diff mbox series

[v3,2/6] s390, dcssblk: kaddr and pfn can be NULL to ->direct_access()

Message ID 20180730071548.9172-3-yehs2007@zoho.com (mailing list archive)
State New, archived
Headers show
Series kaddr and pfn can be NULL to ->direct_access() | expand

Commit Message

Huaisheng Ye July 30, 2018, 7:15 a.m. UTC 
From: Huaisheng Ye <yehs1@lenovo.com>

dcssblk_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 either of them is equal 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>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 drivers/s390/block/dcssblk.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index ed60728..23e526c 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -922,9 +922,11 @@  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;
-	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
-			PFN_DEV|PFN_SPECIAL);
+	if (kaddr)
+		*kaddr = (void *) 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;
 }