[SCSI] scsi_dh: attach to hardware handler from dm-mpath

multipath keeps a separate device table which may be
more current than the built-in one.
So we should make sure to always call ->attach whenever
a multipath map with hardware handler is instantiated.
And we should call ->detach on removal, too.

[sekharan: update as per comments from agk]
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
index e90df9dd3e65..a9159681ff27 100644
--- a/drivers/scsi/device_handler/scsi_dh.c
+++ b/drivers/scsi/device_handler/scsi_dh.c
@@ -369,6 +369,70 @@ int scsi_dh_handler_exist(const char *name)
 }
 EXPORT_SYMBOL_GPL(scsi_dh_handler_exist);
 
+/*
+ * scsi_dh_handler_attach - Attach device handler
+ * @sdev - sdev the handler should be attached to
+ * @name - name of the handler to attach
+ */
+int scsi_dh_attach(struct request_queue *q, const char *name)
+{
+        unsigned long flags;
+        struct scsi_device *sdev;
+        struct scsi_device_handler *scsi_dh;
+        int err = 0;
+
+        scsi_dh = get_device_handler(name);
+        if (!scsi_dh)
+                return -EINVAL;
+
+        spin_lock_irqsave(q->queue_lock, flags);
+        sdev = q->queuedata;
+        if (!sdev || !get_device(&sdev->sdev_gendev))
+                err = -ENODEV;
+        spin_unlock_irqrestore(q->queue_lock, flags);
+
+        if (!err) {
+                err = scsi_dh_handler_attach(sdev, scsi_dh);
+
+                put_device(&sdev->sdev_gendev);
+        }
+        return err;
+}
+EXPORT_SYMBOL_GPL(scsi_dh_attach);
+
+/*
+ * scsi_dh_handler_detach - Detach device handler
+ * @sdev - sdev the handler should be detached from
+ *
+ * This function will detach the device handler only
+ * if the sdev is not part of the internal list, ie
+ * if it has been attached manually.
+ */
+void scsi_dh_detach(struct request_queue *q)
+{
+        unsigned long flags;
+        struct scsi_device *sdev;
+        struct scsi_device_handler *scsi_dh = NULL;
+
+        spin_lock_irqsave(q->queue_lock, flags);
+        sdev = q->queuedata;
+        if (!sdev || !get_device(&sdev->sdev_gendev))
+                sdev = NULL;
+        spin_unlock_irqrestore(q->queue_lock, flags);
+
+        if (!sdev)
+                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);
+        }
+        put_device(&sdev->sdev_gendev);
+}
+EXPORT_SYMBOL_GPL(scsi_dh_detach);
+
 static struct notifier_block scsi_dh_nb = {
         .notifier_call = scsi_dh_notifier
 };