[PATCH stable 5.4+] nvme: fix possible hang when ns scanning fails during error recovery

[Sagi Grimberg <sagi@grimberg.me>]

When the controller is reconnecting, the host fails I/O and admin
commands as the host cannot reach the controller. ns scanning may
revalidate namespaces during that period and it is wrong to remove
namespaces due to these failures as we may hang (see 205da2434301).

One command that may fail is nvme_identify_ns_descs. Since we return
success due to having ns descriptor list optional, we continue to
validate ns identifiers in nvme_revalidate_disk, obviously fail and
return -ENODEV to nvme_validate_ns, which will remove the namespace.

Exactly what we don't want to happen.

Fixes: 22802bf742c2 ("nvme: Namepace identification descriptor list is optional")
Tested-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 31b7dcd791c2..8ce9b4fbc821 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1746,7 +1746,7 @@ static int nvme_report_ns_ids(struct nvme_ctrl *ctrl, unsigned int nsid,
 		if (ret)
 			dev_warn(ctrl->device,
 				 "Identify Descriptors failed (%d)\n", ret);
-		if (ret > 0)
+		if (ret > 0 && !(ret & NVME_SC_DNR))
 			ret = 0;
 	}
 	return ret;
-- 
2.20.1