target: Add target_submit_cmd() for process context fabric submission

This patch adds a target_submit_cmd() caller that can be used by fabrics
to submit an uninitialized se_cmd descriptor to an struct se_session +
unpacked_lun from workqueue process context.  This call will invoke the
following steps:

- transport_init_se_cmd() to setup se_cmd specific pointers
- Obtain se_cmd->cmd_kref references with target_get_sess_cmd()
- set se_cmd->t_tasks_bidi
- transport_lookup_cmd_lun() to setup struct se_cmd->se_lun from
  the passed unpacked_lun
- transport_generic_allocate_tasks() to setup the passed *cdb, and
- transport_handle_cdb_direct() handle READ dispatch or WRITE
  ready-to-transfer callback to fabric

v2 changes from hch feedback:

*) Add target_sc_flags_table for target_submit_cmd flags
*) Rename bidi parameter to flags, add TARGET_SCF_BIDI_OP
*) Convert checks to BUG_ON
*) Add out_check_cond for transport_send_check_condition_and_sense
   usage

v3 changes:

*) Add TARGET_SCF_ACK_KREF for target_submit_cmd into
   target_get_sess_cmd to determine when the fabric caller is expecting
   a second kref_put() from fabric packet acknowledgement.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index af088a9e4905..28190dc10eef 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -226,6 +226,11 @@ enum tcm_sense_reason_table {
 	TCM_RESERVATION_CONFLICT		= 0x10,
 };
 
+enum target_sc_flags_table {
+	TARGET_SCF_BIDI_OP		= 0x01,
+	TARGET_SCF_ACK_KREF		= 0x02,
+};
+
 /* fabric independent task management function values */
 enum tcm_tmreq_table {
 	TMR_ABORT_TASK		= 1,