1 files changed, 33 insertions, 17 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d9ca1dfab154..976c936029cb 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -164,7 +164,7 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
  * for a requeue after completion, which should only occur in this
  * file.
  */
-static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
+static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
 {
 	struct scsi_device *device = cmd->device;
 	struct request_queue *q = device->request_queue;
@@ -220,7 +220,7 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
  */
 void scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 {
-	__scsi_queue_insert(cmd, reason, 1);
+	__scsi_queue_insert(cmd, reason, true);
 }
 
 
@@ -318,22 +318,39 @@ static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
 		cmd->cmd_len = scsi_command_size(cmd->cmnd);
 }
 
-void scsi_device_unbusy(struct scsi_device *sdev)
+/*
+ * Decrement the host_busy counter and wake up the error handler if necessary.
+ * Avoid as follows that the error handler is not woken up if shost->host_busy
+ * == shost->host_failed: use call_rcu() in scsi_eh_scmd_add() in combination
+ * with an RCU read lock in this function to ensure that this function in its
+ * entirety either finishes before scsi_eh_scmd_add() increases the
+ * host_failed counter or that it notices the shost state change made by
+ * scsi_eh_scmd_add().
+ */
+static void scsi_dec_host_busy(struct Scsi_Host *shost)
 {
-	struct Scsi_Host *shost = sdev->host;
-	struct scsi_target *starget = scsi_target(sdev);
 	unsigned long flags;
 
+	rcu_read_lock();
 	atomic_dec(&shost->host_busy);
-	if (starget->can_queue > 0)
-		atomic_dec(&starget->target_busy);
-
-	if (unlikely(scsi_host_in_recovery(shost) &&
-		     (shost->host_failed || shost->host_eh_scheduled))) {
+	if (unlikely(scsi_host_in_recovery(shost))) {
 		spin_lock_irqsave(shost->host_lock, flags);
-		scsi_eh_wakeup(shost);
+		if (shost->host_failed || shost->host_eh_scheduled)
+			scsi_eh_wakeup(shost);
 		spin_unlock_irqrestore(shost->host_lock, flags);
 	}
+	rcu_read_unlock();
+}
+
+void scsi_device_unbusy(struct scsi_device *sdev)
+{
+	struct Scsi_Host *shost = sdev->host;
+	struct scsi_target *starget = scsi_target(sdev);
+
+	scsi_dec_host_busy(shost);
+
+	if (starget->can_queue > 0)
+		atomic_dec(&starget->target_busy);
 
 	atomic_dec(&sdev->device_busy);
 }
@@ -998,11 +1015,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		break;
 	case ACTION_RETRY:
 		/* Retry the same command immediately */
-		__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
+		__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, false);
 		break;
 	case ACTION_DELAYED_RETRY:
 		/* Retry the same command after a delay */
-		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
+		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, false);
 		break;
 	}
 }
@@ -1128,7 +1145,7 @@ EXPORT_SYMBOL(scsi_init_io);
  * Called from inside blk_get_request() for pass-through requests and from
  * inside scsi_init_command() for filesystem requests.
  */
-void scsi_initialize_rq(struct request *rq)
+static void scsi_initialize_rq(struct request *rq)
 {
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
@@ -1136,7 +1153,6 @@ void scsi_initialize_rq(struct request *rq)
 	cmd->jiffies_at_alloc = jiffies;
 	cmd->retries = 0;
 }
-EXPORT_SYMBOL(scsi_initialize_rq);
 
 /* Add a command to the list used by the aacraid and dpt_i2o drivers */
 void scsi_add_cmd_to_list(struct scsi_cmnd *cmd)
@@ -1532,7 +1548,7 @@ starved:
 		list_add_tail(&sdev->starved_entry, &shost->starved_list);
 	spin_unlock_irq(shost->host_lock);
 out_dec:
-	atomic_dec(&shost->host_busy);
+	scsi_dec_host_busy(shost);
 	return 0;
 }
 
@@ -2020,7 +2036,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	return BLK_STS_OK;
 
 out_dec_host_busy:
-       atomic_dec(&shost->host_busy);
+	scsi_dec_host_busy(shost);
 out_dec_target_busy:
 	if (scsi_target(sdev)->can_queue > 0)
 		atomic_dec(&scsi_target(sdev)->target_busy);