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Drivers: scsi: storvsc: Implement a eh_timed_out handler 

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>
Cc: <stable@vger.kernel.org>
[hch: added a better comment explaining the issue]
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
K. Y. Srinivasan 2014-07-12 09:48:30 -07:00 committed by Christoph Hellwig
parent adb6f9e1a8
commit 56b26e69c8
1 changed files with 12 additions and 0 deletions
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12
drivers/scsi/storvsc_drv.c
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@ -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,