[PATCH v7 09/11] device-dax: set mapping prior to vmf_insert_pfn{,_pmd,pud}()

[Joao Martins <joao.m.martins@oracle.com>]

Normally, the @page mapping is set prior to inserting the page into a
page table entry. Make device-dax adhere to the same ordering, rather
than setting mapping after the PTE is inserted.

The address_space never changes and it is always associated with the
same inode and underlying pages. So, the page mapping is set once but
cleared when the struct pages are removed/freed (i.e. after
{devm_}memunmap_pages()).

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 drivers/dax/device.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 9c87927d4bc2..19a6b86486ce 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -121,6 +121,8 @@ static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
 
 	*pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
 
+	dax_set_mapping(vmf, *pfn, fault_size);
+
 	return vmf_insert_mixed(vmf->vma, vmf->address, *pfn);
 }
 
@@ -161,6 +163,8 @@ static vm_fault_t __dev_dax_pmd_fault(struct dev_dax *dev_dax,
 
 	*pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
 
+	dax_set_mapping(vmf, *pfn, fault_size);
+
 	return vmf_insert_pfn_pmd(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
 }
 
@@ -203,6 +207,8 @@ static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
 
 	*pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
 
+	dax_set_mapping(vmf, *pfn, fault_size);
+
 	return vmf_insert_pfn_pud(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
 }
 #else
@@ -217,7 +223,6 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 		enum page_entry_size pe_size)
 {
 	struct file *filp = vmf->vma->vm_file;
-	unsigned long fault_size;
 	vm_fault_t rc = VM_FAULT_SIGBUS;
 	int id;
 	pfn_t pfn;
@@ -230,23 +235,18 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 	id = dax_read_lock();
 	switch (pe_size) {
 	case PE_SIZE_PTE:
-		fault_size = PAGE_SIZE;
 		rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
 		break;
 	case PE_SIZE_PMD:
-		fault_size = PMD_SIZE;
 		rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
 		break;
 	case PE_SIZE_PUD:
-		fault_size = PUD_SIZE;
 		rc = __dev_dax_pud_fault(dev_dax, vmf, &pfn);
 		break;
 	default:
 		rc = VM_FAULT_SIGBUS;
 	}
 
-	if (rc == VM_FAULT_NOPAGE)
-		dax_set_mapping(vmf, pfn, fault_size);
 	dax_read_unlock(id);
 
 	return rc;
-- 
2.17.2