namei: massage lookup_slow() to be usable by lookup_one_len_unlocked()

Return dentry and don't pass nameidata or path; lift crossing mountpoints
into the caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-03-06 14:03:27 -05:00
commit e3c1392808