linux-kernel - [PATCH 3/5] s390, dcssblk: Allow a NULL-kaddr to ->direct

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Message-Id: <20180724084510.6104-4-yehs2007@zoho.com>
Date:   Tue, 24 Jul 2018 16:45:08 +0800
From:   Huaisheng Ye <yehs2007@...o.com>
To:     linux-nvdimm@...ts.01.org, dan.j.williams@...el.com
Cc:     ross.zwisler@...ux.intel.com, willy@...radead.org,
        vishal.l.verma@...el.com, dave.jiang@...el.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        viro@...iv.linux.org.uk, martin.petersen@...cle.com,
        axboe@...nel.dk, gregkh@...uxfoundation.org,
        bart.vanassche@....com, jack@...e.cz, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        chengnt@...ovo.com, Huaisheng Ye <yehs1@...ovo.com>
Subject: [PATCH 3/5] s390, dcssblk: Allow a NULL-kaddr to ->direct_access()

From: Huaisheng Ye <yehs1@...ovo.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@...ovo.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