1 files changed, 59 insertions, 0 deletions
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index ba7888c4f650..a9eb5e4cf153 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -56,6 +56,65 @@ struct xfs_error_cfg {
 	long		retry_timeout;	/* in jiffies, -1 = infinite */
 };
 
+#ifdef CONFIG_XFS_LIVE_HOOKS
+struct xfs_hooks {
+	struct srcu_notifier_head	head;
+};
+#else
+struct xfs_hooks { /* empty */ };
+#endif
+
+/*
+ * If hooks and jump labels are enabled, we use jump labels (aka patching of
+ * the code segment) to avoid the minute overhead of calling an empty notifier
+ * chain when we know there are no callers.  If hooks are enabled without jump
+ * labels, hardwire the predicate to true because calling an empty srcu
+ * notifier chain isn't so expensive.
+ */
+#if defined(CONFIG_JUMP_LABEL) && defined(CONFIG_XFS_LIVE_HOOKS)
+# define DEFINE_STATIC_XFS_HOOK_SWITCH(name) \
+	static DEFINE_STATIC_KEY_FALSE(name)
+# define xfs_hooks_switch_on(name)	static_branch_inc(name)
+# define xfs_hooks_switch_off(name)	static_branch_dec(name)
+# define xfs_hooks_switched_on(name)	static_branch_unlikely(name)
+#elif defined(CONFIG_XFS_LIVE_HOOKS)
+# define DEFINE_STATIC_XFS_HOOK_SWITCH(name)
+# define xfs_hooks_switch_on(name)	((void)0)
+# define xfs_hooks_switch_off(name)	((void)0)
+# define xfs_hooks_switched_on(name)	(true)
+#else
+# define DEFINE_STATIC_XFS_HOOK_SWITCH(name)
+# define xfs_hooks_switch_on(name)	((void)0)
+# define xfs_hooks_switch_off(name)	((void)0)
+# define xfs_hooks_switched_on(name)	(false)
+#endif /* JUMP_LABEL && XFS_LIVE_HOOKS */
+
+#ifdef CONFIG_XFS_LIVE_HOOKS
+struct xfs_hook {
+	/* This must come at the start of the structure. */
+	struct notifier_block		nb;
+};
+
+typedef	int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action,
+		void *data);
+
+void xfs_hooks_init(struct xfs_hooks *chain);
+int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook);
+void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook);
+int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action,
+		void *priv);
+
+static inline void xfs_hook_setup(struct xfs_hook *hook, xfs_hook_fn_t fn)
+{
+	hook->nb.notifier_call = (notifier_fn_t)fn;
+	hook->nb.priority = 0;
+}
+
+#else
+# define xfs_hooks_init(chain)			((void)0)
+# define xfs_hooks_call(chain, val, priv)	(NOTIFY_DONE)
+#endif
+
 #ifdef CONFIG_XFS_DRAIN_INTENTS
 /*
  * Passive drain mechanism.  This data structure tracks a count of some items