Re: [PATCH v2 12/14] nvme-fc: Decouple error recovery from controller reset
From: James Smart
Date: Wed Feb 04 2026 - 19:08:24 EST
On 2/3/2026 4:11 PM, Mohamed Khalfella wrote:
On Tue 2026-02-03 11:19:28 -0800, James Smart wrote:...
On 1/30/2026 2:34 PM, Mohamed Khalfella wrote:
+static void nvme_fc_start_ioerr_recovery(struct nvme_fc_ctrl *ctrl,> +> + dev_warn(ctrl->ctrl.device, "NVME-FC{%d}: starting error
+ char *errmsg)
+{
+ if (!nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_RESETTING))
+ return;
recovery %s\n",
+ ctrl->cnum, errmsg);
+ queue_work(nvme_reset_wq, &ctrl->ioerr_work);
+}
+
Disagree with this.
The clause in error_recovery around the CONNECTING state is pretty
important to terminate io occurring during connect/reconnect where the
ctrl state should not change. we don't want start_ioerr making it RESETTING.
This should be reworked.
Like you pointed out this changes the current behavior for CONNECTING
state.
Before this change, as you pointed out the controller state stays in
CONNECTING while all IOs are aborted. Aborting the IOs causes
nvme_fc_create_association() to fail and reconnect might be attempted
again.
The new behavior switches to RESETTING and queues ctr->ioerr_work.
ioerr_work will abort oustanding IOs, swich back to CONNECING and
attempt reconnect.
Well, it won't actually switch to RESETTING, as CONNECTING->RESETTING is not a valid transition. So things will silently stop in start_ioerr_recovery when the state transition fails (also a reason I dislike silent state transition failures).
When I look a little further into patch 13, I see the change to FENCING added. But that state transition will also fail for CONNECTING->FENCING. It will then fall into the resetting state change, which will silently fail, and we're stopped. It says to me there was no consideration or testing of failures while CONNECTING with this patch set. Even if RESETTING were allowed, its injecting a new flow into the code paths.
The CONNECTING issue also applies to tcp and rdma transports. I don't know if they call the error_recovery routines in the same way.
To be honest I'm not sure I remember the original reasons this loop was put in, but I do remember pain I went through when generating it and the number of test cases that were needed to cover testing. It may well be because I couldn't invoke the reset due to the CONNECTING->RESETTING block. I'm being pedantic as I still feel residual pain for it.
nvme_fc_error_recovery() ->
nvme_stop_keep_alive() /* should not make a difference */
nvme_stop_ctrl() /* should be okay to run */
nvme_fc_delete_association() ->
__nvme_fc_abort_outstanding_ios(ctrl, false)
nvme_unquiesce_admin_queue()
nvme_unquiesce_io_queues()
nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_CONNECTING)
if (port_state == ONLINE)
queue_work(ctrl->connect)
else
nvme_fc_reconnect_or_delete();
Yes, this is a different behavior. IMO it is simpler to follow and
closer to what other transports do, keeping in mind async abort nature
of fc.
Aside from it is different, what is wrong with it?
See above.
...
static int
@@ -2495,39 +2506,6 @@ __nvme_fc_abort_outstanding_ios(struct nvme_fc_ctrl *ctrl, bool start_queues)
nvme_unquiesce_admin_queue(&ctrl->ctrl);
}
-static void
-nvme_fc_error_recovery(struct nvme_fc_ctrl *ctrl, char *errmsg)
-{
- enum nvme_ctrl_state state = nvme_ctrl_state(&ctrl->ctrl);
-
- /*
- * if an error (io timeout, etc) while (re)connecting, the remote
- * port requested terminating of the association (disconnect_ls)
- * or an error (timeout or abort) occurred on an io while creating
- * the controller. Abort any ios on the association and let the
- * create_association error path resolve things.
- */
- if (state == NVME_CTRL_CONNECTING) {
- __nvme_fc_abort_outstanding_ios(ctrl, true);
- dev_warn(ctrl->ctrl.device,
- "NVME-FC{%d}: transport error during (re)connect\n",
- ctrl->cnum);
- return;
- }
This logic needs to be preserved. Its no longer part of
nvme_fc_start_ioerr_recovery(). Failures during CONNECTING should not be
"fenced". They should fail immediately.
I think this is similar to the point above.
Forgetting whether or not the above "works", what I'm pointing out is that when in CONNECTING I don't believe you should be enacting the FENCED state and delaying. For CONNECTING, the cleanup should be immediate with no delay and no CCR attempt. Only LIVE should transition to FENCED.
Looking at patch 14, fencing_work calls nvme_fence_ctrl() which unconditionally delays and tries to do CCR. We only want this if LIVE. I'll comment on that patch.
There is a small difference here in that The existing code avoids doing
the ctrl reset if the controller is NEW. start_ioerr will change the
ctrl to RESETTING. I'm not sure how much of an impact that is.
I think there is little done while controller in NEW state.
Let me know if I am missing something.
No - I had to update my understanding I was really out of date. Used to be NEW is what initial controller create was done under. Everybody does it now under CONNECTING.
...
static enum blk_eh_timer_return nvme_fc_timeout(struct request *rq)
{
struct nvme_fc_fcp_op *op = blk_mq_rq_to_pdu(rq);
@@ -2536,24 +2514,14 @@ static enum blk_eh_timer_return nvme_fc_timeout(struct request *rq)
struct nvme_fc_cmd_iu *cmdiu = &op->cmd_iu;
struct nvme_command *sqe = &cmdiu->sqe;
- /*
- * Attempt to abort the offending command. Command completion
- * will detect the aborted io and will fail the connection.
- */
dev_info(ctrl->ctrl.device,
"NVME-FC{%d.%d}: io timeout: opcode %d fctype %d (%s) w10/11: "
"x%08x/x%08x\n",
ctrl->cnum, qnum, sqe->common.opcode, sqe->fabrics.fctype,
nvme_fabrics_opcode_str(qnum, sqe),
sqe->common.cdw10, sqe->common.cdw11);
- if (__nvme_fc_abort_op(ctrl, op))
- nvme_fc_error_recovery(ctrl, "io timeout abort failed");
- /*
- * the io abort has been initiated. Have the reset timer
- * restarted and the abort completion will complete the io
- * shortly. Avoids a synchronous wait while the abort finishes.
- */
+ nvme_fc_start_ioerr_recovery(ctrl, "io timeout");
Why get rid of the abort logic ?
Note: the error recovery/controller reset is only called when the abort
failed.
I believe you should continue to abort the op. The fence logic will
kick in when the op completes later (along with other io completions).
If nothing else, it allows a hw resource to be freed up.
The abort logic from nvme_fc_timeout() is problematic and it does not
play well with abort initiatored from ioerr_work or reset_work. The
problem is that op aborted from nvme_fc_timeout() is not accounted for
when the controller is reset.
note: I'll wait to be shown otherwise, but if this were true it would be horribly broken for a long time.
Here is an example scenario.
The first time a request times out it gets aborted we see this codepath
nvme_fc_timeout() ->
__nvme_fc_abort_op() ->
atomic_xchg(&op->state, FCPOP_STATE_ABORTED)
ops->abort()
return 0;
there's more than this in in the code:
it changes op state to ABORTED, saving the old opstate.
if the opstate wasn't active - it means something else changed and it restores the old state (e.g. the aborts for the reset may have hit it).
if it was active (e.g. the aborts the reset haven't hit it yet) it checks the ctlr flag to see if the controller is being reset and tracking io termination (the TERMIO flag) and if so, increments the iocnt. So it is "included" in the reset.
if old state was active, it then sends the ABTS.
if old state wasn't active (we've been here before or io terminated by reset) it returns -ECANCELED, which will cause a controller reset to be attempted if there's not already one in process.
nvme_fc_timeout() always return BLK_EH_RESET_TIMER so the same request
can timeout again. If the same request hits timeout again then
__nvme_fc_abort_op() returns -ECANCELED and nvme_fc_error_recovery()
gets called. Assuming the controller is LIVE it will be reset.
The normal case is timeout generates ABTS. ABTS usually completes quickly with the io completing and the io callback to iodone, which sees abort error status and resets controller. Its very typical for the ABTS to complete long before the 2nd EH timer timing out.
Abnormal case is ABTS takes longer to complete than the 2nd EH timer timing. Yes, that forces the controller reset. I am aware that some arrays will delay ABTS ACC while they terminate the back end, but there are also frame drop conditions to consider.
if the controller is already resetting, all the above is largely n/a.
I see no reason to avoid the ABTS and wait for a 2nd EH timer to fire.
nvme_fc_reset_ctrl_work() ->
nvme_fc_delete_association() ->
__nvme_fc_abort_outstanding_ios() ->
nvme_fc_terminate_exchange() ->
__nvme_fc_abort_op()
__nvme_fc_abort_op() finds that op already aborted. As a result of that
ctrl->iocnt will not be incrmented for this op. This means that
nvme_fc_delete_association() will not wait for this op to be aborted.
see missing code stmt above.
I do not think we wait this behavior.
To continue the scenario above. The controller switches to CONNECTING
and the request times out again. This time we hit the deadlock described
in [1].
I think the first abort is the cause of the issue here. with this change
we should not hit the scenario described above.
1 - https://lore.kernel.org/all/20250529214928.2112990-1-mkhalfella@xxxxxxxxxxxxxxx/
Something else happened here. You can't get to CONNECTING state unless all outstanding io was reaped in delete association. What is also harder to understand is how there was an io to timeout if they've all been reaped and queues haven't been restarted. Timeout on one of the ios to instatiate/init the controller maybe, but it shouldn't have been one of those in the blk layer.
return BLK_EH_RESET_TIMER;
}
@@ -3352,6 +3320,26 @@ nvme_fc_reset_ctrl_work(struct work_struct *work)
}
}
+static void
+nvme_fc_error_recovery(struct nvme_fc_ctrl *ctrl)
+{
+ nvme_stop_keep_alive(&ctrl->ctrl);
Curious, why did the stop_keep_alive() call get added to this ?
Doesn't hurt.
I assume it was due to other transports having it as they originally
were calling stop_ctrl, but then moved to stop_keep_alive. Shouldn't
this be followed by flush_work((&ctrl->ctrl.async_event_work) ?
Yes. I added it because it matches what other transports do.
nvme_fc_error_recovery() ->
nvme_fc_delete_association() ->
nvme_fc_abort_aen_ops() ->
nvme_fc_term_aen_ops() ->
cancel_work_sync(&ctrl->ctrl.async_event_work);
The above codepath takes care of async_event_work.
True, but the flush_works were added for a reason to the other transports so I'm guessing timing matters. So waiting till ther later term_aen call isn't great. But I also guess, we haven't had an issue prior and since we did take care if it in the aen routines, its likely unneeded now. Ok to add it but if so, we should keep the flush_work as well. Also good to look same as the other transports.
+ nvme_stop_ctrl(&ctrl->ctrl);
+
+ /* will block while waiting for io to terminate */
+ nvme_fc_delete_association(ctrl);
+
+ /* Do not reconnect if controller is being deleted */
+ if (!nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_CONNECTING))
+ return;
+
+ if (ctrl->rport->remoteport.port_state == FC_OBJSTATE_ONLINE) {
+ queue_delayed_work(nvme_wq, &ctrl->connect_work, 0);
+ return;
+ }
+
+ nvme_fc_reconnect_or_delete(ctrl, -ENOTCONN);
+}
This code and that in nvme_fc_reset_ctrl_work() need to be collapsed
into a common helper function invoked by the 2 routines. Also addresses
the missing flush_delayed work in this routine.
Agree, nvme_fc_error_recovery() and nvme_fc_reset_ctrl_work() have
common code that can be refactored. However, I do not plan to do this
part of this change. I will take a look after I get CCR work done.
Don't put it off. You are adding as much code as the refactoring is. Just make the change.
-- james