X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=blobdiff_plain;f=lustre%2Fobdclass%2Fobd_mount_server.c;h=9945ef0fd6da98890c50fb733766012a7b2d73d9;hp=c8c90ec8262e6729e96feb2157caafe6c9435f0c;hb=bccfc65d04dbd59bedb5dc1509bbdc732fc09b53;hpb=1929bfe81379a9c986bfa4202265f76d201a49bc

diff --git a/lustre/obdclass/obd_mount_server.c b/lustre/obdclass/obd_mount_server.c
index c8c90ec..9945ef0 100644
--- a/lustre/obdclass/obd_mount_server.c
+++ b/lustre/obdclass/obd_mount_server.c
@@ -389,7 +389,18 @@ EXPORT_SYMBOL(tgt_name2lwp_name);
 
 static struct list_head lwp_register_list =
 	LIST_HEAD_INIT(lwp_register_list);
-static DEFINE_MUTEX(lwp_register_list_lock);
+static DEFINE_SPINLOCK(lwp_register_list_lock);
+
+static void lustre_put_lwp_item(struct lwp_register_item *lri)
+{
+	if (atomic_dec_and_test(&lri->lri_ref)) {
+		LASSERT(list_empty(&lri->lri_list));
+
+		if (*lri->lri_exp != NULL)
+			class_export_put(*lri->lri_exp);
+		OBD_FREE_PTR(lri);
+	}
+}
 
 int lustre_register_lwp_item(const char *lwpname, struct obd_export **exp,
 			     register_lwp_cb cb_func, void *cb_data)
@@ -406,15 +417,12 @@ int lustre_register_lwp_item(const char *lwpname, struct obd_export **exp,
 	if (lri == NULL)
 		RETURN(-ENOMEM);
 
-	mutex_lock(&lwp_register_list_lock);
-
 	lwp = class_name2obd(lwpname);
 	if (lwp != NULL && lwp->obd_set_up == 1) {
 		struct obd_uuid *uuid;
 
 		OBD_ALLOC_PTR(uuid);
 		if (uuid == NULL) {
-			mutex_unlock(&lwp_register_list_lock);
 			OBD_FREE_PTR(lri);
 			RETURN(-ENOMEM);
 		}
@@ -428,31 +436,40 @@ int lustre_register_lwp_item(const char *lwpname, struct obd_export **exp,
 	lri->lri_cb_func = cb_func;
 	lri->lri_cb_data = cb_data;
 	INIT_LIST_HEAD(&lri->lri_list);
+	/*
+	 * Initialize the lri_ref at 2, one will be released before
+	 * current function returned via lustre_put_lwp_item(), the
+	 * other will be released in lustre_deregister_lwp_item().
+	 */
+	atomic_set(&lri->lri_ref, 2);
+
+	spin_lock(&lwp_register_list_lock);
 	list_add(&lri->lri_list, &lwp_register_list);
+	spin_unlock(&lwp_register_list_lock);
 
 	if (*exp != NULL && cb_func != NULL)
 		cb_func(cb_data);
+	lustre_put_lwp_item(lri);
 
-	mutex_unlock(&lwp_register_list_lock);
 	RETURN(0);
 }
 EXPORT_SYMBOL(lustre_register_lwp_item);
 
 void lustre_deregister_lwp_item(struct obd_export **exp)
 {
-	struct lwp_register_item *lri, *tmp;
+	struct lwp_register_item *lri;
 
-	mutex_lock(&lwp_register_list_lock);
-	list_for_each_entry_safe(lri, tmp, &lwp_register_list, lri_list) {
+	spin_lock(&lwp_register_list_lock);
+	list_for_each_entry(lri, &lwp_register_list, lri_list) {
 		if (exp == lri->lri_exp) {
-			if (*exp)
-				class_export_put(*exp);
-			list_del(&lri->lri_list);
-			OBD_FREE_PTR(lri);
-			break;
+			list_del_init(&lri->lri_list);
+			spin_unlock(&lwp_register_list_lock);
+
+			lustre_put_lwp_item(lri);
+			return;
 		}
 	}
-	mutex_unlock(&lwp_register_list_lock);
+	spin_unlock(&lwp_register_list_lock);
 }
 EXPORT_SYMBOL(lustre_deregister_lwp_item);
 
@@ -499,20 +516,32 @@ EXPORT_SYMBOL(lustre_find_lwp_by_index);
 
 void lustre_notify_lwp_list(struct obd_export *exp)
 {
-	struct lwp_register_item *lri, *tmp;
+	struct lwp_register_item *lri;
 	LASSERT(exp != NULL);
 
-	mutex_lock(&lwp_register_list_lock);
-	list_for_each_entry_safe(lri, tmp, &lwp_register_list, lri_list) {
+again:
+	spin_lock(&lwp_register_list_lock);
+	list_for_each_entry(lri, &lwp_register_list, lri_list) {
 		if (strcmp(exp->exp_obd->obd_name, lri->lri_name))
 			continue;
 		if (*lri->lri_exp != NULL)
 			continue;
 		*lri->lri_exp = class_export_get(exp);
+		atomic_inc(&lri->lri_ref);
+		spin_unlock(&lwp_register_list_lock);
+
 		if (lri->lri_cb_func != NULL)
 			lri->lri_cb_func(lri->lri_cb_data);
+		lustre_put_lwp_item(lri);
+
+		/* Others may have changed the list after we unlock, we have
+		 * to rescan the list from the beginning. Usually, the list
+		 * 'lwp_register_list' is very short, and there is 'guard'
+		 * lri::lri_exp that will prevent the callback to be done
+		 * repeatedly. So rescanning the list has no problem. */
+		goto again;
 	}
-	mutex_unlock(&lwp_register_list_lock);
+	spin_unlock(&lwp_register_list_lock);
 }
 EXPORT_SYMBOL(lustre_notify_lwp_list);