linux-kernel - Re: [PATCH v4 22/28] cxl/region/extent: Expose region extent information in sysfs

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Message-ID: <20241021103752.00002741@Huawei.com>
Date: Mon, 21 Oct 2024 10:37:52 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ira Weiny <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>, "Navneet
 Singh" <navneet.singh@...el.com>, Jonathan Corbet <corbet@....net>, "Andrew
 Morton" <akpm@...ux-foundation.org>, Dan Williams <dan.j.williams@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>, "Alison Schofield"
	<alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>,
	<linux-btrfs@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <nvdimm@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 22/28] cxl/region/extent: Expose region extent
 information in sysfs

On Fri, 18 Oct 2024 13:26:14 -0500
Ira Weiny <ira.weiny@...el.com> wrote:

> Jonathan Cameron wrote:
> > On Mon, 07 Oct 2024 18:16:28 -0500
> > ira.weiny@...el.com wrote:
> >   
> > > From: Navneet Singh <navneet.singh@...el.com>
> > > 
> > > Extent information can be helpful to the user to coordinate memory usage
> > > with the external orchestrator and FM.
> > > 
> > > Expose the details of region extents by creating the following
> > > sysfs entries.
> > > 
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/length
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/tag
> > > 
> > > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > > Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> > > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > >   
> > Trivial comments inline.
> > 
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>  
> 
> Thanks!
> 
> >   
> > > ---
> > > Changes:
> > > [djiang: Split sysfs docs up]
> > > [iweiny: Adjust sysfs docs dates]
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-cxl | 32 ++++++++++++++++++
> > >  drivers/cxl/core/extent.c               | 58 +++++++++++++++++++++++++++++++++
> > >  2 files changed, 90 insertions(+)
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> > > index b63ab622515f..64918180a3c9 100644
> > > --- a/Documentation/ABI/testing/sysfs-bus-cxl
> > > +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> > > @@ -632,3 +632,35 @@ Description:
> > >  		See Documentation/ABI/stable/sysfs-devices-node. access0 provides
> > >  		the number to the closest initiator and access1 provides the
> > >  		number to the closest CPU.
> > > +
> > > +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
> > > +Date:		December, 2024
> > > +KernelVersion:	v6.13
> > > +Contact:	linux-cxl@...r.kernel.org
> > > +Description:
> > > +		(RO) [For Dynamic Capacity regions only] Users can use the
> > > +		extent information to create DAX devices on specific extents.
> > > +		This is done by creating and destroying DAX devices in specific
> > > +		sequences and looking at the mappings created.   
> > 
> > Similar to earlier patch, maybe put this doc for the directory, then
> > have much less duplication?
> >   
> 
> But none of the other directories are done this way so I'm inclined to keep it.

Fair enough. Maybe a topic for a future cleanup to reduce duplication.

> 
> >   
> > > Extent offset
> > > +		within the region.
> > > +
> > > +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/length
> > > +Date:		December, 2024
> > > +KernelVersion:	v6.13
> > > +Contact:	linux-cxl@...r.kernel.org
> > > +Description:
> > > +		(RO) [For Dynamic Capacity regions only] Users can use the
> > > +		extent information to create DAX devices on specific extents.
> > > +		This is done by creating and destroying DAX devices in specific
> > > +		sequences and looking at the mappings created.  Extent length
> > > +		within the region.
> > > +
> > > +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/tag
> > > +Date:		December, 2024
> > > +KernelVersion:	v6.13
> > > +Contact:	linux-cxl@...r.kernel.org
> > > +Description:
> > > +		(RO) [For Dynamic Capacity regions only] Users can use the
> > > +		extent information to create DAX devices on specific extents.
> > > +		This is done by creating and destroying DAX devices in specific
> > > +		sequences and looking at the mappings created.  Extent tag.  
> > 
> > Maybe say we are treating it as a UUID?  
> 
> ok...  How about?
> 
> <quote>
> ...  looking at the mappings created.  UUID extent tag.
That's fine.

> </quote>
> 
> > > diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
> > > index 69a7614ba6a9..a1eb6e8e4f1a 100644
> > > --- a/drivers/cxl/core/extent.c
> > > +++ b/drivers/cxl/core/extent.c
> > > @@ -6,6 +6,63 @@  
> >   
> > > +static struct attribute *region_extent_attrs[] = {
> > > +	&dev_attr_offset.attr,
> > > +	&dev_attr_length.attr,
> > > +	&dev_attr_tag.attr,
> > > +	NULL,  
> > No need for trailing comma (one of my 'favourite' review comments :)  
> 
> I'm noticing...  :-D
Maybe I'll one day add to checkpatch.  If it weren't written in perl
I'd do it now ;)

Jonathan

> 
> Ira
>