[PATCH] dax: Fix use of zero page

[Matthew Wilcox <willy@infradead.org>]

I plucked this patch from my XArray work.  It seems self-contained enough
that it could go into the DAX tree for merging this cycle.

>From 8cb56f4ba36af38814ca7b8ba030a66384e59a21 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <mawilcox@microsoft.com>
Date: Thu, 29 Mar 2018 22:41:18 -0400
Subject: [PATCH] dax: Fix use of zero page

Use my_zero_pfn instead of ZERO_PAGE, and pass the vaddr to it so it
works on MIPS and s390.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 fs/dax.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6a26626f20f3..f643e8fc34ee 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1006,17 +1006,9 @@ static vm_fault_t dax_load_hole(struct address_space *mapping, void *entry,
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
 	vm_fault_t ret = VM_FAULT_NOPAGE;
-	struct page *zero_page;
 	void *entry2;
-	pfn_t pfn;
-
-	zero_page = ZERO_PAGE(0);
-	if (unlikely(!zero_page)) {
-		ret = VM_FAULT_OOM;
-		goto out;
-	}
+	pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
 
-	pfn = page_to_pfn_t(zero_page);
 	entry2 = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
 			DAX_ZERO_PAGE, false);
 	if (IS_ERR(entry2)) {
-- 
2.17.0

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