在block/blk-sysfs.c 中定義了一個rotational 的sysctl變數可以判斷當前盤是ssd和hdd
static struct queue_sysfs_entry queue_nonrot_entry = {
	.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
	.show = queue_show_nonrot,
	.store = queue_store_nonrot,
};
從蝦下面的定義可以看出ssd的話返回0，hdd的話返回1
#define QUEUE_FLAG_NONROT	9	/* non-rotational device (SSD) */

[
 
[email protected] ~]# cat /sys/block/sda/queue/rotational
1
[[email protected] ~]#