disk_stats
bdev->bd_stats = alloc_percpu(struct disk_stats);
struct disk_stats *cpu_dkstats;
struct disk_stats stat;
struct disk_stats *stat)
memset(stat, 0, sizeof(struct disk_stats));
struct disk_stats *ptr = per_cpu_ptr(part->bd_stats, cpu);
struct disk_stats stat;
struct disk_stats __percpu *bd_stats;
sizeof(struct disk_stats));