scsi: qla2xxx: Initialize free_work before flushing it

Target creation triggers a new BUG_ON introduced in in commit 4d43d395
("workqueue: Try to catch flush_work() without INIT_WORK().").  The BUG_ON
reveals an attempt to flush free_work in qla24xx_do_nack_work before it's
initialized in qlt_unreg_sess:

  WARNING: CPU: 7 PID: 211 at kernel/workqueue.c:3031 __flush_work.isra.38+0x40/0x2e0
  CPU: 7 PID: 211 Comm: kworker/7:1 Kdump: loaded Tainted: G            E     5.3.0-rc7-vanilla+ #2
  Workqueue: qla2xxx_wq qla2x00_iocb_work_fn [qla2xxx]
  NIP:  c000000000159620 LR: c0080000009d91b0 CTR: c0000000001598c0
  REGS: c000000005f3f730 TRAP: 0700   Tainted: G            E      (5.3.0-rc7-vanilla+)
  MSR:  800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 24002222  XER: 00000000
  CFAR: c0000000001598d0 IRQMASK: 0
  GPR00: c0080000009d91b0 c000000005f3f9c0 c000000001670a00 c0000003f8655ca8
  GPR04: c0000003f8655c00 000000000000ffff 0000000000000011 ffffffffffffffff
  GPR08: c008000000949228 0000000000000000 0000000000000001 c0080000009e7780
  GPR12: 0000000000002200 c00000003fff6200 c000000000161bc8 0000000000000004
  GPR16: c0000003f9d68280 0000000002000000 0000000000000005 0000000000000003
  GPR20: 0000000000000002 000000000000ffff 0000000000000000 fffffffffffffef7
  GPR24: c000000004f73848 c000000004f73838 c000000004f73f28 c000000005f3fb60
  GPR28: c000000004f73e48 c000000004f73c80 c000000004f73818 c0000003f9d68280
  NIP [c000000000159620] __flush_work.isra.38+0x40/0x2e0
  LR [c0080000009d91b0] qla24xx_do_nack_work+0x88/0x180 [qla2xxx]
  Call Trace:
  [c000000005f3f9c0] [c000000000159644] __flush_work.isra.38+0x64/0x2e0 (unreliable)
  [c000000005f3fa50] [c0080000009d91a0] qla24xx_do_nack_work+0x78/0x180 [qla2xxx]
  [c000000005f3fae0] [c0080000009496ec] qla2x00_do_work+0x604/0xb90 [qla2xxx]
  [c000000005f3fc40] [c008000000949cd8] qla2x00_iocb_work_fn+0x60/0xe0 [qla2xxx]
  [c000000005f3fc80] [c000000000157bb8] process_one_work+0x2c8/0x5b0
  [c000000005f3fd10] [c000000000157f28] worker_thread+0x88/0x660
  [c000000005f3fdb0] [c000000000161d64] kthread+0x1a4/0x1b0
  [c000000005f3fe20] [c00000000000b960] ret_from_kernel_thread+0x5c/0x7c
  Instruction dump:
  3d22001d 892966b1 7d908026 91810008 f821ff71 69290001 0b090000 2e290000
  40920200 e9230018 7d2a0074 794ad182 <0b0a0000> 2fa90000 419e01e8 7c0802a6
  ---[ end trace 5ccf335d4f90fcb8 ]---

Fixes: 1021f0bc ("scsi: qla2xxx: allow session delete to finish before create.")
Cc: Quinn Tran <qutran@marvell.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191125165702.1013-4-r.bolshakov@yadro.comAcked-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_init.c

@@ -4852,6 +4852,7 @@ qla2x00_alloc_fcport(scsi_qla_host_t *vha, gfp_t flags)
 	}
 
 	INIT_WORK(&fcport->del_work, qla24xx_delete_sess_fn);
+	INIT_WORK(&fcport->free_work, qlt_free_session_done);
 	INIT_WORK(&fcport->reg_work, qla_register_fcport_fn);
 	INIT_LIST_HEAD(&fcport->gnl_entry);
 	INIT_LIST_HEAD(&fcport->list);

drivers/scsi/qla2xxx/qla_target.c

@@ -1161,7 +1161,6 @@ void qlt_unreg_sess(struct fc_port *sess)
 	sess->last_rscn_gen = sess->rscn_gen;
 	sess->last_login_gen = sess->login_gen;
 
-	INIT_WORK(&sess->free_work, qlt_free_session_done);
 	queue_work(sess->vha->hw->wq, &sess->free_work);
 }
 EXPORT_SYMBOL(qlt_unreg_sess);