isci: atomic device lookup and reference counting
We have unsafe references to remote devices that are notified to
disappear at lldd_dev_gone. In order to clean this up we need a single
canonical source for device lookups and stable references once a lookup
succeeds. Towards that end guarantee that domain_device.lldd_dev is
NULL as soon as we start the process of stopping a device. Any code
path that wants to safely lookup a remote device must do so through
task->dev->lldd_dev (isci_lookup_device()).
For in-flight references outside of scic_lock we need reference counting
to ensure that the device is not recycled before we are done with it.
Simplify device back references to just scic_sds_request.target_device
which is now the only permissible internal reference that is maintained
relative to the reference count.
There were two occasions where we wanted new i/o's to be treated as
SAS_TASK_UNDELIVERED but where the domain_dev->lldd_dev link is still
intact. Introduce a 'gone' flag to prevent i/o while waiting for libsas
to take action on the port down event.
One 'core' leftover is that we currently call
scic_remote_device_destruct() from isci_remote_device_deconstruct()
which is called when the 'core' says the device is stopped. It would be
more natural for the final put to trigger
isci_remote_device_deconstruct() but this implementation is deferred as
it requires other changes.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/scsi/isci/remote_device.h b/drivers/scsi/isci/remote_device.h
index 2b6a5bb..05842b5 100644
--- a/drivers/scsi/isci/remote_device.h
+++ b/drivers/scsi/isci/remote_device.h
@@ -56,6 +56,7 @@
#ifndef _ISCI_REMOTE_DEVICE_H_
#define _ISCI_REMOTE_DEVICE_H_
#include <scsi/libsas.h>
+#include <linux/kref.h>
#include "scu_remote_node_context.h"
#include "remote_node_context.h"
#include "port.h"
@@ -134,7 +135,9 @@
#define IDEV_STOP_PENDING 1
#define IDEV_ALLOCATED 2
#define IDEV_EH 3
+ #define IDEV_GONE 4
unsigned long flags;
+ struct kref kref;
struct isci_port *isci_port;
struct domain_device *domain_dev;
struct list_head node;
@@ -145,6 +148,26 @@
#define ISCI_REMOTE_DEVICE_START_TIMEOUT 5000
+/* device reference routines must be called under scic_lock */
+static inline struct isci_remote_device *isci_lookup_device(struct domain_device *dev)
+{
+ struct isci_remote_device *idev = dev->lldd_dev;
+
+ if (idev && !test_bit(IDEV_GONE, &idev->flags)) {
+ kref_get(&idev->kref);
+ return idev;
+ }
+
+ return NULL;
+}
+
+void isci_remote_device_release(struct kref *kref);
+static inline void isci_put_device(struct isci_remote_device *idev)
+{
+ if (idev)
+ kref_put(&idev->kref, isci_remote_device_release);
+}
+
enum sci_status isci_remote_device_stop(struct isci_host *ihost,
struct isci_remote_device *idev);
void isci_remote_device_nuke_requests(struct isci_host *ihost,