fsdax: use a saner calling convention for copy_cow_page_dax

Just pass the vm_fault and iomap_iter structures, and figure out the rest
locally.  Note that this requires moving dax_iomap_sector up in the file.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-14-hch@lst.deSigned-off-by: Dan Williams <dan.j.williams@intel.com>

fs/dax.c

@@ -709,26 +709,31 @@ int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
 	return __dax_invalidate_entry(mapping, index, false);
 }
 
-static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_dev,
-			     sector_t sector, struct page *to, unsigned long vaddr)
+static sector_t dax_iomap_sector(const struct iomap *iomap, loff_t pos)
 {
+	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
+}
+
+static int copy_cow_page_dax(struct vm_fault *vmf, const struct iomap_iter *iter)
+{
+	sector_t sector = dax_iomap_sector(&iter->iomap, iter->pos);
 	void *vto, *kaddr;
 	pgoff_t pgoff;
 	long rc;
 	int id;
 
-	rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
+	rc = bdev_dax_pgoff(iter->iomap.bdev, sector, PAGE_SIZE, &pgoff);
 	if (rc)
 		return rc;
 
 	id = dax_read_lock();
-	rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
+	rc = dax_direct_access(iter->iomap.dax_dev, pgoff, 1, &kaddr, NULL);
 	if (rc < 0) {
 		dax_read_unlock(id);
 		return rc;
 	}
-	vto = kmap_atomic(to);
-	copy_user_page(vto, kaddr, vaddr, to);
+	vto = kmap_atomic(vmf->cow_page);
+	copy_user_page(vto, kaddr, vmf->address, vmf->cow_page);
 	kunmap_atomic(vto);
 	dax_read_unlock(id);
 	return 0;
@@ -1005,11 +1010,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 }
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 
-static sector_t dax_iomap_sector(const struct iomap *iomap, loff_t pos)
-{
-	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
-}
-
 static int dax_iomap_pfn(const struct iomap *iomap, loff_t pos, size_t size,
 			 pfn_t *pfnp)
 {
@@ -1332,19 +1332,16 @@ static vm_fault_t dax_fault_synchronous_pfnp(pfn_t *pfnp, pfn_t pfn)
 static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf,
 		const struct iomap_iter *iter)
 {
-	sector_t sector = dax_iomap_sector(&iter->iomap, iter->pos);
-	unsigned long vaddr = vmf->address;
 	vm_fault_t ret;
 	int error = 0;
 
 	switch (iter->iomap.type) {
 	case IOMAP_HOLE:
 	case IOMAP_UNWRITTEN:
-		clear_user_highpage(vmf->cow_page, vaddr);
+		clear_user_highpage(vmf->cow_page, vmf->address);
 		break;
 	case IOMAP_MAPPED:
-		error = copy_cow_page_dax(iter->iomap.bdev, iter->iomap.dax_dev,
-					  sector, vmf->cow_page, vaddr);
+		error = copy_cow_page_dax(vmf, iter);
 		break;
 	default:
 		WARN_ON_ONCE(1);