Re: [PATCH 08/15] libata: improve ATAPI draining

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> For misc ATAPI commands which transfer variable length data to the
> host, overflow can occur due to application or hardware bug.  Such
> overflows can be ignored safely as long as overflow data is properly
> drained.  libata HSM implementation has this implemented in
> __atapi_pio_bytes() but it isn't enough.  Improve drain logic such
> that...
> 
> * Multiple PIO data phases are allowed.  Not allowing this used to be
>   okay when transfer chunk size was set to 8k unconditionally but with
>   transfer hcunk size set to allocation size, treating extra PIO data
>   phases as HSM violations cause a lot of trouble.
> 
> * Limit the amount of draining to ATAPI_MAX_DRAIN (16k currently).
> 
> * Don't whine if overflow is allowed and safe.  When unexpected
>   overflow occurs, trigger HSM violation and report the problem using
>   ehi error description.
> 
> * Properly calculate the number of bytes to be drained considering
>   actual number of consumed bytes for partial draining.
> 
> * Add and use ata_drain_page for draining.  This change fixes the
>   problem where LLDs which do 32bit IOs consumes 4 bytes on each 2
>   byte draining resulting in draining twice more data than requested.
> 
> This patch fixes ATAPI regressions introduced by setting transfer
> chunk size to allocation size.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> Cc: Albert Lee <albertcc@tw.ibm.com>

I'm dropping this one, since a good portion of it is already upstream 
as140b5e59119a172a91b5fa13d54ca4f79bbefee1

	Jeff