fs: fix kernel_write prototype

Make the position an in/out argument like all the other read/write
helpers and and make the buf argument a void pointer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index 9f4c86c..6acb00f 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -147,6 +147,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
 		 * File content is stored encrypted with randomly generated key.
 		 */
 		size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher));
+		loff_t pos = 0;
 
 		/* prepare aligned data to encrypt */
 		data = kmalloc(enclen, GFP_KERNEL);
@@ -179,7 +180,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
 			goto err_enckey;
 		}
 
-		written = kernel_write(file, data, enclen, 0);
+		written = kernel_write(file, data, enclen, &pos);
 		if (written != enclen) {
 			ret = written;
 			if (written >= 0)