Re: [PATCH] fs: fcntl_setlease defies lease_init assumptions

["Pekka Enberg" <penberg@cs.helsinki.fi>]

Hi Linus,

On 5/8/06, Linus Torvalds <torvalds@osdl.org> wrote:
> Ok, I was actually really surprised that we'd ever allow a non-slab page
> to be free'd as a slab or kmalloc allocation, without screaming very
> loudly indeed. That implies a lack of some pretty fundamental sanity
> checking by default in the slab layer (I suspect slab debugging turns it
> on, but even without it, that's just nasty).
>
> Can you see if this trivial patch at least causes a honking huge
> "kernel BUG" message to be triggered quickly?

page_get_cache and page_get_slab are too late. You would need to do
the check in __cache_free; otherwise the stack pointer goes to per-CPU
caches and can be given back by kmalloc(). Adding PageSlab debugging
to __cache_free is probably too much of a performance hit, though.

                                        Pekka
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