[Devel] Re: [PATCH 01/10] Containers(V10): Basic container framework

[Andrew Morton]

On Wed, 30 May 2007 07:02:00 -0700 "Paul Menage" <menage at google.com> wrote:

> 
> >
> > People have hit unpleasant problems before now running iput() against
> > partially-constructed inodes.
> 
> What kinds of problems? Are there bits of state that I should fully
> construct even if I'm going to iput() it, or is there a better
> function to call? fs/ext3/super.c seems to do the same thing.

I don't recall, actually.  But it crashed.

I guess the fault-injection code could be used to trigger errors here.

> > >
> > > +static inline void get_first_subsys(const struct container *cont,
> > > +                                 struct container_subsys_state **css,
> > > +                                 int *subsys_id) {
> > > +     const struct containerfs_root *root = cont->root;
> > > +     const struct container_subsys *test_ss;
> > > +     BUG_ON(list_empty(&root->subsys_list));
> > > +     test_ss = list_entry(root->subsys_list.next,
> > > +                          struct container_subsys, sibling);
> > > +     if (css) {
> > > +             *css = cont->subsys[test_ss->subsys_id];
> > > +             BUG_ON(!*css);
> > > +     }
> > > +     if (subsys_id)
> > > +             *subsys_id = test_ss->subsys_id;
> > > +}
> >
> > This ends up having several callers and its too large to inline.
> 
> Two large from a compiler PoV or from a style PoV? It's basically just
> six dereferences and two comparisons, plus the BUG_ON()s.

It will end up generating more .text this way.  We figure that this makes
it slower, due to increased icache footprint.