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SubjectNew SCSI subsystem in 2.4, and scsi idle patch
Date
I'm trying to get my 2.4.9 system to spin down my scsi disk(s) when idle.  
Aparently, this is supported on IDE disks, but not SCSI. I found an old
patch to add support for this to the 2.0.34 kernel, and have been trying to
use it as a guide to fixing the 2.4.9 kernel. It seems that major changes
have been done to the scsi layer, so I'm a little confused. Any help is
appreciated. Here is my current status:

It looks like the code path I need to modify is in
drivers/scsi/sd.c:rw_intr(). It looks to me that this function is called
when the HBA completes an SRB and it decides if it was an error or not, and
completes it correctly. I think I need to check for the NOT_READY sense
status here, and if it is found, try to spin up the disk.

Now for my questions:

1) In the old patch, if the spin up failed, it calls
end_scsi_request, and then requeue_sd_request. I'm not sure why it tries to
requeue a failed request, but the it seems that neither of these functions
exist in the 2.4 kernel. What should I use instead?

2) If the spin up worked, the old code called requeue_sd_request, I assume to
send down the original read/write request to the disk now that it is on.
Once again, what should I use instead of requeue_sd_request to do this?
There is a comment still in the 2.4 code describing this function, but the
function itself is not there.

3) The old code called scsi_do_cmd to send down a START_STOP SRB to the drive
when it decides it should spin the drive back up. This function is also no
longer there, so what should I use to send down the START_STOP SRB?

P.S. I'd like to use a user mode daemon to detect disk idle, and issue the
existing ioctl code to spin the disk down, and rely on the kernel to spin it
back up as needed. Isn't there somewhere in /proc that keeps IO counters on
the disk I can monitor? Also, is there a way I could ask the kernel to not
flush dirty pages to disk unless it gets a whole lot of them so the disk
won't be spun up all the time just to write a few KB?

--
--> Phill Susi
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