Re: [PATCH] nommu: Push kobjsize() slab-specific logic down to ksize().

[Paul Mundt <lethal@linux-sh.org>]

On Tue, May 20, 2008 at 04:22:37PM -0500, Matt Mackall wrote:
> On Tue, 2008-05-20 at 12:16 -0700, Christoph Lameter wrote:
> > On Tue, 20 May 2008, Matt Mackall wrote:
> > > > How would that work given that both SLUB and SLOB forward >4k allocs to 
> > > > the page allocator? So any compound page allocation may be a slab 
> > > > allocation. Is there some way to distinguish between a 
> > > > allocations of the page allocator and a slab alloc?
> > > 
> > > We can't do it at all for SLOB. But when debugging is turned on, we can
> > > notice (in SLAB and SLUB) whenever anyone asks for the ksize() of
> > > something that lives on a non-kmalloc slab.
> > 
> > We could mark the pages specially I guess. Add a slab flag for 
> > kmalloc? PageSlab and PageKmalloc?
> 
> No, just warn for the cases where we already have enough information.
> 
If we go in that direction the existing users are already going to
trigger this a lot (ie, commit 4016a1390d07f15b267eecb20e76a48fd5c524ef).
Without this sort of heuristic in place, simply killing off kobjsize()
and calling in to ksize() directly would be a reasonable option.

Having WARN_ON()'s for !PageSlab() pages in ksize() in SLAB/SLUB would
make these cases more visible, at least.

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