ocfs2: use spinlock_irqsave() to downconvert lock in ocfs2_osb_dump()

Commit a75e9cca ("ocfs2: use spinlock irqsave for downconvert lock")
missed an unmodified place in ocfs2_osb_dump(), so it still exists a
deadlock scenario.

    ocfs2_wake_downconvert_thread
    ocfs2_rw_unlock
    ocfs2_dio_end_io
    dio_complete
    .....
    bio_endio
    req_bio_endio
    ....
    scsi_io_completion
    blk_done_softirq
    __do_softirq
    do_softirq
    irq_exit
    do_IRQ
    ocfs2_osb_dump
    cat /sys/kernel/debug/ocfs2/${uuid}/fs_state

This patch still uses spin_lock_irqsave() - replace spin_lock() to solve
this situation.
Signed-off-by: NYiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: NJoseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/super.c

@@ -236,6 +236,7 @@ static int ocfs2_osb_dump(struct ocfs2_super *osb, char *buf, int len)
 	struct ocfs2_recovery_map *rm = osb->recovery_map;
 	struct ocfs2_orphan_scan *os = &osb->osb_orphan_scan;
 	int i, out = 0;
+	unsigned long flags;
 
 	out += snprintf(buf + out, len - out,
 			"%10s => Id: %-s  Uuid: %-s  Gen: 0x%X  Label: %-s\n",
@@ -271,14 +272,14 @@ static int ocfs2_osb_dump(struct ocfs2_super *osb, char *buf, int len)
 				cconn->cc_version.pv_minor);
 	}
 
-	spin_lock(&osb->dc_task_lock);
+	spin_lock_irqsave(&osb->dc_task_lock, flags);
 	out += snprintf(buf + out, len - out,
 			"%10s => Pid: %d  Count: %lu  WakeSeq: %lu  "
 			"WorkSeq: %lu\n", "DownCnvt",
 			(osb->dc_task ?  task_pid_nr(osb->dc_task) : -1),
 			osb->blocked_lock_count, osb->dc_wake_sequence,
 			osb->dc_work_sequence);
-	spin_unlock(&osb->dc_task_lock);
+	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
 
 	spin_lock(&osb->osb_lock);
 	out += snprintf(buf + out, len - out, "%10s => Pid: %d  Nodes:",