[PATCH 2/2] init/do_mounts.c: replace polling for root device with devtmpfs_wait_for_dev

[PATCH 2/2] init/do_mounts.c: replace polling for root device with devtmpfs_wait_for_dev

[tom.leiming]

From: Ming Lei <tom.leiming@gmail.com>

This patch removes the polling for root device if rootwait parameter is
passed to kernel and CONFIG_DEVTMPFS is enabled. This way can lead to
a faster boot, especially booting from some asynchronous block device
(such as usb mass storage, mmc card, ...)

The patch has been verified in beagle board(mmc card as root device).

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 init/do_mounts.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index aa56007..fcf3844 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -364,6 +364,7 @@ void __init mount_root(void)
 void __init prepare_namespace(void)
 {
 	int is_floppy;
+	int ret;
 
 	if (root_delay) {
 		printk(KERN_INFO "Waiting %dsec before mounting root device...\n",
@@ -371,6 +372,7 @@ void __init prepare_namespace(void)
 		ssleep(root_delay);
 	}
 
+#ifndef CONFIG_DEVTMPFS
 	/*
 	 * wait for the known devices to complete their probing
 	 *
@@ -379,6 +381,7 @@ void __init prepare_namespace(void)
 	 * for the touchpad of a laptop to initialize.
 	 */
 	wait_for_device_probe();
+#endif
 
 	md_run_setup();
 
@@ -397,6 +400,7 @@ void __init prepare_namespace(void)
 	if (initrd_load())
 		goto out;
 
+#ifndef CONFIG_DEVTMPFS
 	/* wait for any asynchronous scanning to complete */
 	if ((ROOT_DEV == 0) && root_wait) {
 		printk(KERN_INFO "Waiting for root device %s...\n",
@@ -406,6 +410,18 @@ void __init prepare_namespace(void)
 			msleep(100);
 		async_synchronize_full();
 	}
+#else
+	/*wait for root device, and expire if 120 seconds elapse*/
+	if (!strncmp(saved_root_name, "/dev/", 5)) {
+		ret = devtmpfs_wait_for_dev(saved_root_name, 120);
+		printk(KERN_INFO "wait for %s based on devtmpfs:%d\n",
+			saved_root_name, ret);
+	}
+
+	ROOT_DEV = name_to_dev_t(saved_root_name);
+	if (!ROOT_DEV)
+		printk(KERN_ERR "Root device %s not found!\n", saved_root_name);
+#endif
 
 	is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
 
-- 
1.6.0.GIT

Re: [PATCH 2/2] init/do_mounts.c: replace polling for root device with devtmpfs_wait_for_dev

[Christoph Hellwig]

On Wed, Jun 10, 2009 at 10:28:17PM +0800, tom.leiming@gmail.com wrote:
> From: Ming Lei <tom.leiming@gmail.com>
> 
> This patch removes the polling for root device if rootwait parameter is
> passed to kernel and CONFIG_DEVTMPFS is enabled. This way can lead to
> a faster boot, especially booting from some asynchronous block device
> (such as usb mass storage, mmc card, ...)
> 
> The patch has been verified in beagle board(mmc card as root device).

What tree did you find with devtmpfs in it?  It was pretty clearly
rejected when it came up.

Re: [PATCH 2/2] init/do_mounts.c: replace polling for root device with devtmpfs_wait_for_dev

[Alan Cox]

> What tree did you find with devtmpfs in it?  It was pretty clearly
> rejected when it came up.

For some reason its still in -next

Re: [PATCH 2/2] init/do_mounts.c: replace polling for root device with devtmpfs_wait_for_dev

[Greg KH]

On Wed, Jun 10, 2009 at 04:37:12PM +0100, Alan Cox wrote:
> > What tree did you find with devtmpfs in it?  It was pretty clearly
> > rejected when it came up.
> 
> For some reason its still in -next

Yes, it's still in -next, sorry, I just realized this, as it's in my
driver-core tree.  We will be resubmitting it for .32 later on.
Discussion will happen after the .31 merge window is over.

thanks,

greg k-h