From: Anton Eidelman <anton@lightbitslabs.com>
To: linux-nvme@lists.infradead.org, hch@lst.de,
keith.busch@intel.com, sagi@grimberg.me, hare@suse.de
Cc: Anton Eidelman <anton@lightbitslabs.com>
Subject: [PATCH v2 1/2] nvme-multipath: fix possible io hang after ctrl reconnect
Date: Fri, 18 Oct 2019 11:32:50 -0700 [thread overview]
Message-ID: <20191018183251.501-1-anton@lightbitslabs.com> (raw)
In-Reply-To: <20191018091016.GA25478@lst.de>
The following scenario results in an IO hang:
1) ctrl completes a request with NVME_SC_ANA_TRANSITION.
NVME_NS_ANA_PENDING bit in ns->flags is set and ana_work is triggered.
2) ana_work: nvme_read_ana_log() tries to get the ANA log page from the ctrl.
This fails because ctrl disconnects.
Therefore nvme_update_ns_ana_state() is not called
and NVME_NS_ANA_PENDING bit in ns->flags is not cleared.
3) ctrl reconnects: nvme_mpath_init(ctrl,...) calls
nvme_read_ana_log(ctrl, groups_only=true).
However, nvme_update_ana_state() does not update namespaces
because nr_nsids = 0 (due to groups_only mode).
4) scan_work calls nvme_validate_ns() finds the ns and re-validates OK.
Result:
The ctrl is now live but NVME_NS_ANA_PENDING bit in ns->flags is still set.
Consequently ctrl will never be considered a viable path by __nvme_find_path().
IO will hang if ctrl is the only or the last path to the namespace.
More generally, while ctrl is reconnecting, its ANA state may change.
And because nvme_mpath_init() requests ANA log in groups_only mode,
these changes are not propagated to the existing ctrl namespaces.
This may result in a mal-function or an IO hang.
Solution:
nvme_mpath_init() will nvme_read_ana_log() with groups_only set to false.
This will not harm the new ctrl case (no namespaces present),
and will make sure the ANA state of namespaces gets updated after reconnect.
Note: Another option would be for nvme_mpath_init() to invoke
nvme_parse_ana_log(..., nvme_set_ns_ana_state) for each existing namespace.
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
---
drivers/nvme/host/multipath.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 30de7efef003..d320684d25b2 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -715,7 +715,7 @@ int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
goto out;
}
- error = nvme_read_ana_log(ctrl, true);
+ error = nvme_read_ana_log(ctrl, false);
if (error)
goto out_free_ana_log_buf;
return 0;
--
2.14.1
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next prev parent reply other threads:[~2019-10-18 18:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 17:08 [PATCH] nvme-multipath: fix possible io hang after ctrl reconnect Anton Eidelman
2019-10-17 7:03 ` Hannes Reinecke
2019-10-17 15:22 ` Christoph Hellwig
2019-10-17 18:11 ` Anton Eidelman
2019-10-18 9:10 ` Christoph Hellwig
2019-10-18 18:32 ` Anton Eidelman [this message]
2019-10-18 18:32 ` [PATCH v2 2/2] nvme-multipath: remove unused groups_only mode in ana log Anton Eidelman
2019-10-22 19:48 ` Sagi Grimberg
2019-10-22 19:48 ` [PATCH v2 1/2] nvme-multipath: fix possible io hang after ctrl reconnect Sagi Grimberg
2019-10-23 1:18 ` Keith Busch
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