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

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

On Wed, May 21, 2008 at 08:13:35PM +0300, Pekka J Enberg wrote:
> Hi!
> 
> On Tue, 20 May 2008, Paul Mundt wrote:
> > Moving the existing logic in to SLAB's ksize() and simply wrapping in to
> > ksize() directly seems to do the right thing in all cases, and allows me
> > to boot with any of the slab allocators enabled, rather than simply SLAB
> > by itself.
> > 
> > I've done the same !PageSlab() test in SLAB as SLUB does in its ksize(),
> > which also seems to produce the correct results. Hopefully someone more
> > familiar with the history of kobjsize()/ksize() interaction can scream if
> > this is the wrong thing to do. :-)
> 
> As pointed out by Christoph, it. ksize() works with SLUB and SLOB 
> accidentally because they do page allocator pass-through and thus need to 
> deal with non-PageSlab pages. SLAB, however, does not do that which is why 
> all pages passed to it must have PageSlab set (we ought to add a WARN_ON() 
> there btw).
> 
> So I suggest we fix up kobjsize() instead. Paul, does the following 
> untested patch work for you?
> 
It seems to, but I wonder if compound_order() needs to take a
virt_to_head_page(objp) instead of virt_to_page()?

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