raid: make RAID autodetect default a KConfig option

RAID autodetect has the side effect of requiring synchronisation
of all device drivers, which can make the boot several seconds longer
(I've measured 7 on one of my laptops).... even for systems that don't
have RAID setup for the root filesystem (the only FS where this matters).

This patch makes the default for autodetect a config option; either way
the user can always override via the kernel command line.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: NeilBrown <neilb@suse.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 07d92c11b5d8..8e72c916535f 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -30,6 +30,20 @@ config BLK_DEV_MD
 
           If unsure, say N.
 
+config MD_AUTODETECT
+        bool "Autodetect RAID arrays during kernel boot"
+        depends on BLK_DEV_MD
+        default y
+        ---help---
+          If you say Y here, then the kernel will try to autodetect raid
+          arrays as part of its boot process. 
+
+          If you don't use raid and say Y, this autodetection can cause 
+          a several-second delay in the boot time due to various
+          synchronisation steps that are part of this step.
+
+          If unsure, say Y.
+
 config MD_LINEAR
         tristate "Linear (append) mode"
         depends on BLK_DEV_MD