target: Add SCF_EMULATE_QUEUE_FULL -> transport_handle_queue_full
authorNicholas Bellinger <nab@linux-iscsi.org>
Mon, 13 Jun 2011 21:46:09 +0000 (14:46 -0700)
committerNicholas Bellinger <nab@linux-iscsi.org>
Fri, 22 Jul 2011 09:37:45 +0000 (09:37 +0000)
commit07bde79a5c355dbca66ca4318645aa17b4c0d859
treee602132193959df436a2f5d325cd3da9984ada4f
parent695434e1cbd57f404110bf4ab187a5127ffd79bb
target: Add SCF_EMULATE_QUEUE_FULL -> transport_handle_queue_full

This patch adds SCF_EMULATE_QUEUE_FULL support using -EAGAIN failures
via transport_handle_queue_full() to signal queue full in completion
path TFO->queue_data_in() and TFO->queue_status() callbacks.

This is done using a new se_cmd->transport_qf_callback() to handle
the following queue full exception cases within target core:

*) TRANSPORT_COMPLETE_OK (for completion path queue full)

*) TRANSPORT_COMPLETE_QF_WP (for TRANSPORT_WRITE_PENDING queue full)

*) transport_send_check_condition_and_sense() failure paths in
   transport_generic_request_failure() and transport_generic_complete_ok()

All logic is driven using se_device->qf_work_queue -> target_qf_do_work()
to to requeue outstanding se_cmd at the head of se_dev->queue_obj->qobj_list
for transport_processing_thread() execution.

Tested using tcm_qla2xxx with MAX_OUTSTANDING_COMMANDS=128 for FCP READ
to trigger the TRANSPORT_COMPLETE_OK queue full cases, and a simulated
TFO->write_pending() -EAGAIN failure to trigger TRANSPORT_COMPLETE_QF_WP.

Reported-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
drivers/target/target_core_transport.c
include/target/target_core_base.h