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SubjectRe: [PATCH] nvmet: fix uninitialized work for zero kato
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> Hit a warning:
> WARNING: CPU: 1 PID: 241 at kernel/workqueue.c:1627 __queue_delayed_work+0x6d/0x90
> with trace:
> mod_delayed_work_on+0x59/0x90
> nvmet_update_cc+0xee/0x100 [nvmet]
> nvmet_execute_prop_set+0x72/0x80 [nvmet]
> nvmet_tcp_try_recv_pdu+0x2f7/0x770 [nvmet_tcp]
> nvmet_tcp_io_work+0x63f/0xb2d [nvmet_tcp]
> ...
>
> This could be reproduced easily with a keep alive time 0:
> nvme connect -t tcp -n NQN -a ADDR -s PORT --keep-alive-tmo=0
>
> The reason is:
> Starting an uninitialized work when initiator connects with zero
> kato. Althrough keep-alive timer is disabled during allocating a ctrl
> (fix in 0d3b6a8d213a), ka_work still has a chance to run
> (called by nvmet_start_ctrl to detect dead host).

This should have a "Fixes:" tag.

>
> Initilize ka_work during allocating ctrl, and set a reasonable kato
> before scheduling ka_work.
>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
> drivers/nvme/target/core.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index b7b63330b5ef..3c5b2b065476 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -19,6 +19,8 @@ struct workqueue_struct *buffered_io_wq;
> static const struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
> static DEFINE_IDA(cntlid_ida);
>
> +#define NVMET_DEFAULT_KATO 5
> +
> /*
> * This read/write semaphore is used to synchronize access to configuration
> * information on a target system that will result in discovery log page
> @@ -385,6 +387,11 @@ static void nvmet_keep_alive_timer(struct work_struct *work)
> if (cmd_seen) {
> pr_debug("ctrl %d reschedule traffic based keep-alive timer\n",
> ctrl->cntlid);
> +
> + /* run once, trigger from nvmet_start_ctrl to detect dead link */
> + if (!ctrl->kato)
> + return;
> +
> schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);

It will be better to just schedule/mod the ka_work if kato != 0, other
changes in the patch aren't needed IMO.

> return;
> }
> @@ -403,15 +410,11 @@ static void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl)
> pr_debug("ctrl %d start keep-alive timer for %d secs\n",
> ctrl->cntlid, ctrl->kato);
>
> - INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
> schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
> }
>
> static void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl)
> {
> - if (unlikely(ctrl->kato == 0))
> - return;
> -
> pr_debug("ctrl %d stop keep-alive\n", ctrl->cntlid);
>
> cancel_delayed_work_sync(&ctrl->ka_work);
> @@ -1107,6 +1110,8 @@ static inline u8 nvmet_cc_iocqes(u32 cc)
>
> static void nvmet_start_ctrl(struct nvmet_ctrl *ctrl)
> {
> + u32 kato = ctrl->kato ? ctrl->kato : NVMET_DEFAULT_KATO;
> +

The controller shouldn't have a default value, it should receive
the desired value from the host.

> lockdep_assert_held(&ctrl->lock);
>
> if (nvmet_cc_iosqes(ctrl->cc) != NVME_NVM_IOSQES ||
> @@ -1126,7 +1131,7 @@ static void nvmet_start_ctrl(struct nvmet_ctrl *ctrl)
> * in case a host died before it enabled the controller. Hence, simply
> * reset the keep alive timer when the controller is enabled.
> */
> - mod_delayed_work(system_wq, &ctrl->ka_work, ctrl->kato * HZ);
> + mod_delayed_work(system_wq, &ctrl->ka_work, kato * HZ);
> }
>
> static void nvmet_clear_ctrl(struct nvmet_ctrl *ctrl)
> @@ -1378,6 +1383,7 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
>
> /* keep-alive timeout in seconds */
> ctrl->kato = DIV_ROUND_UP(kato, 1000);
> + INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
>
> ctrl->err_counter = 0;
> spin_lock_init(&ctrl->error_lock);
>

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