Alan Cox wrote:
Not that simple. Most disks don't spin up on SYNCHRONIZE_CACHE if its
cache is clean. Sadly some disks actually spin up when it receives spin
down command while spun down to immediately spin down again, so we would
be fixing problem for some number of disks while breaking others. :-(
Snoop the last command sent to the drive, that tells you if you can skip
the cache flush ?
Thought about that and querying power state before doing shutdown
sequence but things get somewhat ugly because shutdown sequence is
driven from sd->shutdown(). We'll have to snoop both sync and shutdown
commands and check whether the system is shutting down. Also, I felt
very uneasy about faking successful completion to SYNCHRONIZE_CACHE.
I dunno. It's already too late for 2.6.21. I was hoping we could get
distros to update shutdown utilities in not-too-distant future but I
have no experience with that. Is that just a wishful thinking?
--
tejun
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