From a0fb038e50d72f8e60731dc48fb83a3a141b822e Mon Sep 17 00:00:00 2001
From: Joao Martins <joao.m.martins@oracle.com>
Date: Fri, 14 Jan 2022 14:04:36 -0800
Subject: [PATCH] device-dax: factor out page mapping initialization

Move initialization of page->mapping into a separate helper.

This is in preparation to move the mapping set to be prior to inserting
the page table entry and also for tidying up compound page handling into
one helper.

Link: https://lkml.kernel.org/r/20211202204422.26777-9-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 drivers/dax/device.c | 45 ++++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 630de5a795b0..9c87927d4bc2 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -73,6 +73,27 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
 	return -1;
 }
 
+static void dax_set_mapping(struct vm_fault *vmf, pfn_t pfn,
+			      unsigned long fault_size)
+{
+	unsigned long i, nr_pages = fault_size / PAGE_SIZE;
+	struct file *filp = vmf->vma->vm_file;
+	pgoff_t pgoff;
+
+	pgoff = linear_page_index(vmf->vma,
+			ALIGN(vmf->address, fault_size));
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
+
+		if (page->mapping)
+			continue;
+
+		page->mapping = filp->f_mapping;
+		page->index = pgoff + i;
+	}
+}
+
 static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
 				struct vm_fault *vmf, pfn_t *pfn)
 {
@@ -224,28 +245,8 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 		rc = VM_FAULT_SIGBUS;
 	}
 
-	if (rc == VM_FAULT_NOPAGE) {
-		unsigned long i;
-		pgoff_t pgoff;
-
-		/*
-		 * In the device-dax case the only possibility for a
-		 * VM_FAULT_NOPAGE result is when device-dax capacity is
-		 * mapped. No need to consider the zero page, or racing
-		 * conflicting mappings.
-		 */
-		pgoff = linear_page_index(vmf->vma,
-				ALIGN(vmf->address, fault_size));
-		for (i = 0; i < fault_size / PAGE_SIZE; i++) {
-			struct page *page;
-
-			page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
-			if (page->mapping)
-				continue;
-			page->mapping = filp->f_mapping;
-			page->index = pgoff + i;
-		}
-	}
+	if (rc == VM_FAULT_NOPAGE)
+		dax_set_mapping(vmf, pfn, fault_size);
 	dax_read_unlock(id);
 
 	return rc;