On 4/30/2015 2:02 PM, Bart Van Assche wrote:
On 04/30/15 12:13, Sagi Grimberg wrote:
On 4/30/2015 11:59 AM, Bart Van Assche wrote:
Unlike FC, there is no risk that SCSI devices will be offlined
by the error handler if it is started while a reconnect attempt
is ongoing. Hence report timeout errors as soon as possible
if a higher software layer (e.g. multipathd) needs to be informed
about a timeout. It is assumed that if both fast_io_fail_tmo < 0
and rport->dev_loss_tmo < 0 that this means that there is no
need to report timeouts quickly.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: James Bottomley <JBottomley@xxxxxxxx>
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Cc: Sebastian Parschauer <sebastian.riemer@xxxxxxxxxxxxxxxx>
---
drivers/scsi/scsi_transport_srp.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_transport_srp.c
b/drivers/scsi/scsi_transport_srp.c
index 4a44337..6667c2b 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -61,6 +61,11 @@ static inline struct Scsi_Host
*rport_to_shost(struct srp_rport *r)
return dev_to_shost(r->dev.parent);
}
+static inline struct srp_rport *shost_to_rport(struct Scsi_Host *shost)
+{
+ return transport_class_to_srp_rport(&shost->shost_gendev);
+}
+
/**
* srp_tmo_valid() - check timeout combination validity
* @reconnect_delay: Reconnect delay in seconds.
@@ -626,9 +631,11 @@ static enum blk_eh_timer_return
srp_timed_out(struct scsi_cmnd *scmd)
struct scsi_device *sdev = scmd->device;
struct Scsi_Host *shost = sdev->host;
struct srp_internal *i = to_srp_internal(shost->transportt);
+ struct srp_rport *rport = shost_to_rport(shost);
pr_debug("timeout for sdev %s\n", dev_name(&sdev->sdev_gendev));
- return i->f->reset_timer_if_blocked && scsi_device_blocked(sdev) ?
+ return rport->fast_io_fail_tmo < 0 && rport->dev_loss_tmo < 0 &&
+ i->f->reset_timer_if_blocked && scsi_device_blocked(sdev) ?
BLK_EH_RESET_TIMER : BLK_EH_NOT_HANDLED;
}
I'm not sure I understand the purpose of this patch? If the user
requested fast_io_fail_tmo of X, I would assume it wants srp to retry
for the command for X secs. Why should we fail it any earlier than that?
There is a situation where I've seen srp starting the fast_io_fail_tmo
later than expected because the QP retry exceeded error completion
arrives late for certain workloads. Was this the motivation for this
patch?
The purpose of the srp_timed_out() function is not about failing
commands early but about postponing timeout errors. The above patch
causes a SCSI timeout to be handled as soon as the command timer expires
if rport->fast_io_fail_tmo >= 0 or rport->dev_loss_tmo >= 0.
This change is effective only when
time_to_wc_err + fast_io_fail_tmo < cmd_timeout.
If the user chose this configuration, I imagine the wanted behavior is
that the timeout errors won't be propagated as soon as the cmd timeout
expires no?
Today, srp return BLK_EH_RESET_TIMER until fast_io_fail_tmo kicks in,
and at that point, it unblocks the scsi target terminates all the
commands with TRANSPORT_FAIL_FAST. This will change the behavior to
trigger scsi-eh (abort, reset_device) and reset_host will trigger
another reconnect which is redundant (we have reconnect work inflight).
Can you explain the motivation?
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