From: "Huang, Ying" <ying.huang@intel.com>
To: "Verma, Vishal L" <vishal.l.verma@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>,
"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
"Jonathan.Cameron@huawei.com" <Jonathan.Cameron@huawei.com>,
"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 08:56:33 +0800 [thread overview]
Message-ID: <87il54xmpq.fsf@yhuang6-desk2.ccr.corp.intel.com> (raw)
In-Reply-To: <aac91f0ae8774c521469d518585a499da52912a8.camel@intel.com> (Vishal L. Verma's message of "Tue, 12 Dec 2023 08:40:57 +0800")
"Verma, Vishal L" <vishal.l.verma@intel.com> writes:
> On Tue, 2023-12-12 at 08:30 +0800, Huang, Ying wrote:
>> Vishal Verma <vishal.l.verma@intel.com> writes:
>>
>> > Add a sysfs knob for dax devices to control the memmap_on_memory setting
>> > if the dax device were to be hotplugged as system memory.
>> >
>> > The default memmap_on_memory setting for dax devices originating via
>> > pmem or hmem is set to 'false' - i.e. no memmap_on_memory semantics, to
>> > preserve legacy behavior. For dax devices via CXL, the default is on.
>> > The sysfs control allows the administrator to override the above
>> > defaults if needed.
>> >
>> > Cc: David Hildenbrand <david@redhat.com>
>> > Cc: Dan Williams <dan.j.williams@intel.com>
>> > Cc: Dave Jiang <dave.jiang@intel.com>
>> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
>> > Cc: Huang Ying <ying.huang@intel.com>
>> > Tested-by: Li Zhijian <lizhijian@fujitsu.com>
>> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> > Reviewed-by: David Hildenbrand <david@redhat.com>
>> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
>> > ---
>> > drivers/dax/bus.c | 47 +++++++++++++++++++++++++++++++++
>> > Documentation/ABI/testing/sysfs-bus-dax | 17 ++++++++++++
>> > 2 files changed, 64 insertions(+)
>> >
>> > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
>> > index 1ff1ab5fa105..2871e5188f0d 100644
>> > --- a/drivers/dax/bus.c
>> > +++ b/drivers/dax/bus.c
>> > @@ -1270,6 +1270,52 @@ static ssize_t numa_node_show(struct device *dev,
>> > }
>> > static DEVICE_ATTR_RO(numa_node);
>> >
>> > +static ssize_t memmap_on_memory_show(struct device *dev,
>> > + struct device_attribute *attr, char *buf)
>> > +{
>> > + struct dev_dax *dev_dax = to_dev_dax(dev);
>> > +
>> > + return sprintf(buf, "%d\n", dev_dax->memmap_on_memory);
>> > +}
>> > +
>> > +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?
--
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2023-12-12 0:58 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 [this message]
2023-12-12 1:02 ` Verma, Vishal L
2023-12-12 1:00 ` Dan Williams
2023-12-12 10:05 ` David Hildenbrand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87il54xmpq.fsf@yhuang6-desk2.ccr.corp.intel.com \
--to=ying.huang@intel.com \
--cc=Jonathan.Cameron@huawei.com \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=dave.jiang@intel.com \
--cc=david@redhat.com \
--cc=linux-cxl@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizhijian@fujitsu.com \
--cc=nvdimm@lists.linux.dev \
--cc=vishal.l.verma@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.