netdev - Re: [dm-devel] [PATCH v5] fault-injection: introduce kvmalloc fallback options

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Date:   Thu, 26 Apr 2018 11:05:13 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>
cc:     Michal Hocko <mhocko@...nel.org>,
        David Rientjes <rientjes@...gle.com>, dm-devel@...hat.com,
        eric.dumazet@...il.com, mst@...hat.com, netdev@...r.kernel.org,
        jasowang@...hat.com, Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        linux-mm@...ck.org, edumazet@...gle.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        virtualization@...ts.linux-foundation.org,
        David Miller <davem@...emloft.net>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [dm-devel] [PATCH v5] fault-injection: introduce kvmalloc fallback
 options



On Thu, 26 Apr 2018, James Bottomley wrote:

> On Thu, 2018-04-26 at 10:28 -0400, Mikulas Patocka wrote:
> > 
> > On Thu, 26 Apr 2018, Michal Hocko wrote:
> > 
> > > On Wed 25-04-18 18:42:57, Mikulas Patocka wrote:
> > > > 
> > > > 
> > > > On Wed, 25 Apr 2018, James Bottomley wrote:
> > > [...]
> > > > > Kconfig proliferation, conversely, is a bit of a nightmare from
> > both
> > > > > the user and the tester's point of view, so we're trying to
> > avoid it
> > > > > unless absolutely necessary.
> > > > > 
> > > > > James
> > > > 
> > > > I already offered that we don't need to introduce a new kernel
> > option and 
> > > > we can bind this feature to any other kernel option, that is
> > enabled in 
> > > > the debug kernel, for example CONFIG_DEBUG_SG. Michal said no and
> > he said 
> > > > that he wants a new kernel option instead.
> > > 
> > > Just for the record. I didn't say I _want_ a config option. Do not
> > > misinterpret my words. I've said that a config option would be
> > > acceptable if there is no way to deliver the functionality via
> > kernel
> > > package automatically. You haven't provided any argument that would
> > > explain why the kernel package cannot add a boot option. Maybe
> > there are
> > > some but I do not see them right now.
> > 
> > AFAIK Grub doesn't load per-kernel options from a per-kernel file.
> > Even if we hacked grub scripts to add this option, other
> > distributions won't.
> 
> Perhaps find out beforehand instead of insisting on an approach without
> knowing.  On openSUSE the grub config is built from the files in
> /etc/grub.d/ so any package can add a kernel option (and various
> conditions around activating it) simply by adding a new file.

And then, different versions of the debug kernel will clash when 
attempting to create the same file.

And what about other distributions? What about people who the RHEL kernel 
from source with "make"?

The problem with this approach that you are trying to bother more and more 
people with this little silly feature.

> The config files are quite sophisticated, so you can add what looks to 
> be a new kernel, but is really an existing kernel with different options 
> this way.
> 
> James

Mikulas