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Subject: Re: [PATCH 5/5] dax: "Hotplug" persistent memory for use like normal
 RAM
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Michal Hocko <mhocko@suse.com>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        Takashi Iwai <tiwai@suse.de>,
        Ross Zwisler <zwisler@kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>,
        Fengguang Wu <fengguang.wu@intel.com>,
        Yaowei Bai <baiyaowei@cmss.chinamobile.com>,
        "Huang, Ying" <ying.huang@intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Borislav Petkov <bp@suse.de>
References: <20190124231441.37A4A305@viggo.jf.intel.com>
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From:   Brice Goglin <Brice.Goglin@inria.fr>
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To:     Dave Hansen <dave.hansen@intel.com>
Message-ID: <a3bfe739-228e-26fe-90f7-4a4f8ceb3a9a@inria.fr>
Date:   Wed, 13 Feb 2019 09:12:14 +0100
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Le 13/02/2019 à 01:30, Dan Williams a écrit :
> On Tue, Feb 12, 2019 at 11:59 AM Brice Goglin <Brice.Goglin@inria.fr> wrote:
>> # ndctl disable-region all
>> # ndctl zero-labels all
>> # ndctl enable-region region0
>> # ndctl create-namespace -r region0 -t pmem -m devdax
>> {
>>   "dev":"namespace0.0",
>>   "mode":"devdax",
>>   "map":"dev",
>>   "size":"1488.37 GiB (1598.13 GB)",
>>   "uuid":"ad0096d7-3fe7-4402-b529-ad64ed0bf789",
>>   "daxregion":{
>>     "id":0,
>>     "size":"1488.37 GiB (1598.13 GB)",
>>     "align":2097152,
>>     "devices":[
>>       {
>>         "chardev":"dax0.0",
>>         "size":"1488.37 GiB (1598.13 GB)"
>>       }
>>     ]
>>   },
>>   "align":2097152
>> }
>> # ndctl enable-namespace namespace0.0
>> # echo -n dax0.0 > /sys/bus/dax/drivers/device_dax/remove_id
>> <hang>
>>
>> I tried with and without dax_pmem_compat loaded, but it doesn't help.
> I think this is due to:
>
>   a9f1ffdb6a20 device-dax: Auto-bind device after successful new_id
>
> I missed that this path is also called in the remove_id path. Thanks
> for the bug report! I'll get this fixed up.


Now that remove_id is fixed, things fails later in Dave's procedure:

# echo -n dax0.0 > /sys/bus/dax/drivers/device_dax/remove_id
# echo -n dax0.0 > /sys/bus/dax/drivers/device_dax/unbind
# echo -n dax0.0 > /sys/bus/dax/drivers/kmem/new_id
# echo -n dax0.0 > /sys/bus/dax/drivers/kmem/bind
-bash: echo: write error: No such device

(And nothing seems to have changed in /sys/devices/system/memory/*/state)

Brice