From acfecf55d7e68dde3b95f4a60f14e3b9ce425645 Mon Sep 17 00:00:00 2001
From: dholland <dholland@NetBSD.org>
Date: Mon, 29 Jun 2009 05:00:14 +0000
Subject: [PATCH] Add namei_simple_kernel and namei_simple_user. These provide
 the common case functionality of namei in a simple package with only a couple
 flags.

A substantial majority of the namei call sites in the kernel can use
this interface; this will isolate those areas from the changes arising
as the internals of namei are fumigated.
---
 sys/kern/vfs_lookup.c | 77 +++++++++++++++++++++++++++++++++++++++++--
 sys/sys/namei.src     | 32 +++++++++++++++++-
 2 files changed, 106 insertions(+), 3 deletions(-)

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index d81b4307ce98..6807d4415da5 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: vfs_lookup.c,v 1.115 2009/06/26 15:49:03 christos Exp $	*/
+/*	$NetBSD: vfs_lookup.c,v 1.116 2009/06/29 05:00:14 dholland Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.115 2009/06/26 15:49:03 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.116 2009/06/29 05:00:14 dholland Exp $");
 
 #include "opt_magiclinks.h"
 
@@ -1010,3 +1010,76 @@ bad:
 	*vpp = NULL;
 	return (error);
 }
+
+/*
+ * namei_simple - simple forms of namei.
+ *
+ * These are wrappers to allow the simple case callers of namei to be
+ * left alone while everything else changes under them.
+ */
+
+/* Flags */
+struct namei_simple_flags_type {
+	int dummy;
+};
+static const struct namei_simple_flags_type ns_nn, ns_nt, ns_fn, ns_ft;
+const namei_simple_flags_t NSM_NOFOLLOW_NOEMULROOT = &ns_nn;
+const namei_simple_flags_t NSM_NOFOLLOW_TRYEMULROOT = &ns_nt;
+const namei_simple_flags_t NSM_FOLLOW_NOEMULROOT = &ns_fn;
+const namei_simple_flags_t NSM_FOLLOW_TRYEMULROOT = &ns_ft;
+
+static
+int
+namei_simple_convert_flags(namei_simple_flags_t sflags)
+{
+	if (sflags == NSM_NOFOLLOW_NOEMULROOT)
+		return NOFOLLOW | 0;
+	if (sflags == NSM_NOFOLLOW_TRYEMULROOT)
+		return NOFOLLOW | TRYEMULROOT;
+	if (sflags == NSM_FOLLOW_NOEMULROOT)
+		return FOLLOW | 0;
+	if (sflags == NSM_FOLLOW_TRYEMULROOT)
+		return FOLLOW | TRYEMULROOT;
+	panic("namei_simple_convert_flags: bogus sflags\n");
+	return 0;
+}
+
+int
+namei_simple_kernel(const char *path, namei_simple_flags_t sflags,
+			struct vnode **vp_ret)
+{
+	struct nameidata nd;
+	int err;
+
+	NDINIT(&nd,
+		LOOKUP,
+		namei_simple_convert_flags(sflags),
+		UIO_SYSSPACE,
+		path);
+	err = namei(&nd);
+	if (err != 0) {
+		return err;
+	}
+	*vp_ret = nd.ni_vp;
+	return 0;
+}
+
+int
+namei_simple_user(const char *path, namei_simple_flags_t sflags,
+			struct vnode **vp_ret)
+{
+	struct nameidata nd;
+	int err;
+
+	NDINIT(&nd,
+		LOOKUP,
+		namei_simple_convert_flags(sflags),
+		UIO_USERSPACE,
+		path);
+	err = namei(&nd);
+	if (err != 0) {
+		return err;
+	}
+	*vp_ret = nd.ni_vp;
+	return 0;
+}
diff --git a/sys/sys/namei.src b/sys/sys/namei.src
index edca859e1742..b9ed88b400c8 100644
--- a/sys/sys/namei.src
+++ b/sys/sys/namei.src
@@ -1,4 +1,4 @@
-/*	$NetBSD: namei.src,v 1.10 2009/02/11 00:19:11 enami Exp $	*/
+/*	$NetBSD: namei.src,v 1.11 2009/06/29 05:00:14 dholland Exp $	*/
 
 /*
  * Copyright (c) 1985, 1989, 1991, 1993
@@ -196,6 +196,36 @@ extern pool_cache_t pnbuf_cache;	/* pathname buffer cache */
 #define	PNBUF_GET()	pool_cache_get(pnbuf_cache, PR_WAITOK)
 #define	PNBUF_PUT(pnb)	pool_cache_put(pnbuf_cache, (pnb))
 
+/*
+ * Typesafe flags for namei_simple.
+ *
+ * This encoding is not optimal but serves the important purpose of
+ * not being type-compatible with the regular namei flags.
+ */
+struct namei_simple_flags_type; /* Opaque. */
+typedef const struct namei_simple_flags_type *namei_simple_flags_t; /* Gross. */
+extern const namei_simple_flags_t
+	NSM_NOFOLLOW_NOEMULROOT,
+	NSM_NOFOLLOW_TRYEMULROOT,
+	NSM_FOLLOW_NOEMULROOT,
+	NSM_FOLLOW_TRYEMULROOT;
+
+/*
+ * namei_simple_* - the simple cases of namei, with no struct
+ *                  nameidata involved.
+ *
+ * namei_simple_kernel takes a kernel-space path as the first argument.
+ * namei_simple_user takes a user-space path as the first argument.
+ *
+ * A namei call can be converted to namei_simple_* if:
+ *    - the second arg to NDINIT is LOOKUP;
+ *    - it does not need the parent vnode, nd.ni_dvp;
+ *    - the only flags it uses are (NO)FOLLOW and TRYEMULROOT;
+ *    - it does not do anything else gross with the contents of nd.
+ */
+int namei_simple_kernel(const char *, namei_simple_flags_t, struct vnode **);
+int namei_simple_user(const char *, namei_simple_flags_t, struct vnode **);
+
 int	namei(struct nameidata *);
 uint32_t namei_hash(const char *, const char **);
 int	lookup(struct nameidata *);