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

Demi Marie Obenour <[email protected]> Thu, 16 Nov 2023 20:47:22 -0500
Newsgroups	gmane.linux.lvm.general
Message-ID	<ZVbGObxAvSsYqvvo@itl-email>
On Thu, Nov 16, 2023 at 02:37:13PM +0100, Zdenek Kabelac wrote:
> Dne 15. 11. 23 v 20:12 David Teigland napsal(a):
> > On Wed, Nov 15, 2023 at 07:36:57PM +0800, Heming Zhao wrote:
> > >  From the lvm2 code, above description is wrong. By default, system/devices is
> > > disabled status. Because lvm.conf option "use_devicesfile = 0" by default.
> > > under "use_devicesfile = 0", any pvcreate/vgcreate/lvmdevices/vgimportdevices
> > > won't generate/create system/devices file.
> > > If my watching is correct, part discussion of this thread may invalid.
> > The lvm default is use_devicesfile=1, as shown in this commit:
> > 
> > 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?

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).
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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