Re: [PATCH 21/31] 11-dm-mpath.rules: Remember DM_ACTIVATION

From: "Benjamin Marzinski" <bmarzins@redhat.com>
To: Martin Wilck <mwilck@suse.com>
Cc: dm-devel@redhat.com
Subject: Re: [PATCH 21/31] 11-dm-mpath.rules: Remember DM_ACTIVATION
Date: Fri, 15 Sep 2017 15:40:32 -0500	[thread overview]
Message-ID: <20170915204032.GS3145@octiron.msp.redhat.com> (raw)
In-Reply-To: <1505394403.4493.17.camel@suse.com>

On Thu, Sep 14, 2017 at 03:06:43PM +0200, Martin Wilck wrote:
> Hi Ben,
> 
> On Wed, 2017-09-13 at 16:19 -0500, Benjamin Marzinski wrote:
> > On Sun, Sep 03, 2017 at 12:38:50AM +0200, Martin Wilck wrote:
> > > If DM_ACTIVATION is set by the general dm rules, we need to
> > > bring up this device. But if the mpath device is not ready,
> > > that would be dangerous; it could hang or produce lots of IO
> > > errors. So remember this state, and try to activate when the
> > > map becomes usable later.
> > 
> > NAK. See reasons in
> > 
> > [PATCH 20/31] 11-dm-mpath.rules: don't set READY->ACTIVATION
> 
> Sorry for being slow. Re-reading this, I don't understand any more why
> your valid argument against 20/31 invalidates this one as well. 21/31
> affects only the case MPATH_DEVICE_READY!=0, in which case it will add
> another case where DM_ACTIVATION is set.

If we are always setting DM_ACTIVATION when MPATH_DEVICE_READY changes
from zero to non-zero, we don't need to remember that we had to disable
DM_ACTIVATION when the device wasn't ready, and make sure to set it
now, because we are always setting it when we change to a device ready
state... right?

-Ben

> 
> Regards
> Martin
> 
> > 
> > -Ben
> > 
> > > 
> > > Signed-off-by: Martin Wilck <mwilck@suse.com>
> > > ---
> > >  multipath/11-dm-mpath.rules | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/multipath/11-dm-mpath.rules b/multipath/11-dm-
> > > mpath.rules
> > > index 3f47744f..9bfd75f8 100644
> > > --- a/multipath/11-dm-mpath.rules
> > > +++ b/multipath/11-dm-mpath.rules
> > > @@ -4,6 +4,7 @@ ENV{DM_UUID}!="mpath-?*", GOTO="mpath_end"
> > >  
> > >  IMPORT{db}="DM_DISABLE_OTHER_RULES_FLAG_OLD"
> > >  IMPORT{db}="MPATH_DEVICE_READY"
> > > +IMPORT{db}="MPATH_NEEDS_ACTIVATION"
> > >  
> > >  # If this uevent didn't come from dm, don't try to update the
> > >  # device state
> > > @@ -55,6 +56,13 @@ ENV{DM_SUBSYSTEM_UDEV_FLAG0}=="1",
> > > ENV{DM_ACTIVATION}="0"
> > >  # We'd like to avoid this, especially within udev processing.
> > >  ENV{MPATH_DEVICE_READY}=="0", ENV{DM_NOSCAN}="1"
> > >  
> > > +# If DM_ACTIVATION is set, but can't be satisfied, remember it
> > > +# in MPATH_NEEDS_ACTIVATION, and activate at the next opportunity.
> > > +ENV{MPATH_DEVICE_READY}=="0", ENV{DM_ACTIVATION}=="1", \
> > > +	ENV{MPATH_NEEDS_ACTIVATION}="1", ENV{DM_ACTIVATION}="0"
> > > +ENV{MPATH_DEVICE_READY}!="0", ENV{MPATH_NEEDS_ACTIVATION}=="1", \
> > > +	ENV{DM_ACTIVATION}="1", ENV{MPATH_NEEDS_ACTIVATION}=""
> > > +
> > >  # Also skip all foreign rules if no path is available.
> > >  # Remember the original value of DM_DISABLE_OTHER_RULES_FLAG
> > >  # and restore it back once we have at least one path available.
> > > -- 
> > > 2.14.0
> > 
> > 
> 
> -- 
> Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
> HRB 21284 (AG Nürnberg)