linux-kernel - [PATCH AUTOSEL 5.2 132/185] nvme-multipath: fix ana log nsid lookup when nsid is not found

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Message-Id: <20190922184924.32534-132-sashal@kernel.org>
Date:   Sun, 22 Sep 2019 14:48:30 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Anton Eidelman <anton@...htbitslabs.com>,
        James Smart <james.smart@...adcom.com>,
        Hannes Reinecke <hare@...e.com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Sasha Levin <sashal@...nel.org>, linux-nvme@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.2 132/185] nvme-multipath: fix ana log nsid lookup when nsid is not found

From: Anton Eidelman <anton@...htbitslabs.com>

[ Upstream commit e01f91dff91c7b16a6e3faf2565017d497a73f83 ]

ANA log parsing invokes nvme_update_ana_state() per ANA group desc.
This updates the state of namespaces with nsids in desc->nsids[].

Both ctrl->namespaces list and desc->nsids[] array are sorted by nsid.
Hence nvme_update_ana_state() performs a single walk over ctrl->namespaces:
- if current namespace matches the current desc->nsids[n],
  this namespace is updated, and n is incremented.
- the process stops when it encounters the end of either
  ctrl->namespaces end or desc->nsids[]

In case desc->nsids[n] does not match any of ctrl->namespaces,
the remaining nsids following desc->nsids[n] will not be updated.
Such situation was considered abnormal and generated WARN_ON_ONCE.

However ANA log MAY contain nsids not (yet) found in ctrl->namespaces.
For example, lets consider the following scenario:
- nvme0 exposes namespaces with nsids = [2, 3] to the host
- a new namespace nsid = 1 is added dynamically
- also, a ANA topology change is triggered
- NS_CHANGED aen is generated and triggers scan_work
- before scan_work discovers nsid=1 and creates a namespace, a NOTICE_ANA
  aen was issues and ana_work receives ANA log with nsids=[1, 2, 3]

Result: ana_work fails to update ANA state on existing namespaces [2, 3]

Solution:
Change the way nvme_update_ana_state() namespace list walk
checks the current namespace against desc->nsids[n] as follows:
a) ns->head->ns_id < desc->nsids[n]: keep walking ctrl->namespaces.
b) ns->head->ns_id == desc->nsids[n]: match, update the namespace
c) ns->head->ns_id >= desc->nsids[n]: skip to desc->nsids[n+1]

This enables correct operation in the scenario described above.
This also allows ANA log to contain nsids currently invisible
to the host, i.e. inactive nsids.

Signed-off-by: Anton Eidelman <anton@...htbitslabs.com>
Reviewed-by:   James Smart <james.smart@...adcom.com>
Reviewed-by: Hannes Reinecke <hare@...e.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/nvme/host/multipath.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 304aa8a65f2f8..f928bcfc57b5b 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -501,14 +501,16 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
 
 	down_write(&ctrl->namespaces_rwsem);
 	list_for_each_entry(ns, &ctrl->namespaces, list) {
-		if (ns->head->ns_id != le32_to_cpu(desc->nsids[n]))
+		unsigned nsid = le32_to_cpu(desc->nsids[n]);
+
+		if (ns->head->ns_id < nsid)
 			continue;
-		nvme_update_ns_ana_state(desc, ns);
+		if (ns->head->ns_id == nsid)
+			nvme_update_ns_ana_state(desc, ns);
 		if (++n == nr_nsids)
 			break;
 	}
 	up_write(&ctrl->namespaces_rwsem);
-	WARN_ON_ONCE(n < nr_nsids);
 	return 0;
 }
 
-- 
2.20.1