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Subject: [PATCH v2 07/14] libnvdimm,
 pmem: Allow a NULL-pfn to ->direct_access()
From:   Dan Williams <dan.j.williams@intel.com>
To:     akpm@linux-foundation.org
Cc:     Huaisheng Ye <yehs1@lenovo.com>, Jan Kara <jack@suse.cz>,
        vishal.l.verma@intel.com, hch@lst.de, linux-mm@kvack.org,
        jack@suse.cz, linux-nvdimm@lists.01.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 16 Jul 2018 10:00:58 -0700
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From: Huaisheng Ye <yehs1@lenovo.com>

pmem_direct_access() needs to check the validity of pointer pfn for NULL
assignment. If pfn equals to NULL, it doesn't need to calculate the
value. This is in support of asynchronous memmap init and avoid page
lookups when possible.

Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/pmem.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index e8ac6f244d2b..c430536320a5 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -228,7 +228,8 @@ __weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
 					PFN_PHYS(nr_pages))))
 		return -EIO;
 	*kaddr = pmem->virt_addr + offset;
-	*pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
+	if (pfn)
+		*pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
 
 	/*
 	 * If badblocks are present, limit known good range to the