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Subject[PATCH V4 2/5] nvme: add helper interface to flush in-flight requests
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Currently, we use nvme_cancel_request to complete the request
forcedly. This has following defects:
- It is not safe to race with the normal completion path.
blk_mq_complete_request is ok to race with timeout path,
but not with itself.
- Cannot ensure all the requests have been handled. The timeout
path may grab some expired requests, blk_mq_complete_request
cannot touch them.

add two helper interface to flush in-flight requests more safely.
- nvme_abort_requests_sync
use nvme_abort_req to timeout all the in-flight requests and wait
until timeout work and irq completion path completes. More details
please refer to the comment of this interface.
- nvme_flush_aborted_requests
complete the requests 'aborted' by nvme_abort_requests_sync. It will
be invoked after the controller is disabled/shutdown.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
---
drivers/nvme/host/core.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
drivers/nvme/host/nvme.h | 4 +-
2 files changed, 99 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 7b8df47..e26759b 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3567,6 +3567,102 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
}
EXPORT_SYMBOL_GPL(nvme_start_queues);

+static void nvme_abort_req(struct request *req, void *data, bool reserved)
+{
+ if (!blk_mq_request_started(req))
+ return;
+
+ dev_dbg_ratelimited(((struct nvme_ctrl *) data)->device,
+ "Abort I/O %d", req->tag);
+
+ /* The timeout path need identify this flag and return
+ * BLK_EH_NOT_HANDLED, then the request will not be completed.
+ * we will defer the completion after the controller is disabled or
+ * shutdown.
+ */
+ set_bit(NVME_REQ_ABORTED, &nvme_req(req)->flags);
+ blk_abort_request(req);
+}
+
+/*
+ * This function will ensure all the in-flight requests on the
+ * controller to be handled by timeout path or irq completion path.
+ * It has to pair with nvme_flush_aborted_requests which will be
+ * invoked after the controller has been disabled/shutdown and
+ * complete the requests 'aborted' by nvme_abort_req.
+ *
+ * Note, the driver layer will not be quiescent before disable
+ * controller, because the requests aborted by blk_abort_request
+ * are still active and the irq will fire at any time, but it can
+ * not enter into completion path, because the request has been
+ * timed out.
+ */
+void nvme_abort_requests_sync(struct nvme_ctrl *ctrl)
+{
+ struct nvme_ns *ns;
+
+ blk_mq_tagset_busy_iter(ctrl->tagset, nvme_abort_req, ctrl);
+ blk_mq_tagset_busy_iter(ctrl->admin_tagset, nvme_abort_req, ctrl);
+ /*
+ * ensure the timeout_work is queued, thus needn't to sync
+ * the timer
+ */
+ kblockd_schedule_work(&ctrl->admin_q->timeout_work);
+
+ down_read(&ctrl->namespaces_rwsem);
+
+ list_for_each_entry(ns, &ctrl->namespaces, list)
+ kblockd_schedule_work(&ns->queue->timeout_work);
+
+ list_for_each_entry(ns, &ctrl->namespaces, list)
+ flush_work(&ns->queue->timeout_work);
+
+ up_read(&ctrl->namespaces_rwsem);
+ /* This will ensure all the nvme irq completion path have exited */
+ synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(nvme_abort_requests_sync);
+
+static void nvme_comp_req(struct request *req, void *data, bool reserved)
+{
+ struct nvme_ctrl *ctrl = (struct nvme_ctrl *)data;
+
+ if (!test_bit(NVME_REQ_ABORTED, &nvme_req(req)->flags))
+ return;
+
+ WARN_ON(!blk_mq_request_started(req));
+
+ if (ctrl->tagset && ctrl->tagset->ops->complete) {
+ clear_bit(NVME_REQ_ABORTED, &nvme_req(req)->flags);
+ /*
+ * We set the status to NVME_SC_ABORT_REQ, then ioq request
+ * will be requeued and adminq one will be failed.
+ */
+ nvme_req(req)->status = NVME_SC_ABORT_REQ;
+ /*
+ * For ioq request, blk_mq_requeue_request should be better
+ * here. But the nvme code will still setup the cmd even if
+ * the RQF_DONTPREP is set. We have to use .complete to free
+ * the cmd and then requeue it.
+ *
+ * For adminq request, invoking .complete directly will miss
+ * blk_mq_sched_completed_request, but this is ok because we
+ * won't have io scheduler for adminq.
+ */
+ ctrl->tagset->ops->complete(req);
+ }
+}
+
+/*
+ * Should pair with nvme_abort_requests_sync
+ */
+void nvme_flush_aborted_requests(struct nvme_ctrl *ctrl)
+{
+ blk_mq_tagset_busy_iter(ctrl->tagset, nvme_comp_req, ctrl);
+ blk_mq_tagset_busy_iter(ctrl->admin_tagset, nvme_comp_req, ctrl);
+}
+EXPORT_SYMBOL_GPL(nvme_flush_aborted_requests);
+
int nvme_reinit_tagset(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set)
{
if (!ctrl->ops->reinit_request)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 02097e8..3c71c73 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -104,6 +104,7 @@ struct nvme_request {

enum {
NVME_REQ_CANCELLED = 0,
+ NVME_REQ_ABORTED, /* cmd is aborted by nvme_abort_request */
};

static inline struct nvme_request *nvme_req(struct request *req)
@@ -381,7 +382,8 @@ void nvme_wait_freeze(struct nvme_ctrl *ctrl);
void nvme_wait_freeze_timeout(struct nvme_ctrl *ctrl, long timeout);
void nvme_start_freeze(struct nvme_ctrl *ctrl);
int nvme_reinit_tagset(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set);
-
+void nvme_abort_requests_sync(struct nvme_ctrl *ctrl);
+void nvme_flush_aborted_requests(struct nvme_ctrl *ctrl);
#define NVME_QID_ANY -1
struct request *nvme_alloc_request(struct request_queue *q,
struct nvme_command *cmd, blk_mq_req_flags_t flags, int qid);
--
2.7.4
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