scsi_dh: don't allow to detach device handlers at runtime

The I/O submission and completion paths 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>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
index 2e1db5738ae1..9f6511da5023 100644
--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -181,8 +181,10 @@ 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