scsi: target/iscsi: Avoid iscsit_release_commands_from_conn() deadlock

When using SCSI passthrough in combination with the iSCSI target driver
then cmd->t_state_lock may be obtained from interrupt context. Hence, all
code that obtains cmd->t_state_lock from thread context must disable
interrupts first. This patch avoids that lockdep reports the following:

WARNING: inconsistent lock state
4.18.0-dbg+ #1 Not tainted
--------------------------------
inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
iscsi_ttx/1800 [HC1[1]:SC0[2]:HE0:SE0] takes:
000000006e7b0ceb (&(&cmd->t_state_lock)->rlock){?...}, at: target_complete_cmd+0x47/0x2c0 [target_core_mod]
{HARDIRQ-ON-W} state was registered at:
 lock_acquire+0xd2/0x260
 _raw_spin_lock+0x32/0x50
 iscsit_close_connection+0x97e/0x1020 [iscsi_target_mod]
 iscsit_take_action_for_connection_exit+0x108/0x200 [iscsi_target_mod]
 iscsi_target_rx_thread+0x180/0x190 [iscsi_target_mod]
 kthread+0x1cf/0x1f0
 ret_from_fork+0x24/0x30
irq event stamp: 1281
hardirqs last  enabled at (1279): [<ffffffff970ade79>] __local_bh_enable_ip+0xa9/0x160
hardirqs last disabled at (1281): [<ffffffff97a008a5>] interrupt_entry+0xb5/0xd0
softirqs last  enabled at (1278): [<ffffffff977cd9a1>] lock_sock_nested+0x51/0xc0
softirqs last disabled at (1280): [<ffffffffc07a6e04>] ip6_finish_output2+0x124/0xe40 [ipv6]

other info that might help us debug this:
Possible unsafe locking scenario:

      CPU0
      ----
 lock(&(&cmd->t_state_lock)->rlock);
 <Interrupt>
   lock(&(&cmd->t_state_lock)->rlock);

*** DEADLOCK ***

3 locks held by iscsi_ttx/1800:
*0: 00000000c3b711b7 (sk_lock-AF_INET6){+.+.}, at: tcp_sendmsg+0x1e/0x50
*1: 00000000fa81046f (rcu_read_lock){....}, at: inet6_csk_xmit+0xc7/0x2e0 [ipv6]
*2: 00000000c091d70d (rcu_read_lock_bh){....}, at: ip6_finish_output2+0x124/0xe40 [ipv6]

stack backtrace:
CPU: 0 PID: 1800 Comm: iscsi_ttx Not tainted 4.18.0-dbg+ #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
Call Trace:
<IRQ>
dump_stack+0xa4/0xf5
print_usage_bug+0x25b/0x27b
mark_lock+0x70f/0x7b0
__lock_acquire+0xbc2/0x1b50
lock_acquire+0xd2/0x260
_raw_spin_lock_irqsave+0x4a/0x60
target_complete_cmd+0x47/0x2c0 [target_core_mod]
target_complete_cmd_with_length+0x70/0xa0 [target_core_mod]
pscsi_req_done+0x335/0x530 [target_core_pscsi]
__blk_mq_end_request+0xa5/0x140
scsi_end_request+0x112/0x320 [scsi_mod]
scsi_io_completion+0x183/0xa30 [scsi_mod]
scsi_finish_command+0x1c0/0x280 [scsi_mod]
scsi_softirq_done+0x19a/0x230 [scsi_mod]
__blk_mq_complete_request_remote+0x2f/0x40
flush_smp_call_function_queue+0x12a/0x220
generic_smp_call_function_single_interrupt+0x13/0x30
smp_call_function_single_interrupt+0x7a/0x350
call_function_single_interrupt+0xf/0x20
</IRQ>
RIP: 0010:__asan_load4+0x1e/0x80
debug_lockdep_rcu_enabled+0x26/0x40
ip6_finish_output2+0x15a/0xe40 [ipv6]
ip6_finish_output+0x308/0x440 [ipv6]
ip6_output+0x11d/0x3b0 [ipv6]
ip6_xmit+0x639/0xc50 [ipv6]
inet6_csk_xmit+0x198/0x2e0 [ipv6]
__tcp_transmit_skb+0xc1b/0x15b0
tcp_write_xmit+0x42e/0x1f20
__tcp_push_pending_frames+0x59/0x150
tcp_push+0x189/0x270
tcp_sendmsg_locked+0x7b9/0x1680
tcp_sendmsg+0x2c/0x50
inet_sendmsg+0x71/0x250
sock_sendmsg+0x4c/0x60
tx_data+0x12b/0x1f0 [iscsi_target_mod]
iscsit_send_tx_data+0x77/0xe0 [iscsi_target_mod]
iscsit_xmit_pdu+0x2c5/0x740 [iscsi_target_mod]
iscsit_response_queue+0x941/0xd40 [iscsi_target_mod]
iscsi_target_tx_thread+0x23b/0x350 [iscsi_target_mod]
kthread+0x1cf/0x1f0
ret_from_fork+0x24/0x30

Fixes: 064cdd2d ("target: Fix race between iscsi-target connection shutdown + ABORT_TASK")
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>