On Thu, 2017-02-09 at 17:28 -0800, Bart Van Assche wrote:
> target_submit_tmr() only supports the I_T_L nexus for SCSI abort
> and other task management functions. Make it possible for target
> drivers to specify I_T nexus for SCSI abort by passing the
> TARGET_SCF_IGNORE_TMR_LUN flag to target_submit_tmr().
>
> Note: although several SCSI transport layers require in-order
> processing of TMFs per session, using schedule_work() does not
> introduce any new potential reordering. Since TMFs that originate
> from a single session can be queued onto different backend
> device workqueues there is already a potential for reordering.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
> Cc: Giridhar Malavali <giridhar.malavali@xxxxxxxxxx>
> ---
> drivers/target/target_core_tmr.c | 9 ++++++++-
> drivers/target/target_core_transport.c | 23 +++++++++++++++++------
> include/target/target_core_base.h | 1 +
> 3 files changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
> index 311dc3c2f1dc..3330775aa47a 100644
> --- a/drivers/target/target_core_tmr.c
> +++ b/drivers/target/target_core_tmr.c
> @@ -149,6 +149,13 @@ static bool __target_check_io_state(struct se_cmd *se_cmd,
> return kref_get_unless_zero(&se_cmd->cmd_kref);
> }
>
> +/**
> + * core_tmr_abort_task - abort a SCSI command
> + * @dev: LUN specified in task management function or NULL if no LUN has been
> + * specified.
> + * @tmr: Task management function.
> + * @se_sess: Session a.k.a. I_T nexus.
> + */
> void core_tmr_abort_task(
> struct se_device *dev,
> struct se_tmr_req *tmr,
> @@ -161,7 +168,7 @@ void core_tmr_abort_task(
> spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
> list_for_each_entry(se_cmd, &se_sess->sess_cmd_list, se_cmd_list) {
>
> - if (dev != se_cmd->se_dev)
> + if (dev && dev != se_cmd->se_dev)
> continue;
>
> /* skip task management functions, including tmr->task_cmd */
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index 22190003534d..4e233c0f5f68 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -1577,18 +1577,18 @@ static void target_complete_tmr_failure(struct work_struct *work)
> }
>
> /**
> - * target_submit_tmr - lookup unpacked lun and submit uninitialized se_cmd
> - * for TMR CDBs
> + * target_submit_tmr - submit a SCSI task management function to the target core
> *
> * @se_cmd: command descriptor to submit
> * @se_sess: associated se_sess for endpoint
> * @sense: pointer to SCSI sense buffer
> - * @unpacked_lun: unpacked LUN to reference for struct se_lun
> + * @unpacked_lun: LUN the TMR applies to. Ignored if TARGET_SCF_IGNORE_TMR_LUN
> + * has been set in @flags.
> * @fabric_context: fabric context for TMR req
> * @tm_type: Type of TM request
> * @gfp: gfp type for caller
> * @tag: referenced task tag for TMR_ABORT_TASK
> - * @flags: submit cmd flags
> + * @flags: submit cmd flags (TARGET_SCF_*).
> *
> * Callable from all contexts.
> **/
> @@ -1624,7 +1624,14 @@ int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
> return ret;
> }
>
> - ret = transport_lookup_tmr_lun(se_cmd, unpacked_lun);
> + if (flags & TARGET_SCF_IGNORE_TMR_LUN) {
> + WARN_ON_ONCE(tm_type != TMR_ABORT_TASK);
> + se_cmd->se_lun = NULL;
> + se_cmd->se_dev = NULL;
> + se_cmd->se_tmr_req->tmr_dev = NULL;
> + } else {
> + ret = transport_lookup_tmr_lun(se_cmd, unpacked_lun);
> + }
> if (ret) {
> /*
> * For callback during failure handling, push this work off
> @@ -1634,6 +1641,7 @@ int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
> schedule_work(&se_cmd->work);
> return 0;
> }
> + WARN_ON_ONCE(tm_type != TMR_ABORT_TASK && !se_cmd->se_dev);
> transport_generic_handle_tmr(se_cmd);
> return 0;
> }
> @@ -3147,7 +3155,10 @@ int transport_generic_handle_tmr(
> }
>
> INIT_WORK(&cmd->work, target_tmr_work);
> - queue_work(cmd->se_dev->tmr_wq, &cmd->work);
> + if (cmd->se_dev)
> + queue_work(cmd->se_dev->tmr_wq, &cmd->work);
> + else
> + schedule_work(&cmd->work);
> return 0;
> }
> EXPORT_SYMBOL(transport_generic_handle_tmr);
The -v4 patch was using doing a lun lookup from within
core_tmr_abort_task() when !se_tmr->tmr_dev that could trigger a
deadlock.
But this patch doesn't seem to do any lookup at all for
TARGET_SCF_IGNORE_TMR_LUN when !se_tmr->tmr_dev..?
Is that correct..?
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