[PATCH] nvme: cancel pending I/O if nvme controller is in terminal state

[Nilay Shroff]

While I/O is running, if the pci bus error occurs then
in-flight I/O can not complete. Worst, if at this time,
user (logically) hot-unplug the nvme disk then the
nvme_remove() code path can't forward progress until
in-flight I/O is cancelled. So these sequence of events
may potentially hang hot-unplug code path indefinitely.
This patch helps cancel the pending/in-flight I/O from the
nvme request timeout handler in case the nvme controller
is in the terminal (DEAD/DELETING/DELETING_NOIO) state and
that helps nvme_remove() code path forward progress and
finish successfully.

Link: https://lore.kernel.org/all/199be893-5dfa-41e5-b6f2-40ac90ebccc4@linux.ibm.com/
Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 drivers/nvme/host/core.c | 21 ---------------------
 drivers/nvme/host/nvme.h | 21 +++++++++++++++++++++
 drivers/nvme/host/pci.c  |  8 +++++++-
 3 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 27281a9a8951..2ce63474eb47 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -628,27 +628,6 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
 }
 EXPORT_SYMBOL_GPL(nvme_change_ctrl_state);
 
-/*
- * Returns true for sink states that can't ever transition back to live.
- */
-static bool nvme_state_terminal(struct nvme_ctrl *ctrl)
-{
-	switch (nvme_ctrl_state(ctrl)) {
-	case NVME_CTRL_NEW:
-	case NVME_CTRL_LIVE:
-	case NVME_CTRL_RESETTING:
-	case NVME_CTRL_CONNECTING:
-		return false;
-	case NVME_CTRL_DELETING:
-	case NVME_CTRL_DELETING_NOIO:
-	case NVME_CTRL_DEAD:
-		return true;
-	default:
-		WARN_ONCE(1, "Unhandled ctrl state:%d", ctrl->state);
-		return true;
-	}
-}
-
 /*
  * Waits for the controller state to be resetting, or returns false if it is
  * not possible to ever transition to that state.
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index d0ed64dc7380..b564c5f1450c 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -741,6 +741,27 @@ static inline bool nvme_is_aen_req(u16 qid, __u16 command_id)
 		nvme_tag_from_cid(command_id) >= NVME_AQ_BLK_MQ_DEPTH;
 }
 
+/*
+ * Returns true for sink states that can't ever transition back to live.
+ */
+static inline bool nvme_state_terminal(struct nvme_ctrl *ctrl)
+{
+	switch (nvme_ctrl_state(ctrl)) {
+	case NVME_CTRL_NEW:
+	case NVME_CTRL_LIVE:
+	case NVME_CTRL_RESETTING:
+	case NVME_CTRL_CONNECTING:
+		return false;
+	case NVME_CTRL_DELETING:
+	case NVME_CTRL_DELETING_NOIO:
+	case NVME_CTRL_DEAD:
+		return true;
+	default:
+		WARN_ONCE(1, "Unhandled ctrl state:%d", ctrl->state);
+		return true;
+	}
+}
+
 void nvme_complete_rq(struct request *req);
 void nvme_complete_batch_req(struct request *req);
 
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 8e0bb9692685..e393f6947ce4 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1286,6 +1286,9 @@ static enum blk_eh_timer_return nvme_timeout(struct request *req)
 	u32 csts = readl(dev->bar + NVME_REG_CSTS);
 	u8 opcode;
 
+	if (nvme_state_terminal(&dev->ctrl))
+		goto disable;
+
 	/* If PCI error recovery process is happening, we cannot reset or
 	 * the recovery mechanism will surely fail.
 	 */
@@ -1390,8 +1393,11 @@ static enum blk_eh_timer_return nvme_timeout(struct request *req)
 	return BLK_EH_RESET_TIMER;
 
 disable:
-	if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
+	if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING)) {
+		if (nvme_state_terminal(&dev->ctrl))
+			nvme_dev_disable(dev, true);
 		return BLK_EH_DONE;
+	}
 
 	nvme_dev_disable(dev, false);
 	if (nvme_try_sched_reset(&dev->ctrl))
-- 
2.44.0