[PATCH 08/10] scsi_dh: don't allow to detach device handlers at runtime

[Hannes Reinecke <hare@suse.de>]

From: Christoph Hellwig <hch@lst.de>

The I/O submission and completion pathes call into the device handler
without any synchronization agains detachment.  So disallow detaching
device handlers at runtime.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/scsi_dh.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
index 489083c..954ca5e 100644
--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -180,8 +180,10 @@ store_dh_state(struct device *dev, struct device_attribute *attr,
 			/*
 			 * Detach from a device handler
 			 */
-			scsi_dh_handler_detach(sdev);
-			err = 0;
+			sdev_printk(KERN_WARNING, sdev,
+				    "can't detach handler %s.\n",
+				    sdev->handler->name);
+			err = -EINVAL;
 		} else if (!strncmp(buf, "activate", 8)) {
 			/*
 			 * Activate a device handler
-- 
1.8.5.6