Re: discuss about commit 3b0f9ce: filter-mpath: get wwids from sysfs vpd_pg83

On Thu, Nov 16, 2023 at 08:47:22PM -0500, Demi Marie Obenour wrote:
> > > commit 6c22392a3f903d6c086f7cc94978bdf8b072da6e
> > > Author: David Teigland <[email protected]>
> > > Date:   Tue Mar 16 09:52:13 2021 -0500
> > > 
> > >      config: change default use_devicesfile to 1
> > > 
> > > diff --git a/lib/config/defaults.h b/lib/config/defaults.h
> > > index 66eece53aa33..a7a2a06df654 100644
> > > --- a/lib/config/defaults.h
> > > +++ b/lib/config/defaults.h
> > > @@ -322,7 +322,7 @@
> > >   #define DEFAULT_MD_COMPONENT_CHECKS "auto"
> > > -#define DEFAULT_USE_DEVICES_FILE 0
> > > +#define DEFAULT_USE_DEVICES_FILE 1
> > >   #define DEFAULT_DEVICES_FILE "system.devices"
> > > 
> > > 
> > > Later commits that removed DEFAULT_USE_DEVICES_FILE, and tried to replace
> > > it with a configure option, was a failed attempt at building that lvm
> > > source for RHEL8.  It's caused no end of problems and I plan to revert it
> > > and restore define DEFAULT_USE_DEVICES_FILE 1.
> > 
> > 
> > There is no problem with configuring DEFAULT_USE_DEVICES_FILE with
> > 'configure --with-default-use-devices-file= 0/1' and thus no need to change
> > anything here.
> > 
> > Current upstream has set this default value as 0  (in configure.ac)
> > 
> > RHEL builds use this setting as 1.  (Possibly even Fedora nowadays).
> > 
> > The major problem with turning this  to 1 is the distribution must be
> > 'ready' with such relatively invasive change as it changes also requirements
> > on how the boot image is created  (devicesfile must be copied to ramdisk).
> > 
> > So Suse  may try to set this setting  to 1  and see what all breaks.
> > 
> > 
> > Zdenek
> 
> Does this mean that distributions *should* set this to 1 and update
> their installers?

Yes, the devices file is intended to be a default feature of lvm since the
commit above.

> This would have saved Qubes OS a security bulletin (LVM was scanning
> VM-controlled block devices) and might make LVM faster (since it would
> no longer need to scan every device on the system).

These are both advantages of using it.

Dave