[PATCH v2 1/7] nvme: add NVME_CTRL_MARGINAL flag

[Jesse Taube]

From: Bryan Gurney <bgurney@xxxxxxxxxx>

Add a new controller flag, NVME_CTRL_MARGINAL, to help multipath I/O
policies to react to a path that is set to a "marginal" state.

The "marginal" flag is initialized to false in `nvme_init_ctrl` and
cleared in `nvme_fc_ctrl_connectivity_loss` before re-association.
It is only cleared there, not in the generic `nvme_reset_ctrl` path,
because the marginal condition reflects a physical link problem.
An arbitrary controller reset does not signal that a hardware fault has
been resolved. Calling `nvme_fc_ctrl_connectivity_loss` means the FC
association has failed and will be re-established, so the prior link
quality state is no longer meaningful.

Signed-off-by: Bryan Gurney <bgurney@xxxxxxxxxx>
---
V10 -> V1:
 - No change
V1 -> V2:
 - Add nvme_ctrl_assign_marginal
 - Fix nvme_fc_ctrl_connectivity_loss clearing wrong bit.
 - Update commit message
---
 drivers/nvme/host/core.c |  1 +
 drivers/nvme/host/fc.c   |  4 ++++
 drivers/nvme/host/nvme.h | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 453c1f0b2dd0..4ce3c0573707 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -5165,6 +5165,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 	WRITE_ONCE(ctrl->state, NVME_CTRL_NEW);
 	ctrl->passthru_err_log_enabled = false;
 	clear_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags);
+	nvme_ctrl_assign_marginal(ctrl, false);
 	spin_lock_init(&ctrl->lock);
 	mutex_init(&ctrl->namespaces_lock);
 
diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 04363b9c4489..7886c0dcc626 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -788,6 +788,10 @@ nvme_fc_ctrl_connectivity_loss(struct nvme_fc_ctrl *ctrl)
 		"Reconnect", ctrl->cnum);
 
 	set_bit(ASSOC_FAILED, &ctrl->flags);
+
+	/* clear 'marginal' flag as controller will be reset */
+	nvme_ctrl_assign_marginal(&ctrl->ctrl, false);
+
 	nvme_reset_ctrl(&ctrl->ctrl);
 }
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 824651cc898d..640cb4747ba2 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -329,6 +329,7 @@ enum nvme_ctrl_flags {
 	NVME_CTRL_SKIP_ID_CNS_CS	= 4,
 	NVME_CTRL_DIRTY_CAPABILITY	= 5,
 	NVME_CTRL_FROZEN		= 6,
+	NVME_CTRL_MARGINAL		= 7,
 };
 
 struct nvme_ctrl {
@@ -479,6 +480,16 @@ static inline enum nvme_ctrl_state nvme_ctrl_state(struct nvme_ctrl *ctrl)
 	return READ_ONCE(ctrl->state);
 }
 
+static inline bool nvme_ctrl_is_marginal(struct nvme_ctrl *ctrl)
+{
+	return test_bit(NVME_CTRL_MARGINAL, &ctrl->flags);
+}
+
+static inline void nvme_ctrl_assign_marginal(struct nvme_ctrl *ctrl, bool marginal)
+{
+	assign_bit(NVME_CTRL_MARGINAL, &ctrl->flags, marginal);
+}
+
 enum nvme_iopolicy {
 	NVME_IOPOLICY_NUMA,
 	NVME_IOPOLICY_RR,
-- 
2.55.0