Re: flex_array related problems on selinux policy loading

[Dave Hansen <dave@linux.vnet.ibm.com>]

On Wed, 2011-01-26 at 11:23 +0100, Steffen Klassert wrote: 
> Yes, I thought a moment on allocating the basic struct flex_array
> in any case. But I immediately stopped thinking about this when I saw that
> I would allocate a whole page that I don't need afterwards. For the moment
> I don't see any sane way to allocate just the metadata as long as the
> struct flex_array has a fixed size.
> 
> Btw. why the struct flex_array needs to have page size?

It was designed as an alternative to _large_ allocations and we didn't
expect people to want to use it for small things.  But, it doesn't
_need_ to stay that way, we just did it like that for simplicity.

> If we would make
> flex_array of dynamic size, say metadata plus the maximum size of the array
> in the case that the metadata and the array fit into a single page, and
> metadata plus space for all the base pointers we need to dereference the
> parts, if the metadata and array is beyond page size. With this, the struct
> flex_array would have a reasonable size in any case, even if the array to
> store is small or of zero size.

Sounds like a good idea to me.  Done right, it should only really affect
the allocation path since we use kmalloc() already, and we can still
plain kfree() it.

-- Dave