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

[Ouyangzhaowei (Charles)]

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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index fd88dab..20d539b 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1722,9 +1722,10 @@ 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;
+               goto unlock;
        }

        data = kmalloc(sizeof(*data), GFP_KERNEL);
@@ -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);
@@ -1751,6 +1751,8 @@ static struct async_scan_data
*scsi_prep_async_scan(struct Scsi_Host *shost)

  err:
        kfree(data);
+ unlock:
+       mutex_unlock(&shost->scan_mutex);
        return NULL;
 }