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

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

[Sagi Grimberg]

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 identify descriptor list optional, we continue
to compare 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>
---
 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 2df6eb4dfe5c..fd81115edb82 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1125,7 +1125,7 @@ static int nvme_identify_ns_descs(struct nvme_ctrl *ctrl, unsigned nsid,
 		  * Don't treat an error as fatal, as we potentially already
 		  * have a NGUID or EUI-64.
 		  */
-		if (status > 0)
+		if (status > 0 && !(status & NVME_SC_DNR))
 			status = 0;
 		goto free_data;
 	}
-- 
2.20.1


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Re: [PATCH] nvme: fix possible hang when ns scanning fails during error recovery

[Keith Busch]

On Wed, May 06, 2020 at 03:44:02PM -0700, Sagi Grimberg wrote:
> 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 identify descriptor list optional, we continue
> to compare 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.

Looks fine,

Reviewed-by: Keith Busch <kbusch@kernel.org>

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