iov_iter: constify {csum_and_,}copy_to_iter()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/uio.h

@@ -82,7 +82,7 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i);
 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i);
-size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i);
+size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
@@ -145,7 +145,7 @@ static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 {
 	i->count = count;
 }
-size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 
 int import_iovec(int type, const struct iovec __user * uvector,

lib/iov_iter.c

@@ -369,7 +369,7 @@ static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t
 	kunmap_atomic(from);
 }
 
-static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)
+static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 {
 	char *to = kmap_atomic(page);
 	memcpy(to + offset, from, len);
@@ -383,9 +383,9 @@ static void memzero_page(struct page *page, size_t offset, size_t len)
 	kunmap_atomic(addr);
 }
 
-size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i)
+size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
-	char *from = addr;
+	const char *from = addr;
 	if (unlikely(bytes > i->count))
 		bytes = i->count;
 
@@ -704,10 +704,10 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 }
 EXPORT_SYMBOL(csum_and_copy_from_iter);
 
-size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum,
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
 			     struct iov_iter *i)
 {
-	char *from = addr;
+	const char *from = addr;
 	__wsum sum, next;
 	size_t off = 0;
 	if (unlikely(bytes > i->count))