dax: Save the kva from memremap

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.

Reviewed-by: Ira Weiny <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: John Groves <[email protected]>
Link: https://patch.msgid.link/0100019d311d1d08-dd372cb9-5934-43b8-bef8-089660d04a81-000000@email.amazonses.com
Signed-off-by: Ira Weiny <[email protected]>

Author: jagalactic

drivers/dax/dax-private.h

@@ -69,6 +69,7 @@ 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
@@ -83,6 +84,7 @@ struct dev_dax_range {
 struct dev_dax {
 	struct dax_region *region;
 	struct dax_device *dax_dev;
+	void *virt_addr;
 	unsigned int align;
 	int target_node;
 	bool dyn_id;

drivers/dax/fsdev.c

@@ -121,6 +121,7 @@ static int fsdev_dax_probe(struct dev_dax *dev_dax)
 	struct device *dev = &dev_dax->dev;
 	struct dev_pagemap *pgmap;
 	struct inode *inode;
+	u64 data_offset = 0;
 	struct cdev *cdev;
 	void *addr;
 	int rc, i;
@@ -196,14 +197,14 @@ static int fsdev_dax_probe(struct dev_dax *dev_dax)
 	if (pgmap->range.start != dev_dax->ranges[0].range.start) {
 		u64 phys = dev_dax->ranges[0].range.start;
 		u64 pgmap_phys = dev_dax->pgmap[0].range.start;
-		u64 data_offset = 0;
 
 		if (!WARN_ON(pgmap_phys > phys))
 			data_offset = phys - pgmap_phys;
 
 		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;