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[v2,09/14] s390, dcssblk: Allow a NULL-pfn to ->direct_access()

Message ID 153176046886.12695.7487453664953251895.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Dan Williams July 16, 2018, 5:01 p.m. UTC 
From: Huaisheng Ye <yehs1@lenovo.com>

dcssblk_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/s390/block/dcssblk.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
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Patch

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index ed607288e696..a645b2c93c34 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -923,8 +923,9 @@  __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff,
 
 	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 (pfn)
+		*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
+				PFN_DEV|PFN_SPECIAL);
 
 	return (dev_sz - offset) / PAGE_SIZE;
 }