[PATCH] scsi: shost->async_scan should be protected by mutex_lock

["Ouyangzhaowei (Charles)" <ouyangzhaowei@xxxxxxxxxx>]

shost->async_scan should be protected by mutex_lock, otherwise the check
of "called twice" won't work.

Signed-off-by: Ouyang Zhaowei <ouyangzhaowei@xxxxxxxxxx>
---
 drivers/scsi/scsi_scan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index fd88dab..1d1df51 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1722,6 +1722,7 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)
        if (strncmp(scsi_scan_type, "sync", 4) == 0)
                return NULL;

+       mutex_lock(&shost->scan_mutex);
        if (shost->async_scan) {
                shost_printk(KERN_DEBUG, shost, "%s called twice\n",
__func__);
                return NULL;
@@ -1735,7 +1736,6 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)
                goto err;
        init_completion(&data->prev_finished);

-       mutex_lock(&shost->scan_mutex);
        spin_lock_irqsave(shost->host_lock, flags);
        shost->async_scan = 1;
        spin_unlock_irqrestore(shost->host_lock, flags);