[PATCH] add a vfs_permission helper

Most permission() calls have a struct nameidata * available.  This helper
takes that as an argument and thus makes sure we pass it down for lookup
intents and prepares for per-mount read-only support where we need a struct
vfsmount for checking whether a file is writeable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index caa9187..2019899f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -637,7 +637,7 @@
 		if (current->uid != nd->dentry->d_inode->i_uid)
 			return -EPERM;
 	}
-	if (permission(nd->dentry->d_inode, MAY_WRITE, nd))
+	if (vfs_permission(nd, MAY_WRITE))
 		return -EPERM;
 	return 0;
 #endif