linux-kernel - Re: [PATCH V3 03/21] dax: Save the kva from memremap

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Message-ID: <20260108113251.00004f1c@huawei.com>
Date: Thu, 8 Jan 2026 11:32:51 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: John Groves <John@...ves.net>
CC: Miklos Szeredi <miklos@...redi.hu>, Dan Williams
	<dan.j.williams@...el.com>, Bernd Schubert <bschubert@....com>, "Alison
 Schofield" <alison.schofield@...el.com>, John Groves <jgroves@...ron.com>,
	Jonathan Corbet <corbet@....net>, Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>, Matthew Wilcox <willy@...radead.org>, Jan
 Kara <jack@...e.cz>, Alexander Viro <viro@...iv.linux.org.uk>, "David
 Hildenbrand" <david@...nel.org>, Christian Brauner <brauner@...nel.org>,
	"Darrick J . Wong" <djwong@...nel.org>, Randy Dunlap <rdunlap@...radead.org>,
	Jeff Layton <jlayton@...nel.org>, Amir Goldstein <amir73il@...il.com>, Stefan
 Hajnoczi <shajnocz@...hat.com>, Joanne Koong <joannelkoong@...il.com>, Josef
 Bacik <josef@...icpanda.com>, Bagas Sanjaya <bagasdotme@...il.com>, Chen
 Linxuan <chenlinxuan@...ontech.com>, "James Morse" <james.morse@....com>,
	Fuad Tabba <tabba@...gle.com>, "Sean Christopherson" <seanjc@...gle.com>,
	Shivank Garg <shivankg@....com>, Ackerley Tng <ackerleytng@...gle.com>,
	Gregory Price <gourry@...rry.net>, Aravind Ramesh <arramesh@...ron.com>, Ajay
 Joshi <ajayjoshi@...ron.com>, <venkataravis@...ron.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-cxl@...r.kernel.org>,
	<linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH V3 03/21] dax: Save the kva from memremap

On Wed,  7 Jan 2026 09:33:12 -0600
John Groves <John@...ves.net> wrote:

> Save the kva from memremap because we need it for iomap rw support.
> 
> Prior to famfs, there were no iomap users of /dev/dax - so the virtual
> address from memremap was not needed.
> 
> (also fill in missing kerneldoc comment fields for struct dev_dax)

Do that as a precursor that can be picked up ahead of the rest of the series.

> 
> Signed-off-by: John Groves <john@...ves.net>
> ---
>  drivers/dax/dax-private.h | 4 ++++
>  drivers/dax/fsdev.c       | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
> index 0867115aeef2..1bb1631af485 100644
> --- a/drivers/dax/dax-private.h
> +++ b/drivers/dax/dax-private.h
> @@ -69,18 +69,22 @@ struct dev_dax_range {
>   * data while the device is activated in the driver.
>   * @region - parent region
>   * @dax_dev - core dax functionality
> + * @virt_addr - kva from memremap; used by fsdev_dax
> + * @align - alignment of this instance
>   * @target_node: effective numa node if dev_dax memory range is onlined
>   * @dyn_id: is this a dynamic or statically created instance
>   * @id: ida allocated id when the dax_region is not static
>   * @ida: mapping id allocator
>   * @dev - device core
>   * @pgmap - pgmap for memmap setup / lifetime (driver owned)
> + * @memmap_on_memory - allow kmem to put the memmap in the memory
>   * @nr_range: size of @ranges
>   * @ranges: range tuples of memory used
>   */
>  struct dev_dax {
>  	struct dax_region *region;
>  	struct dax_device *dax_dev;
> +	void *virt_addr;
>  	unsigned int align;
>  	int target_node;
>  	bool dyn_id;
> diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c
> index 2a3249d1529c..c5c660b193e5 100644
> --- a/drivers/dax/fsdev.c
> +++ b/drivers/dax/fsdev.c
> @@ -235,6 +235,7 @@ static int fsdev_dax_probe(struct dev_dax *dev_dax)
>  		pr_debug("%s: offset detected phys=%llx pgmap_phys=%llx offset=%llx\n",
>  		       __func__, phys, pgmap_phys, data_offset);
>  	}
> +	dev_dax->virt_addr = addr + data_offset;
>  
>  	inode = dax_inode(dax_dev);
>  	cdev = inode->i_cdev;