From 35de299547d1c3300e078f9f7c6eb01dadae47f9 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 13 Jul 2018 21:49:45 -0700
Subject: [PATCH] device-dax: Set page->index
Git-commit: 35de299547d1c3300e078f9f7c6eb01dadae47f9
Patch-mainline: v4.19-rc1
References: bsc#1107783

In support of enabling memory_failure() handling for device-dax
mappings, set ->index to the pgoff of the page. The rmap implementation
requires ->index to bound the search through the vma interval tree.

The ->index value is never cleared. There is no possibility for the
page to become associated with another pgoff while the device is
enabled. When the device is disabled the 'struct page' array for the
device is destroyed and ->index is reinitialized to zero.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Jan Kara <jack@suse.cz>

---
 drivers/dax/device.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 95cfcfd612df..361a11089591 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -416,6 +416,7 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 
 	if (rc == VM_FAULT_NOPAGE) {
 		unsigned long i;
+		pgoff_t pgoff;
 
 		/*
 		 * In the device-dax case the only possibility for a
@@ -423,6 +424,8 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 		 * mapped. No need to consider the zero page, or racing
 		 * conflicting mappings.
 		 */
+		pgoff = linear_page_index(vmf->vma, vmf->address
+				& ~(fault_size - 1));
 		for (i = 0; i < fault_size / PAGE_SIZE; i++) {
 			struct page *page;
 
@@ -430,6 +433,7 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 			if (page->mapping)
 				continue;
 			page->mapping = filp->f_mapping;
+			page->index = pgoff + i;
 		}
 	}
 	dax_read_unlock(id);
-- 
2.16.4