init: wait for asynchronously scanned block devices
Some buses (e.g. USB and MMC) do their scanning of devices in the
background, causing a race between them and prepare_namespace(). In order
to be able to use these buses without an initrd, we now wait for the device
specified in root= to actually show up.
If the device never shows up than we will hang in an infinite loop. In
order to not mess with setups that reboot on panic, the feature must be
turned on via the command line option "rootwait".
[bunk@stusta.de: root_wait can become static]
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a0362d5..a571495 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1504,6 +1504,10 @@
rootfstype= [KNL] Set root filesystem type
+ rootwait [KNL] Wait (indefinitely) for root device to show up.
+ Useful for devices that are detected asynchronously
+ (e.g. USB and MMC devices).
+
rw [KNL] Mount root device read-write on boot
S [KNL] Run init in single mode