[PATCH] Wait and retry mounting root device (revised)

[Daniel Drake]

Retry up to 20 times if mounting the root device fails.  This fixes booting
from usb-storage devices, which no longer make their partitions immediately
available.

This should allow booting from root=/dev/sda1 and root=8:1 style parameters, 
whilst not breaking booting from RAID or initrd :)
I have also cleaned up the mount_block_root() function a bit.

Based on an earlier patch from William Park <opengeometry@xxxxxxxx>
Replaces the existing waiting-10s-before-mounting-root-filesystem.patch patch 
in 2.6.11-rc1-mm1

Signed-off-by: Daniel Drake <dsd@xxxxxxxxxx>
--- linux-2.6.10/init/do_mounts.c.orig	2005-01-16 19:18:57.000000000 +0000
+++ linux-2.6.10/init/do_mounts.c	2005-01-17 01:42:25.000000000 +0000
@@ -6,6 +6,7 @@
 #include <linux/suspend.h>
 #include <linux/root_dev.h>
 #include <linux/security.h>
+#include <linux/delay.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
@@ -261,6 +262,9 @@ static void __init get_fs_names(char *pa
 static int __init do_mount_root(char *name, char *fs, int flags, void *data)
 {
 	int err = sys_mount(name, "/root", fs, flags, data);
+	if (err == -EACCES && (flags | MS_RDONLY) == 0)
+		err = sys_mount(name, "/root", fs, flags | MS_RDONLY, data);
+
 	if (err)
 		return err;
 
@@ -273,38 +277,56 @@ static int __init do_mount_root(char *na
 	return 0;
 }
 
+static int __init mount_root_try_all_fs(char *name, char *fs_names, int flags, void *data)
+{
+	char *p;
+	int err = -EFAULT;
+
+	for (p = fs_names; *p; p += strlen(p)+1) {
+		err = do_mount_root(name, p, flags, root_mount_data);
+		if (err != -EINVAL)
+			break;
+	}
+
+	return err;
+}
+
 void __init mount_block_root(char *name, int flags)
 {
 	char *fs_names = __getname();
-	char *p;
 	char b[BDEVNAME_SIZE];
+	int tryagain = 20;
 
 	get_fs_names(fs_names);
-retry:
-	for (p = fs_names; *p; p += strlen(p)+1) {
-		int err = do_mount_root(name, p, flags, root_mount_data);
-		switch (err) {
-			case 0:
-				goto out;
-			case -EACCES:
-				flags |= MS_RDONLY;
-				goto retry;
-			case -EINVAL:
-				continue;
-		}
-	        /*
-		 * Allow the user to distinguish between failed sys_open
-		 * and bad superblock on root device.
-		 */
-		__bdevname(ROOT_DEV, b);
-		printk("VFS: Cannot open root device \"%s\" or %s\n",
-				root_device_name, b);
-		printk("Please append a correct \"root=\" boot option\n");
 
-		panic("VFS: Unable to mount root fs on %s", b);
+	while (--tryagain) {
+		int err = mount_root_try_all_fs(name, fs_names, flags, root_mount_data);
+		if (err == 0)
+			goto out;
+
+		/*
+		 * The root device may not be ready yet, so we retry a number of times
+		 */
+		printk(KERN_WARNING "VFS: Waiting %dsec for root device...\n",
+		       tryagain);
+		ssleep(1);
+		if (!ROOT_DEV) {
+			ROOT_DEV = name_to_dev_t(saved_root_name);
+			create_dev(name, ROOT_DEV, root_device_name);
+		}
 	}
-	panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
-out:
+
+	/*
+	 * Allow the user to distinguish between failed sys_open
+	 * and bad superblock on root device.
+	 */
+	__bdevname(ROOT_DEV, b);
+	printk(KERN_CRIT "VFS: Cannot open root device \"%s\" or %s\n",
+	       root_device_name, b);
+	printk(KERN_CRIT "Please append a correct \"root=\" boot option\n");
+	panic("VFS: Unable to mount root fs on %s", b);
+
+ out:
 	putname(fs_names);
 }