On Fri, Sep 15, 2017 at 04:29:11PM -0700, Jaegeuk Kim wrote: > The mntput() in delayed_fput() is the last function call. So before that > moment, > sys_umount() may see mnt_get_count() as 2, so it avoids EBUSY condition. I'm > not > sure why it check over 2 tho.
Because it has just grabbed a reference itself, in addition to the one that keeps the damn thing alive (due to being mounted). So it bloody well should have triggered -EBUSY, if they refer to the same vfsmount.
