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

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Message-ID: <147318058165.30325.16762406881120129093.stgit@dwillia2-desk3.amr.corp.intel.com>
Date:   Tue, 06 Sep 2016 09:49:41 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     linux-nvdimm@...ts.01.org
Cc:     Toshi Kani <toshi.kani@....com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Nilesh Choudhury <nilesh.choudhury@...cle.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kai Zhang <kai.ka.zhang@...cle.com>
Subject: [PATCH 4/5] mm: fix cache mode of dax pmd mappings

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@...ux.intel.com>
Cc: Matthew Wilcox <mawilcox@...rosoft.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Nilesh Choudhury <nilesh.choudhury@...cle.com>
Reported-by: Kai Zhang <kai.ka.zhang@...cle.com>
Reported-by: Toshi Kani <toshi.kani@....com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 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;
 }