vduse: Use memcpy_{to,from}_page() in do_bounce()

kmap_atomic() is being deprecated in favor of kmap_local_page().

The use of kmap_atomic() in do_bounce() is all thread local therefore
kmap_local_page() is a sufficient replacement.

Convert to kmap_local_page() but, instead of open coding it,
use the helpers memcpy_to_page() and memcpy_from_page().
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Message-Id: <20220803045523.23851-3-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_user/iova_domain.c

@@ -138,18 +138,17 @@ static void do_bounce(phys_addr_t orig, void *addr, size_t size,
 {
 	unsigned long pfn = PFN_DOWN(orig);
 	unsigned int offset = offset_in_page(orig);
-	char *buffer;
+	struct page *page;
 	unsigned int sz = 0;
 
 	while (size) {
 		sz = min_t(size_t, PAGE_SIZE - offset, size);
 
-		buffer = kmap_atomic(pfn_to_page(pfn));
+		page = pfn_to_page(pfn);
 		if (dir == DMA_TO_DEVICE)
-			memcpy(addr, buffer + offset, sz);
+			memcpy_from_page(addr, page, offset, sz);
 		else
-			memcpy(buffer + offset, addr, sz);
-		kunmap_atomic(buffer);
+			memcpy_to_page(page, offset, addr, sz);
 
 		size -= sz;
 		pfn++;