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authorUday Shankar <ushankar@purestorage.com>2023-05-25 21:22:03 +0300
committerKeith Busch <kbusch@kernel.org>2023-05-30 19:20:47 +0300
commit774a9636514764ddc0d072ae0d1d1c01a47e6ddd (patch)
tree6382c82bc024e5f9ab79de01d615f50774a83c9b /drivers/nvme
parentea4d453b9ec9ea279c39744cd0ecb47ef48ede35 (diff)
downloadlinux-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.c14
-rw-r--r--drivers/nvme/host/nvme.h1
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;