[lustre-devel] [PATCH 07/37] lustre: obd_type: discard obd_type_lock

[NeilBrown <neilb@suse.com>]

This lock is only used to protect typ_refcnt, so change
that to a refcount_t and discard the lock.

The lock also covers calls to try_module_get and module_put,
but this serves no purpose as it does not prevent the module
from being unloaded.

Finally, the return value for the call to try_module_get is
ignored, which is not safe.

Signed-off-by: NeilBrown <neilb@suse.com>
---
 drivers/staging/lustre/lustre/include/obd.h        |    3 +-
 drivers/staging/lustre/lustre/mdc/mdc_request.c    |    2 +
 drivers/staging/lustre/lustre/mgc/mgc_request.c    |    2 +
 drivers/staging/lustre/lustre/obdclass/genops.c    |   30 +++++++++-----------
 drivers/staging/lustre/lustre/obdclass/lu_object.c |    2 +
 5 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/drivers/staging/lustre/lustre/include/obd.h b/drivers/staging/lustre/lustre/include/obd.h
index 50f33f400075..a67eb9a14879 100644
--- a/drivers/staging/lustre/lustre/include/obd.h
+++ b/drivers/staging/lustre/lustre/include/obd.h
@@ -102,9 +102,8 @@ struct obd_type {
 	struct obd_ops		*typ_dt_ops;
 	struct md_ops		*typ_md_ops;
 	struct dentry		*typ_debugfs_entry;
-	int			 typ_refcnt;
+	refcount_t		 typ_refcnt;
 	struct lu_device_type	*typ_lu;
-	spinlock_t		 obd_type_lock;
 	struct kobject		 typ_kobj;
 };
 #define typ_name typ_kobj.name
diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c b/drivers/staging/lustre/lustre/mdc/mdc_request.c
index 3eb89ec80b7e..db2c045aa1cd 100644
--- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
+++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
@@ -2540,7 +2540,7 @@ static int mdc_init_ea_size(struct obd_export *exp, u32 easize, u32 def_easize)
 static int mdc_precleanup(struct obd_device *obd)
 {
 	/* Failsafe, ok if racy */
-	if (obd->obd_type->typ_refcnt <= 1)
+	if (refcount_read(&obd->obd_type->typ_refcnt) <= 1)
 		libcfs_kkuc_group_rem(0, KUC_GRP_HSM);
 
 	mdc_changelog_cdev_finish(obd);
diff --git a/drivers/staging/lustre/lustre/mgc/mgc_request.c b/drivers/staging/lustre/lustre/mgc/mgc_request.c
index a4dfdc08cc48..a6ee715921b8 100644
--- a/drivers/staging/lustre/lustre/mgc/mgc_request.c
+++ b/drivers/staging/lustre/lustre/mgc/mgc_request.c
@@ -715,7 +715,7 @@ static int mgc_cleanup(struct obd_device *obd)
 	/* COMPAT_146 - old config logs may have added profiles we don't
 	 * know about
 	 */
-	if (obd->obd_type->typ_refcnt <= 1)
+	if (refcount_read(&obd->obd_type->typ_refcnt) <= 1)
 		/* Only for the last mgc */
 		class_del_profiles();
 
diff --git a/drivers/staging/lustre/lustre/obdclass/genops.c b/drivers/staging/lustre/lustre/obdclass/genops.c
index 775e4fa4f6a8..a3437c2d07bb 100644
--- a/drivers/staging/lustre/lustre/obdclass/genops.c
+++ b/drivers/staging/lustre/lustre/obdclass/genops.c
@@ -112,15 +112,17 @@ static struct obd_type *class_get_type(const char *name)
 		}
 	}
 	if (type) {
-		spin_lock(&type->obd_type_lock);
-		type->typ_refcnt++;
-		try_module_get(type->typ_dt_ops->owner);
-		spin_unlock(&type->obd_type_lock);
-		/* class_search_type() returned a counted reference,
-		 * but we don't need that count any more as
-		 * we have one through typ_refcnt.
-		 */
-		kobject_put(&type->typ_kobj);
+		if (try_module_get(type->typ_dt_ops->owner)) {
+			refcount_inc(&type->typ_refcnt);
+			/* class_search_type() returned a counted reference,
+			 * but we don't need that count any more as
+			 * we have one through typ_refcnt.
+			 */
+			kobject_put(&type->typ_kobj);
+		} else {
+			kobject_put(&type->typ_kobj);
+			type = NULL;
+		}
 	}
 	return type;
 }
@@ -128,10 +130,7 @@ static struct obd_type *class_get_type(const char *name)
 void class_put_type(struct obd_type *type)
 {
 	LASSERT(type);
-	spin_lock(&type->obd_type_lock);
-	type->typ_refcnt--;
-	module_put(type->typ_dt_ops->owner);
-	spin_unlock(&type->obd_type_lock);
+	refcount_dec(&type->typ_refcnt);
 }
 
 static void class_sysfs_release(struct kobject *kobj)
@@ -191,7 +190,6 @@ int class_register_type(struct obd_ops *dt_ops, struct md_ops *md_ops,
 	/* md_ops is optional */
 	if (md_ops)
 		*type->typ_md_ops = *md_ops;
-	spin_lock_init(&type->obd_type_lock);
 
 	rc = kobject_add(&type->typ_kobj, &lustre_kset->kobj, "%s", name);
 	if (rc)
@@ -225,8 +223,8 @@ int class_unregister_type(const char *name)
 		return -EINVAL;
 	}
 
-	if (type->typ_refcnt) {
-		CERROR("type %s has refcount (%d)\n", name, type->typ_refcnt);
+	if (refcount_read(&type->typ_refcnt)) {
+		CERROR("type %s has refcount (%d)\n", name, refcount_read(&type->typ_refcnt));
 		/* This is a bad situation, let's make the best of it */
 		/* Remove ops, but leave the name for debugging */
 		kfree(type->typ_dt_ops);
diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c
index 639c298b6a90..69a56cca99f2 100644
--- a/drivers/staging/lustre/lustre/obdclass/lu_object.c
+++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c
@@ -1267,7 +1267,7 @@ void lu_stack_fini(const struct lu_env *env, struct lu_device *top)
 		next = ldt->ldt_ops->ldto_device_free(env, scan);
 		type = ldt->ldt_obd_type;
 		if (type) {
-			type->typ_refcnt--;
+			refcount_dec(&type->typ_refcnt);
 			class_put_type(type);
 		}
 	}