ZIL: Refactor TX_WRITE encryption similar to TX_CLONE_RANGE

It should be purely textual change to make the code more readable.
Should cause no functional difference.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Tom Caputi <caputit1@tcnj.edu>
Reviewed-by: Sean Eric Fagan <sef@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Edmund Nadolski <edmund.nadolski@ixsystems.com>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes openzfs#15543
Closes openzfs#15513

module/os/freebsd/zfs/zio_crypt.c

@@ -1338,19 +1338,14 @@ zio_crypt_init_uios_zil(boolean_t encrypt, uint8_t *plainbuf,
 		 * authenticate it.
 		 */
 		if (txtype == TX_WRITE) {
-			crypt_len = sizeof (lr_write_t) -
-			    sizeof (lr_t) - sizeof (blkptr_t);
-			dst_iovecs[vec].iov_base = (char *)dlrp +
-			    sizeof (lr_t);
+			const size_t o = offsetof(lr_write_t, lr_blkptr);
+			crypt_len = o - sizeof (lr_t);
+			dst_iovecs[vec].iov_base = (char *)dlrp + sizeof (lr_t);
 			dst_iovecs[vec].iov_len = crypt_len;
 
 			/* copy the bp now since it will not be encrypted */
-			memcpy(dlrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    slrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    sizeof (blkptr_t));
-			memcpy(aadp,
-			    slrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    sizeof (blkptr_t));
+			memcpy(dlrp + o, slrp + o, sizeof (blkptr_t));
+			memcpy(aadp, slrp + o, sizeof (blkptr_t));
 			aadp += sizeof (blkptr_t);
 			aad_len += sizeof (blkptr_t);
 			vec++;
@@ -1379,8 +1374,7 @@ zio_crypt_init_uios_zil(boolean_t encrypt, uint8_t *plainbuf,
 			total_len += crypt_len;
 		} else {
 			crypt_len = lr_len - sizeof (lr_t);
-			dst_iovecs[vec].iov_base = (char *)dlrp +
-			    sizeof (lr_t);
+			dst_iovecs[vec].iov_base = (char *)dlrp + sizeof (lr_t);
 			dst_iovecs[vec].iov_len = crypt_len;
 			vec++;
 			total_len += crypt_len;

module/os/linux/zfs/zio_crypt.c

@@ -1513,20 +1513,16 @@ zio_crypt_init_uios_zil(boolean_t encrypt, uint8_t *plainbuf,
 		 * authenticate it.
 		 */
 		if (txtype == TX_WRITE) {
-			crypt_len = sizeof (lr_write_t) -
-			    sizeof (lr_t) - sizeof (blkptr_t);
+			const size_t o = offsetof(lr_write_t, lr_blkptr);
+			crypt_len = o - sizeof (lr_t);
 			src_iovecs[nr_iovecs].iov_base = slrp + sizeof (lr_t);
 			src_iovecs[nr_iovecs].iov_len = crypt_len;
 			dst_iovecs[nr_iovecs].iov_base = dlrp + sizeof (lr_t);
 			dst_iovecs[nr_iovecs].iov_len = crypt_len;
 
 			/* copy the bp now since it will not be encrypted */
-			memcpy(dlrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    slrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    sizeof (blkptr_t));
-			memcpy(aadp,
-			    slrp + sizeof (lr_write_t) - sizeof (blkptr_t),
-			    sizeof (blkptr_t));
+			memcpy(dlrp + o, slrp + o, sizeof (blkptr_t));
+			memcpy(aadp, slrp + o, sizeof (blkptr_t));
 			aadp += sizeof (blkptr_t);
 			aad_len += sizeof (blkptr_t);
 			nr_iovecs++;