with the way fs/namei.c:do_last() had been done, ->atomic_open()
instances needed to recognize the case when existing file got
found with O_EXCL|O_CREAT, either by falling back to finish_no_open()
or failing themselves.  gfs2 one didn't.
Fixes: 6d4ade986f9c (GFS2: Add atomic_open support)
Cc: stable@kernel.org # v3.11
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
                if (!(file->f_mode & FMODE_OPENED))
                        return finish_no_open(file, d);
                dput(d);
-               return 0;
+               return excl && (flags & O_CREAT) ? -EEXIST : 0;
        }
 
        BUG_ON(d != NULL);