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>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 176f956..e4389d4 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1642,6 +1642,80 @@
}
EXPORT_SYMBOL(transport_handle_cdb_direct);
+/**
+ * target_submit_cmd - lookup unpacked lun and submit uninitialized se_cmd
+ *
+ * @se_cmd: command descriptor to submit
+ * @se_sess: associated se_sess for endpoint
+ * @cdb: pointer to SCSI CDB
+ * @sense: pointer to SCSI sense buffer
+ * @unpacked_lun: unpacked LUN to reference for struct se_lun
+ * @data_length: fabric expected data transfer length
+ * @task_addr: SAM task attribute
+ * @data_dir: DMA data direction
+ * @flags: flags for command submission from target_sc_flags_tables
+ *
+ * This may only be called from process context, and also currently
+ * assumes internal allocation of fabric payload buffer by target-core.
+ **/
+int target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
+ unsigned char *cdb, unsigned char *sense, u32 unpacked_lun,
+ u32 data_length, int task_attr, int data_dir, int flags)
+{
+ struct se_portal_group *se_tpg;
+ int rc;
+
+ se_tpg = se_sess->se_tpg;
+ BUG_ON(!se_tpg);
+ BUG_ON(se_cmd->se_tfo || se_cmd->se_sess);
+ BUG_ON(in_interrupt());
+ /*
+ * Initialize se_cmd for target operation. From this point
+ * exceptions are handled by sending exception status via
+ * target_core_fabric_ops->queue_status() callback
+ */
+ transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess,
+ data_length, data_dir, task_attr, sense);
+ /*
+ * Obtain struct se_cmd->cmd_kref reference and add new cmd to
+ * se_sess->sess_cmd_list. A second kref_get here is necessary
+ * for fabrics using TARGET_SCF_ACK_KREF that expect a second
+ * kref_put() to happen during fabric packet acknowledgement.
+ */
+ target_get_sess_cmd(se_sess, se_cmd, (flags & TARGET_SCF_ACK_KREF));
+ /*
+ * Signal bidirectional data payloads to target-core
+ */
+ if (flags & TARGET_SCF_BIDI_OP)
+ se_cmd->se_cmd_flags |= SCF_BIDI;
+ /*
+ * Locate se_lun pointer and attach it to struct se_cmd
+ */
+ if (transport_lookup_cmd_lun(se_cmd, unpacked_lun) < 0)
+ goto out_check_cond;
+ /*
+ * Sanitize CDBs via transport_generic_cmd_sequencer() and
+ * allocate the necessary tasks to complete the received CDB+data
+ */
+ rc = transport_generic_allocate_tasks(se_cmd, cdb);
+ if (rc != 0)
+ goto out_check_cond;
+ /*
+ * Dispatch se_cmd descriptor to se_lun->lun_se_dev backend
+ * for immediate execution of READs, otherwise wait for
+ * transport_generic_handle_data() to be called for WRITEs
+ * when fabric has filled the incoming buffer.
+ */
+ transport_handle_cdb_direct(se_cmd);
+ return 0;
+
+out_check_cond:
+ transport_send_check_condition_and_sense(se_cmd,
+ se_cmd->scsi_sense_reason, 0);
+ return 0;
+}
+EXPORT_SYMBOL(target_submit_cmd);
+
/*
* Used by fabric module frontends defining a TFO->new_cmd_map() caller
* to queue up a newly setup se_cmd w/ TRANSPORT_NEW_CMD_MAP in order to
@@ -3910,13 +3984,21 @@
/* target_get_sess_cmd - Add command to active ->sess_cmd_list
* @se_sess: session to reference
* @se_cmd: command descriptor to add
+ * @ack_kref: Signal that fabric will perform an ack target_put_sess_cmd()
*/
-void target_get_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
+void target_get_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd,
+ bool ack_kref)
{
unsigned long flags;
kref_init(&se_cmd->cmd_kref);
- kref_get(&se_cmd->cmd_kref);
+ /*
+ * Add a second kref if the fabric caller is expecting to handle
+ * fabric acknowledgement that requires two target_put_sess_cmd()
+ * invocations before se_cmd descriptor release.
+ */
+ if (ack_kref == true)
+ kref_get(&se_cmd->cmd_kref);
spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
list_add_tail(&se_cmd->se_cmd_list, &se_sess->sess_cmd_list);