From: "Verma, Vishal L" <vishal.l.verma@intel.com>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: "david@redhat.com" <david@redhat.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"Jonathan.Cameron@huawei.com" <Jonathan.Cameron@huawei.com>,
"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
"lizhijian@fujitsu.com" <lizhijian@fujitsu.com>
Subject: Re: [PATCH v3 2/2] dax: add a sysfs knob to control memmap_on_memory behavior
Date: Tue, 12 Dec 2023 01:02:35 +0000 [thread overview]
Message-ID: <4b61641bdeea6aeeef0e5d76d2f6c7212dcb4ed7.camel@intel.com> (raw)
In-Reply-To: <87il54xmpq.fsf@yhuang6-desk2.ccr.corp.intel.com>
On Tue, 2023-12-12 at 08:56 +0800, Huang, Ying wrote:
> "Verma, Vishal L" <vishal.l.verma@intel.com> writes:
>
> > On Tue, 2023-12-12 at 08:30 +0800, Huang, Ying wrote:
> > >
> > > > +
> > > > +static ssize_t memmap_on_memory_store(struct device *dev,
> > > > + struct device_attribute *attr,
> > > > + const char *buf, size_t len)
> > > > +{
> > > > + struct device_driver *drv = dev->driver;
> > > > + struct dev_dax *dev_dax = to_dev_dax(dev);
> > > > + struct dax_region *dax_region = dev_dax->region;
> > > > + struct dax_device_driver *dax_drv = to_dax_drv(drv);
> > > > + ssize_t rc;
> > > > + bool val;
> > > > +
> > > > + rc = kstrtobool(buf, &val);
> > > > + if (rc)
> > > > + return rc;
> > > > +
> > > > + if (dev_dax->memmap_on_memory == val)
> > > > + return len;
> > > > +
> > > > + device_lock(dax_region->dev);
> > > > + if (!dax_region->dev->driver) {
> > > > + device_unlock(dax_region->dev);
> > > > + return -ENXIO;
> > > > + }
> > >
> > > I think that it should be OK to write to "memmap_on_memory" if no driver
> > > is bound to the device. We just need to avoid to write to it when kmem
> > > driver is bound.
> >
> > Oh this is just a check on the region driver, not for a dax driver
> > being bound to the device. It's the same as what things like
> > align_store(), size_store() etc. do for dax device reconfiguration.
>
> Sorry, I misunderstood it.
>
> > That said, it might be okay to remove this check, as this operation
> > doesn't change any attributes of the dax region (the other interfaces I
> > mentioned above can affect regions, so we want to lock the region
> > device). If removing the check, we'd drop the region lock acquisition
> > as well.
>
> This sounds good to me.
>
> And is it necessary to check driver type with device_lock()? Can driver
> be changed between checking and lock?
>
Oh, good point, the type check should happen with the device lock held.
I'll make that change.
next prev parent reply other threads:[~2023-12-12 1:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-11 22:52 [PATCH v3 0/2] Add DAX ABI for memmap_on_memory Vishal Verma
2023-12-11 22:52 ` [PATCH v3 1/2] Documentatiion/ABI: Add ABI documentation for sys-bus-dax Vishal Verma
2023-12-11 22:52 ` [PATCH v3 2/2] dax: add a sysfs knob to control memmap_on_memory behavior Vishal Verma
2023-12-12 0:30 ` Huang, Ying
2023-12-12 0:40 ` Verma, Vishal L
2023-12-12 0:56 ` Huang, Ying
2023-12-12 1:02 ` Verma, Vishal L [this message]
2023-12-12 1:00 ` Dan Williams
2023-12-12 10:05 ` David Hildenbrand
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