From: "Huang, Ying" <ying.huang@intel.com>
To: "Verma, Vishal L" <vishal.l.verma@intel.com>
Cc: "david@redhat.com" <david@redhat.com>,
"Hocko, Michal" <mhocko@suse.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"osalvador@suse.de" <osalvador@suse.de>,
"aneesh.kumar@linux.ibm.com" <aneesh.kumar@linux.ibm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
"nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"jmoyer@redhat.com" <jmoyer@redhat.com>,
"Jonathan.Cameron@huawei.com" <Jonathan.Cameron@huawei.com>
Subject: Re: [PATCH v5 2/2] dax/kmem: allow kmem to add memory with memmap_on_memory
Date: Tue, 17 Oct 2023 13:54:50 +0800 [thread overview]
Message-ID: <874jip94k5.fsf@yhuang6-desk2.ccr.corp.intel.com> (raw)
In-Reply-To: <7a29c85bda2543a0f31d575ced3e57eb93063fc3.camel@intel.com> (Vishal L. Verma's message of "Tue, 17 Oct 2023 13:44:27 +0800")
"Verma, Vishal L" <vishal.l.verma@intel.com> writes:
> On Tue, 2023-10-17 at 13:18 +0800, Huang, Ying wrote:
>> "Verma, Vishal L" <vishal.l.verma@intel.com> writes:
>>
>> > On Thu, 2023-10-05 at 14:16 -0700, Dan Williams wrote:
>> > > Vishal Verma wrote:
>> > > >
>> > <..>
>> >
>> > > > +
>> > > > + rc = kstrtobool(buf, &val);
>> > > > + if (rc)
>> > > > + return rc;
>> > >
>> > > Perhaps:
>> > >
>> > > if (dev_dax->memmap_on_memory == val)
>> > > return len;
>> > >
>> > > ...and skip the check below when it is going to be a nop
>> > >
>> > > > +
>> > > > + device_lock(dax_region->dev);
>> > > > + if (!dax_region->dev->driver) {
>> > >
>> > > Is the polarity backwards here? I.e. if the device is already
>> > > attached to
>> > > the kmem driver it is too late to modify memmap_on_memory policy.
>> >
>> > Hm this sounded logical until I tried it. After a reconfigure-
>> > device to
>> > devdax (i.e. detach kmem), I get the -EBUSY if I invert this check.
>>
>> Can you try to unbind the device via sysfs by hand and retry?
>>
> I think what is happening maybe is while kmem gets detached, the device
> goes back to another dax driver (hmem in my tests). So either way, the
> check for if (driver) or if (!driver) won't distinguish between kmem
> vs. something else.
>
> Maybe we just remove this check? Or add an explicit kmem check somehow?
I think it's good to check kmem explicitly here.
--
Best Regards,
Huang, Ying
prev parent reply other threads:[~2023-10-17 5:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-05 18:31 [PATCH v5 0/2] mm: use memmap_on_memory semantics for dax/kmem Vishal Verma
2023-10-05 18:31 ` [PATCH v5 1/2] mm/memory_hotplug: split memmap_on_memory requests across memblocks Vishal Verma
2023-10-05 21:20 ` Dan Williams
2023-10-06 16:46 ` Verma, Vishal L
2023-10-06 12:52 ` David Hildenbrand
2023-10-06 22:01 ` Verma, Vishal L
2023-10-09 15:15 ` David Hildenbrand
2023-10-07 8:55 ` Huang, Ying
2023-10-09 15:04 ` David Hildenbrand
2023-10-12 5:53 ` Verma, Vishal L
2023-10-12 8:40 ` David Hildenbrand
2023-10-16 18:19 ` Verma, Vishal L
2023-10-05 18:31 ` [PATCH v5 2/2] dax/kmem: allow kmem to add memory with memmap_on_memory Vishal Verma
2023-10-05 21:16 ` Dan Williams
2023-10-17 0:31 ` Verma, Vishal L
2023-10-17 5:18 ` Huang, Ying
2023-10-17 5:44 ` Verma, Vishal L
2023-10-17 5:54 ` Huang, Ying [this message]
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