iov_iter: pass void csum pointer to csum_and_copy_to_iter

The single caller to csum_and_copy_to_iter is skb_copy_and_csum_datagram
and we are trying to unite its logic with skb_copy_datagram_iter by passing
a callback to the copy function that we want to apply. Thus, we need
to make the checksum pointer private to the function.
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSagi Grimberg <sagi@lightbitslabs.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

include/linux/uio.h

@@ -266,7 +266,7 @@ static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 {
 	i->count = count;
 }
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump, struct iov_iter *i);
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 

lib/iov_iter.c

@@ -1464,10 +1464,11 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
 }
 EXPORT_SYMBOL(csum_and_copy_from_iter_full);
 
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
 			     struct iov_iter *i)
 {
 	const char *from = addr;
+	__wsum *csum = csump;
 	__wsum sum, next;
 	size_t off = 0;