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From: Dan Williams <dan.j.williams@intel.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	device-mapper development <dm-devel@redhat.com>
Subject: Re: [PATCH 1/5] dax, pmem: Add a dax operation zero_page_range
Date: Wed, 5 Feb 2020 16:40:44 -0800
Message-ID: <CAPcyv4iY=gw86UDLqpiCtathGXRUuxOMuU=unwxzA-cm=0x+Sg@mail.gmail.com> (raw)
In-Reply-To: <20200205200259.GE14544@redhat.com>

On Wed, Feb 5, 2020 at 12:03 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Wed, Feb 05, 2020 at 10:30:50AM -0800, Christoph Hellwig wrote:
> > > +   /*
> > > +    * There are no users as of now. Once users are there, fix dm code
> > > +    * to be able to split a long range across targets.
> > > +    */
> >
> > This comment confused me.  I think this wants to say something like:
> >
> >       /*
> >        * There are now callers that want to zero across a page boundary as of
> >        * now.  Once there are users this check can be removed after the
> >        * device mapper code has been updated to split ranges across targets.
> >        */
>
> Yes, that's what I wanted to say but I missed one line. Thanks. Will fix
> it.
>
> >
> > > +static int pmem_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
> > > +                               unsigned int offset, size_t len)
> > > +{
> > > +   int rc = 0;
> > > +   phys_addr_t phys_pos = pgoff * PAGE_SIZE + offset;
> >
> > Any reason not to pass a phys_addr_t in the calling convention for the
> > method and maybe also for dax_zero_page_range itself?
>
> I don't have any reason not to pass phys_addr_t. If that sounds better,
> will make changes.

The problem is device-mapper. That wants to use offset to route
through the map to the leaf device. If it weren't for the firmware
communication requirement you could do:

dax_direct_access(...)
generic_dax_zero_page_range(...)

...but as long as the firmware error clearing path is required I think
we need to do pass the pgoff through the interface and do the pgoff to
virt / phys translation inside the ops handler.
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Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-03 20:00 [RFC PATCH 0/5][V2] dax,pmem: Provide a dax operation to zero range of memory Vivek Goyal
2020-02-03 20:00 ` [PATCH 1/5] dax, pmem: Add a dax operation zero_page_range Vivek Goyal
2020-02-05 18:30   ` Christoph Hellwig
2020-02-05 20:02     ` Vivek Goyal
2020-02-06  0:40       ` Dan Williams [this message]
2020-02-06  7:41         ` Christoph Hellwig
2020-02-07 16:57           ` Dan Williams
2020-02-07 17:01             ` Vivek Goyal
2020-02-07 17:06               ` Dan Williams
2020-02-06 14:34         ` Vivek Goyal
2020-02-07 16:58           ` Dan Williams
2020-02-03 20:00 ` [PATCH 2/5] s390,dax: Add dax zero_page_range operation to dcssblk driver Vivek Goyal
2020-02-05 18:32   ` Christoph Hellwig
2020-02-05 20:04     ` Vivek Goyal
2020-02-03 20:00 ` [PATCH 3/5] dm,dax: Add dax zero_page_range operation Vivek Goyal
2020-02-05 18:33   ` Christoph Hellwig
2020-02-07 16:34     ` Vivek Goyal
2020-02-03 20:00 ` [PATCH 4/5] dax,iomap: Start using dax native zero_page_range() Vivek Goyal
2020-02-05 18:33   ` Christoph Hellwig
2020-02-05 20:10     ` Vivek Goyal
2020-02-07 15:31     ` Vivek Goyal
2020-02-03 20:00 ` [PATCH 5/5] dax,iomap: Add helper dax_iomap_zero() to zero a range Vivek Goyal
2020-02-04  5:17   ` kbuild test robot
2020-02-05 18:36   ` Christoph Hellwig
2020-02-05 20:15     ` Vivek Goyal

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