linux-kernel - Re: revamp vmem_altmap / dev

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Message-ID: <20180108215059.GB1732@dhcp22.suse.cz>
Date:   Mon, 8 Jan 2018 22:50:59 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Christoph Hellwig <hch@....de>, linux-nvdimm@...ts.01.org,
        X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: revamp vmem_altmap / dev_pagemap handling V3

On Mon 08-01-18 13:27:13, Dan Williams wrote:
> On Mon, Jan 8, 2018 at 12:25 PM, Michal Hocko <mhocko@...nel.org> wrote:
> > On Mon 08-01-18 11:44:02, Dan Williams wrote:
> >> On Mon, Jan 8, 2018 at 3:26 AM, Christoph Hellwig <hch@....de> wrote:
> >> > Any chance to get this fully reviewed and picked up before the
> >> > end of the merge window?
> >>
> >> I'm fine carrying these through the nvdimm tree, but I'd need an ack
> >> from the mm folks for all the code touches related to arch_add_memory.
> >
> > I am sorry to be slow here but I am out of time right now - yeah having
> > a lot of fun kaiser time. I didn't get to look at these patches at all
> > yet but the changelog suggests that you want to remove vmem_altmap.
> > I've had plans to (ab)use this for self hosted struct pages for memory
> > hotplug http://lkml.kernel.org/r/20170801124111.28881-1-mhocko@kernel.org
> > That work is stalled though because it is buggy and I was too busy to
> > finish that work. Anyway, if you believe that removing vmem_altmap is a
> > good step in general I will find another way. I wasn't really happy how
> > the whole thing is grafted to the memory hotplug and (ab)used it only
> > because it was handy and ready for reuse.
> 
> You misread, these are keeping vmem_altmap and cleaning up the usage
> to pass the vmem_altmap pointer through all paths rather than the
> tricky radix lookup we were doing previously.

Good to hear. I really didn't get further than reading through email
subjects and for some reason I misread those.

> > Anyway if you need a review of mm parts from me, you will have to wait
> > some more. If this requires some priority then go ahead and merge
> > it. Times are just too crazy right now.
> 
> Since you were planning on reusing vmem_altmap I think these patches
> make your job easier. I don't see the risk in merging these, we've
> squeezed out a few bugs and all the nvdimm unit tests are passing.

Good, then really do not wait for me if this aims to get merged soon.

> > Sorry about that.
> 
> No worries, quite a few of us are in that same boat.

Yeah the boat is quite large I suspect...

-- 
Michal Hocko
SUSE Labs