diff options
author | Uday Shankar <ushankar@purestorage.com> | 2023-05-25 21:22:03 +0300 |
---|---|---|
committer | Keith Busch <kbusch@kernel.org> | 2023-05-30 19:20:47 +0300 |
commit | 774a9636514764ddc0d072ae0d1d1c01a47e6ddd (patch) | |
tree | 6382c82bc024e5f9ab79de01d615f50774a83c9b /drivers/nvme | |
parent | ea4d453b9ec9ea279c39744cd0ecb47ef48ede35 (diff) | |
download | linux-774a9636514764ddc0d072ae0d1d1c01a47e6ddd.tar.xz |
nvme: check IO start time when deciding to defer KA
When a command completes, we set a flag which will skip sending a
keep alive at the next run of nvme_keep_alive_work when TBKAS is on.
However, if the command was submitted long ago, it's possible that
the controller may have also restarted its keep alive timer (as a
result of receiving the command) long ago. The following trace
demonstrates the issue, assuming TBKAS is on and KATO = 8 for
simplicity:
1. t = 0: submit I/O commands A, B, C, D, E
2. t = 0.5: commands A, B, C, D, E reach controller, restart its keep
alive timer
3. t = 1: A completes
4. t = 2: run nvme_keep_alive_work, see recent completion, do nothing
5. t = 3: B completes
6. t = 4: run nvme_keep_alive_work, see recent completion, do nothing
7. t = 5: C completes
8. t = 6: run nvme_keep_alive_work, see recent completion, do nothing
9. t = 7: D completes
10. t = 8: run nvme_keep_alive_work, see recent completion, do nothing
11. t = 9: E completes
At this point, 8.5 seconds have passed without restarting the
controller's keep alive timer, so the controller will detect a keep
alive timeout.
Fix this by checking the IO start time when deciding to defer sending a
keep alive command. Only set comp_seen if the command started after the
most recent run of nvme_keep_alive_work. With this change, the
completions of B, C, and D will not set comp_seen and the run of
nvme_keep_alive_work at t = 4 will send a keep alive.
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: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Diffstat (limited to 'drivers/nvme')
-rw-r--r-- | drivers/nvme/host/core.c | 14 | ||||
-rw-r--r-- | drivers/nvme/host/nvme.h | 1 |
2 files changed, 14 insertions, 1 deletions
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 6417c7928fa3..dbfca1b925f8 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -397,7 +397,16 @@ void nvme_complete_rq(struct request *req) trace_nvme_complete_rq(req); nvme_cleanup_cmd(req); - if (ctrl->kas) + /* + * Completions of long-running commands should not be able to + * defer sending of periodic keep alives, since the controller + * may have completed processing such commands a long time ago + * (arbitrarily close to command submission time). + * req->deadline - req->timeout is the command submission time + * in jiffies. + */ + if (ctrl->kas && + req->deadline - req->timeout >= ctrl->ka_last_check_time) ctrl->comp_seen = true; switch (nvme_decide_disposition(req)) { @@ -1200,6 +1209,7 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, return RQ_END_IO_NONE; } + ctrl->ka_last_check_time = jiffies; ctrl->comp_seen = false; spin_lock_irqsave(&ctrl->lock, flags); if (ctrl->state == NVME_CTRL_LIVE || @@ -1218,6 +1228,8 @@ static void nvme_keep_alive_work(struct work_struct *work) bool comp_seen = ctrl->comp_seen; struct request *rq; + ctrl->ka_last_check_time = jiffies; + if ((ctrl->ctratt & NVME_CTRL_ATTR_TBKAS) && comp_seen) { dev_dbg(ctrl->device, "reschedule traffic based keep-alive timer\n"); diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h index 2dd52739236e..8657811f8b88 100644 --- a/drivers/nvme/host/nvme.h +++ b/drivers/nvme/host/nvme.h @@ -328,6 +328,7 @@ struct nvme_ctrl { struct delayed_work ka_work; struct delayed_work failfast_work; struct nvme_command ka_cmd; + unsigned long ka_last_check_time; struct work_struct fw_act_work; unsigned long events; |