[PATCH 2/4] null_blk: use memcpy_page() in copy_from_nullb()

[Chaitanya Kulkarni <kch@nvidia.com>]

Use library helper memcpy_page() to copy source page into destination
instead of having duplicate code and zero_user() instead of memset as
this removes deprecated API from :include/linux/highmem.h:
"kmap_atomic - Atomically map a page for temporary usage - Deprecated!"

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
---
 drivers/block/null_blk/main.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 947bba174e1e..2b344dcb4382 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1144,7 +1144,6 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
 	size_t temp, count = 0;
 	unsigned int offset;
 	struct nullb_page *t_page;
-	void *dst, *src;
 
 	while (count < n) {
 		temp = min_t(size_t, nullb->dev->blocksize, n - count);
@@ -1153,16 +1152,11 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
 		t_page = null_lookup_page(nullb, sector, false,
 			!null_cache_active(nullb));
 
-		dst = kmap_atomic(dest);
-		if (!t_page) {
-			memset(dst + off + count, 0, temp);
-			goto next;
-		}
-		src = kmap_atomic(t_page->page);
-		memcpy(dst + off + count, src + offset, temp);
-		kunmap_atomic(src);
-next:
-		kunmap_atomic(dst);
+		if (t_page)
+			memcpy_page(dest, off + count, t_page->page, offset,
+				    temp);
+		else
+			zero_user(dest, off + count, temp);
 
 		count += temp;
 		sector += temp >> SECTOR_SHIFT;
-- 
2.29.0