From: Huaisheng Ye <yehs1@lenovo.com>
Date: Mon, 30 Jul 2018 15:15:43 +0800
Subject: libnvdimm, pmem: kaddr and pfn can be NULL to ->direct_access()
Git-commit: 46a590cde0bd17cc983e40e74c195311cc8ba555
Patch-mainline: v4.19-rc1
References: FATE#326060

pmem_direct_access() needs to check the validity of pointers kaddr
and pfn for NULL assignment. If anyone equals to NULL, it doesn't need
to calculate the value.

If pointer equals to NULL, that is to say callers may have no need for
kaddr or pfn, so this patch is prepared for allowing them to pass in
NULL instead of having to pass in a pointer or local variable that
they then just throw away.

Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/nvdimm/pmem.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 68940356cad3..f3096564acb2 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -227,8 +227,11 @@ __weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
 	if (unlikely(is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
 					PFN_PHYS(nr_pages))))
 		return -EIO;
-	*kaddr = pmem->virt_addr + offset;
-	*pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
+
+	if (kaddr)
+		*kaddr = pmem->virt_addr + offset;
+	if (pfn)
+		*pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
 
 	/*
 	 * If badblocks are present, limit known good range to the