A minor, uninvasive change to the vfs will help support external builds of more
recent FUSE code.  Since Bug 193720: Enable FUSE probably won't make 5.1, this
vfs change would at least make it easier for anyone who wants to use/test fuse
with RHEL5.  (there is another non-critical fuse-related vfs change, "fs
subtypes" which would also be nice, but is more invasive & a KABI breaker, so
that one is left out)

Patch as sent to rhkernel-list on 6/6/07:

For Bug 193720: Enable FUSE

This is a very minor change to the vfs for upstream fuse, 
and should not affect anyone else.

From: Miklos Szeredi <miklos@szeredi.hu>
Date: Fri, 29 Sep 2006 08:59:35 +0000 (-0700)
Subject: [PATCH] vfs: define new lookup flag for chdir
X-Git-Tag: v2.6.19-rc1~798
X-Git-Url:
http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=650a898342b3fa21c392c06a2b7010fa19823efa

[PATCH] vfs: define new lookup flag for chdir

In the "operation does permission checking" model used by fuse, chdir
permission is not checked, since there's no chdir method.

For this case set a lookup flag, which will be passed to ->permission(), so
fuse can distinguish it from permission checks for other operations.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

Index: linux-2.6.18-20.EL/fs/open.c
===================================================================
--- linux-2.6.18-20.EL.orig/fs/open.c
+++ linux-2.6.18-20.EL/fs/open.c
@@ -546,7 +546,8 @@ asmlinkage long sys_chdir(const char __u
 	struct nameidata nd;
 	int error;
 
-	error = __user_walk(filename, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &nd);
+	error = __user_walk(filename,
+			    LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);
 	if (error)
 		goto out;
 
Index: linux-2.6.18-20.EL/include/linux/namei.h
===================================================================
--- linux-2.6.18-20.EL.orig/include/linux/namei.h
+++ linux-2.6.18-20.EL/include/linux/namei.h
@@ -56,6 +56,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
 #define LOOKUP_OPEN		(0x0100)
 #define LOOKUP_CREATE		(0x0200)
 #define LOOKUP_ACCESS		(0x0400)
+#define LOOKUP_CHDIR		(0x0800)
 
 extern int FASTCALL(__user_walk(const char __user *, unsigned, struct nameidata
*));
 extern int FASTCALL(__user_walk_fd(int dfd, const char __user *, unsigned,
struct nameidata *));