open-style analog of vfs_path_lookup()

new function: file_open_root(dentry, mnt, name, flags) opens the file
vfs_path_lookup would arrive to.

Note that name can be empty; in that case the usual requirement that
dentry should be a directory is lifted.

open-coded equivalents switched to it, may_open() got down exactly
one caller and became static.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 14 insertions, 0 deletions

diff --git a/fs/open.c b/fs/open.c
index d05e18c60bae..48afc5c139d2 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -959,6 +959,20 @@ struct file *filp_open(const char *filename, int flags, int mode)
 }
 EXPORT_SYMBOL(filp_open);
 
+struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
+                            const char *filename, int flags)
+{
+        struct open_flags op;
+        int lookup = build_open_flags(flags, 0, &op);
+        if (flags & O_CREAT)
+                return ERR_PTR(-EINVAL);
+        if (!filename && (flags & O_DIRECTORY))
+                if (!dentry->d_inode->i_op->lookup)
+                        return ERR_PTR(-ENOTDIR);
+        return do_file_open_root(dentry, mnt, filename, &op, lookup);
+}
+EXPORT_SYMBOL(file_open_root);
+
 long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
 {
         struct open_flags op;