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SubjectRe: [PATCH 1/3] IMA: move read/write counters into struct inode

* Eric Paris <eparis@redhat.com> wrote:

> On Wed, 2010-10-20 at 16:38 +0200, Ingo Molnar wrote:
> > * Eric Paris <eparis@redhat.com> wrote:
> >
> > > Executive summary of the day's work:
> > > Yesterday morning: 944 bytes per inode in core
> > > Yesterday night: 24 bytes per inode in core
> > > Tonight: 4 bytes per inode in core.
> > >
> > > That's a x236 time reduction in memory usage. No I didn't even start looking
> > > at a freezer. Which could bring that 4 down to 0, but would add a scalability
> > > penalty on all inodes when IMA was enabled.
> >
> > Why not use inode->i_security intelligently? That already exists so that way
> > it's 0 bytes.
> >
> > Thanks,
>
> It still wouldn't be 0 bytes since there would be a 1-1 mapping from inode to
> i_security structs. [...]

Only for IMA-affected files, right?

My point is to keep it 0 overhead for the _non IMA common case_.

> The real reason I don't pursue this route is because of the litany of different
> ways this pointer is used in different LSMs (or not used at all.) And we all know
> that LSM authors aren't known for seeing the world the same way as each other. As
> a maintainer of one of those LSMs even I'm scared to try pushing that forward....

Ugh. That's a perfect reason to do it exactly like i suggested.

Thanks,

Ingo


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