Re: SYNCHRONIZE CACHE command from sd on close

[Christoph Hellwig <hch@infradead.org>]

On Fri, Feb 19, 2010 at 01:20:25AM +0100, Douglas Gilbert wrote:
> So send a START_STOP_UNIT(stop) through the SG_IO
> ioctl on a sd device opened RW and as a bonus get
> three INQUIRYs (one standard, two VPD pages) and 5 READ
> commands!
>
> If the device is SCSI (as the scsi_debug driver is
> simulating) then those READs fail because the drive
> is stopped. However if that is an ATA disk behind a
> SAT layer, then the disk will be spun up. That defeats
> the purpose of the pass-though, especially when it
> is being used to spin down the disk.
>
> My guess, reviewing the bug reports flowing into me is
> that this nonsense started around lk 2.6.29 .

We should never send INQUIRY or READ commands from the kernel
in response to opening a device.  But the combination sounds
like something udev might be doing for it's stable device
indentifier and manual partition scan because I don't trust
the kernel thing.  Can you check if these commands come from
udev or one of the realted tools (hal, device-kit-blah, udisks
whatever it is called today)