scsi: Protect SCSI device state changes with a mutex

Serializing SCSI device state changes avoids that two state changes can
occur concurrently, e.g. the state changes in scsi_target_block() and
__scsi_remove_device(). This serialization is essential to make patch
"Make __scsi_remove_device go straight from BLOCKED to DEL" work
reliably.

Enable this mechanism for all scsi_target_*block() callers but not for
the scsi_internal_device_unblock() calls from the mpt3sas driver because
that driver can call scsi_internal_device_unblock() from atomic context.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 82dfe07b1d47..a91537a3abbf 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -719,7 +719,7 @@ static ssize_t
 store_state_field(struct device *dev, struct device_attribute *attr,
 		  const char *buf, size_t count)
 {
-	int i;
+	int i, ret;
 	struct scsi_device *sdev = to_scsi_device(dev);
 	enum scsi_device_state state = 0;
 
@@ -734,9 +734,11 @@ store_state_field(struct device *dev, struct device_attribute *attr,
 	if (!state)
 		return -EINVAL;
 
-	if (scsi_device_set_state(sdev, state))
-		return -EINVAL;
-	return count;
+	mutex_lock(&sdev->state_mutex);
+	ret = scsi_device_set_state(sdev, state);
+	mutex_unlock(&sdev->state_mutex);
+
+	return ret == 0 ? count : -EINVAL;
 }
 
 static ssize_t
@@ -1272,6 +1274,7 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 void __scsi_remove_device(struct scsi_device *sdev)
 {
 	struct device *dev = &sdev->sdev_gendev;
+	int res;
 
 	/*
 	 * This cleanup path is not reentrant and while it is impossible
@@ -1282,7 +1285,15 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		return;
 
 	if (sdev->is_visible) {
-		if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
+		/*
+		 * If scsi_internal_target_block() is running concurrently,
+		 * wait until it has finished before changing the device state.
+		 */
+		mutex_lock(&sdev->state_mutex);
+		res = scsi_device_set_state(sdev, SDEV_CANCEL);
+		mutex_unlock(&sdev->state_mutex);
+
+		if (res != 0)
 			return;
 
 		bsg_unregister_queue(sdev->request_queue);
@@ -1298,7 +1309,10 @@ void __scsi_remove_device(struct scsi_device *sdev)
 	 * scsi_run_queue() invocations have finished before tearing down the
 	 * device.
 	 */
+	mutex_lock(&sdev->state_mutex);
 	scsi_device_set_state(sdev, SDEV_DEL);
+	mutex_unlock(&sdev->state_mutex);
+
 	blk_cleanup_queue(sdev->request_queue);
 	cancel_work_sync(&sdev->requeue_work);