[SCSI] zfcp: Replace fsf_req wait_queue with completion

The combination wait_queue/wakeup in conjunction with the flag
ZFCP_STATUS_FSFREQ_COMPLETED to signal the completion of an fsfreq
was not race-safe and can be better solved by a completion.

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 6 insertions, 20 deletions

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index 7ca2995aaf68..ed06a1d17b73 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -444,23 +444,11 @@ static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req)
 
         if (req->erp_action)
                 zfcp_erp_notify(req->erp_action, 0);
-        req->status |= ZFCP_STATUS_FSFREQ_COMPLETED;
 
         if (likely(req->status & ZFCP_STATUS_FSFREQ_CLEANUP))
                 zfcp_fsf_req_free(req);
         else
-        /* notify initiator waiting for the requests completion */
-        /*
-         * FIXME: Race! We must not access fsf_req here as it might have been
-         * cleaned up already due to the set ZFCP_STATUS_FSFREQ_COMPLETED
-         * flag. It's an improbable case. But, we have the same paranoia for
-         * the cleanup flag already.
-         * Might better be handled using complete()?
-         * (setting the flag and doing wakeup ought to be atomic
-         *  with regard to checking the flag as long as waitqueue is
-         *  part of the to be released structure)
-         */
-                wake_up(&req->completion_wq);
+                complete(&req->completion);
 }
 
 /**
@@ -733,7 +721,7 @@ static struct zfcp_fsf_req *zfcp_fsf_req_create(struct zfcp_adapter *adapter,
 
         INIT_LIST_HEAD(&req->list);
         init_timer(&req->timer);
-        init_waitqueue_head(&req->completion_wq);
+        init_completion(&req->completion);
 
         req->adapter = adapter;
         req->fsf_command = fsf_cmd;
@@ -1309,8 +1297,7 @@ int zfcp_fsf_exchange_config_data_sync(struct zfcp_adapter *adapter,
         retval = zfcp_fsf_req_send(req);
         spin_unlock_bh(&adapter->req_q_lock);
         if (!retval)
-                wait_event(req->completion_wq,
-                           req->status & ZFCP_STATUS_FSFREQ_COMPLETED);
+                wait_for_completion(&req->completion);
 
         zfcp_fsf_req_free(req);
         return retval;
@@ -1405,8 +1392,8 @@ int zfcp_fsf_exchange_port_data_sync(struct zfcp_adapter *adapter,
         spin_unlock_bh(&adapter->req_q_lock);
 
         if (!retval)
-                wait_event(req->completion_wq,
-                           req->status & ZFCP_STATUS_FSFREQ_COMPLETED);
+                wait_for_completion(&req->completion);
+
         zfcp_fsf_req_free(req);
 
         return retval;
@@ -2572,8 +2559,7 @@ out:
         spin_unlock_bh(&adapter->req_q_lock);
 
         if (!retval) {
-                wait_event(req->completion_wq,
-                           req->status & ZFCP_STATUS_FSFREQ_COMPLETED);
+                wait_for_completion(&req->completion);
                 return req;
         }
         return ERR_PTR(retval);