libata: implement EH fast drain

In most cases, when EH is scheduled, all in-flight commands are
aborted causing EH to kick in immediately.  However, in some cases
(especially with PMP), it's unclear which commands are affected by the
error condition and although aborting all in-flight commands work, it
isn't optimal and may cause unnecessary disruption.  On the other
hand, waiting for in-flight commands to drain themselves can take up
to 30seconds.

This patch implements EH fast drain to handle such situations.  It
gives in-flight commands some time to finish up but doesn't wait for
too long.  After EH is scheduled, fast drain timer is started and if
no other completion occurs in ATA_EH_FASTDRAIN_INTERVAL all in-flight
commands are aborted.  If any completion occurred in the interval, the
port is given another interval to finish up itself.

Currently ATA_EH_FASTDRAIN_INTERVAL is 3 secs which should be enough
for finishing up most commands.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 48836b22ce2..564cd234c80 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -151,6 +151,7 @@ extern int ata_bus_probe(struct ata_port *ap);
 extern enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd);
 extern void ata_scsi_error(struct Scsi_Host *host);
 extern void ata_port_wait_eh(struct ata_port *ap);
+extern void ata_eh_fastdrain_timerfn(unsigned long arg);
 extern void ata_qc_schedule_eh(struct ata_queued_cmd *qc);
 
 /* libata-sff.c */