Commit cc1ed754 authored by Pierre Ossman's avatar Pierre Ossman Committed by Linus Torvalds
Browse files

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: default avatarPierre Ossman <drzeus@drzeus.cx>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a19542e

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -1504,6 +1504,10 @@ and is between 256 and 4096 characters. It is defined in the file 


	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

init/do_mounts.c

+22 −2
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ int __initdata rd_doload; /* 1 = load RAM disk, 0 = don't load */ 
int root_mountflags = MS_RDONLY | MS_SILENT;

char * __initdata root_device_name;

static char __initdata saved_root_name[64];

static int __initdata root_wait;



dev_t ROOT_DEV;
@@ -216,6 +217,16 @@ static int __init root_dev_setup(char *line) 


__setup("root=", root_dev_setup);



static int __init rootwait_setup(char *str)

{

	if (*str)

		return 0;

	root_wait = 1;

	return 1;

}



__setup("rootwait", rootwait_setup);



static char * __initdata root_mount_data;

static int __init root_data_setup(char *str)

{
@@ -438,11 +449,20 @@ void __init prepare_namespace(void) 
			root_device_name += 5;

	}



	is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;



	if (initrd_load())

		goto out;



	/* wait for any asynchronous scanning to complete */

	if ((ROOT_DEV == 0) && root_wait) {

		printk(KERN_INFO "Waiting for root device %s...\n",

			saved_root_name);

		while (driver_probe_done() != 0 ||

			(ROOT_DEV = name_to_dev_t(saved_root_name)) == 0)

			msleep(100);

	}



	is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;



	if (is_floppy && rd_doload && rd_load_disk(0))

		ROOT_DEV = Root_RAM0;

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