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

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Message-ID: <20190502173419.GA3048@sasha-vm>
Date:   Thu, 2 May 2019 13:34:19 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        akpm@...ux-foundation.org, mhocko@...e.com,
        dave.hansen@...ux.intel.com, dan.j.williams@...el.com,
        keith.busch@...el.com, vishal.l.verma@...el.com,
        dave.jiang@...el.com, zwisler@...nel.org, thomas.lendacky@....com,
        ying.huang@...el.com, fengguang.wu@...el.com, bp@...e.de,
        bhelgaas@...gle.com, baiyaowei@...s.chinamobile.com, tiwai@...e.de,
        jglisse@...hat.com, david@...hat.com
Subject: Re: [v4 2/2] device-dax: "Hotremove" persistent memory that is used
 like normal RAM

On Wed, May 01, 2019 at 03:18:46PM -0400, Pavel Tatashin wrote:
>It is now allowed to use persistent memory like a regular RAM, but
>currently there is no way to remove this memory until machine is
>rebooted.
>
>This work expands the functionality to also allows hotremoving
>previously hotplugged persistent memory, and recover the device for use
>for other purposes.
>
>To hotremove persistent memory, the management software must first
>offline all memory blocks of dax region, and than unbind it from
>device-dax/kmem driver. So, operations should look like this:
>
>echo offline > echo offline > /sys/devices/system/memory/memoryN/state

This looks wrong :)

--
Thanks,
Sasha