[PATCHSET] libata: various fixes related to EH, take #4

[Tejun Heo <htejun@gmail.com>]

Hello, Jeff.

This patchset is the fourth take of 'various fixes related to EH'
patchset.  From the previous take[1], %01 and %02 made into the tree
and %03 got nacked and #04 acked but didn't make into the tree due to
dependency to %03.  (% denotes patch numbers in the previous take, #
in this take)

Changes from the last take.

* %03 reimplemented using sht->eh_timed_out() callback as Jeff
  suggested[2].

* assert(ata_qc_from_tag(ap, ap->active_tag)) is added to
  ata_scsi_error() in patch %04.

This patchset contains the following patches.

#01-03	: implement and use ata_scsi_timed_out()
#04	: kill NULL qc handling and add above described assertion

I used ATA_QCFLAG_EH_SCHEDULED instead of ATA_QCFLAG_TIMEOUT because
the same flag will be used later by EH patchset in the same manner.

Simulated the following three cases and all work fine.

* normal time out
* timeout wins, but qc completion kicks in before EH
* timeout loses (ata_scsi_timed_out() returns EH_HANDLED)

Thanks.

--
tejun

[1] http://article.gmane.org/gmane.linux.ide/7788
[2] http://article.gmane.org/gmane.linux.ide/7890