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From:   Huaisheng Ye <yehs2007@zoho.com>
To:     linux-nvdimm@lists.01.org
Cc:     dan.j.williams@intel.com, ross.zwisler@linux.intel.com,
        mawilcox@microsoft.com, vishal.l.verma@intel.com,
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        chengnt@lenovo.com, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Huaisheng Ye <yehs1@lenovo.com>
Subject: [PATCH 2/3] drivers/s390/block/dcssblk: check the validity of the pointer pfn
Date:   Wed,  4 Jul 2018 14:40:57 +0800
Message-Id: <20180704064058.1344-2-yehs2007@zoho.com>
In-Reply-To: <20180704064058.1344-1-yehs2007@zoho.com>
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From: Huaisheng Ye <yehs1@lenovo.com>

Some functions within fs/dax don't need to get gfn from direct_access.
Assigning NULL to gfn of dax_direct_access is more intuitive and simple
than offering a useless local variable.

So direct_access needs to check validity of the pointer pfn For NULL
assignment. If pfn equals to NULL, it doesn't need to calculate its
value.

Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
---
 drivers/s390/block/dcssblk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 0a312e4..5cdfa02 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -916,7 +916,8 @@ static DEVICE_ATTR(save, S_IWUSR | S_IRUSR, dcssblk_save_show,
 
 	dev_sz = dev_info->end - dev_info->start + 1;
 	*kaddr = (void *) dev_info->start + offset;
-	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
+	if (pfn)
+		*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
 			PFN_DEV|PFN_SPECIAL);
 
 	return (dev_sz - offset) / PAGE_SIZE;
-- 
1.8.3.1