[PATCH 4.18 159/228] filesystem-dax: Fix use of zero page

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Wilcox <willy@xxxxxxxxxxxxx>

commit b90ca5cc32f59bb214847c6855959702f00c6801 upstream.

Use my_zero_pfn instead of ZERO_PAGE(), and pass the vaddr to it instead
of zero so it works on MIPS and s390 who reference the vaddr to select a
zero page.

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 91d25ba8a6b0 ("dax: use common 4k zero page for dax mmap reads")
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/dax.c |   13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1007,21 +1007,12 @@ static vm_fault_t dax_load_hole(struct a
 {
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
-	vm_fault_t ret = VM_FAULT_NOPAGE;
-	struct page *zero_page;
-	pfn_t pfn;
+	pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
+	vm_fault_t ret;
 
-	zero_page = ZERO_PAGE(0);
-	if (unlikely(!zero_page)) {
-		ret = VM_FAULT_OOM;
-		goto out;
-	}
-
-	pfn = page_to_pfn_t(zero_page);
 	dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE,
 			false);
 	ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
-out:
 	trace_dax_load_hole(inode, vmf, ret);
 	return ret;
 }