Re: wedge like devices and newfs

[Adam Hamsik <haaaad%gmail.com@localhost>]

Hi,
On May,Friday 29 2009, at 11:57 AM, Manuel Bouyer wrote:

> On Fri, May 29, 2009 at 11:09:59AM +0200, Adam Hamsik wrote:
> > Hi folks,
> >
> > During my work on LVM and ZFS I have found that for historical  
> > reasons I
> > need to
> > provide disklables on Logical volumes aka zvols on ZFS. I have found
> > that problem
> > is mostly in newfs because it uses DIOCGDINFO to get info about  
> > disks.
>
> If DIOCGDINFO fails, newfs (and other tools using getdiskinfo())  
> will use
> DIOCGWEDGEINFO.  Maybe having zvols should handle DIOCGWEDGEINFO ?
Yes but DIOCGWEDGEINFO is used only to get name of parent device on  
which
DIOCGDINFO is later called. Everything which was received from  
WEDGEINFO ioctl
was later zeroed and replaced by information from CGDINFO call. Zvols  
and lvm
disk devices supports DIOCGDISKINFO and DIOCGWEDGEINFO. Point of my  
patch is
add real support for WEDGEINFO ioctl to getdiskinfo() and not add it  
to disk
devices.

> > I
> > have written
> > patch against newfs and kernel disk drivers which changes this
> > behaviour. With my patch
> > newfs uses DIOCGDISKINFO and DIOCGWEDGEINFO ioctls to get information
> > about disk/volume
> > size.
> > DIOCGDISKINFO is proplib based ioctl which returns dictionary
> > defined in disk.h with
> > disk and disk geometry info. DIOCGWEDGEINFO is ioctl for wedge like
> > devices(Logical volumes,
> > zvols, dks), other disk devices should still support old disklabel
> > ioctls.
>
> Why is a new ioctl needed ? I can't see what it does which DIOCGDINFO
> and DIOCGWEDGEINFO aren't already doing.

It is not new ioctl, it was implemented for wd and ld disks for some  
time.
Even other disk devices created device properties, but they haven't used
disk_ioctl handler to handle it. DISKINFO ioctl is needed to get info
about disk geometry(size of disk blocks etc.. see disk.h Disk  
information
dictionary), WEDGEINFO is later used to get information about  
partition size,
its offset etc.

Regards

Adam.