DM & udev

DM & udev

[christophe varoqui]

Hello,

what's the rationale behind the enum-style naming of DM in /sys/block ?
a nasty side effect is that /udev names are not the DM name like devfs 
did (/dev/mapper/vg01-vol01), but those dm-0, dm-1, ...

One might insert yet another rule in udev to translate, but I wondered 
if there was a real reason for the dm-* names.

Either way, I can get rid of the mknod code in the multipath tool, and 
let udev react to /sys/blocl/$any-dm-name spawning. Greg if you confirm 
that assertion, I'll submit this patch for the next udev release.

regards,
cvaroqui


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Re: DM & udev

[Greg KH]

On Thu, Feb 05, 2004 at 01:20:27AM +0100, christophe varoqui wrote:
> Hello,
> 
> what's the rationale behind the enum-style naming of DM in /sys/block ?
> a nasty side effect is that /udev names are not the DM name like devfs 
> did (/dev/mapper/vg01-vol01), but those dm-0, dm-1, ...
> 
> One might insert yet another rule in udev to translate, but I wondered 
> if there was a real reason for the dm-* names.
> 
> Either way, I can get rid of the mknod code in the multipath tool, and 
> let udev react to /sys/blocl/$any-dm-name spawning. Greg if you confirm 
> that assertion, I'll submit this patch for the next udev release.

udev should be able to handle dm-* names just fine as long as there is a
'dev' file in the directory for them (which I'm pretty sure there is...)

thanks,

greg k-h


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Re: [dm-devel] Re: DM & udev

[Kevin Corry]

On Thursday 05 February 2004 11:24, Greg KH wrote:
> On Thu, Feb 05, 2004 at 01:20:27AM +0100, christophe varoqui wrote:
> > Hello,
> >
> > what's the rationale behind the enum-style naming of DM in /sys/block ?
> > a nasty side effect is that /udev names are not the DM name like devfs
> > did (/dev/mapper/vg01-vol01), but those dm-0, dm-1, ...
> >
> > One might insert yet another rule in udev to translate, but I wondered
> > if there was a real reason for the dm-* names.
> >
> > Either way, I can get rid of the mknod code in the multipath tool, and
> > let udev react to /sys/blocl/$any-dm-name spawning. Greg if you confirm
> > that assertion, I'll submit this patch for the next udev release.
>
> udev should be able to handle dm-* names just fine as long as there is a
> 'dev' file in the directory for them (which I'm pretty sure there is...)

The dm-* names are due to the separation between the DM core driver and the 
ioctl interface. Only the ioctl interface knows the name of the device given 
by the user. But only the core driver has access to the gendisk entry (and 
hence the sysfs name). So the core assigns the gendisk a simple name based on 
the minor number of the device.

And yes, there's a "dev" file in the dm-* directories, just as with all other 
subdirs in /sys/block/.

-- 
Kevin Corry
kevincorry@sbcglobal.net



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