Re: rootdelay

[David Welton <davidnwelton@gmail.com>]

> Ok, I updated to 2.6.11.8, and indeed it does have problems that
> weren't there before - although in my case it can't mount the root
> partition because it's not quite ready yet.  In part, it seems to be
> caused by the fact that the USB start up sequence introduces a new
> thread that delays the scsi_host_scan by 5 seconds, which is long
> enough to cause problems.  I added some code to wait for not only the
> disk name to be online, but the partition, but even that doesn't seem
> to be quite enough.
 
> Is there anyplace generic that could be hooked that will report when a
> device is actually online and ready to run?  Perhaps I was just lucky
> in the past with add_disk :-/

I "fixed" the problem by not letting storage_probe in storage/usb.c
finish until the scan_thread is done.  That doesn't seem elegant -
perhaps there is a better place to put the
wait_for_completion(&us->scsi_scan_done) call so that the scanning
thread can go off and do its thing, but will still be waited on where
it counts?

I am including a copy of the patch inline, as well as attaching it.  I
suspect that gmail will mangle the inline version some...

Thankyou,
Dave

diff -uprN -X dontdiff linux-2.6.11.8/drivers/block/genhd.c
linux-wakeup/drivers/block/genhd.c
--- linux-2.6.11.8/drivers/block/genhd.c	2005-04-30 03:27:21.000000000 +0200
+++ linux-wakeup/drivers/block/genhd.c	2005-05-02 19:22:13.000000000 +0200
@@ -14,9 +14,14 @@
 #include <linux/slab.h>
 #include <linux/kmod.h>
 #include <linux/kobj_map.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
 
 #define MAX_PROBE_HASH 255	/* random */
 
+DECLARE_WAIT_QUEUE_HEAD(disk_wait_h);
+EXPORT_SYMBOL(disk_wait_h);
+
 static struct subsystem block_subsys;
 
 static DECLARE_MUTEX(block_subsys_sem);
@@ -58,6 +63,49 @@ int get_blkdev_list(char *p)
 }
 #endif
 
+/*
+ * Returns an array of all the block device names and partitions.
+ */
+
+char **get_blkdevs(void)
+{
+	int i = 0;
+	int n = 0;
+	int len = 0;
+	struct list_head *p;
+	char **names = NULL;
+	struct gendisk *sgp;
+	char buf[BDEVNAME_SIZE];
+
+	down_read(&block_subsys.rwsem);
+	
+	list_for_each(p, &block_subsys.kset.list) {
+		len ++;
+	}
+	
+	names = kmalloc(sizeof(char *) * len + 1, GFP_KERNEL);
+
+	list_for_each(p, &block_subsys.kset.list) {
+		sgp = list_entry(p, struct gendisk, kobj.entry);
+		names[i] = kmalloc(strlen(disk_name(sgp, 0, buf)), GFP_KERNEL);
+		strcpy(names[i], disk_name(sgp, 0, buf));
+		
+		for (n = 0; n < sgp->minors - 1; n++) {
+			struct hd_struct *hd = sgp->part[n];
+			if (hd && hd->nr_sects) {
+				names[i] = kmalloc(strlen(disk_name(sgp, n+1, buf)), GFP_KERNEL);
+				strcpy(names[i], disk_name(sgp, n+1, buf));
+				i ++;
+			}
+		}
+	}
+	names[i] = NULL;
+	up_read(&block_subsys.rwsem);
+	return names;
+}
+
+EXPORT_SYMBOL(get_blkdevs);
+
 int register_blkdev(unsigned int major, const char *name)
 {
 	struct blk_major_name **n, *p;
@@ -192,6 +240,11 @@ void add_disk(struct gendisk *disk)
 			    disk->minors, NULL, exact_match, exact_lock, disk);
 	register_disk(disk);
 	blk_register_queue(disk);
+
+	/* Wake up queue in init/main.c. */
+	printk("Waking up queue on %s\n",
+	       disk->disk_name);
+	wake_up_interruptible(&disk_wait_h);
 }
 
 EXPORT_SYMBOL(add_disk);
diff -uprN -X dontdiff linux-2.6.11.8/drivers/usb/storage/usb.c
linux-wakeup/drivers/usb/storage/usb.c
--- linux-2.6.11.8/drivers/usb/storage/usb.c	2005-04-30 03:25:25.000000000 +0200
+++ linux-wakeup/drivers/usb/storage/usb.c	2005-05-03 12:15:29.000000000 +0200
@@ -1009,6 +1009,7 @@ static int storage_probe(struct usb_inte
 
 	/* Start up the thread for delayed SCSI-device scanning */
 	result = kernel_thread(usb_stor_scan_thread, us, CLONE_VM);
+
 	if (result < 0) {
 		printk(KERN_WARNING USB_STORAGE 
 		       "Unable to start the device-scanning thread\n");
@@ -1016,6 +1017,8 @@ static int storage_probe(struct usb_inte
 		goto BadDevice;
 	}
 
+	wait_for_completion(&us->scsi_scan_done);
+
 	return 0;
 
 	/* We come here if there are any problems */
diff -uprN -X dontdiff linux-2.6.11.8/include/linux/genhd.h
linux-wakeup/include/linux/genhd.h
--- linux-2.6.11.8/include/linux/genhd.h	2005-04-30 03:24:13.000000000 +0200
+++ linux-wakeup/include/linux/genhd.h	2005-05-02 12:04:50.000000000 +0200
@@ -16,6 +16,10 @@
 #include <linux/smp.h>
 #include <linux/string.h>
 #include <linux/fs.h>
+#include <linux/wait.h>
+
+/* Wait queue to wait on disks coming online. */
+extern wait_queue_head_t disk_wait_h;
 
 enum {
 /* These three have identical behaviour; use the second one if DOS FDISK gets
@@ -232,6 +236,7 @@ extern struct gendisk *get_gendisk(dev_t
 
 extern void set_device_ro(struct block_device *bdev, int flag);
 extern void set_disk_ro(struct gendisk *disk, int flag);
+extern char **get_blkdevs(void);
 
 /* drivers/char/random.c */
 extern void add_disk_randomness(struct gendisk *disk);
diff -uprN -X dontdiff linux-2.6.11.8/init/do_mounts.c
linux-wakeup/init/do_mounts.c
--- linux-2.6.11.8/init/do_mounts.c	2005-04-30 03:26:32.000000000 +0200
+++ linux-wakeup/init/do_mounts.c	2005-05-02 19:22:51.000000000 +0200
@@ -12,6 +12,8 @@
 #include <linux/nfs_fs_sb.h>
 #include <linux/nfs_mount.h>
 
+#include <linux/genhd.h>
+
 #include "do_mounts.h"
 
 extern int get_filesystem_list(char * buf);
@@ -360,8 +362,35 @@ void __init change_floppy(char *fmt, ...
 }
 #endif
 
+/*
+ * match_root_name - Returns 1 if the root_device_name appears amongst
+ * the list of block devices, 0 otherwise.
+ */
+
+static int __init match_root_name(void) {
+	char **names = NULL;
+	int i = 0;
+	int match = 0;
+	
+	names = get_blkdevs();
+	while (names[i] != NULL) {
+		if (match == 0 && strncmp(names[i],
+					  root_device_name,
+					  strlen(root_device_name)) == 0) {
+			match = 1;
+			printk("Block device %s matches %s root_device_name, continuing\n",
+			       names[i], root_device_name);
+		}
+		kfree(names[i]);
+		i ++;
+	}
+	kfree(names);
+	return match;
+}
+
 void __init mount_root(void)
 {
+
 #ifdef CONFIG_ROOT_NFS
 	if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
 		if (mount_nfs_root())
@@ -383,6 +412,14 @@ void __init mount_root(void)
 			change_floppy("root floppy");
 	}
 #endif
+
+	/* Here, we wait for the root device to show up, or if it's
+	 * already there, we just go on. */
+	while (!match_root_name()) {
+		printk("Waiting for root device to wake us up\n");
+		interruptible_sleep_on(&disk_wait_h);
+	}
+ 
 	create_dev("/dev/root", ROOT_DEV, root_device_name);
 	mount_block_root("/dev/root", root_mountflags);
 }
diff -uprN -X dontdiff linux-2.6.11.8/init/main.c linux-wakeup/init/main.c
--- linux-2.6.11.8/init/main.c	2005-04-30 03:24:18.000000000 +0200
+++ linux-wakeup/init/main.c	2005-05-02 12:04:50.000000000 +0200
@@ -47,6 +47,11 @@
 #include <linux/mempolicy.h>
 #include <linux/key.h>
 
+#include <linux/genhd.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+
+
 #include <asm/io.h>
 #include <asm/bugs.h>
 #include <asm/setup.h>

diff -uprN -X dontdiff linux-2.6.11.8/drivers/block/genhd.c linux-wakeup/drivers/block/genhd.c
--- linux-2.6.11.8/drivers/block/genhd.c	2005-04-30 03:27:21.000000000 +0200
+++ linux-wakeup/drivers/block/genhd.c	2005-05-02 19:22:13.000000000 +0200
@@ -14,9 +14,14 @@
 #include <linux/slab.h>
 #include <linux/kmod.h>
 #include <linux/kobj_map.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
 
 #define MAX_PROBE_HASH 255	/* random */
 
+DECLARE_WAIT_QUEUE_HEAD(disk_wait_h);
+EXPORT_SYMBOL(disk_wait_h);
+
 static struct subsystem block_subsys;
 
 static DECLARE_MUTEX(block_subsys_sem);
@@ -58,6 +63,49 @@ int get_blkdev_list(char *p)
 }
 #endif
 
+/*
+ * Returns an array of all the block device names and partitions.
+ */
+
+char **get_blkdevs(void)
+{
+	int i = 0;
+	int n = 0;
+	int len = 0;
+	struct list_head *p;
+	char **names = NULL;
+	struct gendisk *sgp;
+	char buf[BDEVNAME_SIZE];
+
+	down_read(&block_subsys.rwsem);
+	
+	list_for_each(p, &block_subsys.kset.list) {
+		len ++;
+	}
+	
+	names = kmalloc(sizeof(char *) * len + 1, GFP_KERNEL);
+
+	list_for_each(p, &block_subsys.kset.list) {
+		sgp = list_entry(p, struct gendisk, kobj.entry);
+		names[i] = kmalloc(strlen(disk_name(sgp, 0, buf)), GFP_KERNEL);
+		strcpy(names[i], disk_name(sgp, 0, buf));
+		
+		for (n = 0; n < sgp->minors - 1; n++) {
+			struct hd_struct *hd = sgp->part[n];
+			if (hd && hd->nr_sects) {
+				names[i] = kmalloc(strlen(disk_name(sgp, n+1, buf)), GFP_KERNEL);
+				strcpy(names[i], disk_name(sgp, n+1, buf));
+				i ++;
+			}
+		}
+	}
+	names[i] = NULL;
+	up_read(&block_subsys.rwsem);
+	return names;
+}
+
+EXPORT_SYMBOL(get_blkdevs);
+
 int register_blkdev(unsigned int major, const char *name)
 {
 	struct blk_major_name **n, *p;
@@ -192,6 +240,11 @@ void add_disk(struct gendisk *disk)
 			    disk->minors, NULL, exact_match, exact_lock, disk);
 	register_disk(disk);
 	blk_register_queue(disk);
+
+	/* Wake up queue in init/main.c. */
+	printk("Waking up queue on %s\n",
+	       disk->disk_name);
+	wake_up_interruptible(&disk_wait_h);
 }
 
 EXPORT_SYMBOL(add_disk);
diff -uprN -X dontdiff linux-2.6.11.8/drivers/usb/storage/usb.c linux-wakeup/drivers/usb/storage/usb.c
--- linux-2.6.11.8/drivers/usb/storage/usb.c	2005-04-30 03:25:25.000000000 +0200
+++ linux-wakeup/drivers/usb/storage/usb.c	2005-05-03 12:15:29.000000000 +0200
@@ -1009,6 +1009,7 @@ static int storage_probe(struct usb_inte
 
 	/* Start up the thread for delayed SCSI-device scanning */
 	result = kernel_thread(usb_stor_scan_thread, us, CLONE_VM);
+
 	if (result < 0) {
 		printk(KERN_WARNING USB_STORAGE 
 		       "Unable to start the device-scanning thread\n");
@@ -1016,6 +1017,8 @@ static int storage_probe(struct usb_inte
 		goto BadDevice;
 	}
 
+	wait_for_completion(&us->scsi_scan_done);
+
 	return 0;
 
 	/* We come here if there are any problems */
diff -uprN -X dontdiff linux-2.6.11.8/include/linux/genhd.h linux-wakeup/include/linux/genhd.h
--- linux-2.6.11.8/include/linux/genhd.h	2005-04-30 03:24:13.000000000 +0200
+++ linux-wakeup/include/linux/genhd.h	2005-05-02 12:04:50.000000000 +0200
@@ -16,6 +16,10 @@
 #include <linux/smp.h>
 #include <linux/string.h>
 #include <linux/fs.h>
+#include <linux/wait.h>
+
+/* Wait queue to wait on disks coming online. */
+extern wait_queue_head_t disk_wait_h;
 
 enum {
 /* These three have identical behaviour; use the second one if DOS FDISK gets
@@ -232,6 +236,7 @@ extern struct gendisk *get_gendisk(dev_t
 
 extern void set_device_ro(struct block_device *bdev, int flag);
 extern void set_disk_ro(struct gendisk *disk, int flag);
+extern char **get_blkdevs(void);
 
 /* drivers/char/random.c */
 extern void add_disk_randomness(struct gendisk *disk);
diff -uprN -X dontdiff linux-2.6.11.8/init/do_mounts.c linux-wakeup/init/do_mounts.c
--- linux-2.6.11.8/init/do_mounts.c	2005-04-30 03:26:32.000000000 +0200
+++ linux-wakeup/init/do_mounts.c	2005-05-02 19:22:51.000000000 +0200
@@ -12,6 +12,8 @@
 #include <linux/nfs_fs_sb.h>
 #include <linux/nfs_mount.h>
 
+#include <linux/genhd.h>
+
 #include "do_mounts.h"
 
 extern int get_filesystem_list(char * buf);
@@ -360,8 +362,35 @@ void __init change_floppy(char *fmt, ...
 }
 #endif
 
+/*
+ * match_root_name - Returns 1 if the root_device_name appears amongst
+ * the list of block devices, 0 otherwise.
+ */
+
+static int __init match_root_name(void) {
+	char **names = NULL;
+	int i = 0;
+	int match = 0;
+	
+	names = get_blkdevs();
+	while (names[i] != NULL) {
+		if (match == 0 && strncmp(names[i],
+					  root_device_name,
+					  strlen(root_device_name)) == 0) {
+			match = 1;
+			printk("Block device %s matches %s root_device_name, continuing\n",
+			       names[i], root_device_name);
+		}
+		kfree(names[i]);
+		i ++;
+	}
+	kfree(names);
+	return match;
+}
+
 void __init mount_root(void)
 {
+
 #ifdef CONFIG_ROOT_NFS
 	if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
 		if (mount_nfs_root())
@@ -383,6 +412,14 @@ void __init mount_root(void)
 			change_floppy("root floppy");
 	}
 #endif
+
+	/* Here, we wait for the root device to show up, or if it's
+	 * already there, we just go on. */
+	while (!match_root_name()) {
+		printk("Waiting for root device to wake us up\n");
+		interruptible_sleep_on(&disk_wait_h);
+	}
+ 
 	create_dev("/dev/root", ROOT_DEV, root_device_name);
 	mount_block_root("/dev/root", root_mountflags);
 }
diff -uprN -X dontdiff linux-2.6.11.8/init/main.c linux-wakeup/init/main.c
--- linux-2.6.11.8/init/main.c	2005-04-30 03:24:18.000000000 +0200
+++ linux-wakeup/init/main.c	2005-05-02 12:04:50.000000000 +0200
@@ -47,6 +47,11 @@
 #include <linux/mempolicy.h>
 #include <linux/key.h>
 
+#include <linux/genhd.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+
+
 #include <asm/io.h>
 #include <asm/bugs.h>
 #include <asm/setup.h>