block: ublk_drv: cleanup 'struct ublk_map_data'

'struct ublk_map_data' is passed to ublk_copy_user_pages()
for copying data between userspace buffer and request pages.

Here what matters is userspace buffer address/len and 'struct request',
so replace ->io field with user buffer address, and rename max_bytes
as len.

Meantime remove 'ubq' field from ublk_map_data, since it isn't used
any more.

Then code becomes more readable.
Reviewed-by: Ziyang Zhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ublk_drv.c

@@ -420,10 +420,9 @@ static const struct block_device_operations ub_fops = {
 #define UBLK_MAX_PIN_PAGES	32
 
 struct ublk_map_data {
-	const struct ublk_queue *ubq;
 	const struct request *rq;
-	const struct ublk_io *io;
-	unsigned max_bytes;
+	unsigned long	ubuf;
+	unsigned int	len;
 };
 
 struct ublk_io_iter {
@@ -483,14 +482,14 @@ static inline unsigned ublk_copy_io_pages(struct ublk_io_iter *data,
 static int ublk_copy_user_pages(struct ublk_map_data *data, bool to_vm)
 {
 	const unsigned int gup_flags = to_vm ? FOLL_WRITE : 0;
-	const unsigned long start_vm = data->io->addr;
+	const unsigned long start_vm = data->ubuf;
 	unsigned int done = 0;
 	struct ublk_io_iter iter = {
 		.pg_off	= start_vm & (PAGE_SIZE - 1),
 		.bio	= data->rq->bio,
 		.iter	= data->rq->bio->bi_iter,
 	};
-	const unsigned int nr_pages = round_up(data->max_bytes +
+	const unsigned int nr_pages = round_up(data->len +
 			(start_vm & (PAGE_SIZE - 1)), PAGE_SIZE) >> PAGE_SHIFT;
 
 	while (done < nr_pages) {
@@ -503,13 +502,13 @@ static int ublk_copy_user_pages(struct ublk_map_data *data, bool to_vm)
 				iter.pages);
 		if (iter.nr_pages <= 0)
 			return done == 0 ? iter.nr_pages : done;
-		len = ublk_copy_io_pages(&iter, data->max_bytes, to_vm);
+		len = ublk_copy_io_pages(&iter, data->len, to_vm);
 		for (i = 0; i < iter.nr_pages; i++) {
 			if (to_vm)
 				set_page_dirty(iter.pages[i]);
 			put_page(iter.pages[i]);
 		}
-		data->max_bytes -= len;
+		data->len -= len;
 		done += iter.nr_pages;
 	}
 
@@ -538,15 +537,14 @@ static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
 	 */
 	if (ublk_need_map_req(req)) {
 		struct ublk_map_data data = {
-			.ubq	=	ubq,
 			.rq	=	req,
-			.io	=	io,
-			.max_bytes =	rq_bytes,
+			.ubuf	=	io->addr,
+			.len	=	rq_bytes,
 		};
 
 		ublk_copy_user_pages(&data, true);
 
-		return rq_bytes - data.max_bytes;
+		return rq_bytes - data.len;
 	}
 	return rq_bytes;
 }
@@ -559,17 +557,16 @@ static int ublk_unmap_io(const struct ublk_queue *ubq,
 
 	if (ublk_need_unmap_req(req)) {
 		struct ublk_map_data data = {
-			.ubq	=	ubq,
 			.rq	=	req,
-			.io	=	io,
-			.max_bytes =	io->res,
+			.ubuf	=	io->addr,
+			.len	=	io->res,
 		};
 
 		WARN_ON_ONCE(io->res > rq_bytes);
 
 		ublk_copy_user_pages(&data, false);
 
-		return io->res - data.max_bytes;
+		return io->res - data.len;
 	}
 	return rq_bytes;
 }