know
 	  what you are doing.
 
+config BLK_DEV_XIP
+	bool "Support XIP filesystems on RAM block device"
+	depends on BLK_DEV_RAM
+	default n
+	help
+	  Support XIP filesystems (such as ext2 with XIP support on) on
+	  top of block ram device. This will slightly enlarge the kernel, and
+	  will prevent RAM block device backing store memory from being
+	  allocated from highmem (only a problem for highmem systems).
+
 config CDROM_PKTCDVD
 	tristate "Packet writing on CD/DVD media"
 	depends on !UML