linux-kernel - Re: [v4 2/2] device-dax: "Hotremove" persistent memory that is used like normal RAM

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Message-ID: <CA+CK2bB3G_tO04M1eXPdm4b=OojD6QpYkW51YArj6z44RhQo+g@mail.gmail.com>
Date:   Thu, 2 May 2019 12:47:52 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     James Morris <jmorris@...ei.org>, Sasha Levin <sashal@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Keith Busch <keith.busch@...el.com>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Yaowei Bai <baiyaowei@...s.chinamobile.com>,
        Takashi Iwai <tiwai@...e.de>,
        Jérôme Glisse <jglisse@...hat.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [v4 2/2] device-dax: "Hotremove" persistent memory that is used
 like normal RAM

> Currently the kmem driver can be built as a module, and I don't see a
> need to drop that flexibility. What about wrapping these core
> routines:
>
>     unlock_device_hotplug
>     __remove_memory
>     walk_memory_range
>     lock_device_hotplug
>
> ...into a common exported (gpl) helper like:
>
>     int try_remove_memory(int nid, struct resource *res)
>
> Because as far as I can see there's nothing device-dax specific about
> this "try remove iff offline" functionality outside of looking up the
> related 'struct resource'. The check_devdax_mem_offlined_cb callback
> can be made generic if the callback argument is the resource pointer.

Makes sense, I will do both things that you suggested.

Thank you,
Pasha