[SCSI] FC transport: Locking fix for common-code FC pass-through patch

Fix this:
------------[ cut here ]------------
Badness at block/blk-core.c:244
CPU: 0 Tainted: G W 2.6.31-rc1-00004-gd3a263a #3
Process zfcp_wq (pid: 901, task: 000000002fb7a038, ksp: 000000002f02bc78)
Krnl PSW : 0704300180000000 00000000002141ba (blk_remove_plug+0xb2/0xb8)
R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:3 PM:0 EA:3
Krnl GPRS: 0000000000000001 0000000000000001 0000000022811440 0000000022811798
000000000027ff4e 0000000000000000 0000000000000000 000000002f00f000
070000000006a0f4 000000002af70000 000000002af2a800 00000000228d1c00
0000000022811440 000000000050c708 000000002f02bca8 000000002f02bc80
Krnl Code: 00000000002141b0: b9140022 lgfr %r2,%r2
00000000002141b4: 07fe bcr 15,%r14
00000000002141b6: a7f40001 brc 15,2141b8
>00000000002141ba: a7f4ffbe brc 15,214136
00000000002141be: 0707 bcr 0,%r7
00000000002141c0: ebaff0680024 stmg %r10,%r15,104(%r15)
00000000002141c6: c0d00017c2a9 larl %r13,50c718
00000000002141cc: a7f13fc0 tmll %r15,16320
Call Trace:
([<000000000050e7d8>] C.272.16122+0x88/0x110)
[<00000000002141ec>] __blk_run_queue+0x2c/0x154
[<000000000028013a>] fc_remote_port_add+0x85e/0x95c
[<000000000037596e>] zfcp_scsi_rport_work+0xe6/0x148
[<000000000006908c>] worker_thread+0x25c/0x318
[<000000000006f10c>] kthread+0x94/0x9c
[<000000000001c2b2>] kernel_thread_starter+0x6/0xc
[<000000000001c2ac>] kernel_thread_starter+0x0/0xc
INFO: lockdep is turned off.
Last Breaking-Event-Address:
[<00000000002141b6>] blk_remove_plug+0xae/0xb8

The FC pass-through support triggers the WARN_ON(!irqs_disabled()) in
blk_plug_device. Since blk_plug_device requires being called with
disabled interrupts, use spin_lock_irqsave in fc_bsg_goose_queue to
disable the interrupts before calling into the block layer.

Signed-off-by: Christof Schmitt <[e-mail]>
Acked-by: James Smart <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/scsi_transport_fc.c

···
 fc_bsg_goose_queue(struct fc_rport *rport)
 {
 	int flagset;
+	unsigned long flags;
 
 	if (!rport->rqst_q)
 		return;
 
 	get_device(&rport->dev);
 
-	spin_lock(rport->rqst_q->queue_lock);
+	spin_lock_irqsave(rport->rqst_q->queue_lock, flags);
 	flagset = test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags) &&
 		  !test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags);
 	if (flagset)
···
 	__blk_run_queue(rport->rqst_q);
 	if (flagset)
 		queue_flag_clear(QUEUE_FLAG_REENTER, rport->rqst_q);
-	spin_unlock(rport->rqst_q->queue_lock);
+	spin_unlock_irqrestore(rport->rqst_q->queue_lock, flags);
 
 	put_device(&rport->dev);
 }