[PATCH 3.13 099/187] Drivers: scsi: storvsc: Implement a eh_timed_out handler

Kamal Mostafa
2014-09-15T22:11:38Z

From: "K. Y. Srinivasan" <kys@microsoft.com>

commit 56b26e69c8283121febedd12b3cc193384af46b9 upstream.

On Azure, we have seen instances of unbounded I/O latencies. To deal with
this issue, implement handler that can reset the timeout. Note that the
host gaurantees that it will respond to each command that has been issued.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
[hch: added a better comment explaining the issue]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/scsi/storvsc_drv.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 7e8a642..2b8595b 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -33,6 +33,7 @@
#include <linux/device.h>
#include <linux/hyperv.h>
#include <linux/mempool.h>
+#include <linux/blkdev.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
@@ -1518,6 +1519,16 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
return SUCCESS;
}

+/*
+ * The host guarantees to respond to each command, although I/O latencies might
+ * be unbounded on Azure. Reset the timer unconditionally to give the host a
+ * chance to perform EH.
+ */
+static enum blk_eh_timer_return storvsc_eh_timed_out(struct scsi_cmnd *scmnd)
+{
+ return BLK_EH_RESET_TIMER;
+}
+
static bool storvsc_scsi_cmd_ok(struct scsi_cmnd *scmnd)
{
bool allowed = true;
@@ -1697,6 +1708,7 @@ static struct scsi_host_template scsi_driver = {
.bios_param = storvsc_get_chs,
.queuecommand = storvsc_queuecommand,
.eh_host_reset_handler = storvsc_host_reset_handler,
+ .eh_timed_out = storvsc_eh_timed_out,
.slave_alloc = storvsc_device_alloc,
.slave_destroy = storvsc_device_destroy,
.slave_configure = storvsc_device_configure,
--
1.9.1