"[PATCH] devfs: switch over ubd to ->devfs_name" breaks ubd/sysfs

DISCUSSION Oleg Drokin 2 participants 5 messages Apr 21, 2003 User-mode Linux (UML)

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Oleg Drokin

author

2003-04-21 11:43 UTC #0 lore raw

Hello!

The "[PATCH] devfs: switch over ubd to ->devfs_name" patch that was included into 2.5.68, have broken UML's ubd/sysfs interaction.
Sysfs is very upset when something tries to register several devices with same name, so I was forced to use following patch.
If this is wrong, then please explain to me why, and suggest the correct way of handling this situation.

Thank you.

Bye,
Oleg

===== arch/um/drivers/ubd_kern.c 1.32 vs edited =====

arch/um/drivers/ubd_kern.c +2 -2

@@ -494,7 +494,7 @@
 	disk->first_minor = unit << UBD_SHIFT;
 	disk->fops = &ubd_blops;
 	set_capacity(disk, size / 512);
-	sprintf(disk->disk_name, "ubd");
+	sprintf(disk->disk_name, "ubd%d", unit);
 	sprintf(disk->devfs_name, "ubd/disc%d", unit);
 
 	disk->private_data = &ubd_dev[unit];

@@ -527,7 +527,7 @@
 	if(err) 
 		return(err);
  
-	if(fake_major)
+	if(fake_major != MAJOR_NR)
 		ubd_new_disk(fake_major, dev->size, n, 
 			     &fake_gendisk[n]);

Christoph Hellwig

2003-04-21 12:06 UTC #1 lore raw

Quoted 8 lines · Oleg Drokin

Hello!
The "[PATCH] devfs: switch over ubd to ->devfs_name" patch that was included into 2.5.68, have broken UML's ubd/sysfs interaction.
Sysfs is very upset when something tries to register several devices with same name, so I was forced to use following patch.
If this is wrong, then please explain to me why, and suggest the correct way of handling this situation.

Patch looks okay to me. But I'm still a bit confused about all that fake_major stuff. Someone care to explain it?

Oleg Drokin

author

2003-04-21 12:18 UTC #2 lore raw

Hello!

Quoted 8 lines · Christoph Hellwig

Quoted 6 lines
The "[PATCH] devfs: switch over ubd to ->devfs_name" patch that was included into 2.5.68, have broken UML's ubd/sysfs interaction.
Sysfs is very upset when something tries to register several devices with same name, so I was forced to use following patch.
If this is wrong, then please explain to me why, and suggest the correct way of handling this situation.
Patch looks okay to me. But I'm still a bit confused about all that fake_major stuff. Someone care to explain it?

fake major is easy, it allows you to register ubd device on two majors. This is useful e.g. for installing distros inside of UML. Distro installers are tend to look for IDE disk on major 3, for example. Then if you boot with ubd=3, installer will find the disk ;)

Actually the patch consits of two parts, as there might be more than one ubd device, we need to name them differently.

Actually I just see that if one enables fake major stuff, the sysfs will still be upset, as names for both UBD_MAJOR and fake_major would be the same.

So perhaps fillowing patch should be used.

Bye,
Oleg

===== arch/um/drivers/ubd_kern.c 1.32 vs edited =====

arch/um/drivers/ubd_kern.c +8 -3

@@ -494,8 +494,13 @@
 	disk->first_minor = unit << UBD_SHIFT;
 	disk->fops = &ubd_blops;
 	set_capacity(disk, size / 512);
-	sprintf(disk->disk_name, "ubd");
-	sprintf(disk->devfs_name, "ubd/disc%d", unit);
+	if ( major == MAJOR_NR ) {
+		sprintf(disk->disk_name, "ubd%d", unit);
+		sprintf(disk->devfs_name, "ubd/disc%d", unit);
+	} else {
+		sprintf(disk->disk_name, "ubd_fake%d", unit);
+		sprintf(disk->devfs_name, "ubd_fake/disc%d", unit);
+	}
 
 	disk->private_data = &ubd_dev[unit];
 	disk->queue = &ubd_queue;

@@ -527,7 +532,7 @@
 	if(err) 
 		return(err);
  
-	if(fake_major)
+	if(fake_major != MAJOR_NR)
 		ubd_new_disk(fake_major, dev->size, n, 
 			     &fake_gendisk[n]);

Christoph Hellwig

2003-04-21 12:22 UTC #3 lore raw

Quoted 4 lines · Oleg Drokin

fake major is easy, it allows you to register ubd device on two majors. This is useful e.g. for installing distros inside of UML. Distro installers are tend to look for IDE disk on major 3, for example. Then if you boot with ubd=3, installer will find the disk ;)

Not that I would argue in favour of using devfs, but to make this fake major stuff useful with devfs you'd have to use the devfs entries of the faked devices. So instead of the ubd_fake devfs names you'd better add a string boot option that'll get set into ->devfs_name for those.

Oleg Drokin

author

2003-04-21 12:27 UTC #4 lore raw

Hello!

Quoted 8 lines · Christoph Hellwig

Quoted 4 lines · Oleg Drokin
fake major is easy, it allows you to register ubd device on two majors. This is useful e.g. for installing distros inside of UML. Distro installers are tend to look for IDE disk on major 3, for example. Then if you boot with ubd=3, installer will find the disk ;)
Not that I would argue in favour of using devfs, but to make this fake major stuff useful with devfs you'd have to use the devfs entries of the faked devices. So instead of the ubd_fake devfs names you'd

There is separate option for this. Though it should be fixed, it seems.

But mind you, installers I've seen do not use devfs.

Quoted 2 lines

better add a string boot option that'll get set into ->devfs_name for those.

There is. It is called "fakeide" ;)

This one should be fixed it seems.

Bye,
Oleg