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From:   Huaisheng Ye <yehs2007@zoho.com>
To:     linux-nvdimm@lists.01.org, dan.j.williams@intel.com
Cc:     ross.zwisler@linux.intel.com, willy@infradead.org,
        vishal.l.verma@intel.com, dave.jiang@intel.com,
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        bart.vanassche@wdc.com, jack@suse.cz, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        chengnt@lenovo.com, Huaisheng Ye <yehs1@lenovo.com>
Subject: [PATCH 3/5] s390, dcssblk: Allow a NULL-kaddr to ->direct_access()
Date:   Tue, 24 Jul 2018 16:45:08 +0800
Message-Id: <20180724084510.6104-4-yehs2007@zoho.com>
In-Reply-To: <20180724084510.6104-1-yehs2007@zoho.com>
References: <20180724084510.6104-1-yehs2007@zoho.com>
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From: Huaisheng Ye <yehs1@lenovo.com>

dcssblk_direct_access() needs to check the validity of second rank
pointer kaddr for NULL assignment. If kaddr equals to NULL, it
doesn't need to calculate the 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..9c13dc5 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -915,7 +915,8 @@ static DEVICE_ATTR(save, S_IWUSR | S_IRUSR, dcssblk_save_show,
 	unsigned long dev_sz;
 
 	dev_sz = dev_info->end - dev_info->start + 1;
-	*kaddr = (void *) dev_info->start + offset;
+	if (kaddr)
+		*kaddr = (void *) dev_info->start + offset;
 	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
 			PFN_DEV|PFN_SPECIAL);
 
-- 
1.8.3.1