block: better packing for struct request

Keep the 32-bit CPU and cmd_type flags together to avoid holes on 64-bit
architectures.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

include/linux/blkdev.h

@@ -96,12 +96,11 @@ struct request {
 	struct request_queue *q;
 	struct blk_mq_ctx *mq_ctx;
 
-	u64 cmd_flags;
+	int cpu;
 	unsigned cmd_type;
+	u64 cmd_flags;
 	unsigned long atomic_flags;
 
-	int cpu;
-
 	/* the following two fields are internal, NEVER access directly */
 	unsigned int __data_len;	/* total data len */
 	sector_t __sector;		/* sector cursor */