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author | Uday Shankar <ushankar@purestorage.com> | 2023-05-25 12:22:04 -0600 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-06-28 11:12:36 +0200 |
commit | ba0cc7a2e508d6b8f945afde47689126d9d6b702 (patch) | |
tree | 904fec926243d528c071cf884ca6de76cbc06da1 | |
parent | 06d9ec407f76f895bbeea87501badc601da889c3 (diff) | |
download | linux-ba0cc7a2e508d6b8f945afde47689126d9d6b702.tar.gz |
nvme: improve handling of long keep alives
[ Upstream commit c7275ce6a5fd32ca9f5a6294ed89cf0523181af9 ] Upon keep alive completion, nvme_keep_alive_work is scheduled with the same delay every time. If keep alive commands are completing slowly, this may cause a keep alive timeout. The following trace illustrates the issue, taking KATO = 8 and TBKAS off for simplicity: 1. t = 0: run nvme_keep_alive_work, send keep alive 2. t = ε: keep alive reaches controller, controller restarts its keep alive timer 3. t = 4: host receives keep alive completion, schedules nvme_keep_alive_work with delay 4 4. t = 8: run nvme_keep_alive_work, send keep alive Here, a keep alive having RTT of 4 causes a delay of at least 8 - ε between the controller receiving successive keep alives. With ε small, the controller is likely to detect a keep alive timeout. Fix this by calculating the RTT of the keep alive command, and adjusting the scheduling delay of the next keep alive work accordingly. Reported-by: Costa Sapuntzakis <costa@purestorage.com> Reported-by: Randy Jennings <randyj@purestorage.com> Signed-off-by: Uday Shankar <ushankar@purestorage.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r-- | drivers/nvme/host/core.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 15eb2ee1be66..a7d9b5b42b38 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -1234,6 +1234,20 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, struct nvme_ctrl *ctrl = rq->end_io_data; unsigned long flags; bool startka = false; + unsigned long rtt = jiffies - (rq->deadline - rq->timeout); + unsigned long delay = nvme_keep_alive_work_period(ctrl); + + /* + * Subtract off the keepalive RTT so nvme_keep_alive_work runs + * at the desired frequency. + */ + if (rtt <= delay) { + delay -= rtt; + } else { + dev_warn(ctrl->device, "long keepalive RTT (%u ms)\n", + jiffies_to_msecs(rtt)); + delay = 0; + } blk_mq_free_request(rq); @@ -1252,7 +1266,7 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, startka = true; spin_unlock_irqrestore(&ctrl->lock, flags); if (startka) - nvme_queue_keep_alive_work(ctrl); + queue_delayed_work(nvme_wq, &ctrl->ka_work, delay); return RQ_END_IO_NONE; } |