Re: [RFC PATCH] Multi-threaded device probing

Greg KH
2006-07-26T16:50:34Z

On Wed, Jul 26, 2006 at 10:42:36AM -0600, Matthew Wilcox wrote:
> On Wed, Jul 26, 2006 at 09:16:47AM -0700, Greg KH wrote:
> > > I still think we need a method of renaming block devices, but haven't
> > > looked into it in enough detail yet.
> >
> > That could get "interesting"...
> >
> > But now that we all are using /dev/disk/ and it has persistant device
> > names for block devices, I really don't think it's that big of a deal.
>
> Actually, that's exactly why it's a big deal. The kernel spits out
> messages like:
>
> printk(KERN_DEBUG "%s: Mode Sense: %02x %02x %02x %02x\n",
> diskname, buffer[0], buffer[1], buffer[2], buffer[3]);
>
> where diskname is something like sda. Now the user has to figure out
> what sda means in terms of /dev/disk/ and in terms of scsi h:c:t:l and
> in terms of which sticky label is on which drive. If we let userspace
> change the gendev's disk_name, that printk can be meaningful to the user
> in at least one of those senses.

No, this comes up all the time. Userspace has at least 3 different
mappings to /dev/sda in /dev/disk right now. Which one do you want the
kernel to use?:

$ tree /dev/disk/ | grep sda1
| |-- scsi-SATA_Maxtor_7L250S0_L59FRPQH_L59FRPQH-part1 -> ../../sda1
| |-- boot -> ../../sda1
`-- 9c0ef40c-6de9-46f6-ac79-32296c667cf1 -> ../../sda1

Userspace should be doing the reverse mapping if it wants to, the kernel
should not care about this at all.

thanks,

greg k-h