vfs: Assert that VOP_READDIR sets *eofflag properly

Suggested by:	kib
Reviewed by:	olce, kib
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D51300

sys/kern/vfs_subr.c

@@ -6533,17 +6533,6 @@ vop_read_pgcache_post(void *ap, int rc)
 		VFS_KNOTE_UNLOCKED(a->a_vp, NOTE_READ);
 }
 
-void
-vop_readdir_post(void *ap, int rc)
-{
-	struct vop_readdir_args *a = ap;
-
-	if (!rc) {
-		VFS_KNOTE_LOCKED(a->a_vp, NOTE_READ);
-		INOTIFY(a->a_vp, IN_ACCESS);
-	}
-}
-
 static struct knlist fs_knlist;
 
 static void

sys/kern/vnode_if.src

@@ -380,6 +380,7 @@ vop_symlink {
 
 
 %% readdir	vp	L L L
+%! readdir	pre	vop_readdir_pre
 %! readdir	post	vop_readdir_post
 
 vop_readdir {

sys/sys/vnode.h

@@ -939,7 +939,6 @@ void	vop_mknod_post(void *a, int rc);
 void	vop_open_post(void *a, int rc);
 void	vop_read_post(void *a, int rc);
 void	vop_read_pgcache_post(void *ap, int rc);
-void	vop_readdir_post(void *a, int rc);
 void	vop_reclaim_post(void *a, int rc);
 void	vop_remove_pre(void *a);
 void	vop_remove_post(void *a, int rc);
@@ -1015,6 +1014,34 @@ void	vop_rename_fail(struct vop_rename_args *ap);
 	_error;									\
 })
 
+#ifdef INVARIANTS
+#define	vop_readdir_pre_assert(ap)					\
+	ssize_t nresid, oresid;						\
+									\
+	oresid = (ap)->a_uio->uio_resid;
+
+#define	vop_readdir_post_assert(ap, ret)				\
+	nresid = (ap)->a_uio->uio_resid;				\
+	if ((ret) == 0 && (ap)->a_eofflag != NULL) {			\
+		VNASSERT(nresid != oresid || *(ap)->a_eofflag == 1,	\
+		    (ap)->a_vp, ("VOP_READDIR: eofflag not set"));	\
+	}
+#else
+#define	vop_readdir_pre_assert(ap)
+#define	vop_readdir_post_assert(ap, ret)
+#endif
+
+#define	vop_readdir_pre(ap) do {					\
+	vop_readdir_pre_assert(ap)
+
+#define vop_readdir_post(ap, ret)					\
+	vop_readdir_post_assert(ap, ret);				\
+	if ((ret) == 0) {						\
+		VFS_KNOTE_LOCKED((ap)->a_vp, NOTE_READ);		\
+		INOTIFY((ap)->a_vp, IN_ACCESS);				\
+	}								\
+} while (0)
+
 #define	VOP_WRITE_PRE(ap)						\
 	struct vattr va;						\
 	int error;							\