Re: [PATCH V2 0/4] nvme: fix two kinds of IO hang from removing NSs

[Keith Busch <kbusch@kernel.org>]

On Sun, Jun 25, 2023 at 08:26:48AM +0800, Ming Lei wrote:
> Yeah, but you can't remove the gap at all with start_freeze, that said
> the current code has to live with the situation of new mapping change
> and old request with old mapping.
> 
> Actually I considered to handle this kind of situation before, one approach
> is to reuse the bio steal logic taken in nvme mpath:
> 
> 1) for FS IO, re-submit bios, meantime free request
> 
> 2) for PT request, simply fail it
> 
> It could be a bit violent for 2) even though REQ_FAILFAST_DRIVER is
> always set for PT request, but not see any better approach for handling
> PT request.

I think that's acceptable for PT requests, or any request that doesn't
have a bio. I tried something similiar a while back that was almost
working, but I neither never posted it, or it's in that window when
infradead lost all the emails. :(

Anyway, for the pci controller, I think I see the problem you're fixing.
When reset_work fails, we used to do the mark dead + unquieces via
"nvme_kill_queues()", which doesn't exist anymore, but I think your
scenario worked back then. Currently a failed nvme_reset_work simply
marks them dead without the unquiesce. Would it be enough to just bring
that unqueisce behavior back?

---
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index b027e5e3f4acb..8eaa954aa6ed4 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2778,6 +2778,7 @@ static void nvme_reset_work(struct work_struct *work)
 	nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DELETING);
 	nvme_dev_disable(dev, true);
 	nvme_mark_namespaces_dead(&dev->ctrl);
+	nvme_unquiesce_io_queues(&dev->ctrl);
 	nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DEAD);
 }
 
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