[PATCH 4/5] mm: fix cache mode of dax pmd mappings

[Dan Williams]

track_pfn_insert() is marking dax mappings as uncacheable.

It is used to keep mappings attributes consistent across a remapped range.
However, since dax regions are never registered via track_pfn_remap(), the
caching mode lookup for dax pfns always returns _PAGE_CACHE_MODE_UC.  We do not
use track_pfn_insert() in the dax-pte path, and we always want to use the
pgprot of the vma itself, so drop this call.

Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Nilesh Choudhury <nilesh.choudhury@xxxxxxxxxx>
Reported-by: Kai Zhang <kai.ka.zhang@xxxxxxxxxx>
Reported-by: Toshi Kani <toshi.kani@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 mm/huge_memory.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a6abd76baa72..338eff05c77a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -676,8 +676,6 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return VM_FAULT_SIGBUS;
-	if (track_pfn_insert(vma, &pgprot, pfn))
-		return VM_FAULT_SIGBUS;
 	insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
 	return VM_FAULT_NOPAGE;
 }