target: Fix bug for transport_generic_wait_for_tasks with direct oper…

…ation

This patch fixes a bug in transport_handle_cdb_direct() usage with target_core
where transport_generic_wait_for_tasks() was bypassing active I/O + usage of
cmd->t_transport_stop_comp because cmd->t_transport_active=1 was not being set
before dispatching with transport_generic_new_cmd().  The fix follows existing
usage in transport_generic_handle_cdb*() -> transport_add_cmd_to_queue() and
set these directly, as well as handle transport_generic_new_cmd() exceptions
for QUEUE_FULL and CHECK_CONDITION instead of propigating up to RX context
fabric code.

The bug was manifesting itself with the following SLUB poison overwritten
warnings with iscsi-target v4.1 LUNs using the new process context direct
operation during session reinstatement with active I/O exception handling:

[885410.498267] =============================================================================
[885410.621622] BUG lio_cmd_cache: Poison overwritten
[885410.621791] -----------------------------------------------------------------------------
[885410.621792]
[885410.623420] INFO: 0xffff880000cf3750-0xffff880000cf378d. First byte 0x6a instead of 0x6b
[885410.626332] INFO: Allocated in iscsit_allocate_cmd+0x1c/0xd4 [iscsi_target_mod] age=345 cpu=1 pid=22554
[885411.855189] INFO: Freed in iscsit_release_cmd+0x208/0x217 [iscsi_target_mod] age=1410 cpu=1 pid=22554
[885411.856048] INFO: Slab 0xffffea000002d480 objects=22 used=0 fp=0xffff880000cf7300 flags=0x4080
[885411.856368] INFO: Object 0xffff880000cf33c0 @offset=13248 fp=0xffff880000cf6780

<SNIP>

[885411.955678] Pid: 22554, comm: iscsi_trx Not tainted 3.0.0-rc7+ torvalds#30
[885411.956040] Call Trace:
[885411.957029]  [<ffffffff810e5cf9>] print_trailer+0x12e/0x137
[885412.752879]  [<ffffffff810e61d9>] check_bytes_and_report+0xb9/0xfd
[885412.754933]  [<ffffffff810e62d2>] check_object+0xb5/0x192
[885412.755099]  [<ffffffff810e6445>] __free_slab+0x96/0x13a
[885412.757008]  [<ffffffff810e652a>] discard_slab+0x41/0x43
[885412.758171]  [<ffffffff810e7a4c>] __slab_free+0xf3/0xfe
[885412.761027]  [<ffffffffa030a536>] ? iscsit_release_cmd+0x208/0x217 [iscsi_target_mod]
[885412.761354]  [<ffffffff810e7e95>] kmem_cache_free+0x6f/0xac
[885412.761536]  [<ffffffffa030a536>] iscsit_release_cmd+0x208/0x217 [iscsi_target_mod]
[885412.762056]  [<ffffffffa020e467>] ? iblock_free_task+0x34/0x39 [target_core_iblock]
[885412.762368]  [<ffffffffa0314131>] lio_release_cmd+0x10/0x12 [iscsi_target_mod]
[885412.764129]  [<ffffffffa02c2254>] transport_release_cmd+0x2f/0x33 [target_core_mod]
[885412.805024]  [<ffffffffa02c230e>] transport_generic_remove+0xb6/0xc3 [target_core_mod]
[885412.806424]  [<ffffffff81035b5f>] ? try_to_wake_up+0x1bd/0x1bd
[885412.809033]  [<ffffffffa02c241f>] transport_generic_free_cmd+0x75/0x7d [target_core_mod]
[885412.810066]  [<ffffffffa02c2643>] transport_generic_wait_for_tasks+0x21c/0x22b [target_core_mod]
[885412.811056]  [<ffffffff8139f0b1>] ? mutex_lock+0x11/0x32
[885412.813059]  [<ffffffff8139f0b1>] ? mutex_lock+0x11/0x32
[885412.813200]  [<ffffffffa030b81d>] iscsit_close_connection+0x1d5/0x63a [iscsi_target_mod]
[885412.813517]  [<ffffffffa0300a82>] iscsit_take_action_for_connection_exit+0xdb/0xe0 [iscsi_target_mod]
[885412.813851]  [<ffffffffa03111e9>] iscsi_target_rx_thread+0x11f6/0x1221 [iscsi_target_mod]
[885412.829024]  [<ffffffff81033e8d>] ? pick_next_task_fair+0xbe/0x10e
[885412.831010]  [<ffffffffa030fff3>] ? iscsit_handle_scsi_cmd+0x91d/0x91d [iscsi_target_mod]
[885412.833011]  [<ffffffffa030fff3>] ? iscsit_handle_scsi_cmd+0x91d/0x91d [iscsi_target_mod]
[885412.835010]  [<ffffffff8105388a>] kthread+0x7d/0x85
[885412.837022]  [<ffffffff813a7124>] kernel_thread_helper+0x4/0x10
[885412.838008]  [<ffffffff8105380d>] ? kthread_worker_fn+0x145/0x145
[885412.840047]  [<ffffffff813a7120>] ? gs_change+0x13/0x13
[885412.842007] FIX lio_cmd_cache: Restoring 0xffff880000cf3750-0xffff880000cf378d=0x6

Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c

@@ -1747,13 +1747,17 @@ int transport_generic_handle_cdb(
 }
 EXPORT_SYMBOL(transport_generic_handle_cdb);
 
+static void transport_generic_request_failure(struct se_cmd *,
+			struct se_device *, int, int);
 /*
  * Used by fabric module frontends to queue tasks directly.
  * Many only be used from process context only
  */
 int transport_handle_cdb_direct(
 	struct se_cmd *cmd)
 {
+	int ret;
+
 	if (!cmd->se_lun) {
 		dump_stack();
 		pr_err("cmd->se_lun is NULL\n");
@@ -1765,8 +1769,31 @@ int transport_handle_cdb_direct(
 				" from interrupt context\n");
 		return -EINVAL;
 	}
-
-	return transport_generic_new_cmd(cmd);
+	/*
+	 * Set TRANSPORT_NEW_CMD state and cmd->t_transport_active=1 following
+	 * transport_generic_handle_cdb*() -> transport_add_cmd_to_queue()
+	 * in existing usage to ensure that outstanding descriptors are handled
+	 * correctly during shutdown via transport_generic_wait_for_tasks()
+	 *
+	 * Also, we don't take cmd->t_state_lock here as we only expect
+	 * this to be called for initial descriptor submission.
+	 */
+	cmd->t_state = TRANSPORT_NEW_CMD;
+	atomic_set(&cmd->t_transport_active, 1);
+	/*
+	 * transport_generic_new_cmd() is already handling QUEUE_FULL,
+	 * so follow TRANSPORT_NEW_CMD processing thread context usage
+	 * and call transport_generic_request_failure() if necessary..
+	 */
+	ret = transport_generic_new_cmd(cmd);
+	if (ret == -EAGAIN)
+		return 0;
+	else if (ret < 0) {
+		cmd->transport_error_status = ret;
+		transport_generic_request_failure(cmd, NULL, 0,
+				(cmd->data_direction != DMA_TO_DEVICE));
+	}
+	return 0;
 }
 EXPORT_SYMBOL(transport_handle_cdb_direct);