[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>

diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
index a518f2eff19af1a7dcf86383f287940487ce80f3..53a7385e1b4d22d32767c69ef719d348b8fff361 100644 (file)
--- 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);
 }

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 3f566af3f1017e55338f7754f2b70387e3d126f7..1f3a4c8044c07c7f5281bcd74a4cbe5495dfd1ac 100644 (file)
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -191,6 +191,8 @@ struct scsi_device_handler {
 
 struct scsi_dh_data {
        struct scsi_device_handler *scsi_dh;
+       struct scsi_device *sdev;
+       struct kref kref;
        char buf[0];
 };