3.2.63-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
[hch: added a better comment explaining the issue]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
drivers/staging/hv/storvsc_drv.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- 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(s
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_dr
.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,
--
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