[SCSI] scsi_dh: Reference count scsi_dh_attach

Problem reported: http://marc.info/?l=dm-devel&m=124585978305866&w=2

scsi_dh does not do a refernce count for attach/detach, and this affects
the way it is supposed to work with multipath when a device is not
in the dev_list of the hardware handler.

This patch adds a reference count that counts each attach.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 16 insertions, 7 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
index a518f2eff19a..53a7385e1b4d 100644
--- a/drivers/scsi/device_handler/scsi_dh.c
+++ b/drivers/scsi/device_handler/scsi_dh.c
@@ -153,12 +153,24 @@ static int scsi_dh_handler_attach(struct scsi_device *sdev,
         if (sdev->scsi_dh_data) {
                 if (sdev->scsi_dh_data->scsi_dh != scsi_dh)
                         err = -EBUSY;
-        } else if (scsi_dh->attach)
+                else
+                        kref_get(&sdev->scsi_dh_data->kref);
+        } else if (scsi_dh->attach) {
                 err = scsi_dh->attach(sdev);
-
+                if (!err) {
+                        kref_init(&sdev->scsi_dh_data->kref);
+                        sdev->scsi_dh_data->sdev = sdev;
+                }
+        }
         return err;
 }
 
+static void __detach_handler (struct kref *kref)
+{
+        struct scsi_dh_data *scsi_dh_data = container_of(kref, struct scsi_dh_data, kref);
+        scsi_dh_data->scsi_dh->detach(scsi_dh_data->sdev);
+}
+
 /*
  * scsi_dh_handler_detach - Detach a device handler from a device
  * @sdev - SCSI device the device handler should be detached from
@@ -180,7 +192,7 @@ static void scsi_dh_handler_detach(struct scsi_device *sdev,
                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 
         if (scsi_dh && scsi_dh->detach)
-                scsi_dh->detach(sdev);
+                kref_put(&sdev->scsi_dh_data->kref, __detach_handler);
 }
 
 /*
@@ -474,7 +486,6 @@ int scsi_dh_attach(struct request_queue *q, const char *name)
 
         if (!err) {
                 err = scsi_dh_handler_attach(sdev, scsi_dh);
-
                 put_device(&sdev->sdev_gendev);
         }
         return err;
@@ -505,10 +516,8 @@ void scsi_dh_detach(struct request_queue *q)
                 return;
 
         if (sdev->scsi_dh_data) {
-                /* if sdev is not on internal list, detach */
                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
-                if (!device_handler_match(scsi_dh, sdev))
-                        scsi_dh_handler_detach(sdev, scsi_dh);
+                scsi_dh_handler_detach(sdev, scsi_dh);
         }
         put_device(&sdev->sdev_gendev);
 }