2017-06-17 20:00 GMT+02:00 Jonathan A. Kollasch <jakll...@kollasch.net>:
>
> I really think we need to make ata_xfer_init() private to
> ata_queue_alloc(), and use ata_get_xfer() everywhere.  That we can
> fabricate an xfer on the stack anywhere that will trample all over an
> active command slot is fundamentally wrong.

Any non-NCQ command which goes via atastart() is safe, since that routine
makes sure there is only one non-NCQ command being executed by HBA.

The on-stack xfer was carried over from previous design. I kept it mostly
since I didn't want to change those codepaths to deal with xfer not being
available.

As far as I see, ahcisata(4) reset should be actually fine, since it does
the reset
without using the xfers/slots.

I had a look at siisata_reset_drive(). That thing indeed can't reliably
work as-is.
Arguably it should be changed to use the on-stack xfer, currently it e.g.
doesn't
do anything if all slots are taken, which is wrong. I'll have a look.

> ata_queue_downsize() currently appears to leak xfers.  Additionally once
> you put a QD1 drive on the channel you're stuck there forever, even if
> you replace the channel population entirely with QD32 drives.

Okay, I need to look at this - original assumption was that it's never
called while there are other transfers. This is false with PMP.

Jaromir

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