找到了
http://kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.6
[PATCH] Suspend IDE disks on shutdown
When Patrick removed ide_notify_reboot() in 2.5.42, he didn't notice
that it meant that IDE no longer had any shutdown() functionality.
So we did the right thing on suspend, but not on shutdown.
ide_notify_reboot() was only doing STANDBY on shutdown (because FLUSH
'doesn't work' in 2.4 too) but it worked okay and we still should do STANDBY
on shutdown because some broken disks flush their caches.
Thus just calls bus->suspend() (FLUSH+STANDBY) at shutdown time. We can
add some safety delay later - 2.4 doesn't have any.
真慘..希望可以直接呼叫flush
但是好像為了某些磁碟的相容性..
要不要冒險動手修改Kernrl..將會是我的第一次