Re: [PATCH v4 04/43] hpsa: clean up aborts

[Tomas Henzl <thenzl@redhat.com>]

On 04/16/2015 03:47 PM, Don Brace wrote:
> From: Stephen Cameron <stephenmcameron@gmail.com>
>
> Do not send aborts to logical devices that do not support aborts
>
> Instead of relying on what the Smart Array claims for supporting logical
> drives, simply try an abort and see how it responds at device discovery
> time.  This way devices that do support aborts (e.g. MSA2000) can work
> and we do not waste time trying to send aborts to logical drives that do
> not support them (important for high IOPS devices.)
>
> While rescanning devices only test whether devices support aborts
> the first time we encounter a device rather than every time.
>
> Some Smart Arrays required aborts to be sent with tags in
> the wrong endian byte order.  To avoid having to know about
> this, we would send two aborts with tags with each endian order.
> On high IOPS devices, this turns out to be not such a hot idea.
> So we now have a list of the devices that got the tag backwards,
> and we only send it one way.
>
> If all available commands are outstanding and the abort handler
> is invoked, the abort handler may not be able to allocate a command
> and may busy-wait excessivly.  Reserve a small number of commands
> for the abort handler and limit the number of concurrent abort
> requests to the number of reserved commands.
>
> Reviewed-by: Scott Teel <scott.teel@pmcs.com>
> Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
> Signed-off-by: Don Brace <don.brace@pmcs.com>

Reviewed-by: Tomas Henzl <thenzl@redhat.com>

Tomas