linux-kernel - Re: [PATCH 01/10] Containers(V10): Basic container framework

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Message-Id: <20070530090031.352b7790.akpm@linux-foundation.org>
Date:	Wed, 30 May 2007 09:00:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Paul Menage" <menage@...gle.com>
Cc:	dev@...ru, xemul@...ru, serue@...ibm.com, vatsa@...ibm.com,
	ebiederm@...ssion.com, haveblue@...ibm.com,
	svaidy@...ux.vnet.ibm.com, balbir@...ibm.com, pj@....com,
	cpw@....com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	mbligh@...gle.com, rohitseth@...gle.com, devel@...nvz.org
Subject: Re: [PATCH 01/10] Containers(V10): Basic container framework

On Wed, 30 May 2007 07:02:00 -0700 "Paul Menage" <menage@...gle.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.


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