From: K. Y. Srinivasan <kys@microsoft.com>
Date: Sat, 12 Jul 2014 16:48:30 +0000 (-0700)
Subject: Drivers: scsi: storvsc: Implement a eh_timed_out handler
X-Git-Tag: v3.2.64~213
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5519f195164345cf4f9344b05eca70dca915d6a4;p=pandora-kernel.git

Drivers: scsi: storvsc: Implement a eh_timed_out handler

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>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/staging/hv/storvsc_drv.c b/drivers/staging/hv/storvsc_drv.c
index 8960f1a73546..c43a9e8ecf21 100644
--- a/drivers/staging/hv/storvsc_drv.c
+++ b/drivers/staging/hv/storvsc_drv.c
@@ -32,6 +32,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/hyperv.h>
+#include <linux/blkdev.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_host.h>
@@ -1129,6 +1130,16 @@ static void storvsc_command_completion(struct hv_storvsc_request *request)
 	kmem_cache_free(host_dev->request_pool, cmd_request);
 }
 
+/*
+ * 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_check_scsi_cmd(struct scsi_cmnd *scmnd)
 {
 	bool allowed = true;
@@ -1305,6 +1316,7 @@ 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_configure =	storvsc_device_configure,
 	.cmd_per_lun =		1,